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Group Title: Research Report - University of Florida Central Florida Research and Education Center ; 90-05
Title: Evaluation of selected insecticides for the control of insecticide-resistant diamondback moth, Plutella xylostella
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Permanent Link: http://ufdc.ufl.edu/UF00075884/00001
 Material Information
Title: Evaluation of selected insecticides for the control of insecticide-resistant diamondback moth, Plutella xylostella
Series Title: Research Report - University of Florida Central Florida Research and Education Center ; 90-05
Physical Description: Book
Language: English
Creator: Leibee, Gary L.
Savage, Kenneth E.
Publisher: University of Florida, Central Florida Research & Education Center
Publication Date: 1989
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Bibliographic ID: UF00075884
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 122931091

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HISTORIC NOTE


The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




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CFS





University of Florida
Central Florida Research & Education Center
Sanford, Florida

Research Report SAN 90-05 December 1989

rl ie Eval ation of selected insecticides for the control of
nra Sciee insecticide-resistant diamondback moth, Plutella xylostella
Library
Gary L. Leibee and Kenneth E. Savage
JAN 11 1990

University of Florida Introduction
Diamondback moth (DBM), Plutella xvlostella L., populations have become very
difficult to control with pyrethroids, organophosphates, and carbamates in the
last four years in central Florida (personal observation). Laboratory studies
have indicated a high level of resistance to fenvalerate and methomyl in central
Florida (Leibee, unpublished data). Bacillus thuringiensis based products are
the principle insecticides being used. Effective control of DBM with endosulfan
and various tank mixes have been reported by some growers.

The objective of this study was to evaluate selected insecticides,
individually and some in combination, for the management of the insecticide-
S resistant DBM.

Methods and Materials

'Golden Acre Yellows Resistant' cabbage was transplanted from seed beds on
April 20 and 21, 1989, into Myakka fine sand at the Central Florida Research and
Education Center in Sanford, Florida. Plots consisted of four 50-ft rows with
a 2.5-ft row-spacing and about a 11-in plant spacing. Four rows were left
unplanted between each plot to provide a separation of 12.5 feet. Plots were
arranged in four blocks and the blocks were separated by 25-ft alleyways.
Treatments were assigned to the plots in a randomized complete block design with
four replications. Nemacur 15G, 2 lb ai/acre, was applied pretransplant in 15"
band for nematode control. Randox 4EC and Vegedex 4EC both at 2 lb ai/acre were
applied for weed control two days after transplant. Sprays were applied with
a tractor-mounted, compressed-air sprayer. Three nozzles (D2-25) were used per
row; one overhead and one drop on each side. The delivery rate was 50 gpa with
a boom pressure of about 45 psi and a speed of 2 mph. Application dates were
May 11, 16, 23, June 1, 8, and 16. Insecticides and rates (expressed as pounds
of active ingredient per acre unless stated otherwise) tested were Lorsban (Dow
Chemical Co.) 50W at 1.0, Cymbush (ICI Americas, Inc.) 3EC at 0.06, Javelin
(Sandoz) at 0.5 qt of formulation, Cymbush 3EC at 0.06 tank mixed with Lorsban
50W at 1.0, Cymbush 3EC at 0.06 tank mixed with Javelin at 0.5 qt of formulation,
Lorsban 50W at 1.0 tank mixed with Dipel 2X (Abbott) at 0.5 lb of formulation,
Lorsban 50W at 1.0 tank mixed Javelin at 0.5 qt of formulation, Lannate (I. E.
du Pont de Nemours & Co., Inc.) 1.8L at 0.9, Pounce (FMC) 3.2EC at 0.2, Larvin
* (I. E. du Pont de Nemours & Co., Inc.) 3.2 at 0.75 and 1.0, Larvin 3.2 at 0.75
tank mixed with Phosdrin (I. E. du Pont de Nemours & Co., Inc.) 4EC at 1.0,
Phosdrin 4EC at 1.0, and Thiodan (FMC) 3EC at 1.0. An untreated check was











included. The wetting agent X-77 (Chevron Chemical Co.) was used in all
treatments at the rate of 8 oz per 100 gallons of spray.

