Productivity of HLB-infected citrus trees is enhanced by Asian citrus psyllid control and foliar nutrition

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Sternorrhyncha: Psyllidae), vectors ‘Candidatus Liberibacter asiaticus’ that causes huanglongbing (HLB) throughout commercial citrus-growing regions worldwide. In Florida, HLB incidence is approaching 100% statewide. Yields have decreased and production costs have increased since 2005.  The continued profitability of some groves is attributed to aggressive psyllid control with insecticides and foliar nutritional sprays that may compensate for reduced translocation. However, the value of these practices is debated. A replicated field study employing a factorial design was initiated in 2008 in a 5.4 ha commercial block of ‘Valencia’ sweet orange trees to evaluate individual and combined effects of foliar nutrition and ACP control with threshold-driven insecticide treatments and dormant sprays. The current work summarizes results of the last three growing seasons (2012-2015).  

Insecticide applications consistently reduced ACP populations on insecticide-treated trees in addition to a site-wide reduction. However, neither insecticide nor nutrition applications significantly influenced HLB incidence nor titer in mature trees. In reset trees, foliar nutrition reduced both HLB incidence and titer relative to controls. However, infection continued to build and was 100% in all treatments by October 2013. Greatest yields (kg fruit/ ha) and production (kg s/ ha) were obtained from trees receiving both insecticides and foliar nutrition. All treatments except foliar nutrition applied alone in 2013 resulted in production and financial gains relative to controls in all years. However, the material and application costs associated with the nutrition component offset gains resulting in lower profits than insecticide applied alone.