Mississippi State University
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EVALUATION OF INSECTICIDES FOR THRIPS AND TARNISHED PLANT BUGS MANAGEMENT ON COTTON IN MISSISSIPPI 2001


ABSTRACT: The purpose of this trial was to evaluate insecticides for control of thrips and tarnished plant bugs on cotton. Tests were planted at the Plant Science North Farm at Mississippi State University. Insect pressure was light and no significant crop related effects from thrips occurred. For the tarnished plant bug portion of the trial, tarnished plant bugs were reared on artificial diet from bugs collected in the spring from wild hosts and caged in cloth sleeve cages after plots were sprayed and the spray had dried. Because of low numbers insects in the field, there were no significant treatment related differences in yield as a result of the two applicants (thrips and tarnished plant bugs).

INVESTIGATORS: Jack T. Reed, D. Bao, and C. S. Jackson

LOCATION: Plant Science North Farm at Mississippi State University

MATERIALS AND METHODS: The statistical design was randomized complete block with 4 replicates. Cotton, variety ST 4892 BR untreated, was planted at the Plant Science North Farm at Mississippi State University on 5/03/01 at a seed rate of 3 per ft. Plots were four rows wide and 50 ft (15.2 m) long, arranged with four rows of untreated cotton between plots and a planted 10 foot buffer at the end of each plot. Insecticides for control of thrips were applied on 5/29/01 with a high-clearance plot spray tractor with nozzles (Spray Systems, Tx4, hollow cone) spaced for a 38-in (96.5 cm) row spacing at 19-in (48.3 cm) centers with one nozzle directly over the row and one directly between rows. The carrier was water, and the volumetric application rate was 10 gallons (37.8L) per acre. Wind speed, temperature and relative humidity at time of application was 0 to 2 mph, 84°F and 41.2%, respectively. After 48 hr, five plants from each plot were cut and transferred into a plastic bag for transport to the lab. The samples were then washed in a Clorox-detergent solution to remove the thrips from the plants. Thrips and other arthropods were transferred onto a filter paper for identification and counting by use of a dissection microscope.
An additional spray targeting tarnished plant bugs was applied on 7/17/01. Wind speed, temperature and relative humidity at second application was 0 to 1.3 mph, 86°F and 49.7%, respectively. Cloth sleeves, two per plot, were used to enclose the upper portions of treated plants and thus cage tarnished plant bugs on the plants. The sleeves were placed over the plants, secured with elastic fasteners, gathered at the point of fastening, and completely covered with aluminum foil before spraying. After the spray application was dry, the aluminum foil was removed. Then each sleeve was extended, 10 tarnished plant bugs were placed inside, and the upper end was closed with an elastic fastener or string. These plants were cut after 48 hours and searched for survivors. Plant bugs used in sleeve cages were supplied by Gast Rearing laboratory when they were third instar and were offspring of field collected adults. Additionally, the test for the residual activity of the compounds was made by taking leaf discs (100mm) from leaves that were sprayed (ie. near the top of the plant), and caging 5 third instar nymphs per petri dish, with 10 nymphs per plot (40 per treatment). Yield was estimated by mechanically harvesting the center two rows of each plot and converting the yield to pounds of seed cotton per acre.

RESULTS AND DISCUSSION: The average number of immature thrips on untreated plants were 8.9 thrips per five plants for the sampling period of the study. Most insecticide treatments reduced thrips numbers below threshold through 6/01/01 except DR-A-034. This compound is supposed to have little residual. Immature thrips numbers in DR-A-034, Methyl Parathion, and Orthene had the highest number of thrips on 6/04/01 and did not differ from the untreated plots. The field cage trial resulted in a very high percent mortality of 3rd instar plant bugs in most plots as compared with untreated plots and all compounds. Under the conditions of this test with over a 48 hour period, all treatments provided more than 85 percent mortality of tarnished plant bugs except DR-A-034, which provided less than 16% control. The untreated plots were significantly different from other treated plots. Although populations of plant bugs in the field were low, sweep net samples were made and the main beneficials in this trial were lady beetles. The results of DR-A-34 on third instar tarnished plant bug nymphs placed on leaf discs indicated no control. Pyrethroids resulted in 50-100% mortality of nymphs caged for 48 hr, and organic phosphate resulted in 17-75% mortality. The organic phosphate standard, Bidrin, resulted in 76% mortality. Thus pyrethoids indicated good residual for nymphal plant bug control for at least five days after treatment in this trial. There were no differences in yield between treatments, however most insecticide treatments yielded numerically higher yields than the untreated plots. Results from the trial are presented in Table 1 to 4.

