|KAUR, NAVNEET - Oregon State University|
|Cooper, Rodney - William|
|DURINGER, JENNIFER - Oregon State University|
|RASHED, ARASH - University Of Idaho|
|BADILLO-VARGAS, ISMAEL - Texas A&M University|
|ESPARZA-DIAZ - Texas A&M University|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2020
Publication Date: 7/11/2020
Citation: Kaur, N., Cooper, W.R., Duringer, J., Rashed, A., Badillo-Vargas, I., Esparza-Diaz, Horton, D.R. 2020. Mortality of potato psyllid (Hemiptera: Triozidae) on host clippings inoculated with ergot alkaloids. Journal of Economic Entomology. 113(5):2079-2085. https://doi.org/10.1093/jee/toaa144.
Interpretive Summary: Zebra chip, an economically important disease of potato in the United States, is transmitted to potato by the potato psyllid. Researchers at USDA-ARS Wapato in Washington, in collaboration with scientists from Oregon State University, University of Idaho, and Texas A&M have determined that some species of native and ornamental Convolvulaceae support growth and development of potato psyllid while other species lead to very rapid death of the insect. Biochemistry work showed that toxic species contained a specific class of compounds known as ergot alkaloids, and assays with the pure compounds confirmed that it was indeed these compounds that led to psyllid mortality. This research identifies a new group of organic, plant-produced compounds having strong insecticidal properties that could provide a new tool for use in psyllid-targeted pest control programs.
Technical Abstract: An earlier study presented correlative evidence that the mutualistic association of Convolvulaceae with Periglandula fungi protects plants from potato psyllid (Bactericera cockerelli; Hemiptera: Triozidae) due to the presence of ergot alkaloids. This hypothesis was examined here by inoculating potato clippings with crude plant extracts from five species of morning glories that harbor Periglandula (Ipomoea imperati, Ipomoea leptophylla, Ipomoea pandurata, Ipomoea tricolor, and Turbina corymbosa) and one species (Ipomoea alba) that does not harbor the endophyte, then examining mortality of nymphal potato psyllids after three days. Biochemical analyses showed that ergot alkaloids from three classes (clavines, lysergic acid amides and ergopeptines) were present in potato clippings, thus confirming that leaves had taken up compounds from solutions of crude extracts. Psyllid mortality ranged between 53 and 93% in treatments producing biochemically detectable levels of alkaloids, as compared to 15% mortality in water controls or the alkaloid-free I. alba. We then tested synthetic analogues from each of the three alkaloid classes that had been detected in the crude extracts. Each compound was assayed by inoculating clippings of two host species (potato and tomato) at increasing concentrations (0, 1, 10, and 100 ug/mL in solution). Psyllids exhibited a large and significant jump in mortality rate beginning at the lowest two concentrations, indicating that even very small quantities of these chemicals led to mortality. Feeding by nymphs on artificial diets containing synthetic compounds resulted in 100% mortality within 48 h, irrespective of compound. These results warrant further testing of ergot alkaloids to characterize the mode of action that leads to psyllid mortality.