Plants were sampled on May 31, June 7 and 14, 1989, to determine larval
numbers. Four randomly selected plants per plot (two from the middle of each
center row) were sampled by carefully cutting the stem below the portion of the
plant containing the bud or head and the next four youngest leaves (wrapper
leaves in the head stage). The stem was cut below all the foliage if only four
leaves were present. The four plants were place in a plastic bag for transport
back to the processing area. Each sample of four plants was placed into a
Berlese funnel and subjected to heat for 24 hr. When heads were present, the
infested head leaves were pulled away from the head and the uninfested portion
of the head was cut out to reduce the amount of plant material that went into
the funnel. Larvae were collected into 70% ethyl alcohol. Cabbage looper,
Trichoplusia ni (Hubner), and imported cabbageworm, Pieris rapae (L.), were
categorized according to size (small, medium, and large). DBM was categorized
according to instar by head capsule width. Ten mature plants were rated for
damage on June 16, 1989, using a scale of 1-6, similar to that of Greene et al.,
Jour. of Econ. Entomol. 62(4):798-800: 1 no apparent insect feeding; 2 -
0-1% defoliation of wrapper leaves only; 3 2-5% defoliation of wrapper leaves
only; 4 6-10% defoliation of wrapper leaves and minor feeding damage on head,
head unmarketable during normal market conditions; 5 11-30% defoliation of
wrapper leaves, moderate number of scars on head; 6 over 30% defoliation of
wrapper leaves and numerous feeding scars on head. Percent marketability was
based on the proportion of plants having damage ratings less than or equal to
3 for normal market conditions and less than or equal to 4 for exceptional market
conditions. Percent marketability under exceptional market conditions (DR < 4)
,was provided because a damage rating of 4 indicates a relatively high level of
insect control when compared to damage ratings of 5 and 6. A damage rating of
5 indicates some reduction in feeding damage due to the insecticide, but the
head and wrapper leaves suffer too much damage to be considered marketable. A
damage rating of 6 represents no apparent effect from the insecticide. Damage
ratings were taken on only one plot of the Thiodan treatments due to severe
stunting resulting from excessive soil moisture in three of the plots.

Results and Discussion

Damage ratings (DR) and percent marketability based on frequency of plants
with damage ratings of 3 or less and 4 or less are presented in Table 1. Counts
of DBM larvae (second through the fourth instar combined) per four-plants for
three sampling dates are presented in Table 2. The first instar larva was not
included in the counts because it generally feeds inside the leaf as a leafminer
and would not be subject to retrieval through heat extraction. The infestation
was very heavy and consisted of essentially all DBM. The lack of control of DBM
in this experiment by the cypermethrin, permethrin, methomyl, thiodicarb, and
chlopyrifos indicated that a highly insecticide resistant population was present.
Thiodan was the most effective treatment based on normal market conditions (DR
< 3). The remaining treatments that consisted of one insecticide provided
essentially no marketable cabbage under normal market conditions.

A considerable amount of potentiation was observed in the tank-mixes. The
greatest amount of potentiation was observed in the Cymbush + Lorsban treatment











followed by the Larvin + Phosdrin treatment based on normal marketability
conditions. Based on exceptional market conditions considerable potentiation
was indicated in the following tank-mixes: Cymbush + Lorsban, Cymbush + Javelin,
Lorsban + Dipel, Lorsban + Javelin, and Larvin + Phosdrin. Further
investigations will be conducted to explain the mechanism, or mechanisms,
involved in this potentiation.

It is interesting to note that even though the amount of damage in the
untreated plants fell well within the damage rating of 6, there was visibly more
damage in the pyrethroid plots than in the untreated plots. There were also more
larvae in the pyrethroid plots than in the untreated plots. It is the senior
author's opinion that the lesser amount of damage in the untreated checks was
due to the presence of predators (spiders, wasps, dragonflies, earwigs, carabids)
and parasites (Diadegma spp. and some unidentified chalcids) that were observed
to be in the untreated plots and not in the pyrethroid plots.

