CIRCULAR

163

SEPTEMBER

1968

CONTROL of CATERPILLARS ATTACKING CABBAGE

AGRICULTURAL EXPERIMENT STATION

AUBURN
E. V. Smith, Director

E.RS:IT/ UNIVERSITY
Auburn, Alabama

CONTENTS
Page
CATERPILLARS AND THEIR DAMAGE-3

THE

Cabbage Looper

------------------ ----- 3--4
5

Imported Cabbageworm------------Diamondback M oth

Larvae --------------------------

N atural Enem ies----------------------------------C O N T R OL -- - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - - - -

6

7

Fie ld T e sts - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - 8 Methods and M aterials___________________________
Results and

8

Discussion --------------------------- 10

Three-year Summ ary-----------------------------17
ACKNOW LEDGMENTS ------------------------------------- 18

FIRST PRINTING

3M,

SEPTEMBER

1968

Control of Caterpillars Attacking Cabbage
T. DON CANERDAY, Assistant Professor of Zoology-Entomology* F. S. ARANT, Head Professor of Zoology-Entomology

TMHERE

ARE SEVERAL different species of caterpillars that infest cabbage and other cole crops in the South. Those causing major damage are larvae of the cabbage looper, Trichoplusia ni (Hubner), imported cabbageworm, Pieris rapae (Linne), and the diamondback mbth, Plutella maculipennis (Curtis). Occasionally, the corn earworm, Heliothis zea (Boddie) and cutworms are problems. These caterpillars damage cabbage and other cole crops to the extent that yields of marketable crops and income to southern farmers are reduced in addition to the cost of insect control.

THE CATERPILLARS AND THEIR DAMAGE The cabbage looper, imported cabbageworm, and larva of the diamondback moth are the most important insect pests of cole crops in Alabama. These caterpillars are shown in Figures 1-3. Although feeding habits vary somewhat, damage by these three species is quite similar. On cabbage, they usually feed first on the outer leaves. If plants are attacked during early stages of forming heads, the head will be malformed or no head formed at all. In infestations of older plants, the larvae bore into the head and reduce or destroy market value of the product.
CABBAGE LOOPER

The cabbage looper, Figure 1, is usually the most destructive pest of cole crops. It occurs during most of the growing season and is often difficult to control with insecticides. When the larvae become large, it is almost impossible to control them.
Resigned.

FIG.

1.

Cabbage

looper larva,

pupa,

and adult.

Thdi U ilt(Il il " 4 e Urpish theX middle (dit ,the faint tUi-,ta

llan k(

lUap cX itl ilc(11 I)U(IX nIac I)(tr ?likeUUh)(i u XS.lhcisc

iltr a

Ii

at pr it 1 iitt'(iw ii?(SUi

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FIG. 2.

Imported

cabogeworm

larva

and

adults.

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I

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FIG.

3.

Diamonback

moth larvae,

pupa,

and adult.

Iii

1),ttltiiI)

(( c

il

wl ] ilt

unlri 'l

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4i

FIG. 4.

Parasitized

cabbage

looper.

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144

FIG.

5.

Cabbage

looper killed by

nuclear-polyhedrosis virus disease.

\

'~r ti

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11\ it

l H)!-o i c i

1

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FIG. 6.