Table 1. Mean of insects per five plants, MSU Location.
Immature ThripsTobacco Thrips(Eastern) Flower ThripsWestern Flower ThripsSoybean Thrips
TreatmentRateJun-01-01Jun-01-01Jun-01-01Jun-01-01Jun-01-01
Karate Z0.03 LB A/A1.3 b0.0 e0.0 a0.0 a0.0 a
Asana XL0.036 LB A/A1.5 b0.0 e0.0 a0.0 a0.0 a
Baythroid0.033 LB A/A0.3 b0.0 e0.0 a0.0 a0.0 a
Capture 20.06 LB A/A0.5 b0.0 e0.0 a0.0 a0.0 a
Decis0.023 LB A/A1.0 b0.0 e0.0 a0.0 a0.0 a
Fury0.045 LB A/A0.8 b0.0 e0.3 a0.0 a0.0 a
Bidrin0.4 LB A/A3.3 b1.5 cd0.5 a0.0 a0.0 a
Orthene0.3 LB A/A1.0 b0.5 de0.3 a0.0 a0.0 a
MP0.4 LB A/A7.0 a2.0 bc0.0 a0.0 a0.0 a
Karate Z0.03 LB A/A0.0 b0.0 e0.0 a0.0 a0.0 a
Centric + Leverage0.047 LB A/A + 0.063 LB A/A0.5 b0.0 e0.0 a0.0 a0.0 a
Untreated8.0 a3.5 a0.5 a0.0 a0.0 a
DR-A-0342 GAL/100 GAL6.8 a3.0 ab0.0 a0.0 a0.0 a
LSD (P=.05)3.451.080.550.000.00
Treatment Prob(F)0.00010.00010.44391.00001.0000
Means within a column followed by the same letter do not significantly differ (P=.05, LSD).



Table 1. Continue.
Immature Thrips 5/plantTobacco Thrips 5/plant(Eastern) Flower Thrips 5/plantWestern Flower Thrips 5/plantSoybean Thrips 5/plant
TreatmentRateJun-08-01Jun-08-01Jun-08-01Jun-08-01Jun-08-01
Karate Z0.03 LB A/A0.3 b0.5 b0.0 a0.0 a0.0 a
Asana XL0.036 LB A/A1.0 b0.3 b0.0 a0.0 a0.0 a
Baythroid0.033 LB A/A0.3 b0.3 b0.0 a0.0 a0.0 a
Capture 20.06 LB A/A0.3 b0.0 b0.0 a0.3 a0.0 a
Decis0.023 LB A/A1.3 b0.3 b0.0 a0.0 a0.0 a
Fury0.045 LB A/A1.8 b0.0 b0.0 a0.0 a0.0 a
Bidrin0.4 LB A/A1.8 b0.3 b0.3 a0.0 a0.0 a
Orthene0.3 LB A/A1.8 b0.0 b0.0 a0.0 a0.0 a
MP0.4 LB A/A2.8 b0.0 b0.0 a0.0 a0.3 a
Karate Z0.047 LB A/A1.3 b0.8 b0.0 a0.0 a0.0 a
Centric + Leverage0.047 LB A/A + 0.063 LB A/A0.3 b2.3 a0.0 a0.0 a1.3 a
Untreated7.8 a0.3 b0.0 a0.0 a0.0 a
DR-A-0342 GAL/100 GAL2.8 b0.8 b0.3 a0.0 a0.3 a
LSD (P=.05)2.541.440.280.201.02
Treatment Prob(F)0.00010.18430.56290.46850.5114
Means within a column followed by the same letter do not significantly differ (P=.05, LSD).



