L-v'-l ' ^

WILD GARLIC

Its Characteristics and Control

Agriculture Handbook No. 298

Agricultural Research Service

U.S. DEPARTMENT OF AGRICULTURE

In Cooperation With

Missouri Agricultural Experiment Station
CONTENTS

Page

Origin and distribution. _ 3

Plants that resemble wild garlic 4

Description and growth habit 5

Classification ^

Structure of the wild garlic plant 6

Plant types 6

Bulb types 7

Reproductive cycles 10

Wild garlic: a pest ^^

Pest in small grains 14

Pest of pastures and hay fields 1^

Pest around homes, gardens, and noncrop areas.. 15

How wild garlic spreads. 1^

Control and eradication 1^

Cultural control 1^

Chemical control 1^

Precautions __ ^1

Parasites and diseases 20

Literature cited 22

Washington, D.C. Issued December 1965

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C, 20402 - Price 15 cents
WILD GARLIC

Its Characteristics and Control

By Elroy J. Peters, J. F. Stritzke, and Frank S. Davis, Crops Research Division,

Agricultural Research Service ^

Wild garlic {AlUum vineale L.) is a troublesome weed in the

United States. Significant losses result from the "onion" odor and

flavor that wild garlic gives to milk, small grains, and meat products.

Other conunon names that have been used for Allium vineale L. are

field garlic, meadow garlic, garlic, onion, crow garlic, wild onion, and

vineyard garlic (5, 27),^

ORIGIN AND DISTRIBUTION

The geographical origin of wild

garlic is diflScult to determine. It

probably originated in the area of

the Mediterranean Sea {18),

Wild garlic is found in many

areas of the world. It has spread

^ Dr. Peters and Mr. Stritzke are at the

Missouri Agricultural Experiment Station ; Dr. Davis is at the Texas Agricultural Experiment Station.

This handbook was prepared in cooperation with the Field Crops Department,

Missouri Agricultural Experiment Station, and is published with the approval

of the director. (Journal Series No.

2731.)

throughout western and central

Europe where it is found as far

north as southern Norway, Sweden,

and Finland; and east to the

Dneiper, Crimea, and Transcaucasian regions of the U.S.S.R. (Í5,

31),

It is rare in Austria ; fairly common in Hungary, Italy, Spain, and

Portugal {12) ; and has been reported in North Africa and the

Canary Islands {12), Wild garlic

has spread from Europe to Aus-

^ Italic numbers in parentheses refer to

Literature Cited, p. 22.
tralia (2), New Zealand {36}, and

the United States. Is is particMilarly troublesome in Sweden, England, and the United State« (13, 20,

27, 28),

Wild garlic was probably introduced into the United States from

France in the 17th or early pari: of

the 18th century {3,15). After its

introduction into the United States,

it became a serious weed problem.

Pipal cited a report showing that as

early as 1754, in Philadelphia, an

infestation of wild garlic in a

wheatfield w^as so heavy that one

garlic head was present for every

nine heads of wheat {28).

Wild garlic has continued to

spread and now infests a large part

of the United States. It grows as

far south as Georgia, Mississippi,

and Arkansas ; and as far north as

Massachusetts, New York, Ohio,

and Michigan {10), It is a serious

pest on the eastern seaboard and

extends west to Kansas and Oklahoma {30). Wild garlic has been

mentioned as the cause of garlicflavored milk in Wyoming {6).

Infestations also are present in

western Oregon and Washington.'^

PLANTS THAT RESEMBLE WILD GARLIC

In the United States, wild garlic

sometimes grows in association with

other bulb formers such as Omithogahim mnbeJlatum L., AJlhim oleTdceum L,, A. cernuuinx Roth, A.

Tïiutahïle Michx., A, canadense L.,

Hemerocallis fulva L., and Zigadenus Nuttallii Gray.

The terms "wild garlic" and

"wild onion" are often used interchangeably for many of the bulb

formers. In the United States, the

species most commonly found with

wild garlic are wild onion {A, canadense L.) and star-of-Bethlehem

{Omithogolum unnbellatuni L.).

The wild onion, like wild garlic,

begins growth in mid-August or

early September and matures in late

May or early June. Wild onion

grows 1 to 2 feet tall. It has flat

leaves (fig. 1, 5), which arise from

the base of the plant.

Star-of-Bethlehem often is planted as an ornamental and then

spreads to lawns, gardens, yards,

and waste places. It begins growth

soon after the ground thaws in

early spring. Small, showy white

flowers appear, and then the plants

mature and disappear before warm

weather. Star-of-Bethlehem seldom grows over 8 inches tall. It

has flat leaves, which have a white

stripe down their center (fig. 1, A).

The leaves arise from the base of

the plant.

