Novel insecticides and generalist predators support conservation biological control in cotton

Authors: BORDINI, ISADORA - University Of Arizona; Naranjo, Steven; FOURNIER, AL - University Of Arizona; ELLSWORTH, PETER - University Of Arizona

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2020
Publication Date: 12/8/2020
Citation: Bordini, I., Naranjo, S.E., Fournier, A., Ellsworth, P. 2020. Novel insecticides and generalist predators support conservation biological control in cotton. Biological Control. 154. Article 104502. https://doi.org/10.1016/j.biocontrol.2020.104502.
DOI: https://doi.org/10.1016/j.biocontrol.2020.104502

Interpretive Summary: The integrated pest management (IPM) program developed for management of insect pest of cotton in Arizona is founded on maximizing biological control from the conservation of native arthropod predators. This conservation is based strongly on the use of insecticides that selectively kill the pests while leaving the natural enemies unharmed. Several new insecticide have been recently introduced for cotton production and it is critical that the selectivity of these materials be tested to determine if they are compatible with our existing IPM program. Field studies in 2017 and 2018 were designed to test the selectivity of the insecticides cyantraniliprole, flupyradifurone, pyrifluquinazon and sulfoxaflor on the cotton arthropod community. This includes many common species that we know are critical to suppression of whitefly population. Compared with an untreated control and in contrast to acephate-treated positive controls, predator densities were rarely impacted and the overall arthropod community was conserved by all insecticides. On cccasion reductions in predator abundances were observed but are likely associated with lower prey availability after insecticide sprays rather than direct toxic effects. Also, these insecticides also allowed predator to prey ratios to be equal or exceed those observed in the untreated control. These favorable ratios are associated with functioning biological control. Our study demonstrates that the insecticides tested are selective and compatible with sustainable pest management in the Arizona cotton system, representing new options of insect pest control that conserve natural enemies and support biological control through generally favorable changes to predator to prey ratios. Results will allow cotton growers to continue managing pest populations in the most efficient way possible while having additional options for insecticide choice when sprays are needed.

Technical Abstract: Arizona has a successful integrated pest management plan for arthropod pests of cotton including two key pests, Bemisia argentifolii (= B. tabaci MEAM1) and Lygus hesperus. Central to this plan is conservation of natural enemies through threshold-based use of effective and selective insecticides. Field studies were designed to test the selectivity of the insecticides cyantraniliprole, flupyradifurone, pyrifluquinazon and sulfoxaflor on the cotton arthropod community (27 taxa measured), which includes the key generalist predator taxa: Collops spp., Orius tristicolor, Geocoris spp., Misumenops celer, Drapetis nr. divergens and Chrysoperla carnea s.l. Compared with an untreated check and in contrast to acephate-treated positive controls, predator densities were rarely affected, and the overall arthropod predator community was conserved by all insecticides. Occasional significant reductions in predator abundances were likely associated with lower prey availability after insecticide sprays rather than direct toxic effects. The proportions of time that predator to prey ratios were at or above levels indicative of functioning biological control were either significantly higher or not significantly different from the untreated check for these insecticides. The cotton food web populated by generalist predators is resilient and flexible enough to accommodate temporary reductions in abundance of some species, periods of low prey densities, or other constraints on individual predator species function. Our study demonstrates that the insecticides tested are selective and compatible with sustainable pest management in the Arizona cotton system, representing new options for insect pest control that conserve natural enemies and support biological control through generally favorable changes to predator to prey ratios.