9/15

DOUG AND ANNA CRABTREE’S VILICUS FARM RESTS 

on more than 2,000 acres in northern Montana, and 

it is a model of how cover crops can be a foundation 

of pollinator and beneficial insect management. Like 

many farmers, their approach to cover cropping began 

with an interest in soil health and quickly grew to 

encompass much broader goals as they recognized 

the additional benefits cover crops could provide. 

“We want to implement pollinator conservation 

at the field-level scale,” Doug says. “Anyone can create 

a small wildflower strip, but as we scale up, we need 

conservation areas distributed across the entire operation.”

While the Crabtrees have established permanent 

native wildflower strips around many of their fields to 

provide a skeleton of habitat throughout the farm, 

extensive cover crop rotations provide the muscle that 

makes their operation a rich landscape for bees and 

other beneficial insects. 

This commitment to cover cropping is having clear 

and positive impacts. Flax, sunflower and safflower are 

just a few of the Crabtrees’ regular crops that either 

require or strongly benefit from insect pollination. And, 

because of their commitment to integrating habitat for 

wild pollinators throughout their holdings, the Crabtrees 

have never needed to bring honey bee hives onto the 

farm for pollination. Instead, a walk through their fields 

quickly reveals an abundance of wild bumble bees, 

longhorn bees, sweat bees and more—all supported by 

the farm’s habitat. A farm’s ability to support its own 

pollinator community provides security, especially if 

managed honey bee hives become scarce or expensive.

In addition to supporting the pollinator community, 

cover crops have many traditional uses on a farm. These 

range from preventing erosion and improving soil health 

to managing weeds and serving as an additional source 

of income when part of a double-crop system. With cover 

CONTENTS

INTRODUCTION

 Basic Pollinator Ecology 2

 Other Beneficial Insects 2

COVER CROPS ON 

 YOUR FARM 3

 Opportunities to Use

 Cover Crops 4

 Planting and Managing

 Your Cover Crops 5

PLANT SELECTION 6

 Cover Crop Cocktails 7

 Common and Suggested

 Rotations 7

BALANCING INSECT 

CONSERVATION WITH 

USDA CROP INSURANCE 

RULES 9 

 TABLE: Relative Value of

Cover Crop Species to Bees

and Other Beneficial Insects

10

LIMITATIONS OF COVER

 CROPS 13

BEYOND COVER CROPS 13

INSECTICIDES AND INSECT 

CONSERVATION 14

 Avoiding Pest Increases 14

REFERENCES 15

RESOURCES 16

Available at: www.sare.org/

cover-cropping-for-pollinators 

or order free hard copies at 

(301) 779-1007.

Opportunities in Agriculture

Cover Cropping for Pollinators 

and Beneficial Insects

Doug Crabtree uses many tools to make his Montana farm bee friendly. – Photo by Jennifer Hopwood; Phacelia is an 

attractive pollinator cover crop. – Photo by John Hayden; Clover fixes nitrogen and provides bee forage. – Photo by Judson Reid
2

crops planted on more than 10 million acres annually, 

many farmers already appreciate the role diverse agroecosystems play in improving crop productivity. In the 

2012 and 2013 growing seasons, corn yields increased 

9 percent and 3.1 percent, respectively, when following a 

cover crop, and soybean yields increased 10 percent and 

4.3 percent, according to a two-year survey of farmers 

conducted by North Central Region SARE and the 

Conservation Technology Information Center (CTIC). 

While the CTIC-SARE survey revealed that 38 percent of 

cover crop users already choose plants in order to support 

pollinators [1], cover crops reap many additional benefits. 

Flowering cover crops can fulfill their original purpose 

as a conservation practice while at the same time providing 

valuable forage for wild bees and beneficial insects. This 

added benefit can be significantly enhanced with some 

fine-tuning of management practices and thoughtful 

plant selection.

This bulletin will help you use cover crops to encourage 

populations of pollinators and beneficial insects on your 

farm while you address your other resource concerns. It 

begins with a broad overview of pollinator and beneficial 

insect ecology, then describes cover crop selection and management, how to make cover crops work on your farm, and 

helpful and proven crop rotations. It will also touch on the 

limitations of cover crops and pesticide harm reduction, 

among other topics. 

Basic Pollinator Ecology

IN ADDITION TO THE DOMESTICATED EUROPEAN HONEY

bee, roughly 4,000 species of wild bees can be found in 

the United States. Among these, honey bees and bumble 

bees are social animals, living in complex family units 

with a single queen, female workers (the daughters of the 

queen) and a few male bees called drones. In contrast, 

most wild bees (except for bumble bees) are solitary animals, 

with each female locating and provisioning her own nest. 

Honey bees and wild bees alike are considered important 

agricultural pollinators, and both groups of bees share 

many of the same habitat requirements necessary to thrive. 

Both require reliable and abundant pollen and nectar 

resources throughout the growing season. In the case of 

honey bees, nectar demands can be significant, requiring 

large-scale flowering habitats to produce surplus honey.

In addition to the availability of food, honey bees and 

wild bees require protection from pesticides. While large 

doses of pesticides may be directly lethal to bees, smaller 

doses can result in sublethal impacts, such as reduced 

reproduction or foraging. Interestingly, research suggests 

that diverse pollen and nectar resources may help 

improve the overall health of bees and increase their 

chances of detoxifying low doses of some pesticides. 

Along with food availability and pesticide protection, 

wild bees have a third habitat requirement: undisturbed 

areas for nesting. In the case of many wild bee species, 

the preferred nesting areas are undisturbed soils. These 

soil-nesting wild bees excavate underground tunnels 

and provision them with pollen clumps, onto which they 

lay their eggs. Other wild bee species nest in the hollow 

stems of plants, including the stems of some trees, shrubs, 

large grasses and even large wildflowers. A few species, 

including bumble bees, typically nest in the abandoned 

underground burrows of small rodents, or in other 

similar cavities.

With appropriate plant selection and proper management, flowering cover crops can support the habitat 

requirements of bees through pollen and nectar 

resources to maximize their health and reproductive 

potential, an abundance of nectar to produce surplus 

honey, a refuge from insecticides, and sometimes 

enhanced nesting opportunities for wild bee species. 

Other Beneficial Insects

THE NATURAL ENEMIES OF CROP PESTS THAT SOMETIMES

inhabit farms include a diverse range of predatory beetles, 

aphid-eating flower flies, lacewings, small solitary parasitic 

wasps and many others. 

In addition to preying upon crop pests, most of these 

predatory and parasitoid insects either need or benefit from 

alternative food sources during at least one stage of their 

life. In some cases that alternative food source is nectar or 

Cover crop mixes can offer 

multiple benefits. This mix 

of sunn hemp and radishes

in South Dakota provides 

livestock grazing, pollinator 

forage and brooding cover 

for pheasants. 

– Photo by Ben Lardy, USDA 

NRCS in cooperation with 

Pheasants Forever Inc.
3

pollen. Consequently, like pollinators, many of these natural 

pest enemies also benefit from flowering cover crops. 

A SARE-funded group of University of California 

researchers demonstrated that mixed species of flowering 

cover crops in vineyards increased beneficial insect 

populations [2]. The increase in beneficial insects, brought 

about by a mix of annual buckwheat, lacy phacelia, sweet 

alyssum, bishops weed and wild carrot, resulted in fewer 

pests, such as the vine mealy bug. 

In other cases, cover crops can support beneficial 

insect populations even when they do not flower. Some 

predators and parasitoids do not feed on nectar and 

pollen, but rather need a continuous supply of prey insects 

to maintain their local populations at an effective level. So 

when cash crops are absent, non-flowering cover crops can 

support pests to the extent that they become a stable food 

source for beneficial insects. For example, ground beetles, 

which are generalist predators of slugs, caterpillars and 

grasshopper eggs, can be sustained by leaving some areas 

unmowed or by creating a “beetle bank” of perennial 

grasses outside crop fields. Beetles can overwinter in this 

augmented habitat and their prey can breed in it. Thus, 

these grassy refuges can keep the beetle population high 

by providing both habitat and a food source outside the 

cropping period.

