Journal of Integrated Pest Management, (2019) 10(1): 26; 1–10
doi: 10.1093/jipm/pmz023
ProfileWhitney Cranshaw,1,5 Melissa Schreiner,1 Kadie Britt,2 Thomas P. Kuhar,2,John McPartland,3 and Jerome Grant4
1

Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO 80523, 2Department ofEntomology, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, 3Family Medicine Department, Universityof Vermont College of Medicine, University of Vermont, Burlington, VT 05405, 4Department of Entomology and Plant Pathology,­University of Tennessee, Knoxville, TN 37996, and 5Corresponding author, e-mail: whitney.cranshaw@colostate.edu
Subject Editor: Carlos Bogran
Received 9 April 2019; Editorial decision 2 July 2019

Abstract
Hemp (Cannabis sativa L.) is now being grown within the United States over a much broader geographic area andfor different uses than during its last period of significant production that ended after World War II. Within the past 3
yr, a large number of arthropod species have been documented to feed on hemp in the United States. Among key
pest species, corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), has demonstrated greatest potential
for crop injury, being particularly damaging to flower buds. Hemp russet mite, Aculops cannibicola (Farkas), andcannabis aphid, Phorodon cannabis Passerini, are the two species observed most damaging among those thatsuck plant fluids. Eurasian hemp borer, Grapholita delineana Walker, is widely present east of the Rocky Mountains
and appears to have potential to significantly damage both flower buds and developing seeds. Numerous speciesof caterpillars, grasshoppers, and beetles chew hemp foliage; the severity of these defoliation injuries appears tobe minimal, but needs further study. Similarly, numerous seed feeding hemipterans, most notably stink bugs andLygus bugs, are regularly found in the crop but injury potential remains unclear. Some preliminary efforts havebeen made to develop integrated pest management strategies for these insects, particularly for corn earworm.
Future research can be expected to rapidly resolve many of the data gaps that presently restrict advancing pest
management on the crop. However, a major confounding issue involves the use of pesticides on hemp. Federal
agencies have not yet provided clear direction on this issue, and regulatory decisions have subsequently devolved
to the states.
Key words: Cannabis sativa, hemp, arthropod pest, corn earworm, integrated pest management

The cultivation of hemp (Cannabis sativa L.) in the United States has
a long, but very peculiar history (Deitch 2003). Historically grown
for fiber, production peaked in 1943 when it was grown on 146,200
acres (59,805 ha) in six Midwestern states as a crop to support the
war effort. However, prior to this point, growing the crop became
greatly complicated by passage of the 1937 Marihuana Tax Act,
which classified all C. sativa materials as being marijuana and thus
subject to new tax and drug enforcement laws. Following World War
II, hemp production in the United States sharply declined; by thelate 1950s, all U.S. production had ceased due to a combination of
restrictions related to drug laws and competition with other fibers.
With the passage of the 2014 Farm Bill (U.S. H.R. 2642 –Agricultural Act of 2014 113th Congress [2013–2014]), this situation changed in some important respects. Within it, Section 7606
(Legitimacy of Industrial Hemp Research) provided a formal definition of the crop as ‘the plant C. sativa L. and any part of such plant,
whether growing or not, with a delta-9 tetrahydrocannabinol (THC)

concentration of not more than 0.3% on a dry weight basis’. It also
provided a means for universities to research the crop, and for it tobe commercially grown where state laws allowed it to be produced.
As of 2018, 38 states have passed laws that define industrial hemp
as a distinct crop (from marijuana), and most have removed barriers to its production. In 2017, there were seven states (Colorado,
Kentucky, Oregon, North Dakota, Minnesota, New York, North
Carolina) with over 1,000 licensed acres (405 ha; Anonymous
2018a). Many areas saw substantial increases in acreage in 2018;
Colorado went from 12,042 licensed acres (4,873 ha; 346 growers)
in 2017 to 30,950 (12,525 ha; 835 growers) in 2018.
In the 62 yr since hemp was last grown in the United States (Rens
1995), many things have changed that affect its production as acrop today (Fike 2016). Probably most important is an expansion of
products that are in present demand. Formerly, hemp grown in the
United States was almost entirely produced for bast fiber, and thiscontinues to represent a market. However, there are also markets© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/
licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Forcommercial re-use, please contact journals.permissions@oup.com

1

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 2020

Developing Insect Pest Management Systems for Hemp in
the United States: A Work in Progress

Journal of Integrated Pest Management, 2019, Vol. XX, No. XX

for the seed, either whole or as oilseeds (Fig. 1). More recently, cultivars have been developed that produce compounds of potential
pharmaceutical value, most notably cannabidiol (CBD). CBD has awide range of purported uses including antiemetic, neuroprotective,
antiepileptic, antipsychotic, and anti-inflammatory (Grotenhermenand Müller-Vahl 2016), and one formulation (Epidiolex) was recently approved by the FDA for use in treating severe forms of
epilepsy.
Presently, there are efforts around the country to develop improved cultivars for production of one or more of all of these commodities, and these different forms of hemp often have very different
features (Fike 2016). For example, cultivars grown to maximize oilseed yield will be grown from seed and require pollination. Cultivars
grown for pharmaceutical purpose are typically all-female plants,
often cloned, from which nonfertilized, but enlarged, flower buds
are the primary harvested plant part (Fig. 2). The latter are being
grown both in fields (in summer) and in indoor facilities (in winter).
However, multiuse hemp cultivars (e.g., seed/fiber, CBD/seed) arealso being grown.
The arthropod pests associated with the production of hemp inthis new era have been essentially undescribed, as are the associated pest management needs. There are reviews of pest arthropods ofhemp, most notably by McPartland et al. (2000). Nearly 300 species,
worldwide, are reported to colonize the crop (McPartland 1996),
although only a small percentage of reports from worldwide compilations of hemp insects involve North American observations (Smithand Haney 1973, Miller 1982, Lago and Stanford 1989, McPartland
2002, McPartland and Hillig 2003, Small et al. 2007).
With the current renaissance of hemp as a crop in the UnitedStates, there are new production areas with new crop products tobe cultured—and new associated pests that will affect production.
At this early stage, several steps need to be met before effective pest
management plans can be provided to assist growers. This article
summarizes the situation with hemp insect pest management at theend of 2018, drawing on experiences primarily from three states
where recent research projects have involved defining insect issues
on hemp—Colorado, Virginia, and Tennessee. Clearly, in the near
future, this topic will need to be revisited, but enough information
is now known to provide a base for the subject of arthropods associated with industrial hemp as it is presently produced in the UnitedStates.

Fig. 1. Maturing seed head of a hemp plant.

Fig. 2. Hemp being grown primarily for production of cannabidiol.

The Pest Complex
A great many species of phytophagous arthropods have been observed from hemp over the past 3 yr. Those found feeding on leaves,
flowers, and seeds have been most easily observed and are presently
best known. Stem/stalk feeding insects and, particularly, root feeders
remain more poorly described. Greatest injuries seem to be associated with species that affect female flower buds and developing
seeds.

