Phytoseiids as potential natural enemies of potato psyllids in organic potato production in South Texas, USA

Abstract

We evaluated the organic control of the potato psyllid Bactericera cockerelli and the silverleaf whitey Bemisia tabaci in South Texas, USA, in 2013 and 2014. We found that azadirachtin, pyrethrin, or spinosad did not adequately control B. cockerelli in 2013. However, the numbers of B. tabaci nymphs and phytoseiid mites were significantly lower after azadirachtin and pyrethrin treatments than those after spinosad treatment or in untreated control. The highest numbers of phytoseiids and lowest numbers of potato psyllids in the control plots in 2013 suggested a predator prey relationship between these organisms. In 2014, the tallies of B. cockerelli and B. tabaci were too low in all treated and control plots for reliable conclusions about insecticide treatments. We identified the phytoseiid mites Amblyseius largoensis, Typhlodromips near tennesseensis, and Typhlodromalus near peregrinus and report for first time that A. largoensis is a predator of B. cockerelli eggs and nymphs. We did not study predation by the other two phytoseiid species. In addition, fungivorous tydeid mites of the genus Metapronematus were found in most potato fields. Also, immature stages of Lasioerythraeus (Erythraeidae) were found parasitizing B. cockerelli nymphs in a conventional commercial field. Potato yields did not differ among treatments in both years. However, the high numbers of B. cockerelli in 2013 resulted in smaller tubers and consequently lowered yield (by 1/5-1/3) in 2013 than in 2014. The impact of predacious phytoseiids on B. cockerelli and their potential for mass rearing and release in organic production systems need further evaluations.