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Title: Evaluation of insecticides on cotton fleahopper and beneficial arthropod populations

Author
item Suh, Charles
item PARKER, ROY - Texas A&M Agrilife
item Lopez, Juan De Dios

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/15/2010
Publication Date: 4/19/2010
Citation: Suh, C.P., Parker, R.D., Lopez, J. 2010. Evaluation of insecticides on cotton fleahopper and beneficial arthropod populations. National Cotton Council Beltwide Cotton Conference. p. 951-955.

Interpretive Summary: Although a number of effective insecticides exist to control cotton fleahoppers in cotton, information regarding their impact on beneficial arthropods is generally lacking. Because natural enemies such as spiders and ladybird beetles help maintain cotton fleahopper populations below economically damaging levels and/or prevent outbreaks of secondary pests, conservation of key predators is fundamentally important. The impact of insecticides, commonly used or recommended for cotton fleahopper control on natural enemy populations, was examined. Spiders and ladybird beetles were the most prevalent predators encountered in the study, accounting for 76 to 99 percent of the total abundance of natural enemies. None of the insecticides tested had a detrimental impact on natural enemy populations. However, plots treated with insecticides had the highest numbers of aphids, which can be a detrimental pest in cotton. These studies help researchers and growers better understand the mechanisms by which these insecticides impact natural enemy populations and will guide the recommendations of the use of a particular insecticide in the future.

Technical Abstract: An experiment was initiated in 2009 concurrently with a cotton fleahopper insecticide efficacy trial to determine which products were the most and least detrimental to arthropod natural enemies. Insecticides evaluated included Bidrin 8E, Bidrin XP, Centric 40WG, Discipline 2EC, Intruder 70WP, Orthene 97S, and Trimax Pro. The initial application was made during the second week of squaring and a second application was made 8 d later. With the exception of Trimax Pro at 6 DAT-1 (6 d after first treatment), all tested products reduced and maintained cotton fleahopper populations below the recommended action threshold of 15 fleahoppers per 100 terminals throughout the study period. Ladybird beetles and spiders were the most prevalent predators encountered in the study, accounting for 76 to 99 percent of the total abundance of beneficial arthropods on each sample date. Based solely on the numbers of total predators, none of the insecticides appeared to have an adverse effect on natural enemy populations. In fact, on the final assessment date (12 DAT-2, 12 d after second treatment), plots treated with Bidrin XP or Discipline 2E contained significantly more beneficial arthropods that the other treated or non-treated plots. Coincidentally, the greatest numbers of aphids were also observed in plots treated with these products, although only Discipline was significantly different. Numerically, Intruder 70WP had the fewest numbers of predators as well as aphids. Given the apparent relationship between aphid densities and predator abundance, additional studies are needed to fully understand the mechanisms by which these insecticides impact natural enemy populations.