Defoliators
Perhaps the most conspicuous insects on the crop have been various
defoliators, although serious defoliation has only rarely been seen.
Among lepidopterans, woollybear caterpillars (Erebidae), bothyellow woollybear, Spilosoma virginica (Fabr.), and saltmarsh caterpillar, Estigmene acrea (Drury), are among the most consistently encountered species east of the Rockies (Fig. 3). Noctuids observed tofeed on foliage include beet armyworm, Spodoptera exigua (Hübner),variegated cutworm, Peridroma saucia (Hübner), yellowstriped
armyworm, Spodoptera ornithigalli (Guenée), and zebra caterpillar,
Melanchra picta (Harris), although the latter two species appear primarily associated with flowers and developing seeds. Other lepidopterans confirmed from hemp in Colorado include beet webworm,
Loxostege sticticalis (L.) (Pyralidae) and the butterflies painted lady,
Vanessa cardui (L.) (Nympalidae), and cotton square borer, Strymon
melinus (Hübner) (Lycaenidae). Bertha armyworm, Mamestra
configurata Walker (Noctuidae), has been reported to skeletonize
hemp in areas in Manitoba (McPartland et al. 2000).
Among the coleopterans, the southern corn rootworm/spotted
cucumber beetle, Diabrotica undecimpunctata howardi Barber

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 2020

2

3

(Chrysomelidae), is the species with the widest geographic range andis very frequently observed in hemp growing east of the Rockies. It
feeds on leaves, but appears to prefer flowers. Japanese beetle, Popillia
japonica Newman (Scarabaeidae), is a highly visible and potentiallysignificant defoliator east of the Mississippi; this species also feeds
readily on hemp flowers (Fig. 4). Very minor injury has been observedby flea beetles (Chrysomelidae): western black flea beetle, Phyllotreta
pusilla Horn, and palestriped flea beetle, Systena blanda Melsheimer,
are regularly present in Colorado hemp. The latter species has beencommonly observed in Tennessee and elongate flea beetle, Systena
elongata (Fabr.), was reported to be abundant on cultivated marijuana in Northern Mississippi by Lago and Stanford (1989).
The most important defoliators in eastern Colorado have been
grasshoppers (Orthoptera: Acrididae), with localized outbreaks reported in 2016 and 2017. At least four species have been observed
to feed on hemp: differential grasshopper, Melanoplus differentialis(Thomas); twostriped grasshopper, M. bivittatus (Say); redlegged
grasshopper, M. femurrubrum (De Geer); and M. lakinus (Scudder).
McPartland et al. (2000) provide accounts of two additional North

American species from hemp: clearwinged grasshopper, Camnula
pellucida (Scudder), and Chloealtis conspersa (Scudder). Unlike
other defoliators of the crop, grasshoppers may also cause extensive
damage to twigs, producing flagging of small branches (Fig. 5).
Separating out the grasshopper species that feed on hemp fromthose that limit feeding to weeds associated with the crop needs
further study. For example, the chenopod specialist Aeoloplides
turnbulli (Thomas) can be common along field edges where Russianthistle (Salsola spp.) is abundant, and the grasshoppers can cause
unwarranted grower alarm. Likely only a small percentage of North
American grasshopper species will use hemp as a host plant.
Other orthopterans have occasionally been encountered in hemp
fields, notably tree crickets, Oecanthus spp. (Gryllidae), and bushkatydids, Scudderia spp. (Tettigoniidae). These are likely incidental
migrants, breeding on plants outside hemp fields, and have only been
observed to cause very minor leaf feeding.
Agromyzid leafminers (Diptera: Agromyzidae) also develop inleaves of hemp, but have only been observed in low numbers andcausing little leaf injury. The North American species in hemp havenot been characterized; McPartland et al. (2000) list six species thathave been reported elsewhere.
To better understand the significance of the defoliator complex,
experiments are needed that will define the relationship of defoliation to hemp growth and yield. Because of the diverse nature of
the various hemp crops, defoliation studies probably will need to bedone to separate effects of leaf loss on seed production (on cultivars
grown for seed), on fiber production (on cultivars grown for fiber
production), and for production of CBD (on cultivars grown for
CBD production). Furthermore, because the threshold concentrationof 0.3% THC cannot be exceeded on this crop, studies also need to
be done to determine whether defoliators may cause changes in plant
production for either THC or CBD.

Sucking Insects and Mites on Leaves

Fig. 3. Several caterpillars, such as yellow woollybear, chew hemp foliage.

Fig. 4. Japanese beetle can be a significant defoliator of hemp and readily
feeds on flowers.

During the course of this new evaluation of hemp insect pests in the
United States, one common species present constitutes a new record
for North America, cannabis aphid, Phorodon cannabis Passerini(Hemiptera: Aphididae) (Cranshaw et al. 2018; Fig. 6). In Colorado,
this insect has been observed to produce high populations in latesummer in some fields every season since 2016. Outdoors, the aphid
is holocyclic on the crop and sexual forms (winged males, apterous
oviparae) appear beginning by early September. Overwintering eggs

Fig. 5. Grasshoppers chew leaves but will often chew and weaken stems ofhemp plants.

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 2020

Journal of Integrated Pest Management, 2019, Vol. XX, No. XXJournal of Integrated Pest Management, 2019, Vol. XX, No. XX

survive on crop debris and volunteer seedlings present the following
spring are colonized after egg hatch; incidence of this insect can be
expected to increase in areas where volunteer seedlings are common
in and around fields. Cannabis aphid can also be a common pest if
there is an indoor production phase (e.g., propagation through cuttings, seedling production of transplants) and may sustain asexual
reproduction year round in plantings with adequate lighting.
McPartland et al. (2000) mention several other aphids that are reported associated with hemp. Of these, only bean aphid, Aphis fabae
Scopoli, has yet been observed from hemp in North America, and thisinvolved a single field in eastern Colorado. However, cotton/melon
aphid, Aphis gossypii Glover, has been recovered from greenhousehemp in Virginia and is found abundant in indoor production of marijuana in the southeastern United States. (S. Wainwright-Evans, personal communication to WC, 2018). Lago and Stanford (1989) only
recorded one aphid species, rusty plum aphid, Hysteroneura setariae(Thomas), from cultivated marijuana in northern Mississippi.
Leafhoppers (Hemiptera: Cicadellidae) are often the most
species-rich insect family associated with hemp, although few appear
to reproduce on the crop. Lago and Stanford (1989) cataloged 19
species in fields of cultivated marijuana in Mississippi, but only two
species were abundant, Graphocephala versuta (Say) and Agallia
constricta (Van Duzee). Fourteen species have been identified so far
from Colorado, but breeding in the crop only appears to occur withthree or four of these. Most of the leafhoppers found on foliage appear to be transient adults, perhaps associated with weeds in thecrop.
Very little, if any, damage appears to be associated with the leafhoppers found in hemp. To date, there are no published records ofleafhopper vectored plant pathogens of the crop (e.g., beet curly top,
aster yellows). No visible evidence of leaf injury has yet been observed associated from leafhoppers, aside from a modest stipplingproduced by an Empoasca species in eastern Colorado. However,
the related potato leafhopper, Empoasca fabae Harris, may be moresignificant in eastern North America. Dudley (1920) reported hemp
as a host for this insect and stated that the injury to hemp resembled‘hopperburn’ on potato. Potato leafhopper also causes hopperburn
to hops (Calderwood et al. 2015), a close relative to hemp. In
Tennessee and Virginia, potato leafhopper is recorded from hemp,
but to date, no signs of hopperburn have been observed.