Cabbage plants-one treated for caterpillar control, the other untreated.
5 1

the effectiveness of several chemical and microbial insecticides for control of caterpillars on cole crops. In 1964, an experiment was conducted at the North Alabama Horticulture Substation, Cullman. In 1965 and 1966, additional tests were conducted at Cullman, Chilton Area Horticulture Substation, Clanton, and the Auburn Horticulture Farm. Evaluations were made on spring-planted cabbage. Round Dutch cabbage plants were set 1 foot apart in 44-inch rows from late March to early April of each year. Plantings were fertilized and cultivated according to recommended horticultural procedures. Irrigation was used as needed to produce maximum yields. In general, plots were 3 rows wide and 25 to 50 feet long. In a few tests, single-row plots were used. All plots were replicated four to five times in a randomized complete block design. The center row in each plot was used as the sample row. Chemical and microbial insecticides in emulsion and/or suspension were applied with a knapsack sprayer at weekly intervals. Volume of finished spray material varied from 10 to 40 gallons per acre; however, 30 gallons were usually applied. Virus suspensions were prepared by grinding diseased larvae in water, counting the number of inclusion bodies (capsules surrounding the virus) and adjusting to desired concentration. Virus rates are expressed as larval equivalents (LE) per acre, i.e., number of particles per large diseased larva, utilizing 109 particles per larva as a standard. An emulsifying agent, Pylac, was added to virus suspensions at the recommended rate. Granular insecticides were applied by hand. Infestation counts were made weekly by recording the number of caterpillars on 2 to 10 plants per plot. Cabbages were harvested one to two times by cutting all firm heads on the sample row in each plot. These heads were counted and examined for insect damage. Heads with one or more feeding holes after removal of the wrapper leaves were considered unmarketable. In 1964, the cabbages from the Cullman experiment were sold to a local dealer and the actual monetary value of each treatment determined. Infestation counts alone were poor criteria for evaluating effectiveness of insecticidal control. The primary objective of caterpillar control on cabbage is to protect the edible head, and infestation counts represented the number of worms on the entire plant. Many larvae were found on the underside of the
[9]

outside wrapper leaves, and resulting damage was of little consequence if a given insecticide afforded protection to the cabbage head. Further, it is extremely difficult to direct spray material to the underside of these leaves. Therefore, infestation data were used primarily to assess population pressure, and degree of control was expressed in yields of marketable cabbage. Results and Discussion North Alabama Horticulture Substation 1964. Results of the experiment conducted at Cullman are summarized in Table 1. The first worm infestation was encountered May 22 and consisted primarily of diamondback moth larvae and imported cabbageworms. The populations of these decreased rapidly, even in untreated plots, and the cabbage looper became the predominant insect pest until harvest. The influence of these populations was reflected in yield of marketable cabbage, Table 1. Only 36 per cent of the heads harvested from the untreated plots were marketable, and the yield was valued at $126 per acre. Treated plots yielded 47 to 90 per cent marketable heads with a value ranging from $152 to $330
TABLE 1. YIELD AND VALUE OF CABBAGE FOLLOWING TREATMENT FOR CONTROL
NORTH ALABAMA HORTICULTURE SUBSTATION, OF CATERPILLARS,

CULLMAN,

ALABAMA,

19641

Treatment

Active per acre

Larvae per plant' CL DB CW No. 1.0 1.1 2.4 2.4 2.0 2.5 2.0 1.9 1.6 2.4 2.2 2.6 2.0 No. 0.2 0.2 0.3 0.3 0.3 0.2 0.3 0.3 0.3 0.3 0.4 0.3 0.4 No. 0.1 0.1 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.3 0.3 0.2

50-lb. bags of Mkt. cabbage mkt. cab/a. Pct. 90a 86a 73b 72b 60b-d 69bc 67bc 57bd 67bc 57bd 47de 54cd 36e No. 189a 186ab 165a-c 155a-d 143b-d 142cd 142cd 132cd 126cd 126cd 115d 110de 72e

Gross ross value per acre Dollars $331a 326ab 289a-c 271a-d 250b-d 249cd 249cd 231cd 221cd 221cd 201d 193de 126e

Lb. 0.50 Parathion........ 1.0 Endosulfan....... 2.0 CL 24055-....... 10 LE + Virus + 1 qt. Thuricide 90T_... 1.0 Naled 0.50 Parathion ...... 10 LE Virus 1.5 Malathion........ 2.0 Naled 1 qt. Thuricide 90T_... 0.5 Diazinon........ 0.5 Phosphamidon ... 0.0 Untreated check..

1 Means followed by the same letter do not differ significantly at the 5 per cent level. Duncans Multiple Range Test. 2 Seasonal average of cabbage loopers (CL), diamondback moth larvae (DB) and imported cabbageworm (CW). ' Applied every 2 weeks, others applied 6 times at weekly interval beginning May 22.