Wild garlic can be distinguished

from wild onion and star-of-Bethlehem by its striate, nearly round

hollow leaves (fig. 1, C), which are

attached at the lower half of the

plant. Wild onion and star-ofBethlehem have their solid flat

leaves attached at the base of the

plant. Moreover, wild garlic has

underground hardshell bulbs, which

are absent on wild onion and starof-Bethlehem. Also, the old bulb

coat of wild garlic is thin and membraneous, but the coat of wild onion

is fibrous matted. Star-of-Bethlehem does not have the "onion" odor

of wild garlic or wild onion.

^ Personal communication from Dr.

Marion Ownbey, Dept. of Botany, Wash.

State Univ.
\

Figure I.—Cross sections of leaf blades of star-of-Bethlehem, wild onion, and wild garlic: A, Leaf

of star-of-Bethlehem showing white striation at the center of the solid flat leaf; B, flat solid leaf

of wild onion; C, round, hollow leaf of wild garlic.

DESCRIPTION AND GROWTH HABIT

Classification

Wild garlic is a bulbous perennial

monocot that has classically been included in the Liliaceae family.

However, Hutchinson (i^) includes

Allium in the Amaryllidaceae family. He considers the umbellate

inflorescence to be of greater taxonomic importance for classification

than the character of superior or

inferior ovary, wliich is usually

used to distinguisli Liliaceae from

Amaryllidaceae. His views have

been supported by other workers

(5, 26); and at present (1965) it

appears that Allium will eventually

be classified as belonging to the

Am^aryllidaceae family.

Five varieties or forms of Allium,

vineale L. have been described in

the United States {15). These are :

{a) forma ty2)icum Beck, with a

loose umbel containing both aerial

bulblets and flowers; (6) forma

comfactum Thuill, with a compact

head consisting only of aerial bulblets, which are greenish or whitish ;

(c) forma fuscenscens Ascherson

and Graebner, with a head containing reddish bulbils; {d) forma

crinitum Jacob, with bulbils on the

head tipped with long, green, capillary appendages; and (e) forina

capsidiferum Koch, with a umbel

consisting of flowers only.
Three forms of wild garlic have

been identified in England, but

their status as varieties has been

questioned by Richens (31). Transitions between forms are often

noted, and they appear to be dependent upon Mendeli an allelic

genes {15). Most AlUuni species

have 16 chromosomes, but Allium

vineaJe L. has 32 chromosomes, a

number that indicates that A.

vineale L. is tetraploid {15). Apogamy is a common occurrence in A.

vineale.

Iltis {15) also observed what he

thought to be genetic differences in

color of aerial bulblets. Seed from

plants with purple bulblets produced plants with purple leaf

sheaths and seed from plants with

green bulblets produced plants with

green leaf sheaths.

Structure of the Wild Garlic

Plant

Wild garlic looks much like the

cultivated onion. Figure 2 shows

a clump of wild garlic as seen in

spring. The leaves are two-ranked

and have sheathing bases. The leaf

blades are circular in cross section

and hollow.

The outer layers of a bulb of a

growing wild garlic plant are

formed from the sheathing bases of

the foliage leaves.

Plant Types

Wild garlic consists of two plant

types—scapigerous and nonscapigerous. The larger, scapigerous

plant bears a scape, which produces

aerial bulblets (fig. 3) and sometimes flowers (fig. 4).

The flowers have a greenish to

purple perianth with lanceolate to

elliptic segments. The segments

are obtuse to acutish and about as

long as the stamens {10). Seeds of

the scapigerous plant are black,

flat on one side, and about oneeighth inch long.

The nimiber of scapigerous

plants in a wild garlic stand varies.

Under conditions in the British

Isles, Richens observed that about

30 percent of the wild garlic population consists of scapigerous plants

in any one season {31). The rest

of the population was made up of

nonscapigerous plants (fig. 5),

which are shorter and less conspicuous than the scapigerous

plants.

Figure 2.—A typical dump of wild garlic in the

spring, showing growth habit and plants of

various sizes. The larger upright plants are

«capigerous and the smaller plants are nonscapigerous.
Nonscapigerous plants have slender foliage and fewer leaves, and

do not produce a scape at the end

of the growmg season.

Bulb Types

Four types of bulbs can be found

on wild garlic at the end of a season's growth in late spring. Various names have been given to the

bulb types. The system of nomenfigure 3.- -Scapigerous garlic plant as seen at

maturity in June.

clature suggested by Davis and

Peters (7) will be used in this

publication.

Aerial Bulblets

As many as 300 aerial bulblets

(fig. 6, Ä) may be formed on the

scape of a scapigerous plant (fig.

3).

The bulblets develop within a

spathe (a large, dry, thin, membranous bract) at the top of the

scape. The spathe contains no

green color and it remains closed

imtil near maturity in late springwhen it bursts, exposing aerial

bulblets and flowers.

The aerial bulblet consists of a

fleshy, cone-shaped scale containing

a growing point at its base. The

fleshy scale is a bladeless storage

leaf. Surrounding the storage leaf

is a protective scale consisting of

two or three cell layers. The protective scale is a bladeless leaf in

most cases, but it may include a

blade, which was referred to by Iltis

(15) as an appendage.

