EFFECTS OF INSECTICIDE TREATMENTS ON PHYTOPHAGOUS STINK BUGS AND BIG-EYED BUGS IN COTTON

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1 EFFECTS OF INSECTICIDE TREATMENTS ON PHYTOPHAGOUS STINK BUGS AND BIG-EYED BUGS IN COTTON John R. Ruberson, Russell. J. Ottens and J. David Griffin Department of Entomology, Univ. of Georgia, Tifton, GA Introduction Georgia s cotton pest complex has undergone dramatic changes in recent years. Phytophagous stink bugs have become more abundant in the cotton system, and are increasingly damaging cotton, with boll weevil eradication and increasing use of transgenic cotton varieties generally viewed as contributing factors. Large and damaging stink bug populations were observed in many areas of Georgia during the 2003 growing season, magnifying the need for specific threshold guidelines and effective management tools. Insecticidal measures are often used by growers to control stink bugs and this report presents the results of a field efficacy trial. It was designed to examine the effects of various insecticidal treatments on populations of phytophagous stink bugs and a beneficial insect, the big-eyed bug Geocoris punctipes, as well as the resulting yield of the cotton crop. Methods On 13 May 2004, DPL 555B/RR cotton was planted at the UGA Coastal Plain Experiment Station s Lang-Rigdon Farm. Sixteen insecticidal treatments including various rates and combinations of Bidrin, Centric, Diamond, Karate, Leverage, Orthene, Trimax, and an untreated control, were applied 26 Aug There were four replications of each treatment arranged in a randomized, complete block design. Each plot was 8 rows wide by 50 feet long, and plots were longitudinally separated by 10-foot long alleyways. The plots were laterally separated by alternations of two rows of peanuts (Georgia Green) or soybeans (DPL 5915RR), planted 12 May expressly for the purpose of attracting stink bugs to the cotton plants. With this layout, each plot was bordered by peanuts on one side and soybeans on the other. All insecticide applications were made using a John Deere 6000 Hi-Cycle sprayer applying 6.4 gallons per acre with TX-6 hollow-cone nozzles, at 60 psi. In addition to natural rainfall, all plots received 0.5 irrigation on 14, 21 May, 0.6 on 31 May, 15 July, and 0.7 on 2, 5, 24 Aug. and 1 Sept The plots were sampled with four shake cloth counts in each plot 1, 4, 7, and 14 days after treatment. The numbers of nymphs and adults of phytophagous stink bugs were recorded. Over 78% of these were the southern green stink bug, Nezara viridula, followed by the brown stink bug, Euschistus servus, and a very few green stink bugs, Acrosternum hilare, as well as occasional E. tristigmus and E. quadrator. All species and life stages were pooled in the data analysis. The numbers of G. punctipes nymphs and adults were also pooled for analysis. Yield was taken by mechanically picking the middle 2 rows of each plot on 8 Oct The experimental results (stink bug 144

2 numbers, big-eyed bug numbers, and yield) were analyzed using the general linear models procedure (GLM) with significant means separated using Duncan s New Multiple Range Test (SAS 1999). Results and Discussion In most instances, the insecticidal treatments did not result in a significant reduction in stink bug numbers (Table 1). Bidrin, Karate alone, and Karate in combination with table salt, Centric and Diamond, showed significant reductions seven days after treatment. At fourteen days after treatment, there were no significant differences relative to the untreated control. Big-eyed bug populations were negatively impacted by many of the treatments at one and four days after application (Table 2). There were no significant differences at seven days and only two treatments showed significant reductions relative to the untreated control at fourteen days after treatment. There were no significant differences in yield among the various treatments (Table 3). The untreated plots had the lowest numerical yield and plots treated with Diamond at 9 oz/acre had the highest. Conclusions Insecticide treatments appeared to have limited impact on stink bug populations in this study, and non-significant effects on yield. Unless the fiber quality of the untreated plots was greatly reduced, it is unlikely that the cost of any insecticidal treatment in this particular study would have been justifiable. The insecticides were detrimental to populations of beneficial big-eyed bugs one to four days after treatment, but this negative effect appeared greatly diminished after seven days. Acknowledgments We appreciate the support of Bayer, Crompton/Uniroyal, Syngenta, and Valent for these studies. We also appreciate the assistance of Alton Hudgins, Timothy Fitzgerald, and Chad Dunn in collecting and processing data. References SAS Institute SAS/STAT User s guide, version SAS Institute, Cary, NC. 145

