Spatial distribution of Diphorina citri(Hemiptera: Liviidae) and its biological control in commercial citrus blocks

Diphorina citri, also known as Asian Citrus Psyllid (ACP), is a vector of the devastating huanglongbing (HLB) disease pathogen. Therefore, psyllid management is critical. Spraying the entire citrus block may not be cost-effective and cause more harm to beneficial organisms such as predators and parasitoids much needed for biological control of ACP and other pests. ACP adults flying into citrus blocks are likely to colonize the perimeter's trees before further spreading into the block. Therefore, block perimeters could serve as a breeding ground for ACP compared to trees in the interior. In such a scenario, block perimeters can be treated with sprays of insecticides more often than the rest of the block for greater ACP suppression and conserve beneficial insects. Trees in the block perimeter and interior were investigated for ACP infestation in conventional and organic blocks in two separate citrus groves.
Interestingly, shoots infestation with ACP immatures was high in the conventional blocks than organic blocks averaging 55% and 24%, respectively. In both production systems, shoot infestation was more in the block perimeter than the interior. On average, 67% of shoots in the perimeter and 43% in the interior were infested in the conventional blocks, and 38% of shoots in the perimeter and 10% in the interior were infested in the organic blocks. These findings suggest that more frequent sprays in the block perimeter than interior may be a useful tactic in enhancing ACP suppression to reduce HLB disease incidence.