Iltis (15) describes three forms

of aerial bulblets found in Virginia,

each form appearing in a separate

head. One form of bulblet is whitish or yellowish with pointed,

greenish, or purple tips that are

bent slightly to one side. The second form is dark purple without

appendages. The third form of

bulblet has green appendages, which

are 2 to 3 inches long. The appendages, or leaf blades, are usually fully

developed within the spathe before

it bursts.

We have observed appendages on

aerial bulblets of wild garlic in

Missouri, and the bulblets appear

much like bulblets that have germinated. However, close observation

shows that the appendage is the leaf

blade of the outer protective leaf

of the aerial bulblet.
v**» *^^ ^

figun 4.—Umbels on scapes of wild garlic. The umbel on the left is a double umbel (single

umbels are more common but plants may have as many as three or four) with aerial bulblels

only. Umbel on the right contains bulblets and flowers (less common).

Hardshell Bulbs

The second most numerous type

of bulb is the hardshell bulb (fig. 6,

B). These bulbs are larger than

aerial bulblets. Hardshell bulbs

have a single bladeless storage leaf,

which contains a growing point at

its base. The storage leaf is surrounded by a bladeless leaf, which

forms a hard protective shell.

Hardshell bulbs are formed underground in the axils of the outer

leaves of scapigerous and nonscapigerous plants (fig. 7).

The hardshell bulb is the only

bulb type that is produced by both

the scapigerous and the nonscapigerous plants.

Central Bulb

The central bulb (fig. 7, B) is

formed underground by nonscapigerous plants and is conspicuous at

the end of a season's growth. It is

formed aromid the main axis of the

plant. The central bulb is circular

in cross section (fig. 6, C) and varies

from the size of an aerial bulblet up

to that of a soft offset bulb.

Its structure is similar to that of

other bulb types. However, it

sometimes does not have an outer

protective scale and is surrounded

only by the withered bases of foliage leaves. If the outer scale is

present, it is prolonged into a sharp

terminal point.

Soff Offsef Bulb

The soft offset bulb (fig. 7, Z>) is

formed undergroimd in the axil of

the innermost leaf of the scapigerous plant. It is similar in structure to the other bulb types and

usually is the largest of the four

types. It is ovate in longitudinal

section and has a convex abaxial

face and a flat adaxial face, which

form two distinct ridges where the

faces meet (fig. 6, Z>). The ridges

tend to clasp the sides of the flattened scape to which they are

attached.
Figure 5.—The nonscapigerous plant as seen af maturity in May. These p|ants usually mature

about a month earlier than the scapigerous plants.

784-31» 0^-65-

^
figure 6.—The four bulb types of wild garlic: A, aerial bulblet; B, hardshell bulb; C, central

bulb; and D, soft offset bulb.

figure 7.—Left: Longitudinal section of the base of a mature nonscapigerous plant showing

lA) the hardshell bulbs and IB) the central bulb. Right: Longitudinal section of the base of

a mature scapigerous plant showing the positions of IC) hardshell bulbs and (0) a soft offset bulb.

REPRODUCTIVE CYCLES

Figure 8 shows the reproductive

cycles of wild garlic.

Each type of bulb is capable of

producing either a scapigerous or

a nonscapigerous plant. The non10

scapigerous plant produces one central bulb and sometimes one or two

hardshell bulbs at maturity. The

scapigerous plant produces both

seed and aerial bulblets above
ground plus one soft offset bulb

and one to six hardshell bulbs below

ground.

Production of seed is insignificant

in most garlic habitats, except near

the southern limits of its range in

the United States, where wild garlic

may produce abundant viable seed

{15, 32). In Virginia and Delaware, for example, seed production

is common (7,15). When seeds are

produced they usually are viable

(13,15). Garlic seeds are produced

in the spring and germinate the following fall. Seedlings evidently

are uonscapigerous; they develop

only one small bulb during the first

year (Í5).

Wild garlic is usually spread by

bulbs rather than by seeds. Aerial

bulblets are more numerous than

other bulb types and, therefore, are

responsible for most of the dispersion of wild garlic.

Aerial bulblets that complete

growth in spring (May and June)

sprout the following fall. Plants

developing from aerial bulblets may

Seed

NONSCAPIGEROUS

PLANT

1 central 1 to 2

bulb hardshell

bulbs

SCAPIGEROUS

PLANT

1 to 6

hardshel I

bulbs

Seeds in

certain oreas

J

20 to 300

aerial bulblets

I soft

offset

bulb

Figure B.—Relation between bulb types, seed, and plant types in the reproductive cycles of wild

garlic. The bulb types will give rise to either a scapigerous or a nonscapigerous plant. These

plants grow during the winter and terminate their growth in late spring or early summer.

Reproductive structures formed by each type of plant are indicated by arrows from each plant.

The number of structures formed on each plant is indicated above the name of the structure.

11
produce scapes {19), but they usually produce nonscapigerous plants,

which develop only leaves above

ground.