A few treehoppers (Hemiptera: Membracidae) also occur inhemp. In both Mississippi (Lago and Stanford 1989) and Colorado,
Micrutalis calva (Say) and threecorned alfalfa treehopper, Spissistilus
festinus (Say), have been recorded from hemp and nymphs have been
observed, indicating that these species can breed on the crop.
No whiteflies (Hemiptera: Aleyrodidae) have yet been observed
developing in hemp fields. However, sweetpotato whitefly, Bemisia
tabaci (Gennadius), has been observed to be a serious pest on indoor
grown marijuana in the southeastern United States (S. WainwrightEvans, personal communication to WC, 2018).
Insects from at least four families of true bugs (suborder
Heteroptera) have been confirmed to feed on hemp: Pentatomidae,
Miridae, Rhopalidae, and Lygaeidae. Most of these appear to feedon flowers, stems, and seeds of the crop.
Lygus spp. (Hemiptera: Miridae) are often among the mostcommonly encountered insects on hemp and breeding does occur
on plants in vegetative growth (Fig. 7); tarnished plant bug, Lygus
lineolaris (Palisot de Beauvois), is common throughout the durationof the growing season wherever hemp is grown and is the most consistently observed phytophagous species in hemp grown in Tennessee
and Virginia. This species is also common in Colorado, where a related species, pale legume bug, Lygus elisus Van Duzee, is often thedominant Lygus species. No visible leaf injuries by Lygus spp. have
yet been noted on hemp, and they are more likely to feed and damage
developing seeds, as they do on other crops such as oilseed rape
(Butts and Lamb 1990). Lago and Stanford (1989) reported garden
fleahopper, Microtechnites bractatus (Say), to be abundant, and thisspecies produces leaf spotting on host plants. Another common miridin many eastern Colorado fields is ragweed plant bug, Chlamydatus
associatus (Uhler), a species that is primarily predatory.
Thrips are regularly found on hemp but remain largely
uncharacterized. Onion thrips, Thrips tabaci (Lindeman)(Thysanoptera: Thripidae), is the only species found commonly on
hemp foliage in eastern Colorado. During indoor phases of hemp
production, onion thrips can cause serious foliage damage. However,during outdoor production, where plants grow rapidly, onion thrips
fail to reach damaging population levels. Western flower thrips,
Frankliniella occidentalis (Pergande), has also been identified inhemp in Colorado, although it appears to be mostly associated withflowers and pollen. Lago and Stanford (1989) reported tobaccothrips, Frankliniella fusca Hinds, as being common on young plants
but appeared to disappear as plants grew older.

Fig. 6. Cannabis aphid is the most common aphid found on the crop.
Decreasing day length, results in production of sexual forms in late
September and early October, shown here, that lay overwintering eggs on
the maturing plants.

Fig. 7. Various kinds of Lygus spp. are among the most commonly observed
phytophagous insects in hemp.

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 20204

5

Twospotted spider mite, Tetranychus urticae Koch (Acari:
Tetranychidae), is a key pest of C. sativa crops wherever there
is an indoor/greenhouse phase of production. In hemp, serious
pest problems can involve mother plants used for clonal propagation and their progeny during indoor growth prior to transplanting. However, high spider mite populations do not appear
to be sustained once plants are transplanted to fields. Broad mite,
Polyphagotarsonemus latus (Banks) (Acari: Tarsenomidae), is also
known as a pest of indoor grown Cannabis crops in the UnitedStates (Wainwright-Evans 2017).
The eriophyid hemp russet mite, Aculops cannibicola (Farkas)(Acari: Eriophyidae), can be a serious pest of hemp in both indoor
and outdoor production. Indoors, extremely high populations candevelop on plants to the point where the mites sometimes completely cover areas of the leaf, becoming visible as a fine powdery
material. Outdoors, sustained population increases can occur; in one
field monitored in Colorado in 2018, russet mite numbers increased
steadily from about 50 per leaf to about 450 per leaf between early
June and early September (MS, unpublished data). In Tennessee, ca.
18% of growers reported serious problems with hemp russet mite in
2018; several growers reported destroying and burning their fields
due to this pest.
Damage by hemp russet mite is more subtle than that producedby twospotted spider mite and has not been well characterized.
Heavily infested leaves often have a slight grayish or bronzed color
change and some growers have reported that the mites have killedplants during indoor propagation. In some cultivars, a slight upward
rolling of the leaf edge may occur; this symptom is not universally
produced and some hemp cultivars normally will produce similarleaf curling in the absence of the mite. More clearly damaging effects occur when hemp russet mite infests developing flower buds ofcultivars grown for CBD production. High populations can reduce
the size of flower buds and resin production, which can result in
reduced yield of extractable cannabinoids (McPartland and Hillig
2003; Fig. 8).
There are more important information gaps involving hemp
russet mite than for any of the other species that have potential to be
key pests of the crop. Fundamental information is almost completely
lacking on the life history of this species. Studies on overwintering
biology, and the possibility of alternate host plants would provide

information that could address important questions needed to help
better manage hemp russet mite.
Biological controls need to be evaluated for this species; populations of potential natural enemies of hemp russet mite (e.g., predatory mites, anthocorids) have been very low in fields in Colorado
even with very high hemp russet mite populations. Currently, noneof the commercially available predatory mites used for greenhousepests have yet been clearly demonstrated to be effective for hemp
russet mite and predatory mites are often limited by the low humidity conditions that normally are associated with hemp being produced in arid areas, such as Colorado. Limited trials have indicatedthat mineral oils appear promising for suppression of hemp russet
mite (WC, unpublished data).

Stem and Stalk Borers
European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera:
Crambidae), is reported to tunnel into larger stems and stalks ofhemp and has the potential to weaken plants to the extent that they
are prone to breakage (Anonymous 2018b). The potential importance of this injury was briefly noted by Willsie et al. (1942) who later
stated ‘hemp is exceptionally resistant to lodging and usually is notaffected by ordinary storms’. This suggests plant damage of the typeproduced by European corn borer injuries (structural weakening ofstalks) may be well tolerated by hemp. Further evidence of this wasindicated by Small et al. (2007) who reported increased branching
and increased seed yields following European corn borer tunneling.
An increased bushiness of growth habit can be desirable in production of CBD cultivars because it can lead to an increase in resin-richbuds. Region-wide population suppression of this insect species has
occurred in the central and eastern United States due to the widespread planting of Bt transgenic corn (Hutchison et al. 2010, Dively
et al. 2018). At the time of this manuscript submission, the only reliable record of European corn borer damage to hemp known by theauthors involved a single specimen discovered by a grower in North
Carolina in 2018 tunneling into the stem at ground level of a young
hemp plant (TK).
Eurasian hemp borer, Grapholita delineana (Walker)(Lepidoptera: Tortricidae), is a much smaller species of stem/stalkborer but may have more potential to cause significant stem andstalk injuries to the crop than European corn borer in some production areas. It appears capable of producing three to four generations
per year, allowing rapid rates of population increase.
There is minimal external evidence of stalk tunneling producedby Eurasian hemp borer. A slight swelling of the stalk may occur, andleaf flagging may occur adjacent to the wounds. Whether these injuries significantly affect yield needs to be studied. Far more damage
is caused by this insect late in the season when stem tunneling destroys buds and developing seeds are consumed.