Similarly, even if prey insects found in cover crops are not 

pests of your cash crops, they can still be an important food 

resource for predator and parasitoid insects that will switch 

their prey preference once cash crop pests become available. 

Finally, like pollinators, predatory beneficial insects 

need protection from insecticide applications and 

vegetative structures for egg-laying or overwintering. 

Well-managed cover crop systems can help meet these 

habitat requirements.

BEYOND SUPPORTING BEE AND BENEFICIAL INSECT

populations, cover crops can reduce your costs for 

herbicide, insecticide and fertilizer, and improve overall 

soil health [3]. Many cover crops can be included in a 

double-crop system or used as animal forage. Cover 

crops can be integrated into most crop or crop-livestock 

systems, including no-till, conventional till, rotational 

no-till and livestock grazing or haying systems. In the 

CTIC-SARE survey, farmers who plant cover crops identified 

these top five reasons for doing so (in order): increase soil 

organic matter, reduce soil erosion, reduce soil compaction, 

manage weeds and provide a nitrogen source [1].

The economic benefits associated with cover crops 

can be both significant and realized in year one. On a 

Georgia cotton farm, a grower reduced costs by $200 

per acre by implementing conservation tillage and cover 

cropping. His cover crop cocktail combined crimson clover, 

an excellent nectar plant and nitrogen source; and rye, a 

soil-builder and nitrogen scavenger. Between the savings 

on fertilizer from the clover’s nitrogen enrichment and 

PERENNIAL COVER FOR ORCHARDS AND VINEYARDS

FAST-GROWING ANNUAL COVER CROP SPECIES SUCH AS RYE AND CRIMSON CLOVER ARE

the most common choice for rotation with annual field crops. However, in perennial farm 

systems such as orchards and vineyards, longer-term ground cover may be desired. In these 

settings, the ground cover may have multiple demands placed upon it, including erosion 

control, nutrient management, and pest and disease suppression. As long as these perennial 

ground covers are combined with a thoughtful and careful approach to pesticide use, 

pollinator conservation can be very compatible with other goals. 

For example, perennial turf grass in orchards can be enhanced for pollinators simply 

by tolerating non-invasive weeds such as violets or dandelions. To go a step further and 

actively increase pollen and nectar resources, such perennial turf grass systems can be 

over-seeded with various low-growing perennial clovers. Where these approaches are 

used, it is critical that insecticides not be over-sprayed and allowed to drift down onto 

flowering plants in the ground cover. Some farmers with these types of ground covers 

simply mow them to remove flowers before spraying. Although a mowed ground cover 

without flowers may significantly reduce the landscape value for pollinators, it is preferable 

to killing bees that might otherwise move on to areas where no spraying is taking place.

In perennial crop systems where no insecticides are used, ground cover options may 

be even more diverse and expansive. In such cases it may be possible to establish an 

entirely native grassland, meadow or diverse prairie as an understory. These systems 

typically provide maximum benefits to pollinators and other beneficial insects, and they 

are well adapted to the local climate and do not require routine mowing or irrigation. 

Cover Crops On Your Farm

Strips of flowering cover 

crops such as lacy 

phacelia and sweet 

alyssum (pictured) can 

manage vineyard pests 

such as the vine mealy 

bug by supporting 

beneficial insects.

– Photo by Miguel Altieri
4

reduced insecticide costs thanks to beneficial insect 

activity, this farmer observed that many pests were no 

longer a problem in his fields [3]. Similarly, a Pennsylvania 

vegetable farmer cut pesticide costs by 40 percent (saving 

$125 per acre) by using a combination of cover crops [4], 

and a North Dakota farmer saw net profits on his barley 

harvest increase by $109 per acre on cover cropped 

fields. He was also able to harvest his cover crops as 

forage for his cattle [5]. 

There are many tools available to farmers as they 

weigh the economics of adding cover crops to their 

system. The USDA Natural Resources Conservation 

Service’s (NRCS) Cover Crop Economics Decision 

Support Tool (see Resources) provides a number of 

cropping system scenarios that explore the costs and 

benefits of cover crops over time. While some systems, 

like a soybean/corn rotation in the absence of cost share, 

only became profitable in the long run, other systems 

realized a net profit in the first year, such as a cotton/

corn rotation that led to a net profit increase of $38.50 per 

acre [6]. All of the default scenarios were immediately 

profitable with a modest cost share. A webinar explaining 

how to use this tool is available through the www.conservationwebinars.net portal.

While a 2005 survey in the Corn Belt found that more 

than half of all farmers said they would use cover crops if 

they received cost-share funds [7], the more recent CTICSARE survey found that farmers are increasingly likely 

to try cover crops without any sort of financial assistance. 

This survey found that 63 percent of farmers said they had 

never received cost-share funds, and only 8 percent 

restricted their cover cropping to times when they received 

funding [1]. Although cost-share programs improve the 

profitability of cover crops, many farmers who use them—

perhaps the majority—look beyond the balance sheet 

when assessing their value. It seems that financial assistance can open the door to cover cropping, but many 

farmers with experience cover cropping do not require it 

[1]. The less easily quantified conservation benefits of 

cover crops, such as their role in soil health and pollinator 

promotion, are the important consideration for many.

Opportunities to Use Cover Crops

ONE OF THE FIRST STEPS WHEN INCORPORATING COVER

crops in your system is identifying available niches. You 

may already have periods in your cropping systems 

which are open to cover crops. Common niches for cover 

crops include during the winter fallow, during a summer 

fallow between cash crops, during a small-grain rotation 

or during a full year of improved fallow [3]. Cover crops 

are often used in a corn/soybean rotation, with specialty 

crops or following small grains [1]. 

Cover crops sown after the cash crop in the winter 

fallow niche serve multiple purposes. They both prevent 

soil erosion and—if they are nitrogen scavengers—can 

prevent nutrient leaching [3]. Available cover crop niches 

will vary with the local climate and the cash crops in your 

rotation. For example, in Minnesota, many growers plant 

cover crops after corn harvest in September for winter 

cover [8]. Meanwhile, in North and South Carolina, cover 

crops are often used to absorb excess nutrients after 

manure applications [9]. 

John and Nancy Hayden grow 30 varieties of tree fruit 

and berries at The Farm Between in Jeffersonville, Vt., and 

maintain a pollinator sanctuary of perennials, trees and 

brush piles on their property. Even with such an abundance 

of flowering plants and habitat, they identified a need for 

summer cover crops. “We notice in July and August here in 

the Northeast there’s a dearth of floral resources,” John 

says. “So for us, it was seeing if we can fill a gap that we 

can’t with our perennials using annual cover crops.”

The next step in getting the most out of your cover 

crop is to identify your conservation needs. You may 

need to break up a plow pan (daikon radish), prevent 

nutrient leaching (non-legumes, cereals), boost soil 

fertility with a green manure (legumes), out-compete 

weeds with a fast-growing plant (buckwheat), provide 

forage for livestock (crimson clover, canola, cereals), 

manage nematodes (brassicas), or prevent erosion 

(cowpea, clovers). Increasingly, farmers are turning to 

cover crops in “prevented planting” situations—that is, 

when the soil is too wet to plant in the spring [1].

The Haydens used a 2013 SARE grant to evaluate three 

cover crop options—phacelia, buckwheat and a commercial 

bee forage mix—for their ability to support bumble bees and 

suppress weeds in vegetable beds where weed pressure had 

built up [10]. The phacelia and buckwheat established well, 

Cotton growing in a 

system using cover crops 

and conservation tillage. 

A cover crop mix of rye 

and crimson clover can 

improve the profitability 

of cotton because the 

clover adds nitrogen to 

the soil and the rye 

attracts beneficial insects.

– Photo by Stephen Kirkpatrick,

USDA NRCS
5

suppressed weeds and attracted pollinators, but the 

commercial mix was outcompeted by weeds and did not 

establish well. “The phacelia we liked a lot,” John says. 