[10]

per acre. Plots treated weekly with 1/2 pound per acre of parathion, or 1 pound per acre of endosulfan, yielded significantly fewer damaged heads, percentage-wise, than other treatments. All treatments except diazinon afforded significant protection to cabbage from this looper population. Yield of marketable cabbage was increased by all insecticidal treatments except phosphamidon, Table 1. Microbial treatments, Thuricide and the looper virus, were as effective as any of the conventional insecticides except parathion or endosulfan. A high degree of protection resulted from CL 24055, an anti-feeding compound. This material did not act as a contact insecticide or a repellent to either larvae or adults; however, larval feeding was inhibited as shown by the yield of marketable cabbage, Table 1. 1965. Results of the experiment conducted at Cullman in 1965 are summarized in Table 2. Infestation trends were similar to those encountered the previous year. The imported cabbageworm was the dominant species during early-head formation and the cabbage looper was the major insect present during further development and maturity of cabbages. Infestations
TABLE 2. CONTROL OF CATERPILLARS ON CABBAGE,

HORTICULTURE

SUBSTATION,

CULLMAN,

NORTH ALABAMA ALABAMA, 1965

Treatment

Active per acre

Larvae per plant CW CL

Marketable cabbage

Lb. No. No. Pct. 1.0-4.0 0.5 0.4 100.0a ACy.-EIC' 0.6 100.0a GC 6506-................ 1.0 0.6 0.5 99.lab 0.3 1.0-0.25 Endosulfan E. Parathion__. 1.1 97.6ab 0.5 1.0 Endosulfan 1.1 97.lab 0.5 0.5 Azodrin 0.8 96.2ab 0.6 0.25 E. Parathion 95.5ab 0.3 0.7 2.0 Naled 95.3ab 0.5 0.6 0.5 Matacil 94.3ab 0.7 2.0-1.5 0.5 Carbaryl + Malathion..... 0.5 93.1ab 0.5 Malathion + virus-........ 1.5-10 LE 92.4ab 0.7 0.6 M. Parathion__ 0.75-0.37 Endosulfan 91.8ab 1.2 1.0 0.4 NIA 10242 91.Sab 0.9 0.5 0.5 E. Parathion 1.6 88.4ab 2.0 0.7 Carbaryl 0.9 85.9ab 0.5 1.5 Malathion 84.3ab 1.3 1 LE 0.5 Virus -................. . 0.6 80.9a-c 10 LE 0.4 . Virus ............. 68.5bc 0.5 0.7 1.0 GS 13005 1.4 36.4c 0.0 0.9 Untreated check 1 Seasonal average of cabbageworms (CW) and cabbage loopers (CL). 2 Means followed by the same letter are not significantly different at the 5 per cent level. Duncans Multiple Range Test. ' Materials were applied 4 times at weekly intervals. The first 2 applications of ACy-EIC were @ 4 pounds per acre.

+

+

[11]

were less intense than in 1964 although a similar percentage of the heads in the untreated check was damaged. As shown in Table 2, all insecticidal treatments including the looper virus afforded a high degree of control as measured by marketable cabbage. A high degree of caterpillar control was achieved in this experiment and all materials tested, excluding GS 13005, resulted in protection of 80 per cent or more of the heads. 1966. Insect infestations experienced at Cullman in 1966 did not follow the patterns recorded at this location the two previous years. The imported cabbageworm was the dominant species encountered. Although treatments were purposely delayed, only a light looper infestation developed, but pressure from the cabbageworm was rather intense, Table 3. Several insecticides provided a significant degree of caterpillar control although only two applications of insecticides were made prior to harvest. As shown in Table 3, plots treated with Azodrin, NIA 10242, endosulfan, Matacil, Thuricide, or Thuricide plus cabbage looper virus at 1 LE yielded significantly fewer damaged cabbage than the untreated plots. Malathion and virus alone and in combination failed to give adequate caterpillar control. This failure was partially a result of the ineffectiveness of malathion against late-instar larvae. Furthermore, the low rate of virus applied and inadequate time for virus incubation undoubtedly limited its effectiveness against the looper population.
TABLE 3. CONTROL OF CATERPILLARS ON CABBAGE, NORTH ALABAMA HORTICULTURE SUBSTATION, CULLMAN, ALABAMA, 1966