Sucking Insects Associated with Flowers and Seeds

Fig. 8. Injury by hemp russet mite can produce a range of symptoms that
often can be subtle. In this plant there is some off-color and reduction in leaf
size, but the primary effect has been to retard bud development, which cangreatly affect yield of cannabidiol cultivars.

Several types of true bugs become abundant in hemp after flowering,feeding primarily on flowers, and developing seeds. The largest andmost conspicuous are various stink bugs (Hemiptera: Pentatomidae),and hemp appears to attract many species. Redshouldered stink bug,
Thyanta custator (Fabr.), and brown stink bug, Euschistus servus(Say), occur on hemp throughout the continental United States(Fig. 9). In the western states, Chlorochroa species appear to be
the most common stink bugs in hemp, particularly the conchuela
stink bug, C. ligata (Say), and Uhler stink bug, C. uhleri (Stål). In
the eastern United States, green stink bug, Chinavia hilaris (Say) is
common and was observed to readily breed on the crop by Lagoand Stanford (1989). In Virginia, in areas where the invasive brown

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 2020

Journal of Integrated Pest Management, 2019, Vol. XX, No. XXJournal of Integrated Pest Management, 2019, Vol. XX, No. XX

marmorated stink bug, Halyomorpha halys (Stål), is established, it
is consistently present on hemp, clearly breeds on the crop, and isviewed as a suspected pest. In outdoor crops, adults appear whenplants become fragrant and have developed inflorescences. Eggs havebeen found on plants and nymphs are able to successfully complete
development to adulthood on a diet of hemp alone (Britt et al. 2019).
Adults of rice stink bug, Oebalus pugnax Fabr. and Cosmopepla
lintneriana (Kirkaldy), have been observed on hemp in Tennessee.
Southern green stink bug, Nezara viridula L., was reported to occur
on feral hemp in Illinois (McPartland et al. 2000).
Plant bugs of the genus Lygus are also extremely common residents of hemp, and at least two species breed on the crop (tarnishedplant bug, pale legume bug). These insects can be found on hemp
plants throughout the growing season, but occur in higher numbers
after flowering. In Virginia, tarnished plant bug is present in hemp
soon after plants emerge from seeds until harvest.
Both stink bugs and Lygus spp. plant bugs feed on flowers,
developing fruit, and seeds of a great many plants, and several of
the species on hemp are important pests in other crops. Flower bud
abscission, seed abortion, and seed deformities are common effects
produced on other crops, which could have implications for hemp
produced for seed. However, data are presently absent to determine
whether any of these seed feeding bugs are significant pests affecting
hemp seed production or quality.
A few species of rhopalids (Hemiptera: Rhopalidae) can be foundon hemp. Hyaline grass bug, Liorhyssus hyalinus (Fabr.), has been
observed breeding in seeds and flowers of hemp in Colorado andeastern Virginia. In Colorado, high populations were found in aseed/fiber hemp field that had produced the crop for two consecutive years. In eastern Virginia, all life stages were found in seed/fiber
hemp. Adults of various Arhyssus spp. also occur in the crop. Thereis no evidence yet that any will breed on hemp, but many Arhyssus
species are associated with various weeds common in agriculturalareas. Most common on hemp flowers in eastern Colorado is false
chinch bug, Nysius raphanus Howard (Hemiptera: Lygaeidae), aubiquitous insect that can be found on most any plant in the region.
This insect primarily breeds on cruciferous plants and nymphs havenot been found in hemp collections.
Cannabis aphid has often been observed to infest maturing
flowers and associated leaflets late in the season and into harvest inColorado. Effects on yield are unknown, but large numbers of these
insects, and their eggs, can be incorporated into harvested floral
parts and it can produce abundant amounts of honeydew.

Fig. 9. Several kinds of stink bugs have been observed in hemp, usuallyappearing after plants begin flowering and seeds develop. Redshouldered
stink bug is one of the most common species that has been found on hemp
and is the one with the widest geographic range.

Chewing Insects that Damage Flower Buds and
Seeds
Eurasian hemp borer was the only insect reported by Haney and
Kuscheid (1975) to seriously damage seeds of feral hemp in central
Illinois. A subsequent publication on the establishment of this species in North America (Miller 1982) indicated that it was present in
at least seven states (Illinois, Iowa, Kentucky, Minnesota, Missouri,
New York, and Wisconsin). Presently, there are records for this insectfrom a majority of the states east of the Mississippi, and Eurasianhemp borer was observed to be present in fields throughout eastern
Colorado in 2017–2018.
Eurasian hemp borer spends almost its entire larval stage withinstems of hemp, with only a brief period of leaf feeding done by the
first-instar larvae (McPartland 2002). Late in the season, tunnelingis concentrated in upper stems, producing girdling wounds thatdamage and often kill terminal buds (Fig. 10). The general appearance of bud injury can superficially resemble that produced by cornearworm; splitting the stem below the injury site can expose larval
tunneling that would indicate Eurasian hemp borer. Larvae may also
tunnel amongst developing seeds and the last-instar larvae, which
are orange or a bit pinkish, have been reported in large numbers at
harvest by some Colorado producers.
McPartland (2002) provided information on the life history
Eurasian hemp borer and its damage potential to the crop, but several information gaps need further research in order for effective

Fig. 10. Eurasian hemp borer can develop in stems, buds, and developing
seeds. In the last instar, larvae turn bright orange.

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 202067

pest management plans to be developed. These include methods tomonitor the insect so that incipient outbreaks can be detected, identification of natural controls, and aspects of its life history including
the use of alternate host plants. The suddenness with which this insect has become prominent in some eastern Colorado hemp fields,in areas where no Cannabis plants were present prior to 2016,strongly suggests nonhemp wild hosts support this insect. Gilligan
and Epstein (2014) mention Humulus spp. and Polygonum spp. asreported hosts in Europe.
Management of Eurasian hemp borer could be particularly challenging in crops grown for seed. Most injury occurs after plants havebegun to flower, and pollinators actively visit the crop where maleplants are present; this can greatly limit insecticide options. All presently allowable insecticides (in some states) for use on hemp havevery short persistence (pyrethrins, azadirachtin) or are stomach poisons (Bacillus thuringiensis). These are unlikely to be satisfactoryfor control of this insect, given its very short period when larvae areexposed on the plant surface.
The insect that has caused the most damage to hemp grown inColorado is corn earworm, Helicoverpa zea (Boddie) (Lepidoptera:
Noctuidae) (Figs 11 and 12). This insect is widely distributed in
North America and has been observed feeding on buds and seedheads of hemp in Illinois, Indiana, Kentucky, Nevada, North
Carolina, Tennessee, Vermont, Virginia, and Wisconsin. Outbreaks
can occur irregularly but serious damage occurred from this insect
in southeastern Colorado in both 2016 and 2018; one grower estimated a loss of over $0.5 million to a hemp crop grown for CBDduring the 2016 outbreak.
Corn earworm becomes attracted to hemp after plants begin toflower and is rarely seen at earlier stages of plant growth. This often
happens late in summer after corn has largely passed the green silk
period and is no longer attractive for egg laying; during this time,
hemp may be one of the most attractive plants available to this insect. Some leaf feeding occurs, but the caterpillars primarily chew
into flower buds and developing seed heads. Corn earworms are particularly damaging to hemp cultivars grown for production of CBD,as larvae can destroy several of the resin-rich buds as they develop.
Significant feeding injuries can occur on hemp grown for seed, anda North Carolina grower estimated a 30% crop loss of grain hemp
due to a late-season corn earworm infestation during 2017.