“We were able to see that bumble bees had a statistically 

significant preference for phacelia over buckwheat.” 

Ideally, your cover crop will be dual-purpose. It should 

both serve as a conservation practice and also boost 

beneficial insect populations. Your cover crop mixture 

must include flowering legumes or forbs to accomplish 

this objective. See Plant Selection for an in-depth 

discussion of choosing plants for multiple objectives. 

Planting and Managing Your Cover Crops

COVER CROPS CAN EITHER BE SOWN AFTER HARVEST OF

a cash crop, or they can be sown into a standing crop 

(over-seeding). Typically, drilling uses fewer seeds than 

broadcast seeding and promotes more uniform stand 

establishment. It can be done post-harvest or into a standing 

crop, and is the technique most commonly used by farmers 

in the CTIC-SARE survey [1]. Other farmers aerially overseed cover crops into a standing crop. Over-seeding is 

most commonly used to give cover crops a head start 

before the winter in regions with a short growing season. 

The CTIC-SARE survey found that the median seed cost 

in the Midwest was $25 per acre in 2013 [1]. 

As you decide when to terminate your cover crop, the 

goal is to do so sufficiently in advance of your cash crop 

for cover crops to decompose, release nutrients and 

recharge soil moisture [11, 12]. You need to weigh these 

demands against the need to minimize the amount of 

time your fields are bare. Appropriate termination time 

for cover crops varies by region.

At the time of this writing, federal crop insurance 

programs have developed region-specific requirements for 

cover crop termination. These rules are intended to reduce 

yield losses of cash crops due to water use by previously 

planted cover crops. They require the termination of cover 

crops in advance of cash crop planting, from at least 

35 days before planting to up to five days after planting, 

depending on the region. For more information, see 

Balancing Insect Conservation with USDA Crop 

Insurance Rules on page 9. 

Cover crops can be terminated by mowing, tillage, 

herbicides, harvesting, rolling or winter kill. An herbicide 

burn down is the most common termination strategy, 

followed by tillage and winter kill [1]. You may also opt 

to graze or hay your cover crop for winter forage. The 

best option will vary depending on plant selection and 

growth stage. Deep tillage should be avoided, as it tends 

to counteract many of the benefits provided by cover 

crops. These range from improved soil tilth to increased 

populations of over-wintering beneficial insects. 

If pollinators are to benefit from your cover crop planting, 

you must give it time to flower. This is not a problem for 

management of legumes or brassicas. Their conservation 

benefits are maximized after they bloom. Management of 

some other plantings can be a little trickier, as is the case 

for buckwheat. Buckwheat must flower for a minimum of 

20 days to build up beneficial insect populations [3]. At 

the same time, buckwheat should be mowed seven to 10 

days after flowering to prevent it from reseeding [3]. 

Because buckwheat is one of the best cover crops for bees 

and beneficial insects, and because it kills so easily with 

mowing, it may be advisable to put off cover crop termination until beneficial insects are established, with the 

expectation of having to mow a field twice to achieve 

cover crop termination. Note, however, that this practice 

could result in unwanted buckwheat (weeds) in subsequent 

crops. Alternatively, a farmer could stagger planting and 

mowing row by row to lengthen the bloom period while 

still preventing buckwheat from reseeding. 

When the Haydens used buckwheat as a summer cover 

crop, they allowed it to flower extensively and go to seed, 

and did not follow it with a fall crop. With unfavorable 

conditions for germinating through the fall and winter, 

volunteer buckwheat was not a problem come spring. 

“From our experience, reseeding would only be a problem 

if you were planting another crop the same season,” John 

Hayden says. “Neither phacelia nor buckwheat presented 

any problems with volunteers the year after planting.”

Another cover crop practice that may require some 

additional tweaking to benefit bees and beneficial insects is 

planting for green manure. Green manure is tilled into the 

soil to increase soil organic matter in the vegetative stage or 

at flowering. This practice can be made more insect-friendly 

by allowing the green manure crop to flower for a few days 

before tilling, but still tilling before seed set.

As a cover crop, fastgrowing buckwheat is 

commonly used to 

suppress weeds. When 

allowed to flower, it can 

provide excellent forage 

for wild pollinators.

– Photo by John Hayden
6

THE PLANTS THAT BEST FIT YOUR NEEDS WILL VARY BY

location and purpose. Different cover crops have different 

strengths. Flowering broadleaf species are a must when 

selecting cover crops for pollinators. Grass cover crops do 

not provide nectar and their pollen typically has lower 

protein content than the pollen of broadleaf plants, thus 

making them only marginally attractive to bees. A flowering 

plant/grass blend may be an ideal solution in situations 

where a grass crop is needed to achieve other management 

priorities, such as preventing nutrient leaching. 

You have more flexibility when selecting plants in support 

of predator and parasitoid insects for pest management, 

with certain grass cover crops supporting alternate prey 

(such as aphids) to help sustain the beneficial insects 

when cash crops are absent. 

Avoid cover crops that serve as alternate host plants 

for crop diseases and those that support large numbers of 

crop pests. An alternate host is another species, different 

from the cash crop, which serves as a reservoir for the 

pest or is necessary for the pest to complete its life cycle. 

For example, if you are growing a brassica vegetable 

crop, do not cover crop with another brassica, as it 

would support similar pests.

However, cover crops that support low levels of crop 

pests may be valuable in some cases, as they can provide a 

consistent food source for beneficial predators. This is well 

documented in the case of pecan orchards with a clover 

understory [14]. The legumes attract aphids, which are 

followed by beneficial insects. When the clover dies back 

and the aphid population drops, the beneficial insects are 

driven up into the trees. These insects, in search of other 

foods, manage pests on the developing pecans [14]. 

Be sure the cover crop you choose is adapted to local 

conditions. A good first step is to look around you and 

see what works for other farmers. Red clover and crimson 

clover are popular cover crops for nitrogen fixation east 

of the Mississippi River [3]. Red clover is a low-bloat 

legume that is excellent forage for grazing animals. 

Clover is also a high-value honey plant. Rapeseed and 

other brassicas are used for pest and nematode

management in fields (biofumigation). Cowpeas, another 

legume, are exceptionally heat and drought tolerant. 

They also have extra-floral nectaries—or nectar-producing glands at leaf stems—which attract beneficial insects. 

These plants are used for erosion control across the 

Southeast and coastal California [3]. They are also used 

for weed suppression in the Deep South. Buckwheat is 

useful as a rapid-growing smother crop in much of the 

United States [3], and it is the premier cover crop for 

attracting beneficial insects. 

Of course, buckwheat is not ideal for every situation. 

Hoping to use buckwheat as a nectar source for predators 

of the glassy-winged leafhopper, a vineyard pest [15], 

SARE-funded University of California-Riverside Extension 

specialists found that the plant struggled to grow during 

the hot, dry southern California summer. Sustaining the 

cover crop with irrigation turned out to be an expensive 

proposition, and actually increased populations of the 

blue-green sharpshooter, another local vineyard pest. 

Ultimately the buckwheat did in fact increase predator 

numbers to help manage glassy-winged leafhoppers, 

but that benefit became more difficult to justify when 

balanced against unexpected challenges. 

Finally, when considering plants, a strong case can 

be made for the role of diversity. Using a SARE grant, 

a graduate student researcher in Florida [16] found 

significant differences in wild bee abundance and 

diversity based upon the number of crops present on 

a farm. At one end of the spectrum, the farm with the 

fewest number of bees (five species) grew only two crops 

and mowed directly up to the field edges. The farm with 

the greatest abundance of bees (14 species) grew nine 

crop species and maintained open, unmowed buffer areas 

around the farm. Interestingly, both farms were relatively 

similar in size. While not explicitly demonstrated in 

the study, it seems likely that multi-species cover crop 

mixes are a relatively simple way to expand plant 

diversity on a farm, with probable benefits to bee 

abundance and diversity. 

