Effects of imidacloprid on potato psyllid, Bactericera cockerelli (Sulc), feeding behavior and disease transmission to potatoes

The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae), is a serious pest of potatoes that can cause yield loss by direct feeding on crop plants and by transmitting a bacterial pathogen. Current pest management practices in potatoes rely on the use of insecticides for control of the potato psyllid to lower disease incidences and increase yields. While many studies have focused on psyllid mortality caused by insecticides, little is known regarding the behavioral responses of the potato psyllid to insecticides or if insecticides can decrease pathogen transmission. Thus, the objectives of this study were 1) to determine and characterize the effects of imidacloprid on adult potato psyllid feeding behavior through direct observations and with electrical penetration graphs (EPGs); 2) determine the residual effects of imidacloprid on potato psyllid feeding behavior over time; and 3) determine the effects of imidacloprid on transmission of Candidatus Liberibacter psyllaurous. Imidacloprid significantly decreased the duration of feeding for up to six weeks post application, lowered ingestion of phloem and xylem sap, and significantly lowered disease transmission for up to four weeks compared to untreated controls. EPG recordings of psyllid feeding revealed five EPG waveforms which include: (NP) non-probing, (C) intercellular stylet penetration, (D) initial contact with phloem tissue, (E1) salivation into phloem sieve elements, (E2) phloem sap ingestion, and (G) ingestion of xylem sap. We discuss the implications of our results for the use of imidacloprid in an integrated pest management program for potato psyllid and disease control.