TreatmentActual Treatmentper acre Lb.
-1.0 Azodrin 1.0 NIA 10242 1.0 Endosulfan.. 1.0 Matacil 1 qt. Thuricide 90TS.......... 0.5 NIA 10242 Thuricide 90TS + virus--- 1 qt. + 1 LE 1 LE Virus Malathion + virus------- 1.5 + 1 LE 1.5 Malathion-0.0 Untreated check SMaterials

2 Larvae per plant CW CL

Marketable cabbage' Pct. 92.6a 90.9a 90.4a 88.5a 88.0a 84.lab 80.2ab 61.8b-d 44.6c-e 39.7de 15.1e

No. 0.9 1.0 1.1 0.9 1.2 0.6 1.2 2.5 1.4 2.1 3.6

No. 0.8 0.4 0.4 0.4 1.1 0.6 1.1 0.5 0.4 0.5 0.7

applied only two times, 6/8 and 6/15. SAverage number of cabbageworms (CW) and cabbage loopers (CL). 3 Means followed by the same letter are not significantly different at the 5 per cent level. Duncans Multiple Range Test.

[12]

Auburn Horticulture Farm 1965. Summarized results on control of caterpillars on cabbage at Auburn in 1965 are given in Table 4. An infestation of imported cabbageworms developed during early-head formation and the cabbage looper was of less importance until about onehalf of the heads were mature. The ratio of cabbageworms to loopers was approximately 3:1 in the untreated plots. Damage was heavy in plots receiving no treatment and less than 20 per cent of the cabbages were marketable. All insecticidal and microbial treatments provided a highly significant degree of control when compared with the untreated check. However, 20 to 30 per cent of the cabbages were damaged in plots receiving the more effective treatments. Endosulfan plus methyl parathion was the most effective material. Malathion plus virus was superior to either material tested alone. The virus was specific for the looper and malathion was more effective against the cabbageworm than the loopers. This resulted from the spectrum of effectiveness of both materials. Malathion, carbaryl, or virus alone failed to give an acceptable degree of caterpillar control, although they all reduced head damage below that of the untreated plots. A single application of virus at early-head formation was as effective as weekly treatments. 1966. The populations of cabbage caterpillars were dissimilar in 1966 to those encountered the previous year. The cabbage
TABLE

4.

CONTROL

OF CATERPILLARS

ON CABBAGE,

HORTICULTURE

FARM,

AUBURN, ALABAMA,

1965

Treatment Treatmentper

Active acre

Larvae per plant' CW CL No. 0.2 0.4 0.4 0.1 0.9 1.0 0.3 1.8 No. 0.4 0.3 0.6 0.5 0.8 0.8 0.6 0.6

Marketable cabbage 2 Pct. 80.5a 72.2ab 71.1a-c 51.0b-d 46.7cd 46.0d 42.7d 18.5e

Lb. Endosulfan + M. Parathion-1.0 + 0.5 -1.5 + 1 LE Malathion + virus 1.5 + 10 LE Malathion + virus 1.5 Malathion 10 LE Virus 8 10 LE Virus 2.0 Carbaryl 0.0 Untreated check

1 Seasonal average number cabbageworms (CW) and cabbage loopers (CL). 2 Means followed by the same letter do not differ significantly at the 5 per cent level. Duncans Multiple Range Test. This material applied only once on May 19, others applied 5 times from May 19 to June 14.