Table 1. Continue.
Immature Thrips 5/plantTobacco Thrips 5/plant(Eastern) Flower Thrips 5/plantWestern Flower ThripsSoybean Thrips 5/plant
TreatmentRateJun-04-01Jun-04-01Jun-04-01Jun-04-01Jun-04-01
Karate Z0.03 LB A/A1.5 c1.0 cd0.0 a0.0 a0.0 a
Asana XL0.036 LB A/A2.0 c0.5 d0.3 a0.3 a0.3 a
Baythroid0.033 LB A/A1.0 c1.7 cd0.0 a0.0 a0.0 a
Capture 20.06 LB A/A1.8 c3.3 bc0.0 a0.0 a0.0 a
Decis0.023 LB A/A1.8 c3.0 bcd0.0 a0.3 a0.0 a
Fury0.045 LB A/A1.8 c2.3 cd0.0 a0.0 a0.0 a
Bidrin0.4 LB A/A4.0 c2.0 cd0.3 a0.0 a0.0 a
Orthene0.3 LB A/A5.8 bc0.5 d0.3 a0.3 a0.5 a
MP0.4 LB A/A12.0 ab6.8 a0.3 a0.3 a0.3 a
Karate Z0.03 LB A/A0.0 c1.3 cd0.0 a0.0 a0.5 a
Centric + Leverage0.047 LB A/A + 0.063 LB A/A0.8 c1.0 cd0.3 a0.0 a0.0 a
Untreated10.8 ab5.3 ab0.0 a0.3 a0.0 a
DR-A-0342 GAL/100 GAL14.5 a5.0 ab0.3 a0.0 a0.0 a
LSD (P=.05)6.452.750.510.440.45
Treatment Prob(F)0.00020.00030.87850.74550.1563
Means within a column followed by the same letter do not significantly differ (P=.05, LSD).



Table 2. Mean of insects per 25 sweeps, MSU Location.
Tarnished Plant Bugs NymphsTarnished Plant Bugs AdultLady BeetleBigeyed Bugs
TreatmentRateJul-11-01Jul-11-01Jul-11-01Jul-11-01
Karate Z0.03 LB A/A0.0 a0.8 a3.5 a0.5 a
Asana XL0.036 LB A/A0.0 a0.5 a3.8 a0.5 a
Baythroid0.033 LB A/A0.0 a0.8 a2.8 a0.0 a
Capture 20.06 LB A/A0.0 a0.5 a0.5 a0.3 a
Decis0.023 LB A/A0.0 a0.5 a3.0 a0.3 a
Fury0.045 LB A/A0.0 a0.3 a3.3 a0.5 a
Bidrin0.4 LB A/A0.0 a0.3 a2.0 a0.5 a
Orthene0.3 LB A/A0.0 a0.0 a3.3 a0.3 a
MP0.4 LB A/A0.5 a0.3 a1.3 a0.3 a
Karate Z0.03 LB A/A0.0 a0.5 a2.3 a0.3 a
Centric + Leverage0.047 LB A/A + 0.063 LB A/A0.0 a0.0 a1.3 a0.0 a
Untreated0.0 a0.5 a2.0 a0.3 a
DR-A-0342 GAL/100 GAL0.0 a0.5 a3.8 a0.3 a
LSD (P=.05)0.401.052.360.86
Treatment Prob(F)0.46850.94130.12780.9790
Means within a column followed by the same letter do not significantly differ (P=.05, LSD).



Table 2. Continued
Tarnished Plant Bug NymphTarnished Plant Bug AdultLady BeetleBigeyed Bugs
TreatmentRateJul-20-01Jul-20-01Jul-20-01Jul-20-01
Karate Z0.03 LB A/A0.0 a0.0 a1.0 cd0.0 a
Asana XL0.036 LB A/A0.0 a0.0 a2.3 abc0.0 a
Baythroid0.033 LB A/A0.0 a0.0 a1.5 cd0.0 a
Capture 20.06 LB A/A0.0 a0.0 a1.5 cd0.0 a
Decis0.023 LB A/A0.0 a0.0 a0.5 d0.0 a
Fury0.045 LB A/A0.0 a0.0 a0.8 cd0.0 a
Bidrin0.4 LB A/A0.0 a0.0 a1.8 bcd0.0 a
Orthene0.3 LB A/A0.0 a0.3 a3.5 a0.0 a
MP0.4 LB A/A0.0 a0.0 a2.3 abc0.0 a
Karate Z0.03 LB A/A0.0 a0.0 a1.5 cd0.0 a
Centric + Leverage0.047 LB A/A + 0.063 LB A/A0.0 a0.3 a0.5 d0.0 a
Untreated0.0 a0.0 a3.3 ab0.0 a
DR-A-0342 GAL/100 GAL0.0 a0.0 a2.3 abc0.0 a
LSD (P=.05)0.000.281.680.00
Treatment Prob(F)1.00000.56290.01181.0000
Means within a column followed by the same letter do not significantly differ (P=.05, LSD).