Plant Selection

Cover Crop Services and Examples of Suitable Pollinator-Friendly Plants [1, 13] 

Conservation Service Pollinator-Friendly Cover Crops

Nitrogen source alfalfa, white clover, red clover, cowpea, lupin, partridge pea, 

sunn hemp, vetch

Nitrogen scavenger phacelia, canola, sunflower

Erosion control canola, cowpea, crimson clover, white clover

Forage value crimson clover, canola, white clover, forage radish

Weed management buckwheat, canola, cowpea, sunn hemp, sunflower

Nematode management canola, other brassicas and mustards

Reducing compaction canola, radish, lupines, brassicas and mustards
7

COVER CROP COCKTAIL EXAMPLES

The following examples represent cover crop cocktails for various regions and seasons. They include pollen and nectar-rich plant species that support a diversity of bees and other beneficial insects, as well as 

vegetative structure that insects may use for egg laying or hibernation. Flowering will vary depending on 

season, planting date and region; these mixes can provide multiple benefits even when terminated before 

all species have flowered.

Sample Cool Season Cocktail (formulated for one acre at 10-15 seeds per sq. ft.)

Species Percent of Mix Quantity (pounds per acre)

Phacelia 8 0.2

Crimson clover 8 0.3

Radish (daikon) 8 0.6

Hairy vetch 8 2.2

Field pea 8 17

Turnip 8 0.2

Fava bean 2 29

Rye 25 6

Oat 25 7

Totals 100 percent 62 pounds per acre

Sample Warm Season Cocktail (formulated for one acre at 15-20 seeds per sq. ft.)

Species Percent of Mix Quantity (pounds per acre)

Buckwheat 16 7

Soybean 16 34

Sunflower 16 3.5

Cowpea 16 28

Sudangrass 12 2.5

Millet 12 1.5

Teff 12 0.1

Totals 100 percent 77 pounds per acre

Sample Tropical Cocktail (formulated for one acre at 15-20 seeds per sq. ft.)

Species Percent of Mix Quantity (pounds per acre)

Buckwheat 12 7

Sunn hemp 12 7

Sunflower 12 3.5

Cowpea 12 26

Yellow sweet clover 12 0.5

Teff 12 0.1

Sudangrass 14 3.5

Millet 14 2.5

Totals 100 percent 50 pounds per acre

Cover Crop Cocktails

MIXTURES OF COVER CROPS, OR COCKTAILS, HAVE 

synergy—they generally work better than each single 

species could alone. In fact, a planting of legumes and 

grasses can result in an overall increase in available nitrogen 

[17]. Legumes build up soil nitrogen quickly, but their residue 

also decomposes quickly, releasing nutrients. A small grain 

does not add soil nitrogen, but it is an excellent nutrient 

scavenger. Additionally, its residue decays over a longer 

period of time, providing a slow-release mechanism for 

soil nutrients. Small grains are also useful for controlling 

erosion, preventing nutrient leaching and suppressing 

winter weeds. Mixing the fertilizing effects of the flowering 

legume with the soil-building small grain can be a winning 

combination for winter cover [1, 18]. 

A pollinator-oriented cocktail may include a mix of 

plants that have different strengths and which flower at 

different times. Buckwheat, rapeseed, lupines, phacelia, 

sunn hemp, cowpeas, partridge pea, sunflowers and 

many clovers are all cover crops that are also beloved 

by bees and beneficial insects. Stacking these pollinator 

plants in one field can lengthen the bloom period. 

For example, if rapeseed blooms in early spring and is 

harvested in May or June, then it can be followed by the 

late-summer blooming sunflower, which can then be 

over-seeded with a winter legume/small grain mix. The 

rapeseed serves to manage nematodes, the sunflowers 

mine nutrients and bring them to the surface, while the 

legume/grain mix adds nitrogen and prevents winter 

erosion. This is just one path using an all-pollinator 

rotation for season-long flowers. All of these plants 

except the small grain have flowers highly preferred 

by pollinators and other beneficial insects. 

Common and Suggested Rotations

THERE ARE A NUMBER OF ROTATIONS THAT WORK WELL

with common crops, and there is likely to be a proven 

cover crop rotation that works with your system. The 

NRCS Cover Crop Economics Decision Support Tool, 

released in 2014, comes pre-loaded with example 

scenarios to help farmers think about the economics 

of including cover crops in their system. For example,

in a three-year corn/soybean/corn rotation with fall 

cover crops every year, including a winter cover crop 

of cereal rye following corn and a cocktail of cereal

rye/crimson clover/brassica following soybeans had 

long-term benefits in terms of fertilizer and pesticide 

savings, with no reduced yield [6]. In another scenario, 

Photos, from left to right: Teff grain, phacelia and a fava bean flower
8

NATIVE AND NEARLY NATIVE COVER CROP MIXES

EXTENSIVE RESEARCH DEMONSTRATES THAT NATIVE PLANTS FOSTER MORE

abundant and diverse pollinator populations than non-native plant species. 

Similarly, other benefits of native plants, such as their adaptation to local climate 

conditions, are well understood. However, the vast majority of cover crop options 

consist of non-native plants. There are some exceptions, described below.

Phacelia (Phacelia tanacetifolia), a vigorous-growing annual native to 

California, and common sunflower (Helianthus annuus), a native of western 

prairie and desert states, are two species that continue to be more common in 

cover crop applications. Both are also extremely attractive to honey bees and a 

variety of native bees. While phacelia (first used as a cover crop in Europe) is 

sometimes planted as a single-species cover crop, both it and sunflower are 

increasingly used as part of diverse cover crop cocktails. While those cocktails 

still do not resemble true native plant communities, the inclusion of these plants 

within their native range may provide special benefits to local pollinator species.

More work is needed to identify and increase the availability of promising 

native plant species. Across eastern, southern and Midwestern states, for 

example, partridge pea (Chameacrista fasciculata), a native annual prairie 

legume, shows particular promise. In addition to its ability to fix nitrogen, 

partridge pea attracts large numbers of pollinators and beneficial insects with 

both flowers and extra-floral nectaries (nectar-producing glands located at leaf 

stems). The abundant biomass production, trailing vetch-like growth habit and 

low-cost commercial availability also make partridge pea an attractive cover 

crop choice for warm-season applications. 

While additional research is needed, farmers looking to experiment with 

local native plants as cover crops might seek out readily available, low-cost 

wildflower species and begin including them in cocktail seed mixes at a low rate. 

Annual species such as California poppy (Eschscholzia californica), Douglas 

meadowfoam (Limnanthes douglasii) and plains coreopsis (Coreopsis tinctoria) 

may soon take their place alongside crimson clover and buckwheat in creating 

diverse cover crop seed mixes that blur the lines between agriculture and ecology.

SPECIAL CONCERNS: TERMINATION AND 

RESIDUE MANAGEMENT FOR GOOD BUGS

WHILE NECESSARY TO PREPARE FOR CASH CROP

planting, the process of terminating a cover crop 

can be very detrimental to pollinators and beneficial 

insects, especially when the cover crop is actively 

flowering when terminated. The risks to insects from 

cover crop termination include direct mortality, such 

as being crushed by cultivation or roller-crimping 

equipment; and indirect harm, such as the rapid loss 

of available food sources. Even when adult insects are 

not present and active in cover crops, nest sites, eggs 

and hibernating adults may all be present in the crop 

canopy or upper soil surfaces. 

Adopting cover crops for pollinators takes careful 

planning and consideration. To reduce some of the 

impact of cover crop termination, we recommend the 

following:

3 Where possible, wait until most of the cover crop 

is past peak bloom before termination. 

3 If waiting until peak bloom is not possible, consider 

leaving strips of the cover crop standing to prevent 

the crash of beneficial insect populations. With 

buckwheat, for example, stagger planting and 

mowing row by row (or groups of rows) to lengthen 

the bloom period while still preventing buckwheat 

from reseeding.

3 Terminate with as little physical disturbance as 

possible. For example, roller-crimping may be 

less disruptive to pollinator nests in the soil 

than cultivation.

