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United States Department of Agriculture

Agricultural Research Service

Research Project: IPM TECHNOLOGIES FOR INSECT PESTS OF ORCHARD CROPS

Location: Subtropical Insects and Horticulture Research

Title: Evaluation of management programs for protecting young citrus plantings from huanglongbing

Authors
item Hall, David
item Gottwald, Timothy
item Stover, Ed
item Beattie, Andrew -

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 18, 2013
Publication Date: March 25, 2013
Citation: Hall, D.G., Gottwald, T.R., Stover, E., Beattie, G.A.C. 2013. Evaluation of management programs for protecting young citrus plantings from huanglongbing. HortScience. 48:330-337.

Interpretive Summary: Huanglongbing (citrus greening disease) is a devastating disease of citrus associated in North America with the bacterium ‘Candidatus Liberibacter asiaticus’ vectored by the Asian citrus psyllid. Psyllid management is considered a vital component of a program aimed at reducing the incidence and spread of huanglongbing. Considerable research had been published comparing the efficacy of different insecticides for psyllid control as well as on seasonal strategies for applying psyllid insecticides. However, published information was largely lacking for even the most intense insecticide programs on their effectiveness for keeping the disease out of a new citrus planting in Florida citrus. Two experiments were therefore conducted on protecting young citrus from the disease using different psyllid management programs. The combined results of the two experiments indicated that up to eight monthly pesticide treatments per year applied on a calendar schedule were ineffective for preventing young citrus from becoming diseased.

Technical Abstract: Asiatic huanglongbing (HLB) is a devastating disease of citrus associated in North America with the bacterium ‘Candidatus Liberibacter asiaticus’ (LAS) vectored by the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. ACP management is considered a vital component of a program aimed at reducing the incidence and spread of HLB. Considerable research has been published comparing the efficacy of different insecticides for ACP control as well as on seasonal strategies for applying ACP insecticides. However, published information was largely lacking for even the most intense insecticide programs on their effectiveness for keeping HLB out of a new citrus planting in Florida citrus. We therefore conducted two experiments on protecting young citrus from HLB using different ACP management programs. An intensive insecticide program was evaluated in each experiment: eight annual calendar applications of traditional insecticides (hereafter referred to as the ‘complete’ program). In one experiment, citrus was either planted alone and subjected to the complete program or citrus was interplanted with orange jasmine, Murraya exotica L. (a favored ACP host plant), and subjected to a reduced insecticide program (4 calendar sprays of traditional insecticides). There was one set of plots in which both jasmine and citrus were treated with insecticides and one set in which jasmine was not treated at all. In the second experiment, citrus was either subjected to the complete program or to one of two other programs: a reduced insecticide program consisting of five calendar applications of traditional insecticides or a mineral oil program (oil applications every three weeks plus one dormant insecticide spray). The results of the two experiments were similar. Relatively good ACP control was achieved under each ACP management program during the first year but, as the experiments progressed and trees increased in size, ACP outbreaks occurred regardless of the psyllid management program. Little HLB developed under any ACP management program during the first year, but thereafter HLB increased and large percentages of the trees in each experiment became LAS-infected in less than two to three years. The combined results of the experiments indicated that up to eight monthly pesticide treatments per year applied on a calendar schedule were ineffective for preventing young citrus from becoming diseased. Of probable significance is that the planting where the two experiments were conducted was subjected to a minimal psyllid management program and contained many older trees known to be infected by the HLB pathogen, thus the ACP management programs we evaluated might have been more effective if ACP in the surrounding areas had been more aggressively controlled and diseased trees in the surrounding areas removed to reduce inoculum loads.

Last Modified: 9/23/2014