Pheromone trap-based monitoring systems for corn earworm exist
and are commonly used for other crops, notably sweet corn (Olmstead
et al. 2016). These can help identify periods when high numbers ofcorn earworm moths are active, which may be associated with intensity of egg laying. Combined with information on what stages of hemp
are attractive to female moths for egg laying, insecticide treatments
can be timed to control the damage. Recommendations for control
of corn earworm used in Colorado during 2018 included formulations of B. thuringiensis var. aizawi (Agree WG, XenTari BiologicalInsecticide) or the Helicoverpa armigera nucleopolyhedrovirus/
HearNPV (Helicovex), which are allowable for use in the state under
the regulatory guidelines developed by the Colorado Department ofAgriculture (2016). In hemp, corn earworm feeds more on the surfaceof the plant than it does with some other crops (e.g., corn, peppers,
tomato), improving the potential of these microbial insecticides to beingested in sufficient quantities to kill larvae. These products also havethe advantage of being selective in their effects, conserving existing
natural enemies and being compatible with visiting bees that collectpollen from the crop.
Several of the defoliators seen on the crop appeared to be most abundant during flowering and would readily feed on flowers. These include
Japanese beetle, yellowstriped armyworm, and zebra caterpillar.

Fig. 11. Corn earworm is often the insect that is most damaging to hemp,
tunneling into maturing flower buds and developing seeds. Injury is greatest
on cannabidiol cultivars where large flower buds are produced.

Root Feeders
The complex of arthropods associated with the root system of hemp
plants has received very little attention. Willsie et al. (1942) mention
that white grubs could damage young plants in Iowa, and Lago andStanford (1989) reported collecting several larvae of Phyllophaga
tristis (Fabr.) (Coleoptera: Scarabaeidae) from roots of cultivatedmarijuana. It is likely that some leaf beetles of generalist habit withsoil-dwelling larval stages may feed on hemp roots (e.g., southern
corn rootworm, some flea beetles).
In western Colorado, larvae of a Prionus sp. (Coleoptera:
Cerambycidae) damaged a limited area of a field that had recently
been converted from an area of sagebrush. This is a long-lived insect
and, in this situation, the larvae appear to have originated from rootsof the sagebrush remaining within the field. Damage to seedlings
and small transplants by pavement ant, Tetramorium caespitum(L.) (Hymenoptera: Formicidae), also was seen in western Colorado
in 2018. Seedlings located near nest entrances were damaged justbelow the soil line, constricting the stem, which resulted in wilting
and death of plants as they got older.

Fig. 12. Flower bud of hemp destroyed by corn earworm.

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 2020

Journal of Integrated Pest Management, 2019, Vol. XX, No. XXJournal of Integrated Pest Management, 2019, Vol. XX, No. XX

The most common aphid reported from indoor marijuana production in Colorado is rice root aphid, Rhopalosiphum abdominalis(Sasaki) (Hemiptera: Aphididae), and plants supporting large populations can show a significant decline. This species develops almost
entirely below ground on Cannabis. Most stages found on aboveground parts of plants are winged forms, and these are often observed dead and caught on the leaf surface. Some colonization offoliage occurs, but most progeny produced on foliage by migrant
winged forms are observed to migrate to the roots.
Rice root aphid has not yet been recorded from either indoor
or outdoor grown hemp. It is unlikely that this is due to differencesin host plants, as marijuana and hemp are identical insect hosts inmost important respects. It is more likely that the greater incidenceof problems on marijuana results from differences in plant culture.
Marijuana is often grown in continuous indoor culture and withsystems involving live soil often involves use of surface mulches,
which has been shown to favor the establishment of rice root aphid(Kindler et al. 2004, Hesler and Kindler 2007). Comparatively, indoor production phases of hemp are typically more limited, withsome maintenance of a few mother plants between growing seasons
and with a short period when transplants produced from cuttings
are produced, prior to field planting.
Rice root aphid is widespread in North America, most often associated with various grain crops. This species may have a holocyclic
life cycle in some parts of the world, laying overwintering eggs on
Prunus. Use of these winter hosts has not been recorded in North
America, and the species can survive year round on roots of cereals
at least as far north as Illinois (Capinera 2001).

because it is predaceous on root aphids (Sabrosky 1935). A local
species that may support this species is sugarbeet root aphid,
Pemphigus betae Doane (Hemiptera: Aphididae), which develops
on various crops and weeds in the family Amaranthaceae (Pretorius
et al. 2016). The near ubiquitous presence of T. glabra in hemp fields
may also indicate the presence of root-feeding aphids that have notbeen identified (Fig. 14).
Although hemp is an annual crop, several kinds of spiders havebeen observed to colonize hemp fields. Most consistently encounteredin eastern Colorado fields are crab spiders in the genus Mecaphasa,
running crab spiders (primarily Philodromus sp.), several genera ofjumping spiders, and longjawed spiders (Tetragnatha sp.).
The type of hemp being grown may also affect the natural enemy
complex. Hemp that flowers and produces pollen may improve foodresources for predatory species that also use pollen in their diet.
Pollen may also support some primarily phytophagous species (e.g.,western flower thrips) that in turn can provide hosts for generalist
predators (e.g., Orius insidiosus). Conversely, pollen-bearing male
flowers are often absent in fields for CBD production. Furthermore,this production system results in large, unfertilized female flower‘buds’ that are densely covered with sticky, resin-rich trichomes. The

Natural Enemy Species
Hemp fields may support a robust complement of natural enemy
species, most of which will reflect the types of species typically present in some other row crops. The incidence of these natural enemies
will be affected by the availability of hosts/prey as well as the growthstage and type of hemp being grown.
For example, in fields supporting large numbers of cannabis
aphid in Colorado, lady beetles become particularly prominent.
Most common are convergent lady beetle, Hippodamia convergens
Guérin-Méneville, and multicolored Asian lady beetle, Harmonia
axyridis (Pallas) (Coleoptera: Coccinellidae), but at least four otherlady beetle species often occur in Colorado hemp (Fig. 13). Three
species of green lacewings (Neuroptera: Chrysopidae) can be found,with Chrysopa oculata Say and Chrysoperla plorabunda (Fitch)
being most common. Larvae of at least four species of predaceous
syrphids (Diptera: Syrphidae) and Aphidoletes aphidimyza (Rondani)(Diptera: Cecidomyiidae) also were observed feeding on cannabis
aphids in hemp fields. Parasitism by braconids (Hymenoptera:
Braconidae) and infections by entomopathogenic fungi (unidentified) have been observed in fields infrequently. Numerous othergeneralist predators observed in hemp are probably predaceous on
cannabis aphid, including predatory hemipterans—Orius insidiosus(Say) (Anthocoridae), Nabis alternatus Parshley (Nabidae), Geocoris
punctipes (Say) (Geocoridae), and Chlamydatus associatus (Uhler)(Miridae)—and predatory dipterans—Platypalpus sp. Macquart(Diptera: Hybotidae), and Condylostylus sp. Bigot (Diptera:
Dolichopodidae). In Virginia and Tennessee the most frequently observed natural enemies have been the coccinellids multicolored Asianlady beetle and Coleomegilla maculata (De Geer), along with bigeyed bugs, Geocoris spp.
A very common species found in almost all eastern Colorado
hemp fields has been the chloropid Thaumatomyia glabra (Meigan)(Diptera: Chloropidae). This species is unusual among chloropids

Fig. 13. Several kinds of lady beetles are common in hemp crops, including
convergent lady beetle (above), multicolored Asian lady beetle, andColeomegilla maculata.

