EFFICACY OF DIAMOND INSECTICIDE IN PREVENTING YIELD LOSSES TO TARNISHED PLANT BUGS IN COTTON IN NORTH AND CENTRAL ALABAMA
Tim Reed and Ron Smith, Auburn University
Materials and Methods: Test plots were DPL 174 RF (no Bt) planted at Belle Mina and Prattville and PHY 375 planted at Tallassee. . There were 12 treatments utilized at Belle Mina and Prattville. The first insecticide of each treatment was applied at Belle Mina on 7/2 and the second insecticide applied at Belle Mina on 8/8. Due to the extremely low numbers of tarnished plant bugs (TPB's) and worms at Prattville only the first insecticide spray for each treatment was applied at Prattville on 7/5. Treatments were as follows: (1). untreated-untreated (2). untreated-Diamond 9 oz. (3). Centric 2 oz- Centric 2 oz. (4). Centric 2 oz.-untreated (5). untreated-Centric 2 oz. (6). Centric 2 oz.-Diamond 9 oz. (7). Centric 2 oz.-Diamond 6 oz. (8) Belt 3 oz + bifenthrin 5 oz.-Belt 3 oz.+ bifenthrin 5 oz. (9). Diamond 6 oz.-Diamond 6 oz. (10). Diamond 9 oz.-Diamond 9 oz. (11). Diamond 9 oz.-untreated) (12). untreated-untreated. Plots were 8 rows x 40 feet at Belle Mina and 8 rows X 60 feet at Prattville. There were 4 reps/treatment with treatments arranged in a RCB design. The test at Tallassee compared the efficacy of Diamond and other selected insecticide treatments in controlling TPB's.
Chemical treatments , application rates and timing of all applications are presented in Table 1. There were 4 replications per treatment with treatments arranged in a RCB design at Tallassee. Treatments were applied using a Spider Sprayer equipped with TX-VS4 nozzles that delivered 11.8 gpa at 60 psi. Plants were sampled using a drop cloth.
Results at Belle Mina: There was no statistically significant effect with respect to treatments applied on 7/2 at Belle Mina on the number of tarnished plant bugs per 25 blooms on 8/1 (range = 0.75 to 3.5) (P>F = 0.56). There was no statistically significant effect with respect to treatments applied on 7/2 at Belle Mina on the numbers of big eyed bugs(P>F=0.41), spiders (P>F=0.27), lady beetles (P>F=049) or total number of predators (P>F=0.24) collected in sweep net samples taken 7/5. However The 4 plots treated with Belt + bifenthrin averaged 61% fewer total predators/plot than the 16 untreated plots. There was no significant effect with respect to treatment on the % ( worms in blooms + worm-damaged blooms) (P>F= 0.56) one month after application of the first plot spray. This percentage ranged from 8% in the Diamond 6 oz. treatment to 3.8% in the untreated plots. There was a significant effect with respect to treatment on the number of worm-damaged bolls (=WDB's) per 40 row ft. (P>F=0.0053) on 10/25 and yield (P>F=0.0002). Two applications of Belt + bifenthrin had significantly fewer WDB's (7/40 ft.) than 9 of the other treatments including 6 and 9 oz. of Diamond applied twice. Yields obtained with 2 sprays of Belt + bifenthrin (3639 lbs./acre) were significantly greater than all other treatments (range = 2915 to 3322 lbs/acre) (LSD 0.1 = 277). Yields obtained with 2 applications of Centric (3085 lbs./acre) were not significantly different from that obtained with 2 applications of Diamond at the 6 oz. (2930 lbs./A) or 9 oz. (2932lbs./A) rate.
Results at PARU: A total of 48 sweep net samples (15 sweeps each) on 7/11 (6 DAA) yielded a total of only 4 tarnished plant bugs and 2 clouded plant bugs. There was a significant effect with respect to treatments applied on 7/5 at Prattville with respect to the number of big eyed bugs (P>F=0.029) and lady beetles (P>F=0.0031) collected in sweep net samples taken 7/11. There was no significant treatment effect with respect to collections of spiders (0.37), reduviids (P>F=0.56) or total predators (P>F=0.108). Numerically the average total number of predators sampled per 15 sweeps was lowest in the Belt + bifenthrin treatment (11.25). Mean total predator counts for other treatments were: Centric -13, untreated- 15.9, Diamond 9 oz.- 15.1 and Diamond 6 oz.-18. No worms or worm-damaged blooms were found in plots on 7/11. There was no significant treatment effect with respect to number of WDB's/60 ft. on 11/8 (P>F= 0.22) or yield (P>F=0.87). Mean numbers of WDB's ranged from 3.5 in the untreated plots to 5 in the Diamond 6 oz. treatment. Mean seed cotton yields/A were Belt + bifenthrin = 2393, untreated = 2517 Centric = 2566, Diamond 9 oz.= 2635 and Diamond 6 oz. = 2699.
Results at Tallassee: Resultsat Tallassee are presented in Table 1. Tarnished plant bug numbers were slightly less than one per foot of row when this trial was initiated and remained at a treatable level in the untreated control over the following 21 days. The mean number of TPB's present in the untreated control across all sample dates was 5 per row foot. All the different treatments provided similar levels of control of tarnished plant bugs and all provided a significant reduction in the number of tarnished plant bugs in comparison to the control on all sampling dates. There was no significant effect on yield of seed cotton with respect to the different treatments. However there was a numeric trend toward higher yields in Trt #'s 2-6.