3 Table 1. Phytophagous stink bug numbers (per shake sample) in relation to insecticide treatment. Tift Co., GA, No. Stink bugs 27 Aug. 1 DAT 30 Aug. 4 DAT 2 Sept. 7 DAT 9 Sept. 14 DAT Untreated 0.75ab 0.62ab 0.59a 0.19a Karate 2.6 oz/acre 0.25b 0.06b 0.0c 0.12a Diamond 0.83EC 6 oz/acre 0.50ab 0.62ab 0.38abc 0.12a Diamond 0.83EC 9 oz/acre 0.75ab 0.50ab 0.56a 0.12a Diamond 0.83EC 12 oz/acre 1.00a 0.81a 0.44abc 0.19a Diamond 0.83EC 6 oz/acre + 1 pt crop oil 0.44ab 0.62ab 0.31abc 0.12a Diamond 0.83EC 6 oz/a+ Karate 1.6 oz/a 0.12b 0.0b 0.0c 0.0a Trimax 4F 1 oz/acre 0.12b 0.31ab 0.12abc 0.25a Trimax 4F 1.5 oz/acre 0.31b 0.12b 0.31abc 0.19a Leverage 2.7SE 3.75 oz/acre 0.06b 0.31ab 0.12abc 0.06a Bidrin 8EC 0.25 lb ai/a 0.12b 0.19ab 0.06bc 0.19a Karate 2 oz/a + Centric 40WP 35 g/acre 0.19b 0.0b 0.0c 0.0a Karate 2 oz/a + Centric 40WP 42 g/acre 0.12b 0.0b 0.06bc 0.06a Karate 2 oz/a + Centric 40WP 53 g/acre 0.12b 0.0b 0.12abc 0.12a Orthene 0.5 lb/acre 0.38ab 0.19ab 0.50ab 0.19a Karate 1.6 oz/a + 10 g/liter salt 0.12b 0.06b 0.0c 0.06a Centric 40WP 35 g/acre + 10 g/liter salt 0.19b 0.06b 0.19abc 0.06a Means in columns followed by the same letter are not significantly different (P>0.05). 146

4 Table 2. Big-eyed bug numbers (per shake sample) in relation to insecticide treatment. Tift Co., GA, No. Big-eyed bugs 27 Aug. 1 DAT 30 Aug. 4 DAT 2 Sept. 7 DAT 9 Sept. 14 DAT Untreated 1.22ab 1.09ab 0.50a 0.56a Karate 2.6 oz/acre 0.56b 0.38bcd 0.50a 0.31ab Diamond 0.83EC 6 oz/acre 1.19ab 0.44bcd 0.25a 0.25ab Diamond 0.83EC 9 oz/acre 1.38ab 1.44a 0.31a 0.0b Diamond 0.83EC 12 oz/acre 2.19a 1.06abc 0.50a 0.06ab Diamond 0.83EC 6 oz/acre + 1 pt crop oil 0.94b 0.62bcd 0.12a 0.06ab Diamond 0.83EC 6 oz/a+ Karate 1.6 oz/a 0.38b 0.81abcd 0.50a 0.06ab Trimax 4F 1 oz/acre 0.31b 0.75abcd 0.38a 0.06ab Trimax 4F 1.5 oz/acre 0.19b 0.31cd 0.19a 0.31ab Leverage 2.7SE 3.75 oz/acre 0.19b 0.50bcd 0.19a 0.25ab Bidrin 8EC 0.25 lb ai/a 0.94b 0.38bcd 0.44a 0.06ab Karate 2 oz/a + Centric 40WP 35 g/acre 0.75b 0.44bcd 0.31a 0.06ab Karate 2 oz/a + Centric 40WP 42 g/acre 0.62b 0.31cd 0.06a 0.06ab Karate 2 oz/a + Centric 40WP 53 g/acre 0.50b 0.50bcd 0.06a 0.19ab Orthene 0.5 lb/acre 0.81b 0.12d 0.12a 0.06ab Karate 1.6 oz/a + 10 g/liter salt 0.56b 0.50bcd 0.50a 0.06ab Centric 40WP 35 g/acre + 10 g/liter salt 0.31b 0.56bcd 0.31a 0.0b Means in columns followed by the same letter are not significantly different (P>0.05). 147

5 Table 3. Seed cotton yields of insecticide treatments for stink bug control. Tift Co., GA, Pounds Seed Cotton/Acre Untreated a Karate 2.6 oz/acre a Diamond 0.83EC 6 oz/acre a Diamond 0.83EC 9 oz/acre a Diamond 0.83EC 12 oz/acre a Diamond 0.83EC 6 oz/acre + 1 pt crop oil a Diamond 0.83EC 6 oz/a+ Karate 1.6 oz/a a Trimax 4F 1 oz/acre a Trimax 4F 1.5 oz/acre a Leverage 2.7SE 3.75 oz/acre a Bidrin 8EC 0.25 lb ai/a a Karate 2 oz/a + Centric 40WP 35 g/acre a Karate 2 oz/a + Centric 40WP 42 g/acre a Karate 2 oz/a + Centric 40WP 53 g/acre a Orthene 0.5 lb/acre a Karate 1.6 oz/a + 10 g/liter salt a Centric 40WP 35 g/acre + 10 g/liter salt a Means followed by the same letter are not significantly different (P>0.05). 148