It is also interesting that the cypermethrin plots suffered more damage and
the larval numbers increased faster than in the permethrin plots. The senior
author has also noticed a similar relationship with fenvalerate and permethrin
in past experiments (unpublished data).

Yield data were not taken due to uncontrollable variations in plant size
due to soil moisture conditions. No problems with formulations were encountered
and no phytotoxicity was observed.














Table 1. Effects of selected insecticidal treatments
for the control of diamondback moth on damage ratings and two
levels of marketability for cabbage.


Damagea Marketability
Treatment rating (DR3) (DR<4)
6/16 6/16 6/16


Untreated check
Lorsban 50W 1.0
Cymbush 3EC 0.06
Javelin 0.5 qt
Cymbush 3EC 0.06 +
Lorsban 50W 1.0
Cymbush 3EC 0.06 +
Javelin 0.5 qt
Lorsban 50W 1.0 +
Dipel 2X 0.5
Lorsban 50W 1.0 +
Javelin 0.5 qt
Lannate 1.8L 0.9
Pounce 3.2EC 0.2
Larvin 3.2 1.0
Larvin 3.2 0.75
Larvin 3.2 0.75 +
Phosdrin 4EC 1.0
Phosdrin 4EC 1.0
Thiodan 3EC 1.0


6.0
5.2
6.0
5.1


0.0
2.5
0.0
0.0


3.5 ef

4.9 d

4.0 e


3.9
5.9
6.0
5.7
5.7


e
ab
a
abc
abc


3.7 ef
5.4 bcd
3.4 -b


40.0 d

0.0 f

17.5 e


12.5
0.0
0.0
0.0
0.0

22.5
0.0
50.0


0.0
10.0
0.0
20.0


95.0 a

40.0 b

82.5 a


95.0
0.0
0.0
0.0
0.0


87.5 a
5.0 cd
100.0 -b


aMeans in the same column followed by the same letter are not
significantly different at the 0.05 level by DMRT. Except
for damage ratings, analyses of variance performed on
transformed data (arc sine)

bUnreplicated. See methods and materials section for
explanation.














Table 2. Effects of selected insecticidal treatments on
larval (2-4 instar combined) counts for diamondback moth on
cabbage.

2-4 instar DBM/4 plants


Treatment


5/31


6/14


Untreated check
Lorsban 50W 1.0
Cymbush 3EC 0.06
Javelin 0.5 qt
Cymbush 3EC 0.06 +
Lorsban 50W 1.0
Cymbush 3EC 0.06
+ Javelin 0.5 qt
Lorsban 50W 1.0 +
Dipel 2X 0.5
Lorsban 50W 1.0 +
Javelin 0.5 qt
Lannate 1..8L 0.9
Pounce 3.2EC 0.2
Larvin 3.2 1.0
Larvin 3.2 0.75
Larvin 3.2 0.75 +
Phosdrin 4EC 1.0
Phosdrin 4EC 1.0
Thiodan 3EC 1.0


7.3
0.8
7.8
3.5


ab
fgh
a
bcd


0.3 gh

1.3 e-h

1.8 d-g


0.8
6.5
6.8
2.8
6.0


fgh
ab
ab
def
abc


1.0 fgh
3.0 cde
0.8 fgh


5.0
2.3
10.0
3.7


cde
e-h
a
c-f


11.0
3.3
31.8
5.5


1.7 e-h


bcd
def
a
cde


2.8 ef


6.7 bcd 14.3 abc


1.7 e-h


1.0
2.3
9.3
13.0
7.7


fgh
d-g
abc
ab
abc


1.3 fgh
1.0 fgh
1.0 fgh


3.5 def


2.0
17.5
24.8
21.8
33.0


ef
abc
ab
ab
a


8.5 b-e
6.3 def
3.5 def


aMeans in the same column followed by the same letter are not
significantly different at the 0.05 level by DMRT. Analyses
of variance performed on transformed data [log(X + 1.5)].


c




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