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Copyright 2005, Board of Trustees, University
CENTRAL FLORIDA EXPERIMENT STATION
ES f7-S Sanford, Florida
Minro Report CFES-5 July 18, 1967
SAUG 1 1967
CONTROL OF CABBAGE LOOPERS ON CAB AGE
The results shown in this report are not intended as insect control recom-
mendations but are compiled to indicate the performance of the materials tested.
Control of cabbage looper (Trichoplusia ni) larvae is nearly impossible
to obtain using currently recommended materials, particularly when larvae become
abundant. It has become necessary to test various new materials in hopes of
finding new control materials for this major insect pest of cabbage.
All materials used in these experiments were applied using a tractor-
mounted sprayer with a 3 row boom. Six nozzles were used for each row, two
nozzles directly over the row and two on each side of the plant. One of the
size nozzles was directed towards the top of the cabbage plants; the other
towards the base of the plants just above the soil surface. The tractor speed
was approximately 3 mph and 100 gal of water per acre were used at 250 psi
Data collected at harvest were the same for each experiment. The
rating system used was based on a scale ranging from 0 to 5 as follows:
O = no insect feeding, 1 = minor insect feeding on wrapper leaves, 2 =
moderate insect feeding on wrapper leaves with no head damage, 3 = minor
feeding extending to the head, probably unmarketable, 4 = moderate feeding
on both wrapper and head leaves with feeding scars on the head, 5 = severe
damage to wrapper and head leaves and considerable feeding on the head.
Twenty five heads were selected at random from the middle row of the 3 row,
50 ft long plot and rated. In each plot the first 8 plants were not sampled
to avoid plants where sprayer pressure was stabilizing.
Cabbage plants for this experiment were set in the field November 17 and
30, 1966. Four cabbage varieties were used, one for each replicate: A. Marion
Market, B. Market Packer, C. Badger Blue Boy, and D. Globe. Weekly applications
/ Assistant Entomologist, Central Florida Experiment Station, Sanford,
of each material were made from December 8 until February 14. The percentage
of the plants damaged was recorded January 12, 1967, and the final harvest
ratings March 1, 1967.
Table 1.- Cabbage looper damage readings
insecticides at Sanford during
and weights of plants
Per cent of
220 plants Harvest
Rate Pounds/ 2/ damaged rating % unmarketable/
Material (per acre) 100 heads- Jan. 12-67 Meansi heads
GC 6506 1#A/A 249 1.0 0.01 a 0
Azodrin 0.5#A/A 0.5 0.03 a 1
Matacil l#A/A 0.0 0.04 a 1
Azodrin 0.5#A/A 1.0 0.07 a 1
DuPont 1642 0.75#A/A 0.0 0.07 a 2
Lannate 1#A/A 235 0.5 0.09 a 2
Thuricide, 90TS 2 qt/A 250 1.0 0.11 a 2
Niagara 10242 1#A/A 0.0 0.18 a 3
Parathion & 0.5#A/A
Toxaphene 2#A/A 211 3.0 0.20 a 1
Thuricide, SS 2 qt/A 0.5 0.22 a 2
Guthion 0.75#A/A 242 0.0 0.24 a 4
Parathion & 0.25#A/A
Thiodan 0.50#A/A 235 0.1 0.33 a 8
Thuricide, SS 1 qt/A 2.0 0.35 a 8
TH 346-1 0.5#A/A 211 8.2 2.31 b 43
EP-316 1#A/A 105 6.4 3.13 c 64
Check -- 239 34.0 3.61 d 77
Check -- 36.0 3.71 de 82
Check -- 54.0 4.09 e 86
/ Two materials used in the plots are not included in this table. Thuricide
dust, was not effective and was discontinued. Temik, known to be ineffective
on looper larvae was used for aphid control in one plot.
2/ The LSD at the 5% level was 60 pounds. Weights were taken only from plots
showing color change due to insecticide applications.
/ Means followed by the same letters) are not significantly different at the
5% level using Duncan's multiple range test.
4/ The unmarketable heads are those with a numerical rating of 3 or higher.
Comparing the pre harvest ratings in Table 1 to the harvest reading there
was a considerable increase in damage from January 12 to March 1. The looper
population greatly increased during that period. Damage readings in the Guthion,
Niagara 10242, Thuricide SS and 1 and 2 qt/acre, and the Parathion combinations
indicate that these materials were not as effective on heavy looper populations
as on lighter populations up to January 12. Even though these treatments were
not different statistically from the five best materials, they did not control
the loopers as well. None of the best five materials are registered for com-
mercial use at this time.
Some materials were phytotoxic or simply caused a color change in the
plants. Heads from these treatments were weighed to see if materials affected
yield weights. Only one material, EP-316, reduced head weight significantly,
but two materials, Parathion + Toxaphene and TH 346-1 tended to reduce head
size. Parathion + Toxaphene reduced yields of Marion Market and Globe varieties,
but did not appear to affect Badger Blue Boy or Market Packer.
