Crude extracts and alkaloids derived from Ipomoea-Periglandula symbiotic association cause mortality of Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae)

Authors: CHEN, XUE DONG - University Of Florida; KAUR, NAVNEET - Oregon State University; Horton, David; Cooper, William - Rodney; QURESHI, JAWWAD - University Of Florida; STELINSKI, LUKASZ - University Of Florida

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2021
Publication Date: 10/12/2021
Citation: Chen, X., Kaur, N., Horton, D.R., Cooper, W.R., Qureshi, J.A., Stelinski, L.L. 2021. Crude extracts and alkaloids derived from Ipomoea-Periglandula symbiotic association cause mortality of Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae). Insects. 12(10). Article 929. https://doi.org/10.3390/insects12100929.
DOI: https://doi.org/10.3390/insects12100929

Interpretive Summary: Fungi in the genus Periglandula live inside of the tissues of morning glories and related plants. These fungi produce compounds called ergot alkaloids that protect the plants from insect attack. Researchers at the USDA-ARS laboratory in Wapato, WA, Oregon State University, and University of Florida tested whether ergot alkaloids from morning glories kill Asian citrus psyllid, the vector of citrus greening disease (aka Huanglongbing disease). They found that commercially available ergot alkaloids and crude extracts from ergot-producing morning glories are toxic to citrus psyllid when the psyllids ingest the compounds from treated citrus leaves. This finding opens new avenues to develop treatments to control citrus psyllid and citrus greening disease using ergot alkaloids.

Technical Abstract: Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is an important economic pest of citrus crops because it vectors the causal pathogen of huanglongbing (HLB; aka citrus greening). Population suppression of D. citri with insecticides has been disproportionally relied on for HLB management and a greater diversity of more sustainable tools is needed. Periglandula is a fungal endosymbiont (family Clavicipitaceae) that forms a mutualistic relationship with members of plants in family Convolvulaceae. This association results in the production of ergot alkaloids that were previously documented as having psyllicidal properties. We investigated the mortality and behaviors of D. citri exposed to crude extracts from morning glories in the plant family Convolvulaceae, as well as synthetic ergot alkaloids. Nymphs and adults were exposed to the crude plant extracts from Periglandula positive species of Convolvulaceae, as well as five synthetic ergot alkaloids. Treatments were prepared by exposing clippings of citrus to 100 ng/µL of crude extract from Periglandula-positive species of Ipomoea (I. imperati, I. leptophylla, I. pandurata and I. tricolor), and Turbina corymbosa, and from one Periglandula-negative species (I. alba) (100 ng/µL). Mortality of adult and nymphal D. citri was significantly higher than the control after exposure to extracts from I. tricolor and I. imperati. The synthetic ergot alkaloids, lysergol (10-100 ng/µL), ergonovine maleate (100 ng/µL), agroclavine (10-100 ng/µL), and ergosine (10-100 ng/µL) increased mortality of D. citri nymphs, while ergosine (100 ng/µL) and agroclavine (100 ng/µL) increased mortality of adults compared to water controls. Fewer D. citri adults settled on plants treated with crude extracts or synthetic ergot alkaloids than on water controls at 48 hours after release. D. citri that fed on citrus leaves treated with 10 ng/µL solution of crude extract of Periglandula-positive species of Ipomoea (I. imperati, I. leptophylla, I. pandurata, I. tricolor), and Turbina corymbosa excreted significantly less honeydew compared with a negative water control and Periglandula-negative species (I. alba). Our results indicate that crude extracts and ergot alkaloids exhibit toxic and sub-lethal effects on D. citri that could be useful for management of this pest.