The growth of the nonscapigerous plant is unique because it terminates a season's growth with the

formation of one central bulb containing a stem apex and sometimes

two hardshell bulbs in the axils of

the foliage leaves (fig. 7). In

Missouri, development of central

bulbs first becomes apparent in early

winter and development of hardshell bulbs usually becomes apparent in February or March. Figure

9 shows a longitudinal section of

the basal portion of a nonscapigerous plant as seen in April.

Plants developing from aerial

bulblets may, in some instances, produce a scape, a soft offset bulb, and

hardshell bulbs in one season.

Freeman (11), in Kentucky, found

that about 33 percent of the plants

from aerial bulblets produced scapes

the first year.

Iltis {16), in Virginia, and Pipal

{28), in Indiana, have reported that

plants growing from aerial bulblets

develop secondary bulblets at the

base of primary bulblets in the fall,

and the secondary bulblets grow

into separate plants during the

winter.

A development similar to this was

described, but was shown to be

growth from two bulblets located

close together within the same

covering leaf (^5). Observation in

Missouri has shown that frequently

two bulblets can be found within

the same covering leaf, giving the

impression that only one bulblet is

present.

Figure 10 shows the developmental stage of the scapigerous

plant in April.

The first bulbs developed in the

scapigerous plant are the hardshell

bulbs, which form in the axils of

the outer foliage leaves. Growth of

figure 9.—Longitudinal section of the base of

a nonscapigerous garlic plant on April 15

showing the origin of the central bulb lA)

and the hardshell bulb (B).

the scapigerous plant is terminated

with the formation of the spathe

on the plant axis and the formation

of one soft offset bulb in the axil

of the innermost foliage leaf (fig.

10, B).

Central bulbs and soft offset

bulbs start sprouting in early fall.

These bulbs usually produce large

plants, three-fourths of which produce scapes {11)-

Central bulbs, soft offset bulbs,

and aerial bulblets sprout during

the fall of the year in which they

are formed. But only 25 to 40 percent of the newly formed hardshell

bulbs sprout in the fall of their

first year. The rest of them are

12
figure 10.—Longitudinal section of the base of a scapigerous garlic plant on April 15 showing

the origin o< the scape (»), soft offset bulb (B), and hardshell bulbs (C).

controlled by a dormancy mechanism that releases them m the fall

of subsequent years; some may remain dormant for 6 years (33).

Sprouting of hardshell bulbs

starts in mid-August or early September and nearly ceases by October or November. Our studies in

Missouri showed essentially no

sprouting after November. However, many shoots of sprouted bulbs

did not emerge from the soil until

spring. Freeman and Kavanaugh

(12) and Mitchell and Sherwood

(^) reported that wild garlic was

observed emerging from the soil in

March and April.

Freeman (11) found that about

two-thirds of the plants produced

from hardshell bulbs were nonscapigerous their first year.

The mechanism that determines

whether a bulb produces a scapigerous or a nonscapigerous plant is

not known. It is thought that plant

type is determined in the early

13
development of the plant {31)^ and

that it is associated with food reserve in the bulb. Planting of soft

offset and central bulbs at depths

of 4 inches or more reduces the

number of scapes formed from

these bulbs {21), All plants from

bulbs planted 2 inches deep produced scapes, but only 76 percent

of the plants from bulbs planted 4

inches deep produced scapes. Increasing the depth of planting to

8 inches decreased the percentage

of scape-producing plants to 52 percent. This indicates that food reserves are consumed in emergence,

and plants growing from great

depths cannot replenish their food

reserves and produce scapes.

WILD GARLIC: A PEST

Wild garlic contains allyl sulfide,

which has a disagreeable odor and

imparts a garlicy flavor to agricultural products tainted with it.

Wild garlic is a poor competitor

and, therefore, generally does not

reduce crop yields, but it often persists under row-crop culture.

Because wild garlic is drought

hardy, cold hardy, and tolerant to

wet soils, it is found on poorly

drained land along rivers and

creeks, as well as on hillsides (25,

31), Wild garlic grows in many

types of soil (Í7), but it is best

adapted to heavy soil (31).

Pest in Small Grains

Wild garlic is a pest of fallplanted crops and is especially

troublesome in small grains, which

have a growing season similar to

that of wild garlic.

Aerial bulblets are present when

small grains ripen and often are

harvested with the grain. Harvesting bulblets with wheat that is used

for flour is particularly objectionable because the bulblets taint the

flour. Products made from garlicy

flour usually have a garlicy flavor.

Wheat is graded garlicy when

two or more green aerial bulblets, or

an equivalent of dry or partially

dry bulblets, are present in 1,000

grams of wheat {35).

Aerial bulblets also have a high

moisture content; when they are

harvested with wheat their moisture

adds to the problems of milling the

wheat.

Because wheat kernels and aerial

bulblets are similar in size (fig. 11),

the fresh bulblets cannot be removed

from the wheat with conventional

grain-cleaning equipment.