'

[13]

looper appeared earlier and was present throughout head mation. Infestation data from the untreated check showed a ratio of loopers to cabbageworms of approximately 2:1. As shown in Table 5, all materials applied as sprays reduced caterpillar damage when compared with the untreated check. Plots treated with endosulfan, 1.0 pound per acre; GC 6506, 0.5 pound per acre; Thuricide plus virus, 1 qt. and 100 LE per acre; or Matacil, 0.5 pound per acre, yielded to 100 per cent marketable cabbages. Treatments with the virus at 100 LE per acre afforded a high degree of crop protection; however, the virus applied in combination with malathion was no more effective than malathion alone. As in the previous year, one application of the virus at early-head formation was as effective as weekly applications. NIA 10242 applied as a sidedress in a granular formulation appeared to offer promise in caterpillar control. Other granular systemic insecticides failed to give any significant degree of control.

for-

foliar

95

TABLE

5.

CONTROL

OF CATERPILLARS

ON CABBAGE,

HORTICULTURE

FARM,

AUBURN, ALABAMA,

1966

Marketable Method of Active per acre applications1 cabbageLb. Pct. Endosulfan --------------1.0 Spray 100.a GC 6506----------------------------------0.5 Spray 100.0a Azodrin ---------------------------------------0.75 Spray 98.2ab Thuricide 90TS ± Virus 1 qt. + 100 LE Spray 95.9ab Matacil-------------------------0.5 Spray 95.7a-c Malathion----------------1.5 Spray 88.7b-f Malathion Virus-------------------- 1.5 + 100 LE Spray 88.6b-f CS 10128------------------1.0 Spray 75.4c-e Virus ----------------------100 LE Spray 74.8d-h CS 10133------------------1.0 Spray 74.3e-h 3
Treatment

---------

+

Virus ----------------------NIA NIA

10242------------------

100 LE 2.0

Spray Sidedress

62.5f -j

NIA 10242-----------------Thimet--------------------Bay. 37289-----------------Thimet

10242------------------

1.0 1.0
0.5

62.1g-1
52.Oh-k 34.6k-q
27.9k-s

Sidedress Sidedress
Sidedress

DiSyston-------------------Cygon ---------------------DiSyston -------------------UC 21149-----------------UC 21149-----------------Untreated check

---------------------

1.0
0.5

Sidedress
Sidedress

24.3n-s
21.4i-s

-------------

1.0 1.0 0.5 1.0 0.5
0.0

Sidedress Sidedress Sidedress Sidedress Sidedress

16.Oo-s 13.9q-s 11.3r-s 10.6p-e 6.5s
20.4m-s

x Sprays applied 5 times from May 27 to June 23; granular materials as sidedress, May 8. Means followed by the same letter are not significantly different at the 5 per cent level.

'Applied

once, May 27.

[ 14 ]

Chilton Area Horticulture Substation 1965. The cabbage looper was the dominant species of importance in this experiment, Table 6. Population density of the looper averaged approximately three caterpillars per plant and the cabbageworm was observed only occasionally. The influence of this population pressure is reflected in the low percentage of marketable cabbage in the untreated plots. Only 19 per cent of these were marketable, Table 6. All insecticidal and microbial treatments reduced caterpillar damage. American Cyanimid EIC was the most effective material tested in this experiment; however, it was applied at a high rate of 4 pounds per acre for the first three applications. Parathion, Matacil, endosulfan, or malathion plus virus protected 70 per cent or more of the heads. Virus alone and in combination with malathion was more effective than malathion alone. This apparently resulted from a high degree of looper control with the virus, whereas, malathion was relatively ineffective against this caterpillar. 1966. Caterpillar infestations in this experiment were similar to those encountered at the same location in 1965. Treatment was purposely delayed to permit a heavy looper population to develop, and the average number of loopers was 5.4 per plant in the untreated check plots, Table 7. Cabbageworms were present throughout the experiment but were of lesser imporTABLE 6. CONTROL OF CATERPILLARS ON CABBAGE, CHILTON AREA HORTICULTURE SUBSTATION, CLANTON, ALABAMA, 1965

Treatment

Active per acre Lb. 1.0-4.0 1.5 + 10 LE 1.0 1.0 0.5 10 LE 0.5 1.0 2.0 0.5 1.5 0.0

