Evaluation of Rotations of Transform with Key Insecticides for Control of Tarnished Plant Bug on Cotton, 2016

The tarnished plant bug (TPB) is a very serious pest in cotton in the mid-South. The damage from their feeding mostly causes pinhead squares to abort, causing significant yield loss. A variety of insecticide sprays were evaluated for control of TPB in PHY495W3RF or WideStrike 3 cotton at Lee Farm in Hayward, MO, which is field location for the Fisher Delta Research Center. PHY495W3RF or WideStrike 3, features the Cry1Ac and Cry1F proteins and a vegetative insecticidal protein (Vip3A) from Bacillus thuringiensis (Bt). Cotton was planted on 9 Jun. Insecticide applications were initiated during the first week of full bloom. Treatments 2–6 were initiated on 12 Aug and applied weekly thereafter. Treatment 7 was sprayed only once in 12 Aug at threshold, which was four TPBs per 20 row feet. Applications were made with a high clearance sprayer calibrated to deliver the specified amount of insecticide per acre for each individual treatment at 32 psi with 80,015 flat fan nozzles. The test was arranged in an RCB design with four replicates. Individual plots/replicates were 13 × 40 ft with four rows planted at a rate of 41,414 seeds per acre. Treatments were evaluated by sampling for TPB at two random stops per plot by standard black, 3 × 3 ft shake sheet. Means per two samples are presented (Table 1). First sampling was conducted immediately prior to initiating the insecticide applications (12 Aug) and then weekly thereafter before the next spray application counting both adults and nymphs through 30 Sep. Data were subjected to ANOVA and means were separated using a protected LSD.

For pretreatment sample in 12 Aug, nymphal counts were statistically similar between plots designated for treatments and untreated check (Table 1). However, adults were significantly more in plots designated for treatments 4, 5, and 7. At (14 DAT, 26 Aug), double rotations of Transform, Strafer with Diamond, and Strafer had the least number of nymphs, while Transform alone and with rotations had significantly less adult TPB present. Fewer nymphs and adults were present with Transform, Strafer/Diamond mix, and Strafer rotations (Treatments 4–7) than the other treatments or untreated check 3 wk after spray application in 12 Aug. At Week 4 (21 DAT, 2 Sep), Treatments 5–7 had the least number of TPB. At Weeks 5 and 6 (28 DAT, 9 Sep, 35 DAT, 16 Sep), Treatments 6 and 7 had the fewest number of adults and nymphs. Transform sprayed at threshold worked best for control of adult TPB, whereas a back-to-back spray of Transform starting at Week 5 and continuing to end of trial, Weeks 7 and 8 (42 DAT, 23 Sep, 49 DAT, 30 Sep) showed no difference to that of the control plots. At Week 7, all treatments still had significantly fewer nymphs than the untreated check and Transform sprayed at threshold had the least number. In conclusion, the single spray of Transform at threshold performed better at controlling nymphs and adults of TPB than any of the rotation treatment (Table 1). No phytotoxicity was observed with any treatment. This research was partially supported by industry gifts of pesticide and seed.