After seeing the light larval populations during the winter, it was felt
that a weekly spray schedule may not be needed. The second set of chemical tests
were applied bi-weekly rather than weekly. Cabbage plants were set for this
experiment January 24, 1967. The first insecticide was applied March 9 and a
total of 4 applications were made. Looper larvae were common on the plants when
the first application was made. The application methods and ratings previously
mentioned were used here except for the 14 day interval.
Table 2.- Damage
to cabbage plants
by cabbage looper larvae until harvest of bi-
rating % unmarketable
Material Rate Means/ head 2?
Azodrin 0.75#A/A 2.26 a 9
DuPont 1642 0.5#A/A 2.30 ab 8
Thuricide SS 2 qt/A 2.68 abc 21
Lannate 1179 0.5#A/A 2.79 abc 18
Thuricide + 1 pt/A
Parathion 8E 0.5#A/A 2.81 bc 25
Biotrol 2#/A 2.98 c 25
Dursban 1#A/A 3.14 c 40
Parathion 8E + 1#A/A
Toxaphene 8E 2#A/A 3.15 c 38
GC 6506 l#A/A 3.19 c 41
Guthion 0.75#A/A 3.27 cd 44
Toxaphene 8E + 2#A/A
DDT 2E 1#A/A 3.73 de 57
Check -- 3.93 e 70
Check 3.99 e 72
l/ Means are based on ratings of 100 plants.
are not significantly different at the 5%
Those followed by the same letters)
level using Duncan's multiple range
2 The unmarketable heads are those with a numerical rating of 3 or higher.
The bi-weekly spray interval was too long during the spring when looper
populations were extremely high. This should be tested during the winter months
when populations are low.
The first four materials in Table 1 did give a measure control even under
these severe conditions. One of these materials, Thuricide, is available for
commercial use. Parathion + Toxaphene, DDT + Toxaphene, and Guthion did not give
good worm control. DDT + Toxaphene was a little better than the check plot. One
week after the first application the Parathion + Toxaphene and DDT + Toxaphene
plots were observed to have few small worms but as many large worms as plants in
the check plots.
There is considerable interest in the use of biological agents for control
of loopers. An experiment was conducted using bacteria and virus. The virus
material (Nuclear Polyhedrosis Virus, Trichoplusia 5 X 10 10 PIB/gm) was sup-
plied by Bioferm. Marion Market cabbage plants were set in the field on January
11 and 24 and weekly application were made from February 1 to April 27 except
for 2 treatments which were bi-weekly. These plots were 12 to 30 rows wide
permitting collection of more accurate data from the biological agents which
cannot be obtained from smaller plots.
Table 3.- Cabbage looper counts
taken March 17, 1967, from plots treated with
Thuricide Virus Virus
Check 90TS 2 qt/acre 6 gm/acre 12 gm/acre
Dead 4 1 19 6
Small 46 14 54 18
Medium sized 12 O 2 0
Large 3 0 2 0
Total 65 15 77 24
Size was not recorded, but are estimated based on field observations.
b/ The lower number of dead larvae recorded compared to the 6 gm plot may be
from not seeing the dead larvae because they died at a smaller size in the
12 gm plot.
- 6 -
Table 4.- Cabbage looper damage readings taken at harvest from plants treated with
2/ rating % unmarketable
Material/ Rate Meansal/ heads
Thuricide SS 2 qt/A 1.71 a 6
Thuricide 90TS 2 qt/A 1.77 a 10
Thuricide SS 2 qt/A/ 2.63 b 20
Thuricide 90TS 2 qt/A/ 2.94 b 27
Virus 12 gm/A 3.00 b 35
6 gm/A 3.03 b 36
Check 4.57 c 93
1/ Means followed by the same letter are not significantly different at the 5%
level using Duncan's multiple range test.
2/ Thuricide treatments were applied with 1# casein sticker/A and virus treatments
with 118 ml. Plyac/A.
3/ These plots were treated every 14 days beginning March 16 when looper larvae
were evident and continued until April 27 for a total of 4 applications.
The number of larvae on the 50 check plants (Table 3) was considerably
higher than on either the Thuricide or the 12 gm/A virus treated plants. These
two treatments appeared to be controlling the larvae while they were very small
or soon after hatching. The low number of dead larvae recorded from the Thuricide
plot was due to death of very small larvae which were not seen when the counts
were being made. The lower virus rate plot had more larvae than the heck plot
indicating a heavier natural population in that block.
As many as 20 cabbage loopers per plant were observed during this test.
Looper control with weekly applications of Thuricide (Table 4) was good. At the
same time several grower fields were heavily damaged particularly where Phosdrin
was being used. Phosdrin was not effective due to the weather conditions.
Worm control by the virus was much better than the data in Table 4 indicate
that many worms were being killed was evident, because few live pupae were found
in these plots. The virus disease kills the larvae before they pupate or when
they are nearly full grown, but they have done considerable feeding before they
die. Even though there was extensive feeding damage to the plants in the virus
plots, it was significantly less in the check plot. Some of the damage in the
virus plots resulted from feeding by diamond back larvae which were not controlled
by the virus.