Looper larvae per plant No. 1.0 3.1 2.4 2.4 3.0 3.0 3.6 3.1 3.3 3.9 2.8 3.1

Marketable cabbage2 Pct. 99.1a 86.3b 77.5b 76.0b 71.3bc 68.6bc 67.8bc 50.7cd 48.2cd 41.8d 39.6d 17.3e

ACy-EIC Malathion ± Virus.......... Endosulfan.... Matacil Parathion Virus Matacil GS 13005 Carbaryl GS 13005 Malathion Untreated check

applied 4 times from June 3 to June 23, ACy-EIC applied at 4 pounds per acre June 3 and June 9. 2 Means followed by the same letter are not significantly different at the 5 per cent level. Duncan's Multiple Range Test.

'Materials

[15]

tance. The ratio of loopers to cabbageworms was greater than 5:1. The impact of this population pressure was reflected in the yield of marketable cabbage. The untreated plants were virtually destroyed - only 3.5 per cent were marketable, Table 7. Most of the materials tested failed to give an acceptable degree of control. Azodrin at 1 pound per acre was the only material that afforded adequate protection to cabbage against this heavy looper population. Data from this experiment serve to demonstrate the importance of starting a control program before heavy populations of caterpillars become established. This is especially important if loopers are the predominant pest. Mode of action of the virus is such that control of an established population cannot be achieved before crop damage occurs.
TABLE 7. CONTROL OF CATERPILLARS ON CABBAGE, CHILTON AREA HORTICULTURE
SUBSTATION, CLANTON, ALABAMA, 1966

per acre Lb. 1.0 Azodrin 1.0 Endosulfan 2.0 Carbaryl......... . 1 qt. Thuricide 90TS........ 0.75 Matacil Thuricide 90TS - virus 1 qt. + 1 LE 0.5 CC 6506-............. 0.2-2.0 Hercules 93264........ 1.0 GS 13005 1.0 SD 8447 1 LE .. V irus .............. 1.5 M alathion............. 1.0 GS 10128 virus..... 1.5 + 1 LE Malathion 1.0 GS 10133 0.0 Untreated check........

Active

Larvae per plant'

CW No. 0.4 0.8 0.4 0.4 0.4 0.6 0.3 0.4 0.4 0.3 1.3 0.5 0.7 0.5 0.3 1.0

Marketable

CL No. 2.5 2.9 3.3 6.6 5.5 3.1 3.6 4.3 3.4 4.6 3.9 4.0 7.0 5.8 4.2 5.4

cabbage' Pct. 90.0a 67.5a-c 64.0a-d 60.6a-d 59.3a-d 58.7a-d 52.3a-e 38.5b-h 30.0c-i 28.4d-j 26.1e-j 16.4f-j 12.9h-j 10.1g-j 7.8i-j 3.5j

+

applied 3 times, June 6-June 20. number of cabbageworms (CW) and cabbage loopers (CL). 3Means followed by the same letter are not significantly different at the 5 per cent level. Duncan's Multiple Range Test. 2 applications made at 0.2 pound per acre.

2Av.

1 Materials

'First

[ 16]

