Assessment of renewable compounds as biopesticides for Asian citrus psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Psyllidae).

The Asian citrus psyllid (ACP), Diaphorina citri, Kuwayama (Hemiptera: Liviidae), is the vector of Candidatus Liberibacter asiaticus and Ca. Liberibacter americanus, both associated with Huanglongbing, the most destructive disease of citrus worldwide. ACP control mainly depends on the use of synthetic insecticides. However, the dependence on and overuse of synthetic insecticides can lead to insecticide resistance, adverse environmental effects. Due to this, as well as consumer demand for organic food and changing regulations, there is an urgent need to develop additional and more sustainable methods of control. Fatty acid-based and phenolic biopesticides derived from lignocellulosic biomass could be safe and inexpensive alternatives to synthetic insecticides. Thus, the objective of this work was to study the toxicity of two novel, naturally derived molecules—sucrose fatty acid ester (SFAE) and 2-methoxy-4-propylphenol (2M4P)—to ACP, and compare them with fenpropathrin and pyrethrum extract. Mortality of adult psyllids (3-7 days old) exposed to SFAE, 2M4P, the pyrethrum extract and fenpropathrin in topical application bioassays were compared at 1, 24 and 48 h post-treatment at different doses. Mortality of adults exposed to SFAE, 2M4P and the pyrethrum extract were also compared in whole plant assays under greenhouse conditions. In the topical bioassays all compounds worked rapidly against ACP, with the natural and synthetic pyrethroids showing significantly more toxicity than SFAE and 2M4P. Under greenhouse conditions, mortality caused by 2M4P was the highest, followed by the pyrethrum extract. Mortality caused by SFAE was not significantly different when compared to the control.