3 Maintain permanent conservation areas on the 

farm to sustain beneficial insects in the absence 

of the cover crop.

3 Leave as much cover crop residue as possible to 

protect beneficial insect eggs and any hibernating 

adults. 

3 Minimize insecticide use in the cash crops that follow 

cover crops to avoid harm to beneficial insects that 

may still be nesting in crop residue. At a minimum 

you should follow a comprehensive integrated pest 

management (IPM) plan that includes specific risk 

mitigation strategies that protect pollinators and

beneficial insects. 

Including native flowering species in a cover crop mix 

can help attract pollinators and beneficial insects, 

as in this South Dakota field.

– Photo by Mieko Alley, USDA NRCS

8
9

a two-year cotton/corn rotation that included winter 

cover crops of crimson clover following cotton and a 

cereal rye/crimson clover/brassica cocktail following 

corn provided immediate financial and environmental 

savings [6]. Brassicas, such as mustards, oilseed radishes, 

tillage radishes, canola and others, are often part of 

vegetable rotations because of their role in managing

soil pests.

There are other examples of successful rotations. In 

Ohio, a typical corn/soybean rotation might include the 

cover crops cereal rye, wheat, cowpea and sunn hemp 

[19]. Brassicas are also an option for a winter cover crop. 

In Missouri, it is possible to double-crop buckwheat or 

sunflowers after harvesting a winter crop of canola or 

wheat in early summer [20]. After winter wheat, Michigan 

State University Extension recommends the soil-improving 

cocktail of annual ryegrass/red clover/hairy vetch/oilseed radish to add nitrogen, reduce compaction and 

improve tilth [21]. Alternatively, the cocktail of crimson 

clover/annual ryegrass provides many of these same 

benefits, minus the soil aeration, and is also excellent 

pasture [21].

A new, cost-efficient rotation is meadowfoam (Limnanthes alba), a winter annual, following seed grasses. 

Grown in northern California and Oregon, meadowfoam 

over-winters as a rosette. Its dense flowers attract pollinators and beneficial insects in the spring. This emerging 

species is useful as both a cover crop and an oilseed. The oil 

produced is highly shelf stable, and is quite valuable to the 

cosmetics industry. However, seeds can be hard to find.

THE USDA’S NRCS, RISK MANAGEMENT AGENCY (RMA)

and Farm Service Agency (FSA) came together in 2014 to 

develop standardized termination recommendations for 

non-irrigated cover crops in four different regions or zones 

in the United States [12]. They sought recommendations 

that would achieve optimal balance between conservation 

benefits and soil water conservation for cash crops, and 

would provide consistent guidance for cover crop policy 

across the three agencies. For the purpose of crop insurance, 

cover crops must be terminated according to these recommendations in order for the following crop to receive 

insurance coverage. California and the Intermountain 

West (zone 1) require the longest gap between cover crops 

and a cash crop, with a recommended cover crop termination date at least 35 days before planting. For much of the 

country’s bread basket, the Central Plains (zone 2), farmers 

should terminate the cover crop at least 15 days before planting. In the eastern prairie states and south Florida (zone 3), 

cover crops can be terminated at planting. Finally, in the 

eastern states (zone 4), growers can terminate cover crops up 

to five days after planting, but before cash crop emergence. 

A major challenge of these rules is the loss of pollen and 

nectar resources when cover crops are terminated before 

they have fully bloomed. Even when partial bloom occurs, 

rapid termination of that bloom results in boom and bust 

conditions for insects. To mitigate some of the impact of early 

termination, consider supplementing cover crops with other 

pollen and nectar resources such as hedgerows, permanent 

wildflower meadows, or other high-quality natural areas. 

Similarly, consider leaving small sections of the field (even 

a single outer row) in the cover crop, rather than terminating it entirely. Even such small sections can help sustain 

pollinators in the absence of other forage sources. 

For current guidance on cover cropping and federal 

crop insurance, consult your local NRCS office or crop 

insurance program agent, or see “NRCS Cover Crop 

Termination Guidelines” [12] in the References section.

Balancing Insect Conservation with USDA Crop Insurance Rules
Relative Value of Cover Crop Species to Bees and Other Beneficial Insects

Cover Crop Life Cycle Seeding Rate Seeding Honey Bee Wild Bee Beneficial Insect Alternative Host of Notes

(pounds/acre Depth Value Value Value (predators Crop Pestssingle species) (inches) and parasitoids)

GRASSESAnnual Annual 10-20 1⁄2 None None Low Unknown Probably only useful to beneficial insects when includedryegrass as part of a diverse seed mixBarley Annual 60-125 11⁄2 None None Low Oat and Russian wheat Best adapted to dry, cool (but not cold) climates

aphids, various smallgrain diseases

Millet Annual 5-25 1⁄2 None None Low Unknown Seeding rates for foxtail millet can be reduced to the(foxtail, proso lower end of the described rangeand pearl)Oats Annual 60-120 11⁄2 None None Low Oat and Russian wheat Cool-season plant; limited cold tolerance with most

aphids, various small varieties subject to winter kill in cold climatesgrain diseases

Rye, cereal Annual 60-120 1 None None Low Russian wheat aphids, Potentially allelopathic to other crops

various small grain diseases

Sorghum/ Annual 10-40 1 None None Moderate Corn aphids Attractiveness to grass-specific aphids may make this asudangrass useful insectary plant for attracting aphid predators (in

non-grass crop systems); lower end of seeding rates areappropriate for sorghum and sorghum-sudangrass hybrids; potentially allelopathic to other crops

Teff Annual 5-10 1⁄4 None None Low Unknown Seed may have limited availability

Triticale Annual 60-120 1 None None Low Russian wheat aphids, Potentially allelopathic to other crops

various small grain diseases

LEGUMESAlfalfa Perennial 10-25 1⁄4 High High Moderate Pea aphids Top honey plant, also attractive to large numbers of 

diverse wild bees

Birdsfoot Perennial 5-10 1⁄4 Moderate Moderate Moderate Spittlebugs, alfalfa plant Can be weedy and invasive

trefoil bugs, potato leafhoppers 

and others

Clover, Annual 8-20 1⁄4 High High Moderate Likely a host for various Best adapted to Mediterranean climatesberseem leafhoppers, true bugs

and generalist aphids

Clover, Annual 15-25 1⁄4 High High Moderate Pea aphids, tarnished Grows very well in combination with cerealcrimson plant bugs rye and other cool season grassesClover, Perennial 5-15 1⁄4 High High Moderate Various leafhoppers, Poor seedling vigor and slow to establish; considered akura true bugs and top honey plant

generalist aphids
Clover, Perennial 5-20 1⁄4 Moderate High Low Various leafhoppers, Typically short-lived; high value for bumble bees

red true bugs and 

generalist aphids

Clover, Annual 10-25 1⁄4 Moderate High Moderate Various leafhoppers, Excellent bumble bee plantrose true bugs and 

generalist aphids

Clover, Perennial 5-15 1⁄4 High High Moderate Unknown Can be weedy and invasive

strawberryClover, Annual 10-20 1⁄4 None None Low Pea aphids, tarnished Flowers are inconspicuous and do notsubterranean plant bugs attract pollinatorsClover, Perennial 5-15 1⁄4 High High Moderate Various leafhoppers, Considered a top honey plantwhite true bugs and 

generalist aphids 

Chickpea Annual 80-120 11⁄2 Low Low Low Pea borers, wireworms Beneficial insects are attracted to extrafloral nectaries

Cowpea Annual 30-90 1 High High High Various stink bugs, Extensive extra-floral nectaries attract large numbers of

leaf-footed bugs, beneficial parasitoid wasps as well as other beneficial

aphids insects

Fava bean Annual 80-160 3 Low Moderate Moderate Unknown

Lablab Annual 30-40 1-4 Moderate Moderate Moderate Unknown Vining growth habitat; more common in subtropical climates

Lupin Annual 40-120 1-2 Low Moderate Moderate Unknown

Medic Annual 10-20 1⁄2 Low Low Low Alfalfa weevils, Small, nondescript flowers attract few beneficial insects