A garlicy odor often remains in

wheat even when the bulblets are

removed from it.

However, if wheat containing

aerial bulblets is stored for 6

months, the bulblets generally will

be dry enough to remove with a

fanning mill {27).

Artificial heat also has been used

with some success for drying bulblets in wheat {28).

Aerial bulblets float when wheat

containing them is immersed in

water, but the wheat then has to be

dried. Drying makes the largescale use of the immersion technique

of removal impractical {27).

Investigations have been made to

determine the effects of storage on

germination of wheat containing

aerial bulblets {16). It was found

that germination of wheat is not adversely affected by 7 months of storage, and that most aerial bulblets

are no longer viable after 7 months

of storage. In one test, however,

14
some aerial bulblets remained viable

for about 2 years {16).

Attempts to destroy the viability

of aerial bulblets in wheat by rollinj^

(crushing) also have been made

{16). One rolling did not afl'ect

sprouting and two rollings only

slightly reduced sprouting of aerial

bulblets.

Pest of Pastures and Hay

Fields

Losses due to wild garlic probably are greatest in the dairy industry. Milk from cows grazed on

garlic-infested pastures has offflavors. A small amount of garlic

in the ration of dairy cows taints

dairy products made from their

milk.

Arbuckle (.|) stated that garlic

was the main cause of off-flavor in

milk in Maryland.

Many authorities believe that removing cattle from garlic-infested

pastures for 3 or 4 hours before

milking reduces or eliminates the

flavor in milk {4,6,27). But Pipal

{28) stated that off-flavor persisted

in milk for several days after dairy

cows were removed from garlicinfested pastures. lie also rei)orted

that cattle grazed on wild garlic

had garlic-flavored meat. In one

case, the garlic flavor persisted in

the meat of a cow that had been removed from a garlic-infested pasture 10 days before slaughter. Because of garlic infestations, many

pastures cannot be used in fall or

spring when the garlic is growing.

Pest Around Homes and in

Noncrop Areas

Wild garlic is unsightly around

homes and gardens, on roadsides,

and in noncrop areas.

It also gives lawns a disagreeable

odor. When heavily infested

lawns are mowed, garlic odor becomes intense in the general area

of the lawn, on the mower, and on

the clothes of the person mowing

the lawn.

Populations of wild garlic build

up in lawns, gardens, and waste

areas where they serve as sources of

infestations to adjoining areas.

Figure M.—A, Grains of wheat. B, Aerial bulblets of wild garlic showing the similarity in size.

15
HOW WILD GARLIC SPREADS

Wild garlic spreads from one

place to another mainly through

movement of bulblet-infested small

grains, hay, straw, and manure.

But all types of bulbs can be

spread in soil moved during construction of buildings, ponds, terraces, and roads.

Garlic infestations in lawns most

often are the result of planting infested sod, but infestations may

also result when infested soil is used

for fill or when building is done on

a garlic-contaminated site.

Spread of wild garlic seed and

aerial bulblets by wind is of minor

significance. Spread of aerial

bulblets by water, on the other

hand, probably accounts for widespread infestations on lands subject

to flooding.

CONTROL AND ERADICATION

Where a few plants of wild garlic are found, eradication can be obtained by removing the plants and

all underground bulbs. Because

garlic bulbs are not killed by uprooting, they should be burned or

destroyed by some other method

that will kill the growing points.

Where wild garlic infestations

are extensive, eradication is difficult. Central bulbs, soft offset

bulbs, and aerial bulblets will germinate during the fall of the year in

which they are formed, and most

of these plants can be killed by repeated tillage or with several applications of herbicides. However,

hardshell bulbs that remain dormant in the soil for as long as 5 or

6 years will continue to reestablish

the garlic stand (5).

This means that tillage and herbicide treatments would have to be

continued for at least 6 years to

eradicate wild garlic.

Cultural Control

Wild garlic is not easily killed by

tillage because it possesses a great

deal of food reserves and is able to

reestablish itself and resume

growth after tillage. Lazenby

{23) evaluated the effects of tillage

and disturbance on wild garlic

growing in England. He found

that plants with large bulbs remained green for 7 weeks when allowed to lie on dry soil exposed to

high temperatures. The more frequently the plant was disturbed, so

that it broke contact with the soil,

the more the size of the plant was

reduced.

Eepeated pulling and replanting

of growing plants reduced the number and size of underground bulbs

{23). Plants that had originated

from aerial bulblets were stimulated by one pulling in mid-March

and increased in size. Uprooting

the plants every 2 weeks and immediately replanting them over a

4-month period did not kill the

plants, but yields of the underground structures were reduced.

The date on which a disturbance

took place influenced the ability of

the plant to recover {23). When

disturbed on March 15, plants originating from aerial bulblets remained green for 4 to 5 weeks before death; but during this time

food reserves were exhausted in the

production of new bulbs. Plants

16
disturbed in April or June immediately transferred their food reserves into a small bulb varying

from one-half to three-fourths of

the size of the original bulblet.