Fig. 14. Several kinds of hemipteran predators are present in hemp including
damsel bugs (above), big-eyed bugs, and minute pirate bugs.

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 202089effects of these sticky trichomes on activity of natural enemy species
also need study.

Several conditions can affect the value of hemp as a pollen resource. Regional differences are likely, as in areas of higher rainfall—and greater availability of late summer pollen resources—thepotential contribution of hemp will probably diminish. Lago andStanford (1989) recorded only three species of bees in cultivatedmarijuana—A. mellifera, Bombus impatiens Harris, and Dialictus
imitatus (Smith)—all of which were noted as being either rare or
uncommon in the crop.
More fundamentally important is the type of hemp crop being
grown. Although hemp being grown for seed and/or fiber will havean abundance of pollen-bearing male flowers, the great majority ofhemp currently being grown in Colorado and Tennessee is for the
production of the nonpsychoactive pharmacological compound,cannabidiol (CBD), which is one of many plant-produced cannabinoids. In this production system, typically only all-female plants
are grown and pollination is undesirable since seed production reduces CBD yield. These types of hemp will have no value as a pollen
source.
The use of this crop by pollinators also has potential implications
with pesticide use. Many insects, notably seed feeding hemipteransand Eurasian hemp borer, develop highest and most damaging populations during periods when the crop is in flower and being used bybees. This will be a confounding factor to consider in the registration
and use of pesticides on hemp during periods when pollen production makes plants attractive to bees.

Pollinators and Hemp
Hemp is wind-pollinated, and plants may be either dioecious ormonoecious. Very abundant amounts of pollen are produced, typically for a period of several weeks, but the plants do not produce
nectar. Fiber/seed cultivars may be visited heavily for pollen by several species of bees.
Flowering hemp can be a significant source of pollen for bothhoney bees and many kinds of native bees during late summer (Fig.
15). Although honey bee (Apis mellifera L.) (Hymenoptera: Apidae)
is usually the most noticeable bee, a considerable diversity of species
may be found in the crop. Trapping of bees in hemp during 2015 and2016 in northern Colorado found honey bee to be the most abundant species, but close to half of the total captures involved various
longhorned bees (Apidae: Eucerini), particularly Melissoides spp.
(O’ Brien and Arathi 2019). Other Apidae found in high numbers
included bumble bees (Bombus spp.) and digger bees (Anthophoraspp.). Solitary bees of other families represented a small percentageof the total captures; five genera of Halictidae were found, andsmaller numbers of bees in the Megachilidae and Andrenidae werealso collected. In agricultural areas where suitable wild flowering
forbs are limited during the period when hemp is in flower (typically August and early September in Colorado), integrating hemp into
agricultural systems has the potential to significantly contribute toimproving resources for pollinators that collect hemp pollen.

Fig. 15. Flowering hemp produces an abundance of pollen and this may beheavily used by many kinds of bees in areas where alternative pollen sources
are not available.

Pesticide Issues
The situation regarding pesticide use on hemp in the United Stateshas been chaotic, has created enormous confusion, and remains amajor impediment to the development of effective pest managementon the crop.
At the root of the problem is unresolved tension between the2014 Farm Bill, which allowed the legal production of hemp, andthe Controlled Substance Act of 1970, which continued to define all
C. sativa crops as a Schedule I drug (Sandler et al. 2019). This has
had the effect of paralyzing all federal regulatory action that could
enable registration and oversight of pesticides on this new crop.
In the absence of federal action and in response to the very realneed for some direction regarding pesticide use, the regulation ofpesticides on Cannabis crops (marijuana, hemp) has functionally devolved to the states. Predictably, there has been a wide range in how
state regulatory agencies have responded to the question of pesticide
use on hemp.
To date, the majority of states that have allowed hemp production have not addressed the issue, taking the position that only thefederal government can regulate pesticide use on the crop. Extending
this reasoning, because federal regulatory agencies do not recognize
hemp as a crop site, there can exist no registered pesticides on thecrop.
Where this is the position, no registered pesticides are allowed
to be used in hemp production within the state. Growers, then, canlegally respond in a couple of ways: use no pesticides; use pesticides illegally; use Section 25(b) products that are exempted from
FIFRA registration requirements; or use pesticidal products that
do not make claims as a pesticide. Examples of the latter would bemarketing of neem oil as a ‘leaf shine’ product, or soap/detergent
products as a ‘plant wash’.
A different model has evolved in other states, where state regulatory agencies have developed regulations that allow certain registered pesticides to be used. This has happened primarily in states

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 2020

Journal of Integrated Pest Management, 2019, Vol. XX, No. XXJournal of Integrated Pest Management, 2019, Vol. XX, No. XX

that had previously passed state laws or constitutional amendmentsallowing production of medical and/or recreational marijuana; theseregulations then were applied to all C. sativa crops, including hemp.
This involves a finesse of federal regulations, first developed by
Washington and released in August 2013; Colorado followed witha similar regulations released in March 2015. In this model, certain
pesticide products, registered by the EPA and the state, are allowed
if they meet a set of criteria. The first of these is that the active ingredient is exempt from the requirements of a tolerance on all foodcrops, as established under 40 C.F.R. Part 180 Subparts D and E.
This has the effect of limiting the available insect control products
largely to certain microbial insecticides (e.g., certain strains of B.
thuringiensis, Isaria fumosorosea), certain plant-derived insecticides(e.g., azadirachtin, pyrethrins), various horticultural oils (e.g., mineral oils, seed-derived oils), and insecticidal soaps.
The second criterion involves the label language associated withthe specific product. Label use directions must be broadly written, sothat they allow use on unspecified crops, which could be interpreted
to include—or at least not to exclude—hemp (or marijuana). For example, language statements that allow use on ‘Crops such as…’, followed by a long list of crops, among which hemp could be included,
would be allowable. Label instructions that more strictly define sites
of use would not be allowable. With this interpretation, these allowable pesticides are seen as not being in conflict with the federal
label; they are not allowed. This can create a bit of a patchworkof allowable products not strictly tied to active ingredient. For example, at present, two Beauveria bassiana products that also containpyrethrins are allowed by the Colorado Department of Agriculture,
whereas a similar B. bassiana product without pyrethrins, butslightly different label use directions, is not allowed.
Both Colorado and Washington state further limit registeredproducts by requiring that they also either be registered for tobacco (Colorado) or ‘data from pyrolysis studies have not led toan exceedance in the level of concern (LOC) or other parametersand have not resulted in EPA denying use of the active ingredienton tobacco’ with the product (Washington State Department ofAgriculture 2018). Additionally, in the Washington/Colorado model,
25(b) minimum risk products that are exempt from federal registration are allowed if they are registered with the state prior to
distribution.
In this model, the state develops and provides a list of specificregistered pesticides, regularly updated, that are allowed to be usedin production of Cannabis-derived crops. The Oregon Departmentof Agriculture seems to have similarly followed this model, but otherstates have not. For example, in California, where pesticides are
regulated by the Department of Pesticide Regulation, the first criteria for use, exemption from food crop tolerance, is given as guidance on what products are allowed on Cannabis crops, and a list of
specific allowable pesticides are not provided to growers (California
Department of Pesticide Regulation 2018).
The pesticides that are allowed by states that use this model generally provide products that can be used to adequately manage manyof the likely arthropod pest problems that develop on this crop, particularly when used with other pest management methods (e.g., crop
rotation, elimination of volunteer plants). For other types of pests ofthe crop—plant pathogens and, particularly, weeds—adequate pesticides are not available.
Language in the recently passed U.S. Farm Bill of 2018 that establishes hemp as a federally recognized crop may provide a paththat allows federal agencies to assume the primary role for regulation of pesticide use on hemp. At that point in time, there likely will
be several different regulatory paths for different forms of hemp.