(a few pea aphids, tarnishedspecies are plant bugsperennial)

Partridge Annual 10-20 1⁄4-3⁄4 Moderate High High Various leafhoppers Extensive extra-floral nectaries attract large numbers pea of beneficial parasitoid waspsPea, field Annual 50-100 2 Low Low Low Tarnished plant bugs

Sainfoin Perennial 40-80 1⁄2 High High Moderate Unknown Considered a top honey plant

Soybean Annual 35-120 1 Moderate Moderate Moderate Wireworms, bean leaf 

beetles, potato leafhoppersand various others

Sunn Annual 20-40 3⁄4 Moderate High Moderate Unknown Attracts wild carpenter and leafcutter bees in

hemp tropical farm systems; supports parasitoids of

corn earworm in the Pacific Islands region

Sweet clover Biennial 6-20 1⁄2 High High High Unknown Considered a top honey plant; may be weedy or invasive

in some areas

Vetch Annual; 15-30 1⁄2-21⁄2 Moderate High High Pea aphids, tarnished plant Standard options include common vetch, hairy vetch and

perennial bugs, two-spotted spider purple vetch; may be weedy or invasive in some areas

mites
10

Relative Value of Cover Crop Species to Bees and Other Beneficial Insects cont.

Cover Crop Life Cycle Seeding Rate Seeding Honey Bee Wild Bee Beneficial Insect Alternative Host of Notes

(pounds/acre Depth Value Value Value (predators Crop Pestssingle species) (inches) and parasitoids)

FORBS/BROADLEAVESBeet Biennial 6-10 1 Low Low Low Unknown Wind-pollinated flowers are only marginally attractive to bees

Buckwheat Annual 30-80 1 High High High Tarnished plant Top honey plant with nectar flow typically occurring in

bugs the morning; shallow flowers attract parasitoid wasps

Canola Annual 3-10 1⁄2 High High High Flea beetles Excellent honey plant

Chicory Perennial 3-5 1⁄2 Low Low Low Unknown Flowers are considered self-fertile and attract few insects

Flax Annual 25-50 3⁄4-11⁄2 Moderate Moderate Moderate Unknown Reports of bee attractiveness vary; probably most valuable 

to pollinators as part of a diverse mix

Kale Biennial 3-10 1⁄2 High High High Cabbage loopers, Aphid-susceptible varieties likely support the more predatory

flea beetles, insects such as lady beetles and lacewings; rapid-bloomingcabbage aphids varieties most beneficial to bees

Mustard, Annual 5-20 1⁄2 High High High Flea beetles Can be weedy and invasive in CaliforniatamePhacelia Annual 5-15 Surface High High High Tarnished plant Major honey bee nectar plant; produces volunteer seedlings

bugs in moderate climates 

Radish Biennial 8-20 1⁄4 High High High Club root of brassicas, Deep-rooted varieties are promoted for reducing compaction

flea beetles, cabbage and adding soil organic matter; not tolerant of prolongedaphids, root maggots freezing

Safflower Annual 25-35 1 Moderate Moderate Moderate Sunflower head Relatively drought tolerant with surprisingly deep 

moths, tarnished tap roots (in some cases exceeding 8 feet)plant bugs, wireworms

Sunflower Annual 4-6 1⁄2 High High High Sunflower head moths, Both flowers and extra-floral nectaries attract huge

various beetles, numbers of pollinators and beneficial insects, in mosttarnished plant bugs cases outweighing any risk of attracting pests

Turnip Biennial 2-12 1⁄2 High High High Club root of brassicas, Turnips tend to be more cold tolerant than radishes, 

flea beetles, cabbage allowing them to flower in the spring unless terminatedaphids, wireworms, 

cabbage loopers
13

YOU MAY BE ASKING YOURSELF, “IF COVER CROPS ARE

so great, why doesn’t everyone use them?” While some 

farmers may not know where to start, perhaps the greater 

barrier to adoption is that the financial and environmental 

benefits of cover cropping oftentimes accrue gradually 

[22, 23, 24], while the startup costs in time and money 

are immediate. State and federal agricultural incentive 

programs which offset this initial investment can be very 

successful in encouraging the use of cover crops [22].

Of course, not all systems are equally suited to 

cover cropping. In some cases, existing long-season 

cash crop rotations may not be compatible with cover 

crops. In other regions, a cover crop’s water usage may 

hurt cash crop yields [23]. This impact can be mitigated 

to some extent by terminating a cover crop well prior to 

establishing a cash crop, allowing soil water to recharge. 

Additionally, over the long term, cover crops increase 

soil organic matter, soil water infiltration and soil water 

capacity. Initial declines in available water are often 

offset by later, long-term increases [23]. 

Other limitations of cover crops include expenditures 

for new equipment, more complicated management 

practices and time spent seeding and terminating 

cover crops rather than managing cash crops [23]. 

It is important to run the figures for your own operation 

to decide if cover crops are right for you. Should you 

decide that the benefits outweigh the drawbacks, plan 

to ease into cover cropping, starting with a small area 

and gradually expanding your cover cropped land as 

you get the hang of it.

Limitations of Cover Crops

ALTHOUGH COVER CROPS CAN PROVIDE SIGNIFICANT 

pollen and nectar resources for bees, they do have 

constraints. For example, because most cover crop 

species have a short bloom period, single species cover 

crops typically offer a feast-or-famine situation for bees. 

A shortage of food is followed by abundance, followed 

by another shortage. Under such circumstances wild 

pollinators may have trouble sustaining their populations. 

(Honey bees may be more resilient under such conditions 

due to their ability to store food reserves.) 

Moreover, because most cover crop plants are nonnative species, their attractiveness to wild native bees 

may be highly variable. The cover crops highlighted in 

this bulletin will attract mostly generalist species of wild 

bees that are relatively common in most landscapes. 

Less common species of native bees often require more 

permanent plant communities comprised primarily of 

native plant species. In general, to maximize the diversity 

and abundance of beneficial wild insects, flowering 

cover crops should be combined with the restoration 

and maintenance of permanent, high-quality, pesticidefree native plant habitat in other areas of the farm. 

Adding pollinator hedgerows, establishing pollinator 

plantings on marginal lands and borders, and other 

practices to boost habitat can all fit into other USDA 

conservation practices. 

Regarding pollinator borders specifically, two SAREfunded research projects in Michigan demonstrated the 

value of permanent native wildflower strips adjacent to 

crops. In one of these studies [25], researchers found 

that corn borer egg parasitism was measurably higher 

in fields adjacent to perennial native wildflower strips. 

In the other study [26], researchers found that blueberries 

planted adjacent to perennial wildflower strips had berries 

that were 22-40 percent heavier, due to enhanced pollination by wild bees. 

Beyond Cover Crops

John Hayden tested a summer 

cover crop of buckwheat for 

its ability to suppress weeds 

and attract bumble bees, an 

important pollinator on his 

Vermont fruit farm. It worked 

well, and after going to seed 

did not return in the spring as 

a weed. – Photo by Nancy Hayden
14

INSECTICIDES SHOULD NOT BE APPLIED TO COVER CROPS 

where pollinator and beneficial insect conservation is a priority. In most cases it is unnecessary, regardless of your 

cover crop objectives. Both organic and conventional pesticides can harm pollinators and other beneficial insects. 

Cover crops are themselves often used to break pest 

cycles and manage nematodes, and can help reduce your 

overall use of insecticides. 

However, where cover crops are planted in rotation 

with insecticide-treated cash crops, the residual impact 

of cash crop insecticides may still be a concern. You can 

reduce risk to pollinators and beneficial insects by implementing IPM on your farm and only applying insecticides 

when the threshold for economic damage has been crossed. 

You can also start your course of treatment with the least 

harmful insecticide that will accomplish your management 

need. You can reduce harm to good bugs from insecticides 

by following label instructions, avoiding the application 

of insecticides to flowering plants, spraying at dawn or 

dusk and by using chemicals that have low residuals and 

do not accumulate in the soil or plant.