Soft offset bulbs and central

bulbs lying on the soil surface for

2 weeks began to shrivel, but some

of these bulbs ^yere still viable after

2 months {23). Hardshell bulbs

attached to the dried soft offset or

central bulbs seemed to persist.

Wild garlic bulbs are also able to

tolerate deep planting; and soft

offsets and central bulbs often

emerge from a depth of 16 inches

(21). Deep planting, however, reduced the number of offsets and

scapes produced on all bulbs. All

plants from soft offsets and central

bulbs planted at a depth of 2 inches

or less produced scapes, but the percentage of scapigerous plants that

were produced decreased as depth

of planting increased. Deepplanted hardshell bulbs had fewer

scapes and offsets than shallowplanted bulbs, but, in addition,

length of dormancy of hardshell

bulbs increased as the depth of

planting increased. Nearly all

hardshell bulbs left on the soil surface or planted V2 ^'^^^ deep

sprouted after 2 years, but when

planted at depths of 8 and 16

inches, half of them remained dormant (^i).

Because aerial bulblets are smaller

than other bulbs they do not have

the food reserve to emerge from

great depths. There was a large reduction in the number and weight

of reproductive structures on plants

developed from aerial bulblets

planted at a depth of 4 inches or

more (21).

Experiments show that time of

tillage is important and that tillage

should be repeated each time new

growth appears. Eepeated tillage

is necessary to reduce reproduction

of bulbs because the wild garlic

plant, even when disturbed, is able

to translocate material to new bulbs.

Deep plowing is only partially effective because wild garlic can sprout

and grow from great depths.

Tillage should be done after

emergence because tillage before

plant emergence merely redistributes bulbs and does nothing toward

control. This principle was recognized by Tinney (33), who recommended an annual plowing in

November for 6 years followed by

frequent cultivations in spring.

Frequent tillage gradually exhausts

food reserves and if continued long

enough eventually prevents reproduction of underground bulbs.

An immediate effect of tillage is

to prevent the production of scapes

bearing aerial bulbs.

Deep plowing in fall to completely bury garlic plants followed

by shallow plowing in the spring

has been recommended in Illinois

and Indiana (^7,^5). Clean tillage

during spring and summer following plowing was then recommended.

Talbot (32) recommended the

growing of row crops that could be

tilled to cut off the garlic plants.

Lazenby (22) showed that time

of tillage for planting cereals had

important effects on garlic. Tillage

for spring cereals reduced the number of plants, the number of hardshells, the number of plants bearing scapes, and the size of central

bulbs and soft offset bulbs compared

with tillage for fall-planted grains.

Wild garlic apparently had not

used much of its food reserves at

the time of fall tillage and was thus

able to recover.

The effects of competition on wild

garlic was studied by Lazenby {19^

20). 'Ryegrsiss (LolmmmuUiflorum

and L. perenne) sown with aerial

bulblets did not affect the establishment of wild garlic, but competitive

effects of the ryegrass later reduced

the growth rate of wild garlic and

reduced the weight of its underground parts to one-fifth of those

17
grown alone {19), Competition

from wheat reduced the size of

garlic plants and the weight of

their underground parts {20).

After 7 years of competition from

Phalaris tuberosa, wild garlic lost

its vigor, and the plants grew only

3 inches tall and failed to produce

scapes {3),

Frequent mowing, beginning in

April, reduced the size of garlic

plants and the weight of their underground parts {2It). Close cutting was more injurious to garlic

than high cutting. Cutting in April

was more effective than cutting in

June.

Chemical Control

Because of the difficulty of controlling wild garlic with cultural

methods, much attention has been

given to the possibility of chemical

control. Control of wild garlic

with chemicals has been attempted

for at least 60 years. In the early

1900's crankcase oil, carbolic acid,

sulfuric acid, fuel oil, orchard heating oil, sodium chloride, and sodium

aresenite were tried on wild garlic

{28), These materials were unsatisfactory because they killed the

associated crop.

Although the effects of tillage

have not been directly compared

with the effects of modern-day

herbicides, the nature of herbicide

activity indicates that herbicides are

more effective than tillage {9),

Plants of wild garlic treated with

2,3,6-TBA (2,3,6-trichlorobenzoic

acid) or 2,4-D (2,4-dichlorophenoxyacetic acid) were killed, and the

hardshell and soft offset bulbs attached to the plants usually showed

growth modifications and often

were killed {9), Central bulbs were

more frequently killed than other

bulb types. Herbicides evidently

were translocated through the

plants to the underground reproductiv^e parts.

