Determining field insecticide efficacy on whiteflies with maximum dose bioassays

Authors: CREMONEZ, PAULO - University Of Georgia; PERIER, JERMAINE - University Of Georgia; Simmons, Alvin; RILEY, DAVID - University Of Georgia

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/29/2022
Publication Date: 6/1/2023
Citation: Cremonez, P.S., Perier, J.D., Simmons, A.M., Riley, D.G. 2023. Determining field insecticide efficacy on whiteflies with maximum dose bioassays. Insects. 14:510. https://doi.org/10.3390/insects14060510.
DOI: https://doi.org/10.3390/insects14060510

Interpretive Summary: Whiteflies are a problem in vegetable crops, and insecticides are commonly used by growers to try to control this pest. However, populations of this pest continue to develop resistance against insecticides. To help delay the build up of insecticide resistance by whiteflies, research was conducted on the development of a rapid test of the efficacy of insecticides against whitefly field populations. The results of this study indicate that a 24-hour leaf dip test of 10 common whitefly insecticides was effective at predicting the performance of the insecticides against whiteflies in the field. This information is useful to researchers and the agricultural community to provide an insecticide resistance management tool to develop the most effective rotation of insecticides in near real time.

Technical Abstract: We evaluated a rapid bioassay method to assess insecticide efficacy for controlling Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) adults in squash and cucumber cropping systems before spraying the insecticide. We tested the assumption that a 24-h bioassay at maximum dose would accurately predict insecticide product efficacy in the field, so that these data could be used to select the best product before the field application. This would provide an insecticide resistance management (IRM) tool for developing the most effective insecticide rotations in near real time. Leaf-dip bioassays of 10 insecticides commonly used for the control of B. tabaci were conducted to evaluate efficacy in eight cucurbit field experiments in Georgia, USA, in the 2021 and 2022 field seasons. A maximum dose was used for all bioassays, here defined as the highest labeled rate of an insecticide diluted in the equivalent of 935 L ha-1 (100 gal acre-1) of water. The whitefly adult mortality (24 and 48 h) observed in the bioassay were compared to a whitefly adult counts at one and six days after a single field spray application. Additionally, a low dose (1/10 rate) was used in the same bioassays of imidacloprid, flupyradifurone, pyriproxyfen, and cyantraniliprole, to see determine a rate response would improve the assessment of insecticide tolerance in the whitefly population. Overall, there was a significant positive correlation between laboratory bioassay adult survival and field efficacy after 24 h of application as explained by 50% to 91% of the observed variation. The addition of the low dosage was helpful in that no rate response was consistent with susceptibility to the tested insecticide, whereas a rate response was associated with a loss of susceptibility between 2021 and 2022.