By Lukasz Stelinski
Vector control is considered a basic component of HLB management even under high disease incidence scenarios. A recent study compared the effects of three different economic thresholds (ET-0.2, ET-0.5 and ET-1.0) and one calendar-based application schedule on the incidence of Asian citrus psyllid (ACP) and beneficial species in plots of commercially grown citrus. The study also examined end-of-season yield and overall management costs.
The results suggest that reducing spray frequency from eight to as few as four sprays per year had little effect on counts of pests and beneficial insects in the field. The numbers of ACP and that of a secondary weevil pest were similar between plots treated with the calendar-based spray plots and plots managed with the ET-1.0. Furthermore, spider numbers were higher in the ET-1.0 plots, while ant numbers were lower compared with calendar-sprayed plots.
Management input costs were lower under economic thresholds (ET-0.5 and ET-1.0) than with monthly calendar-based sprays, while yield losses were only slightly greater in the lower threshold of 0.2 mean psyllids per tap than with calendar sprays. Overall, management savings of more than 100% made up for this difference.
A dormant-season application timed to budbreak is needed to reduce the ACP population prior to spring flush in order to adequately maintain low ACP populations with threshold-based spray decisions. Together, these results suggest that implementing a spray program of rotated chemistries based on an economic threshold of 0.5 to 1.0 adult psyllids per stem tap could provide both economic and ecological benefit.
Read more about the benefits of reducing ACP populations during key periods.
Lukasz L. Stelinski is a professor at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.