Unfortunately for beneficial insect conservation, there 

are a number of widely used systemic insecticides with 

persistent chemical residues in soil and plant matter. 

Systemic insecticides are those which are absorbed into 

the plant tissue and move through the vascular system of 

the plant, making most parts of it toxic to insect pests. In 

some cases the insecticide may even be present in flower 

nectar, resulting in the lethal or sublethal poisoning of 

bees and other pollinating insects. 

The most common class of systemic insecticides currently 

in use is neonicotinoids. These include the active ingredients 

imidacloprid, thiamethoxam, clothianidin, acetamiprid, 

thiacloprid and dinotefuran. These insecticides may be 

applied in crop fields as foliar sprays, root drenches and 

as seed treatments (the latter commonly used for corn 

and soybeans). They can persist in the soil and crop 

residue for multiple years, and can be reabsorbed by later 

crops that were not treated. Due to a growing body of 

research demonstrating the potential risk posed to pollinators and beneficial insects from neonicotinoid insecticides 

[27, 28, 29, 30, 31], and our knowledge of neonicotinoid crop 

residues, farmers should avoid planting cover crops in rotation with neonicotinoid-treated cash crops where possible, 

especially when bee and beneficial insect conservation is a 

goal. Instead, producers should focus their conservation 

efforts on other areas of the farm which are untreated. 

Following the precautionary principle means that we 

should not put beneficial insect habitat on lands contaminated by systemics—that is to say, in the absence of scientific 

proof that residue from previous use of systemic insecticides 

does not harm pollinators, it is safer to assume that it does. 

Growers of conventional corn and soybeans could instead 

focus their insect conservation efforts on hedgerows, roadsides and other areas not sprayed with systemic insecticides. 

They could also make their preference for untreated seed 

known to their supplier. In 2014 the Environmental Protection Agency (EPA) confirmed that there is little to no benefit 

from pre-treating soybeans; if enough growers request 

untreated seeds, then it is likely more will become available.

Similarly, cover crops should not be directly treated 

with any class of insecticide. An exception would be in 

the case of a cover crop being used for another primary 

purpose, such as livestock forage, where it must be 

protected from catastrophic pest damage. However, 

treatment of cover crops with insecticides is rare. 

Furthermore, it is critical to protect cover crops from 

adjacent insecticide drift. Any use of insecticides should 

fully adhere to label recommendations. 

Avoiding Pest Increases

WHILE ADDITIONAL RESEARCH IS NEEDED, THERE IS 

strong evidence that diverse cover crop cocktails will 

routinely reduce pests, by increasing populations of 

beneficial predatory and parasitoid insects. In contrast, 

single-species cover crops may increase populations of 

undesirable crop pests, by providing a more limited 

range of resources than plantings which can support a 

diverse population of predators. 

To further reduce the possibility of increasing crop 

pests, use caution when considering cover crops that are 

closely related to cash crop species. For example, if 

brassicas such as broccoli or cabbage are primary cash 

crops, minimize the use of cover crops such as turnip, 

radish or mustard, all of which may host the same pests 

and diseases as the cash crops. 

During their SARE-funded project, the Haydens 

observed that the pure stand of phacelia provided habitat 

for the tarnished plant bug, a pest of tree fruits and berries. 

“From what we have learned, we will continue to plant 

multi-functional cover crops timed to bloom in July and 

August,” Nancy Hayden says. “Our seeding mix will 

include buckwheat and phacelia, as well as mustard and 

annual white sweet clover."

Insecticides and Insect Conservation

You can reduce risk 

to pollinators and 

beneficial insects 

by implementing 

IPM on your farm 

and only applying 

insecticides when 

the threshold for 

economic damage 

has been crossed.
15

AMONG LARGE-SCALE FIELD CROPS, COTTON IS 

high on the list for susceptibility to multiple major 

pests. Cotton bollworm, tobacco budworm, cotton 

aphid, tarnished plant bug and various stink bugs 

are some of the biggest offenders for cotton growers in the Southeast. Any management strategy 

that can make a dent in the populations of these 

pests without relying on insecticides is good news.

One such successful strategy came about 

through a SARE-funded research project in Georgia 

[32] that investigated the use of cover crops to 

increase the number of insect predators that prey 

upon some of those pests. This research was based 

on the fact that many beneficial insects need alternate food sources, such as nectar, to sustain themselves when prey are absent. These beneficial 

insects also typically need vegetation on which to 

lay eggs or hibernate over the winter. In this study, 

researchers hypothesized that various cover crops 

might provide those habitat requirements.

Starting with standard cotton fields where 

cover crops were not used, the researchers 

compared pest and beneficial insect populations 

to those in cotton fields where cover crops of 

crimson clover, cereal rye and a legume mix were 

used in rotation and as intercropping cover. For 

a few beneficial insects like the predatory minute 

pirate bug, there was not a significant population 

difference between traditional cotton fields and 

those with cover crops. However, most pest and 

beneficial insect population responses strongly 

indicated that cover crops had a measureable 

and positive impact on pest management. For 

example, predatory big-eyed bug numbers were 

demonstrably higher in cotton fields following a 

crimson clover cover crop. Aphid-eating lady 

beetles also seemed to move directly from cover 

crops into cotton. 

In the case of pests, researchers also found 

that cotton bollworm and tobacco budworm were 

the only two pests that exceeded economic 

thresholds in both the cover cropped fields and 

the regular cotton fields. Interestingly however, 

the pests exceeded those damage thresholds more 

often in regular cotton fields than those where 

crimson clover and rye cover crops were used. 

RESEARCH CASE STUDY: 

USING COVER CROPS TO INFLUENCE NATURAL PREDATION OF COTTON PESTS

 1. Conservation Technology Information Center (CTIC). 2014. Report of 

the 2013-14 Cover Crops Survey. CTIC and North Central SARE.

www.sare.org/2013-cover-crop-survey.

 2. Altieri, M., and H. Wilson. 2010. Restoring Plant Diversity and Soil Health in 

Napa and Sonoma Vineyards: Scaling Up an Agroecologically Based Pest 

Management Strategy. Project funded by USDA-SARE. To access, visit 

www.sare.org/project-reports and search by project number FW08-311. 

 3. Clark, A. (ed.). 2007. Managing Cover Crops Profitably, 3rd ed. SARE: 

College Park, MD. www.sare.org/mccp.

 4. Altieri, M., C. Nicholls, and M. Fritz. 2005. Manage Insects on Your Farm: A Guide 

to Ecological Strategies. SARE: College Park, MD. www.sare.org/manage-insects.

 5. Tallman, S. 2012. No-Till Case Study, Miller Farm: Restoring Grazing Land 

with Cover Crops. The National Center for Appropriate Technology – 

National Sustainable Agriculture Information Service (NCAT-ATTRA): 

Butte, MT. https://attra.ncat.org/field.html.

 6. Cartwright, L., and B. Kirwan. 2014. Cover Crop Economics Decision Support 

Tool. USDA Natural Resources Conservation Service (NRCS). 

www.nrcs.usda.gov/wps/portal/nrcs/main/mo/soils/health.

 7. Singer, J. W., S. M. Nusser, and C. J. Alf. 2007. Are Cover Crops Being Used in the 

U.S. Corn Belt?. Journal of Soil and Water Conservation 62(5): 353-358. 

 8. Minnesota Department of Agriculture. Cover Crops. In Conservation Practices: 

Minnesota Conservation Funding Guide. 

www.mda.state.mn.us/protecting/conservation/practices/covercrops.aspx.

 9. Morris, R. August 23, 2013. Flax Being Grown for Fiber in North Carolina. 

A North Carolina Department of Agriculture and Consumer Services press 

release. www.ncagr.gov/paffairs/release/2013/8-13flax.htm.

10. Hayden, J. 2014. Investigating Ways to Improve Native Pollinator Floral Resources 

by Comparing Multipurpose Cover Crops of Phacelia, Buckwheat, and a Commercial 

Bee Forage Mix. Project funded by USDA-SARE. To access, visit 

www.sare.org/project-reports and search by project number FNE13-781. 

