By Jawwad A. Qureshi
The impact of the Asian citrus psyllid continues to intensify through devastation of its vectored huanglongbing (HLB) disease. Although there is no permanent solution for HLB yet, psyllid suppression reduces its impact.
Chemical control is the most implemented method. Its strategic use helps reduce psyllid resistance and collateral damage to non-target organisms, including beneficial organisms needed for managing a wide range of pests.
Psyllids develop and reproduce on young shoots. Although HLB compromises normal plant functions, mature trees still produce most new shoots in spring, followed by sporadic growth in summer and early fall. Therefore, targeting overwintering psyllid adults with an insecticide spray before the spring flush reduces psyllids and HLB multiplication and spread.
Additional sprays in the growing season can be adjusted to target psyllids slightly before or during the flush cycles with rotation of insecticide mode of action. With this approach, significant reductions in psyllid populations were observed compared to calendar-based sprays. This approach also reduces insecticide applications, costs and environmental impacts.
University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) research indicated higher densities of psyllids in the block perimeter than in the interior. Therefore, implementing sprays in the perimeter and sparing the interior will not only kill psyllids but also provide refuge for biological control and opportunity to reduce insecticide use and cost. Predators and parasitoids targeting psyllids and several other pests of citrus warrant conservation and augmentation to support integrated and sustainable pest management (See more here).
Young trees flush more often and are therefore at greatest risk of contracting and spreading HLB. Trees can be planted under individual protective covers to protect them from psyllids and HLB for two to three years or through production in citrus under protective screen (CUPS). Other pests such as scales, mites, mealybugs, thrips and leafminers have been observed in these protected structures. Therefore, monitoring and targeted chemical treatments may be needed.
Over the years, a few Asian citrus psyllid adults have been observed in CUPS on yellow sticky cards. However, shoot infestation with nymphs was only observed when hurricanes and storms damaged screens. This required manual removal and destruction of infested shoots, followed by insecticide sprays to kill any residual populations. Significant activity of predatory mites and parasitoids of scales, mealybugs and leafminers have been observed in CUPS, suggesting potential for biological control.
Jawwad A. Qureshi is an associate professor at the UF/IFAS Southwest Florida Research and Education Center in Immokalee.