The Incorporation of Conservation Biological Control into the Management of Bemisia tabaci (MEAM1) in Cotton

Abstract

Natural enemies provide critical population regulation of many pest species, though their effects are not commonly incorporated into agricultural management decisions. Conservation biological control is an important tool that can be implemented to minimize pest damage, but applying it requires appropriate understanding of pest and natural enemy relationships. Through experimental cotton field trials, I identified predator: prey ratios based on key arthropod predators as action thresholds of the whitefly pest Bemisia tabaci MEAM1 (Dinsdale et al. 2010; equivalent to Bemisia argentifolii Bellows et al. 1994 [Hemiptera: Aleyrodidae]), validated their efficacy, and promoted them to cotton pest managers. This dissertation begins with a multi-year field trial where whitefly and natural enemy populations were manipulated with a series of insecticidal treatments to identify key arthropod predators. The critical abundance of four key predators necessary to suppress whiteflies was estimated through predator: prey ratios. These ratios were refined for commercial pest management and developed to conform to the current whitefly IPM framework as a simple to use management-decision tool that would be readily adopted and used by pest managers. Predator: prey ratios were then validated in 1) a second field trial, 2) commercial fields in Arizona and northern Mexico and 3) historical field trials conducted from 1997-2010, where whitefly management decisions made with the standard threshold and ratios, were compared with the standard threshold alone. I found no difference in management outcomes when decisions were made with the standard threshold alone, or with predator: prey ratios in the field trial, but analysis of potential decisions on commercial farms and with historical trial data indicated that the majority of sprays could be delayed if control decisions incorporated ratio-based thresholds. Finally, an outreach program was developed and deployed to present ratios as decision-making tools for cotton pest managers that reduce uncertainty in control decisions and optimize spray outcomes. Pest managers indicated positive changes in knowledge and a gradual adoption of ratios for decision-making. The implementation of whitefly control decisions that incorporate predator: prey ratios may reduce pest managers' uncertainty in decision-making, as well as insecticide use and management costs.