Three-Year Summary Seven small-plot field experiments were conducted at three locations in which 25 chemical and microbial insecticides were evaluated for effectiveness against caterpillars attacking cabbage. Several of these materials were tested at various rates and in various combinations. Both foliar and granular treatments were tested. Emphasis was placed on evaluation of the cabbage looper nuclear-polyhedrosis virus at various rates alone and in combination with malathion. The mean number of cabbage loopers in untreated plots ranged from 0.6 to 5.4 per plant in the seven experiments. The imported cabbageworm was present in all experiments and population levels ranged from a mean of 0.1 to 3.6 worms per plant. The impact of these populations was reflected in the damage to untreated plots. Yield of marketable cabbage was reduced 63 to 96.5 per cent where the crop was not protected. Larvae of the diamondback moth were occasionally observed but were of no significance in most experiments. Two to six weekly applications of one or more chemical or microbial insecticides or both reduced insect damage. Effective insecticides resulted in protection of 70 to 100 per cent of the treated crop. In general, the degree of protection, expressed as per cent marketable cabbage, was directly related to population pressure and number and timing of applications. Of the materials most extensively tested, endosulfan, 1.0 pound per acre or parathion 0.5 to 1.0 pound per acre, consistently afforded a high degree of control. These materials were considered as standards for comparing effectiveness of others. Chemical insecticides found to be generally as effective as the standards included Azodrin, General Chemical 6506, and Matacil. Niagara 10242 appeared to offer promise both as a foliar treatment and when applied in a granular formulation as a sidedress. Results with two microbial agents, Thuricide and the looper virus, were encouraging. Thuricide at one quart per acre was generally as effective as the standards when applied alone or in combination with the virus. Plots treated with virus alone yielded fewer damaged cabbages than the untreated plots in all experiments. However, the degree of control obtained with virus treatments was not considered economically acceptable in most tests. This is not surprising inasmuch as both cabbage loopers and imported cabbageworms were present in the plantings, and the virus is effective only against the looper. The virus
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applied in combination with malathion was as effective as the standard conventional insecticide when applications were initiated at early head formation. Further, a combination of virus and malathion was usually superior to either material applied alone. This was a result of the spectrum of activity of these materials. The looper virus was effective at 1, 10, and 100 LE per acre. One application of 10 or 100 LE per acre at early-head formation appeared to be as effective as weekly application. The residual effectiveness apparently resulted from a cyclic infection and inoculum liberation in a restricted area. It was concluded from these experiments that utilization of the virus as an insecticide is restricted by its host specificity. However, the virus can be of significant value when used in combination with an effective broad spectrum insecticide. The virus is slower in producing death than an effective chemical, but has merit in its safety. To ensure crop protection, applications must be made sufficiently early before crop maturity and before a heavy looper population becomes established because of the time required for the virus to establish a lethal infection. It is usually advisable to approach insect control in general on cole crops on a preventative basis. ACKNOWLEDGEMENTS Field experiments reported herein were conducted on the Substations of Auburn University Agricultural Experiment Station System at Clanton and Cullman and on the Auburn Horticulture Farm. The cooperation and assistance of C. C. Carlton, M. H. Hollingsworth, superintendents of these respective units, and their staffs, and J. L. Turner, Department of Horticulture, is gratefully acknowledged by the authors. Portions of the research were supported by grants from Geigy Agricultural Chemical Company; Hercules Powder Company; Niagara Chemical Division, Food Machinery and Chemical Corporation; and Shell Chemical Company.

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AGRICULTURAL EXPERIMENT STATION SYSTEM OF ALABAMA'S LAND-GRANT UNIVERSITY

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With an agricultural research unit in every major soil area, Auburn University serves the needs of field crop, livestock, forestry, and horticultural producers in each region in Alabama. Every citizen of the State has a stake in this research program; since any advantage from new and more economical ways of producing and handling farm products directly benefits the consuming public.

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Research Unit Identification *Main
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.

Agricultural Experiment Station, Auburn.

Tennessee Valley Substation, Belle Mina. Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman. Upper Coastal Plain Substation, Winfield. Alexandria Experiment Field, Alexandria. Forestry Unit, Fayette County. Thorsby Foundation Seed Stocks Farm, Thorsby. Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa ,County. Piedmont Substation, Camp Hill. Plant Breeding Unit, Tallassee. Forestry Unit, Autauga County. Prattville Experiment Field, Prattville. Black Belt Substation, Marion Junction. Tuskegee Experiment Field, Tuskegee. Lower Coastal Plain Substation, Camden. Forestry Unit, Barbour County. Monroeville Experiment Field, Monroeville. Wiregrass Substation, Headland. Brewton Experiment Field, Brewton. Ornamental Horticulture Field Station, Spring Hill. Gulf Coast Substation, Fairhope.