For example, hemp being grown strictly for seed or fiber may beconsidered to fall within the Oilseed Group (Crop group 20), whichcontains crops such as cottonseed, flax seed, and sunflowers. Such adesignation could accelerate additional registrations, either throughlabel changes or through Special Local Needs registrations.
Hemp grown for CBD will have a far more difficult path todevelop and expand pesticide registrations. Among existing cropgroups, it is perhaps closest to the Herbs and Spices Group (Cropgroup 19), but there are important differences related to how CBD
hemp is handled after harvest and used by consumers. Solvents, suchas CO2, butane, or ethanol, are used to extract CBD and other desired plant materials (producing CBD ‘oil’), and these extraction
methods may concurrently extract certain pesticide residues (Raberet al. 2015). Also, CBD products are consumed in many different
forms—ingested, inhaled, or dermally applied. To sufficiently satisfy
registration requirements, all of these issues will probably require
new studies. Costs of these types of studies will be very large. Given
the very small market for pesticides on hemp, it is unlikely that it
will be attractive for many, if any, potential pesticide registrants to
conduct the studies.

Conclusion
In the few years since the ‘new’ crop, industrial hemp, has beengrown in the United States, most attention involving insect pest management has involved a descriptive phase, where the kinds of arthropods associated with the crop in different regions are described andkey species of the crop identified. In this brief period, substantial
progress has been made and the broad outlines of pest management
needs have emerged. Several potential key pests have already been
identified—corn earworm, Eurasian hemp borer, cannabis aphid,
hemp russet mite, grasshoppers—and many other phytophagous
species may develop into significant pests as the crop becomes more
widely established. Furthermore, it appears that present issues with
insect/mite pest management on hemp vary in almost every way
from what was reported when hemp was last grown widely in the
United States over 70 yr ago.
Many studies are now required to address gaps of information that would allow production of pest management plans, theDevelopment Phase. This includes basic information on the life history of several species, assessment of injury potential, identificationof monitoring methods, and evaluation of various types of controls (e.g., biological, cultural, chemical). Some work is presently inprogress that will answer these questions, but a great deal more isneeded. With one insect (corn earworm), in one location (Colorado),
on one form of hemp (CBD cultivars), a prototype Implementation
Phase project has been started.
Over the past 4 yr, almost everything about production of hemp
in the United States, including pest management, has been in a stateof enormous flux. Growers have constantly experimented with ways
to grow the crop, and many different production systems are being
used. Overall, acreage has steadily increased, but the crop is grown
for many different markets, all of which are still developing, andcrop prices have been very unstable. Some of these problems are related to the uncertainties involving federal laws affecting the crop,and it can be hoped that language in the newly passed 2018 FarmBill may better resolve many of these issues. Clarity in pesticide regulation involving the crop at the federal level is greatly needed, andthat will happen at some point to come.
Changes in pest problems will also result as production systems
for hemp evolve. For example, CBD hemp is often asexually propagated through the use of cuttings, which helps sustain continuous
populations of some pest species (e.g., hemp russet mite). Breeding

Downloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 2020

10

11

and horticultural developments that produce CBD cultivars grownfrom seed will diminish these challenges. On the other hand, more
extensive cultivation of hemp, with more volunteer seedlings in thevicinity of production sites, may increase problems with other pest
species, particularly those that are largely restricted to C. sativa (e.g.,cannabis aphid, Eurasian hemp borer). How this will ultimately playout is unknown, but the entomology of hemp in the United Statespromises to be an extremely dynamic area in the foreseeable future.