11. Johnson, J. Termination Time for Cover Crops. USDA Natural Resources Conservation 

Service (NRCS) Iowa. 

www.nrcs.usda.gov/wps/portal/nrcs/detail/ia/home/?cid=stelprdb1086071.

12. USDA Natural Resources Conservation Service (NRCS). Cover Crop Termination 

Guidelines, Version 3. www.nrcs.usda.gov/wps/portal/nrcs/detailfull/national/landuse/crops/?cid=stelprdb1077238#Guidelines.

References 
16

13. USDA Agricultural Research Service (ARS). 2015. Cover Crop Chart. USDA-ARS 

Northern Great Plains Research Laboratory: Mandan, ND. 

www.ars.usda.gov/Main/docs.htm?docid=20323.

14. McCraw, D., and M. Smith. Use of Legumes in Pecan Orchards. Oklahoma 

Cooperative Extension Service fact sheet HLA-6250. http://pods.dasnr.okstate.

edu/docushare/dsweb/Get/Document-2570/HLA-6250.pdf.

15. Irvin, N., and M. Hoddle. 2010. Using Nectar Cover Cropping in Vineyards for 

Sustainable Pest Management. Project funded by USDA-SARE. To access, visit 

www.sare.org/project-reports and search by project number SW07-022. 

16. Johnson, R., and K. Sieving. 2013. Do Human Modified Landscapes Affect Solitary 

Bee Diversity, Foraging, and Reproduction in Northern Florida?. Project funded 

by USDA-SARE. To access, visit www.sare.org/project-reports and search by 

project number GS10-092. 

17. Salon, P. R. 2012. Diverse Cover Crop Mixes for Good Soil Health. USDA-NRCS 

Big Flats Plant Materials Center: Corning, NY. www.hort.cornell.edu/expo/proceedings/2012/Cover%20Crops/Cover%20Crops%20Salon.pdf.

18. Groff, S. 2008. Mixtures and Cocktails: Soil is Meant to be Covered. 

Journal of Soil and Water Conservation 63(4): 110A-111A.

19. Hoorman, J. J., R. Islam, and A. Sundermeier. 2009. Sustainable Crop Rotations 

with Cover Crops. Ohio State University Sustainable Agriculture Fact Sheets. 

http://ohioline.osu.edu/sag-fact/pdf/0009.pdf. 

20. Pullins, E. E., R. L. Myers, and H. C. Minor. 1997. Alternative Crops in DoubleCrop Systems for Missouri. University of Missouri Extension Publications. 

http://extension.missouri.edu/p/G4090.

21. Gross, P., C. Curell, and D. Mutch. 2012. Cover Crop Choices Following Winter 

Wheat. Michigan State University Extension. 

www.mccc.msu.edu/extension_material.html.

22. Union of Concerned Scientists. 2013. Cover Crops: Public Investments Could 

Produce Big Payoffs. http://www.ucsusa.org/food_and_agriculture/solutions/advance-sustainable-agriculture/cover-crops.html.

23. Hoorman, J. J. 2009. Using Cover Crops to Improve Soil and Water Quality.

Ohio State University Sustainable Agriculture Fact Sheets. http://www.mccc.msu.

edu/states/Ohio/OH_CoverCrops_to_Improve_Soi&Water_Quality.pdf. 

24. Kaspar, T. C., E. J. Kladivko, J. W. Singer, S. Morse, and D. R. Mutch. 2008. Potential 

and Limitations of Cover Crops, Living Mulches, and Perennials to Reduce Nutrient 

Losses to Water Sources from Agricultural Fields in the Upper Mississippi River 

Basin. In Final Report: Gulf Hypoxia and Local Water Quality Concerns Workshop: 

127-148. American Society of Agricultural and Biological Engineers: St. Joseph, MI.

25. Blaauw, B., and R. Isaacs. 2011. Native Plant Conservation Strips for Sustainable 

Pollination and Pest Control in Fruit Crops. Project funded by USDA-SARE. 

To access, visit www.sare.org/project-reports and search by project number 

LNC08-297. 

26. Walton, N. 2009. Evaluation of Supplemental Flowering Plant Strips for Sustainable 

Enhancement of Beneficial Insects. Project funded by USDA-SARE. To access, visit 

www.sare.org/project-reports and search by project number GNC07-086.

27. Hopwood, J., M. Vaughan, M. Shepherd, D. Biddinger, E. Mader, S. H. Black, and 

C. Mazzacano. 2012. Are Neonicotinoids Killing Bees?. Xerces Society for Invertebrate 

Conservation: Portland, OR. www.xerces.org/neonicotinoids-and-bees.

28. Scholer, J., and V. Krischik. 2014. Chronic Exposure of Imidacloprid and Clothianidin 

Reduce Queen Survival, Foraging, and Nectar Storing in Colonies of Bombus 

impatiens. PLOS ONE 9(3), e91573.

29. Easton, A. H., and D. Goulson. 2013. The Neonicotinoid Insecticide Imidacloprid 

Repels Pollinating Flies and Beetles at Field-Realistic Concentrations. PLOS ONE

8(1), e54819.

30. Whitehorn, P. R., S. O’Connor, F. L. Wackers, and D. Goulson. 2012. Neonicotinoid 

Pesticide Reduces Bumble Bee Colony Growth and Queen Production. Science

336(6079): 351-352.

31. Blacquiere, T., G. Smagghe, C. A. Van Gestel, and V. Mommaerts. 2012. Neonicotinoids 

in Bees: A Review on Concentrations, Side-Effects and Risk Assessment. 

Ecotoxicology 21(4): 973-992.

32. Schomberg, H. 2004. Enhancing Sustainability in Cotton Production Through 

Reduced Chemical Inputs, Cover Crops, and Conservation Tillage. Project funded 

by USDA-SARE. To access, visit www.sare.org/project-reports and search by project number LS01-121.

SARE’s Cover Crops Topic Room

This online collection of educational materials was developed out of decades of 

SARE-funded cover crop research. www.sare.org/cover-crops. 

Attracting Native Pollinators

Illustrated with hundreds of color photographs and dozens of specially created 

illustrations, this book provides rich detail on creating and managing pollinator 

habitat. www.xerces.org/store/#books. 

The USDA-NRCS Cover Crop Economics Decision Support Tool

This user-friendly economic assessment tool helps determine the costs and 

benefits of incorporating cover crops into a crop rotation.

www.nrcs.usda.gov/wps/portal/nrcs/detailfull/il/soils/health.

Manage Insects on Your Farm: A Guide to Ecological Strategies.

A guide on how to apply ecological pest management principles to your farming 

system. www.sare.org/manage-insects. 

Managing Cover Crops Profitably, 3rd Edition

This definitive book explores how and why cover crops work and provides all the 

information needed to build cover crops into any farming operation.

www.sare.org/mccp. 

Bees and Cover Crops

This four-page Penn State bulletin describes the use of flowering cover crops for native pollinator conservation. www.sare.org/native-bees-and-flowering-cover-crops. 

Habitat Management in Vineyards

This University of California manual provides practical steps for managing pests by 

improving biodiversity at the field and landscape levels. 

www.sare.org/habitat-management-in-vineyards. 

Resources 

This bulletin was co-written by Xerces Society for Invertebrate Conservation 

staff members Eric Lee-Mader, Anne Stine, Jarrod Fowler, Jennifer Hopwood 

and Mace Vaughan, with contributions from the USDA Natural Resources Conservation Service (NRCS).

It was produced by Sustainable Agriculture Research and Education (SARE), 

supported by the National Institute of Food and Agriculture (NIFA), U.S. 

Department of Agriculture under award number 2014-38640-22173. USDA is 

an equal opportunity employer and service provider. Any opinions, findings, 

conclusions or recommendations expressed in this publication are those of 

the author(s) and do not necessarily reflect the view of the USDA.