Many herbicides have been evaluated for use on wild garlic. Dalapon (2,2-dichloropropionic acid),

TCA (trichloroacetic acid), MCPA

(2 - methyl - 4 - chlorophenoxyacetic

acid), amitrole (3-amino-l,2,4-triazole), 2,4,5-T (2,4,5-trichlorophenoxyacetic acid), MH (maleic hydrazide), 2,4-DB [4- (2,4-dichlorophenoxy) butyric acid], and dicamba (2-methoxy-3-6-dichlorobenzoic

acid) have given some control. The

suggested rates and effectiveness of

herbicides vary from location to location. None of the herbicides

available in 1965 will eliminate wild

garlic in a single application. Even

when tops of garlic plants are killed

complettíy, viable hardshell or soft

offset bulbs often remain in the soil

and the garlic stand is not eradicated {8\. Raleigh {29) reported

germination of soft offset bulbs

after 3 successive years of top kill

with 2,4-D.

Davis et al, {9) evaluated a number of herbicides and showed that

15 pounds per acre of dalapon, 6

pounds per acre of MH, 6 pounds

per acre of amitrole, 4 pounds per

acre of 2,3,6-TBA, and 2 pounds per

acre of 2,4-D gave reasonable control of wild garlic. In this study,

the ester of 2,4-DB at 4 pounds per

acre gave fair control of wild garlic.

Because of low rates of application needed for control (1 to 2

pounds per acre) and relatively low

cost, 2,4-D has been investigated

extensively. The esters of 2,4-D

have been more effective than the

amines, perhaps because the esters

penetrate the wax on wild garlic

leaves better than do the amines.

Time of herbicide treatment influences the amount of kill obtained

on wild garlic. More garlic plants

receive treatment when herbicide is

applied after March 15 than when

applied earlier, because wild garlic

begins to emerge in late summer

18
and continues to emerge until

March 15 (ü). However, early

treatments will kill wild garlic

plants before new bulbs have been

developed in the axils of the lower

leaves. Formation of new bulbs

usually becomes apparent sometime

in February. Well-developed

bulbs often survive when the old

plant to which they are attached

has been killed by herbicides (5).

Growth modifications of new bulbs

that occur after 2,4-D or 2,3,6-

TBA has been applied indicated

that these herbicides are translocated from the old plant to the

new bulbs. Many of these bulbs

with growth modifications will

grow and reproduce (8). In the

case of 2,3,6-TBA, time of application may not be as critical as with

2,4-D because 2,3,6-TBA remains

in the soil for some time and is

probably absorbed over a period of

time by the root system of the garlic

plants; thus plants that are not up

at the time of a fall application of

2,3,6-TBA will not receive a foliage

application, but the herbicide may

be absorbed by the roots of the

garlic plant.

Chemical Control ¡n Turf

Of the herbicides available in

1965 only 2,4-D, 2,4-DB, 2,3,6-

TBA, and dicamba should be considered for use on turf. Dalapon

and TCA are general grass killers

that will kill turf grasses. Amitrol discolors grasses, and MH has

an inhibitory effect on growth of

grasses.

Annually repeated applications

of low-volatile esters of 2,4-D or

amine salts of 2,4-D at 1 to 2

pounds per acre will control wild

garlic. The addition of a detergent

or wetting agent to the spray solution may improve the wetting of

garlic leaves and cause more herbicide to enter the plants and give

better control. For best results,

spraying should be done in November or early December and repeated

in Februaiy or March. Sprayings

will have to be repeated twice

yearly for at least 2 years to give

control and for 5 years or longer to

approach eradication. Where legumes such as white clover are present in the turf, 2,4-DB may be substituted for 2,4-D to avoid killing

the legume. However, 2,4-D is

more effective on garlic.

If trees or shrubs are present on

garlic-infested lawns, herbicides

should be carefully applied so that

they do not come in contact with

the trees and shrubs. Spraying on

windy days may cause particles of

spray to drift where it is not

wanted. Use of amine or low-volatile ester formulations will reduce

the amount of vapors and lessen

the hazard from this source.

D i c a m b a and 2,3,6-TBA are

equal to, and often are more effective than, 2,4-D for controllingwild garlic. Both of these herbicides persist in the soil and may

leach to the roots of woody ornamentals and injure or kill them.

For this reason, dicamba or 2,3,6-

TBA should be sprayed only on

areas beyond the root zone of

shrubs and trees. These herbicides

will also kill legumes.

Cheniical Confro/ m Pastures

On garlic-infested pastures, lowvolatile esters or amine salts of

2,4-D in repeated annual applications give good control. Time and

frequency of 2,4-D application are

similar to the suggestions for turf.

If the pastures are grazed before

spraying, the garlic tops may be

eaten or damaged so that little or

none of the garlic leaf surface will

remain. In these cases, the herbicide will not be received by the

leaves of the garlic plants and

translocated in maximum amounts

for good control.

If legumes are present in a garlicinfested pasture, 2,4-DB can be

19
Precautions

Some herbicides are poisonous to

man and animals. Read and follow

the directions on all herbicide labels

and heed all precautions.

Keep herbicides in closed, welllabeled containers in a dry place.

Store them where they will not contaminate food or feed, and where

children and pets cannot reach

them.