Table 3. Result of Plant Parameters Affected by Thrips, Plant Bugs Cage Trial and Yield, MSU Location.
Plant Height (cm) 5/plantPlant Height (cm) 5/plantPlant Bug %mortality 10/cageYield lb seed cotton/ac
TratementRateJun-01-01Jun-15-01Jul-19-01Sep-28-01
Karate Z0.03 LB A/A5.47 a15.75 a91.8 a2859.3 a
Asana XL0.036 LB A/A5.70 a14.65 a84.5 a2683.8 a
Baythroid0.033 LB A/A6.50 a15.45 a85.7 a2824.9 a
Capture 20.06 LB A/A5.93 a14.10 a96.8 a2704.4 a
Decis0.023 LB A/A6.07 a13.57 a88.0 a2656.3 a
Fury0.045 LB A/A5.43 a13.42 a89.4 a2866.2 a
Bidrin0.4 LB A/A5.67 a12.10 a76.2 ab2701.0 a
Orthene0.3 LB A/A5.22 a14.17 a89.2 a2701.0 a
MP0.4 LB A/A5.93 a15.43 a98.4 a2873.0 a
Karate Z0.03 LB A/A6.90 a14.10 a88.8 ab3062.3 a
Centric + Leverage0.047 LB A/A + 0.063 LB A/A6.40 a13.13 a83.5 a3000.3 a
Untreated5.68 a14.75 a56.8 b2893.7 a
DR-A-0342 GAL/100 GAL5.95 a14.18 a16.9 c2959.1 a
LSD (P=.05)1.4482.65927.253478.90
Treatment Prob(F)0.59330.31500.0010.8124
Means within a column followed by the same letter do not significantly differ (P=.05, LSD).

Table 4. Result of Tarnished Plant Bug, Five Per Leaf Discs, MSU Location.
Tarnished Plant Bugs (live)Tarnished Plant Bug (dead)Tarnished Plant Bug (moribund)Plant Bugs %mortality (bio assay)
TreatmentRateJul-22-01Jul-22-01Jul-22-01Jul-22-01
Karate Z0.03 LB A/A0.0 c7.7 a1.7 bc100.0 a
Asana XL0.036 LB A/A2.7 bc4.3 abc1.7 bc70.7 abc
Baythroid0.033 LB A/A4.7 ab3.3 abc1.3 bc50.3 bcd
Capture 20.06 LB A/A4.7 ab4.0 abc0.7 c50.3 bcd
Decis0.023 LB A/A5.0 ab4.3 abc0.7 c50.0 bcd
Fury0.045 LB A/A1.3 bc7.0 ab1.7 bc86.6 ab
Bidrin0.4 LB A/A2.3 bc7.0 ab0.3 c75.9 ab
Orthene0.3 LB A/A7.0 a3.0 bc0.0 c30.0 cd
MP0.4 LB A/A7.7 a1.3 c0.3 c17.0 d
Karate Z0.03 LB A/A1.7 bc4.0 abc4.3 a83.3 ab
Centric + Leverage0.047 LB A/A + 0.063 LB A/A2.0 bc5.0 abc3.0 ab80.0 ab
Untreated7.7 a2.7 bc0.0 c26.6 d
DR-A-0342 GAL/100 GAL7.7 a1.7 c0.0 c20.0 d
LSD (P=.05)4.234.502.1441.164
Treatment Prob(F)0.00440.13790.00860.0023
Means within a column followed by the same letter do not significantly differ (P=.05, LSD).

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