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Finding an optimal spatial scale for citrus health management in California
W. LUO (1), T. R. Gottwald (2). (1) Center for Integrated Pest Management, Raleigh, NC, U.S.A.; (2) USDA ARS, Fort Pierce, FL, U.S.A.

Citrus huanglongbing (HLB), spread by its vector Asian Citrus Psyllid (ACP), is a devastating disease in all infected citrus growing areas worldwide. The disease is endemic in FL, and the recent finds of HLB in Los Angeles residential basin and ACP in the CA central valley underscores the urgency of citrus health management. Citrus Health Management Areas (CHMAs) facilitate the coordinated control of ACP populations, the clean-up of abandoned groves, and the removal of infected trees. Growers cooperating within a CHMA have been effective in suppressing ACP populations and slowing the spread of HLB in FL, indicating CHMAs are a viable management strategy. However, the boundaries of CHMAs in FL are not optimized in size, but constructed primarily on arbitrary boundaries with an attempt to combine resources and garner neighbor participation. Improving from CHMA design deficiency in FL, we constructed CHMA boundaries in CA based on estimated HLB/ACP risk level under 1-mile2 grid resolution. Through cluster analysis and spatial statistics, 13 CHMAs are proposed for central valley (230,423 acres), 5 for coastal area (32,439 acres) and 10 for southern CA (43,780 acres), in representing citrus areas as homogenous as possible for HLB/ACP risk. In addition to HLB/ACP epidemiological factors, other abiotic factors (e.g. total citrus acreage and spray facility logistics) will also be considered to refine CHMAs with manageable size to better optimize cost-effective control.

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