Technology Fact Sheet. (http://idtools.org/id/leps/tortai/Grapholita_delineana.htm) Accessed 23 November 2018.
Grotenhermen, F., and K. Müller-Vahl. 2016. Medicinal uses of marijuana andcannabinoids. Crit. Rev. Plant Sci. 35: 378–405.
Haney, A., and B. B. Kuscheid. 1975. An ecological study of naturalized hemp
(Cannabis sativa L.) in east central Illinois. Am. Midl. Nat. 93: 1–24.
Hesler, L. S., and S. D. Kindler. 2007. Abundance of rice root aphid among
selected plant species and on plants grown with different soil-surface
media. Great Lakes Entomol. 40: 84–91.
Hutchison, W. D., E. C. Burkness, P. D. Mitchell, R. D. Moon, T. W. Leslie, S. J.
Fleischer, M. Abrahamson, K. L. Hamilton, K. L. Steffey, M. E. Gray, et al.
2010. Areawide suppression of European corn borer with Bt maize reaps
savings to non-Bt maize growers. Science 330: 222–225.
Kindler, D., L. Hesler. N. Elliot, K. Shufran, and T. Springer. 2004. Cereal andgrass hosts of the rice root aphid, Rhopalosiphum abdominalis (Sasaki),and a description of an efficient greenhouse rearing technique. J. Agric.
Urban Entomol. 21: 51–59.
Lago, P. K., and D. F. Stanford. 1989. Phytophagous insects associated withcultivated marijuana (Cannabis sativa L.) in northern Mississippi. J.
Entomol. Sci. 24: 437–445.
McPartland, J. M. 1996. Cannabis pests. J. Int. Hemp Assoc. 3: 52–55.
McPartland, J. M. 2002. Epidemiology of the hemp borer, Grapholitadelineana Walker (Lepidoptera: Oleuthreutidae), a pest of Cannabis sativa
L. J. Ind. Hemp 7: 25–42.
McPartland, J. M., and K. W. Hillig. 2003. The hemp russet mite. J. Ind. Hemp
8: 107–112.
McPartland, J. M., R. C. Clarke, and D. P. Watson. 2000. Chapter 4. Insects
and mites. In J. M. McPartland, R. C. Clarke, and D. P. Watson (eds.),
Hemp diseases and pests: management and biological control – an advanced treatise. CABI Publishing, Oxfordshire, UK. pp. 251.
Miller, W. E. 1982. Grapholita delineana (Walker), a Eurasian hemp moth, discovered in North America. Ann. Entomol. Soc. Am. 75: 184–186.
O’Brien, C., and H. S. Arathi. 2019. Bee diversity and abundance in flowering
hemp (Cannabis sativa L.). Biomass Bioenergy 122: 331–335.
Olmstead, D. L., B. A. Nault, and A. M. Shelton. 2016. Biology, ecology, andevolving management of Helicoverpa zea (Lepidoptera: Noctuidae) insweet corn in the United States. J. Econ. Entomol. 109: 1667–1676.
Pretorius, R. J., G. L. Hein, and J. D. Bradshaw. 2016. Ecology and management of Pemphigus betae (Hemiptera: Aphididae) in sugar beet. J. Integr.
Pest Manag. 7: 10.
Raber, J. C., S. Elzinga, and C. Kaplan. 2015. Understanding dabs: contamination concerns of cannabis concentrates and cannabinoid transfer during
the act of dabbing. J. Toxicol. Sci. 40: 797–803.
Rens, D. 1995. America’s hemp king. Self-published by author. Waupun, WI.
(http://newheadnews.com/hemp/Rens.hempstory.Wis/).
Sabrosky, C. W. 1935. The Chloropidae of Kansas (Diptera). Trans. Am.
Entomol. Soc. 61: 207–268.
Sandler, L. N., J. L. Beckerman, F. Whitford, and K. A. Gibson. 2019. Cannabis
as conundrum. Crop Prot. 117: 37–44.
Smith, G. E., and A. Haney. 1973. Grapholita tristrigana (Clemens)(Lepidoptera: Tortricidae) on naturalized hemp (Cannabis sativa L.) ineast-central Illinois. Trans. Ill. State Acad. Sci. 66: 38–41.
Small, E., D. Marcus, G. Butler, and A. R. McElroy. 2007. Apparent increasein biomass and seed productivity in hemp (Cannabis sativa) resulting
from branch proliferation caused by the European corn borer (Ostrinia
nubilalis). J. Ind. Hemp 12: 15–26.
Wainwright-Evans, S. 2017. Take control of mites on cannabis crops. Greenhouse Grower. 22 September 2017. (https://w w w. g r e e n h o u s e g r o w e r. c o m / p r o d u c t i o n / i n s e c t - c o n t r o l /take-control-of-mites-in-cannabis-crops/).
Washington State Department of Agriculture. April 2018. Criteria for pesticides used for the production of marijuana in Washington. (https://agr.
wa.gov/FP/Pubs/docs/398-WSDACriteriaForPesticideUseOnMarijuana.
pdf) (Accessed 13 December 2018).
Willsie, C. P., E. S. Dyas, and A. G. Norman. 1942. Hemp – a war crop for
Iowa. Iowa State College Agricultural Experiment Station/Agricultural
Extension Service Bulletin P49. Iowa State College, Ames, IA. p. 587–600.

Acknowledgments
Virginia studies were assisted by Mika Pagani, Emily Rutkowski, Jamie Hogue,
other members of the Kuhar Lab, Jabari Byrd, John Fike, Carol Wilkinson, andthe numerous Virginia and North Carolina growers who allowed us to visit theirfields for this research. A special thanks is extended to Cody Seals for providing information, input, and data related to incidence of insects and mites on
hemp in Tennessee. Access to Hemp Agronomic Reports by Katherine Kilbourne
and the Tennessee Department of Agriculture and the use of research plots ofDr. Eric Walker, University of Tennessee, have also been very helpful to the understanding of hemp pest issues in the state. Work in Colorado has been ably assisted
by Wendlin Burns and Andrew Miller. The cooperation of numerous cooperating
hemp producers has also been invaluable, with a special thanks to Colorado
Cultivars. Colorado activities were supported, in part, by Colorado Agricultural
Experiment Station Project COL00618B and the Western IPM Center.

References Cited
Anonymous. 2018a. Hemp Industry Daily. Hemp Report: Top 10 U.S. States.
pp.
13.
(https://mjbizdaily.com/wp-content/uploads/2018/04/HempReport_Top-10-US-States.pdf) (Accessed 6 December 2018).
Anonymous. 2018b. Production. Insects and pests. Canadian Hemp Trade
Alliance website. (http://www.hemptrade.ca/eguide/production/insectsand-pests) (Accessed 19 November 2018).
Britt, K. E., M. K. Pagani, and T. P. Kuhar. 2019. First report of brown
marmorated stink bug (Hemiptera: Pentatomidae) associated with
Cannabis sativa in the U.S. J. Integr. Pest Manag. 10: 17.
Butts, R. A., and R. J. Lamb. 1990. Injury to oilseed rape caused by mirid bugs
(Lygus) (Heteroptera: Miridae) and its effects on seed production. Ann.
Appl. Biol. 117: 253–266.
Calderwood, L. B., S. A. Lewins, and H. M. Darby. 2015. Survey of northeastern
hop arthropod pests and their natural enemies. J. Integr. Pest Manag. 6: 18.
California Department of Pesticide Regulation. 2018. Cannabis pesticides thatare legal to use. (https://www.cdpr.ca.gov/docs/cannabis/can_use_pesticide.pdf) (Accessed 13 December 2018).
Capinera, J. L. 2001. Handbook of vegetable insects. Academic Press, San
Diego and London. pp. 729.
Colorado Department of Agriculture. 2016. Factual and policy issues related
to the use of pesticides on Cannabis. (https://www.colorado.gov/pacific/
agplants/pesticide-use-cannabis-production-information) (Accessed 13
December 2018).
Cranshaw, W. S., S. E. Halbert, C. Favret, K. E. Britt, and G. L. Miller. 2018.
Phorodon cannabis Passerini (Hemiptera: Aphididae), a newly recognizedpest in North America found on industrial hemp. Insecta Mundi 06570662: 1–12.
Deitch, R. 2003. Hemp: American history revisited: the plant with a divided
history. Algora Publishing, New York. pp. 244.
Dively, G. P., D. Venugopal, R. Bean, J. Whalen, K. Holmstrom, T. P. Kuhar,
H. B. Doughty, T. Patton, and W. D. Hutchinson. 2018. Regional pest suppression from Bt maize benefits vegetable growers. Proc. Natl. Acad. Sci.
USA 115: 3320–3325.
Dudley, J. E., Jr. 1920. Control of the potato leafhopper (Empoasca mali LeB.)
and prevention of “hopperburn”. J. Econ. Entomol. 13: 408–415.
Fike, J. 2016. Industrial hemp: renewed opportunities for an ancient crop. Crit.
Rev. Plant Sci. 35: 406–424.
Gilligan, T. M., and M. E. Epstein. 2014. Grapholita delineana. TortAI tortricids of agricultural importance. Center for Plant Health Science andDownloaded from https://academic.oup.com/jipm/article-abstract/10/1/26/5555744 by Colorado State University user on 08 January 2020

Journal of Integrated Pest Management, 2019, Vol. XX, No. XX