Glycerin‐based dispensers of fir oil reduce response of Asian citrus psyllid, Diaphorina citri, to citrus odours

Abstract

The Asian citrus psyllid, Diaphorina citri Kuwayama, transmits the bacterial pathogen associated with huanglongbing, a fatal citrus disease. Alternatives to insecticides for D. citri management are being explored, given the development of insecticide resistance and the lack of efficient biological controls. Essential oils as pest repellents have shown some efficacy in laboratory and field evaluations; however, lack of an effective dispenser for field deployment has prevented their application. In this investigation, we evaluated glycerin‐based dispensers releasing fir (Abies spp.) oil as repellents for D. citri. In olfactometer tests, glycerin dispensers loaded with fir oil at 20% w/w repelled psyllids from citrus odours but did not cause repellency at lower loading dosages. Field evaluations were conducted with dispensers at the 20% loading dosage based on laboratory results. In open‐air cage bioassays, fewer psyllids alighted on trees treated with 2 dispensers per tree than on control trees. Similarly, fewer psyllids were found on mature lime trees in homeowner landscapes treated with 4 dispensers per tree compared to paired control trees. In small plot experiments in commercial grapefruit, psyllid infestation of young leaf flush shoots was reduced in plots treated with at least 250 dispensers/ha compared to untreated control plots. Our results indicate that these glycerin‐based fir oil dispensers can reduce infestation of citrus by D. citri. However, the efficacy observed within replicated small plots of citrus grown in monoculture was judged insufficient to manage this vector as a stand‐alone treatment. Larger scale evaluations at higher loading dosages of fir oil and/or in combination with other management tools are warranted based on the outcomes of these initial experiments.

Evaluation of a push-and-pull strategy using volatiles of host and non-host plants for the management of pear psyllids in organic farming

“…A similar approach investigating the use of fir oil as repellent against D. citri was investigated recently. In this study, the authors assessed a reduction in the number of insects collected in areas treated with glycerin dispensers containing fir oil (Chuang et al, 2023). Research on H. halys by Zhang et al, 2014 found that plant essential oil blends (clove, lemongrass, and spearmint oil), as well as individual plant volatiles from those essential oils (e.g.…”