|Weathersbee Iii, Albert|
Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 24, 2005
Publication Date: December 1, 2005
Citation: Weathersbee III, A.A., McKenzie, C.L. 2005. Effect of a neem biopesticide on repellency, mortality, oviposition and development of Diaphorina citri (Homoptera: Psyllidae). Florida Entomologist. 88(4):401-407. Interpretive Summary: The Asian citrus psyllid, Diaphorina citri Kuwayama, is a recently introduced insect pest of citrus and ornamental plants. The greatest danger posed by this pest is its ability to transmit citrus greening disease caused by the bacterium, Liberobactor asiaticum (L.) Jack. The disease apparently has not been detected in the North America, but if it is introduced the damage caused to commercial citrus potentially could devastate the industry. Controlling spread of this disease may be achieved by effectively managing Asian citrus psyllid populations. We investigated a commercial biopesticide containing the compound, azadirachtin, to determine if it was an effective control agent for Asian citrus psyllid. The biopesticidal compound is extracted from seeds of the neem tree, Azadirachta indica A. Juss. Azadirachtin was found to be an effective developmental inhibitor of psyllid nymphs. Psyllid populations were controlled by azadirachtin concentrations as low as 10 ppm. Additionally, the compound has minimal toxicity to beneficial insects, increasing its potential value to pest management programs for horticultural crops.
Technical Abstract: The biological effects of a neem-based biopesticide, containing 4.5% azadirachtin, were assessed against the Asian citrus psyllid, Diaphorina citri, a recently introduced insect pest and potential disease vector of citrus in the United States. Over the concentration range 11-180 ppm azadirachtin, no mortality of adult psyllids was observed when they were exposed to treated plants. Adult psyllids demonstrated a small but significant repellent effect from treated plants in a choice experiment, but showed no preference to oviposit on treated or untreated plants. Psyllid nymphs were susceptible to azadirachtin at very low concentrations and activity was due to developmental inhibition. At a concentration of 22.5 ppm azadirachtin, ecdysis was arrested within 4 d after treatment and all nymphs were dead within 7 d. The densities of psyllid nymphs in a treated greenhouse population were significantly reduced by concentrations as low as 10 ppm azadirachtin. Over the range of concentrations used in these experiments, the product caused no phytotoxicity to tender foliage of either citrus or orange jasmine plants. Field trials are warranted to determine suitability of neem-based biopesticides for inclusion in citrus integrated pest management programs.