AA^oid repeated or prolonged contact of herbicides with the skin.

Avoid spilling herbicides on your

skm, and keep them out of the eyes,

nose, and mouth. If any is spilled

on skin or clothing, wash it off the

skin and change clothing immediately.

To protect fish and wildlife, do

not contaminate lakes, streams, or

ponds with herbicide. Do not clean

spraying equipment or dump excess

spray material near such water.

Avoid drift of herbicide sprays

to nearby crops and other desirable

plants.

Empty containers of poisonous

chemicals are particularly hazardous. Burn empty bags and cardboard containers in the open or bury

them. Crush and bury bottles or

cans.

substituted for 2,4-D, but the pasture should not be grazed for 30

days after spraying. 2",4-DB is less

effective than 2,4-D. Dicamba and

2,3,6-TBA are effective for control

of wild garlic in pastures, but pesticide regulations presently (1965)

do not allow the use of these materials in pastures.

Chemical Control in SmallGrain Fields

When wild garlic is present in

small-grain fields, 2,4-D ester at 1/2

or ^ pound per acre will usually

prevent grain from being graded

garlicy. This amount of herbicide

will not effectively kill wild garlic

plants, but the production of aerial

bulblets will be greatly reduced,

and the tops of the garlic plants

will be knocked down so that a

grain combine will pass over them

without picking up bulblets.

Fall-planted small gi^ain will be

injured if herbicide is applied in

the fall. Herbicides should be applied in the spring after the grain

has tillered but before rapid elongation or jointing of the stems occurs. Small grains are injured and

grain yields are reduced if herbicides are applied before tillering or

when the grain is in the boot stage.

Oats are most susceptible to 2,4-D

damage ; barley is moderately tolerant ; wheat is most tolerant.

Chemical Control in Waste

Areas

The proper herbicide to use ior

wild garlic control in waste areas

such as ditchbanks, drainageways,

and other noncrop areas is determined by the vegetation that is to

be maintained on the site. If

grasses are to be maintained on the

site, 2,3,6-TBA or dicamba at 2 to

4 pounds per acre, and 2,4-D ester

at 2 pounds per acre should be considered. Dicamba and 2,3,6-TBA

are more effective than 2,4-D, but

dicamba may slightly injure

grasses. MH or amitrole at 3 to

6 pounds per acre may also be used,

but slight to moderate injury to

grass can be expected. If the roots

of desirable trees or shrubs are

under the area to be treated, dicamba and 2,3,6-TBA should not be

used. The possibility of injury

from drift of herbicide sprays

20
should be considered when using

2,1-D. Dahipon at 4 to 8 pounds

per acre may be used in areas where

no grass is present or where retaining the existing grass is not

important.

PARASITES AND DISEASES

Although Avild garlic is grazed

readily, it is not seriously injured

by animals. We have found that

aerial bulblets on the soil surface or

other bulbs growing near the soil

surface may be eaten by field mice

when this rodent population is high.

Richens {31 ) reports that bulb tissue may be eaten by slugs {Agriollmonx agrestis L.), millipedes, and

nematodes ( AnguiUulina dipsaci

Kuhn). Widespread damage from

insect pests has not been reported

on wild garlic, but Freeman^ reported damage to soft offset bulbs

from the cabbage maggot.

At the Missouri Agricultural Experhnent Station, much damage to

soft offset bulbs was found during

the summer of 196-1: from insects

tentatively identified as the cabbage

maggot {Hylemya hrassicae

Bouche) and onion maggot {H.

Antiqua Meigen).

Several fungi have been reported

to attack wild garlic. Infestations

of Botrytis allii Munn. have been

observed in Missouri. Richens {31 )

^Personal communication from J. F.

Freeman, Kentucky Agricultural Experiment Station.

also reports Botrytis present in the

British Isles. The disease causes

deterioration and decay of the central and soft offset bulbs, and sometimes may^ attack immature hardshell bulbs. The hard coat of the

hardshell bulb may be a factor in

preventing invasion of the fungus.

The disease is distinguished by the

dark bluish color apparent at the

points of infection.

Richens {31) states that rotting

of young bulbs can sometimes be

caused by Pénicillium, and Fnsarium species. Sclerotium cepivorum

Berk also attacks the central and

soft offset bulbs of garlic as well as

immature hardshells {31), The infection is characterized by fine white

mycelium covering the surface of

the bulb. Later in the season, black

sclerotia fill th^ cavity left by the

rotting bulbs. Both Botrytis and

Sclerotium may attack the plant at

the same time. Leaf spot {Heterosporvuin allii Ell. and Mart.) has

been reported on wild garlic in

Delaware, Illinois, and New Jersey

The diseases cause serious damage

to garlic plants in small localized

areas, but the diseases do not become epiphytotic.

POCUOWTNB VMÊMK.

21
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1930. WILD GARLIC OR CROW GARLIC

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L. V.

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23

U.S. GOVERNMENT PRINTING OFFICE: 1965 O—784-319