ARS | Publication request: Gut content examination of the citrus predator assemblage for the presence of Homalodisca vitripennis remains

Submitted to: Biocontrol
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 11, 2012
Publication Date: N/A

Interpretive Summary: Glassy-winged sharpshooter (GWSS) is a serious pest of many crops in California. GWSS transmits a bacterial disease into a wide variety of economically important plants including citrus and grapevines. Citrus is considered to be a key overwintering and first generation reproductive host for GWSS and plays an important role in disease outbreaks in nearby vineyards. To date, the primary disease management tactic used has been implementation of an area-wide insecticide application program to reduce GWSS populations in citrus groves, urban areas, and vineyards. However, over-reliance on insecticide applications to suppress GWSS populations in citrus orchards could potentially eliminate GWSS egg parasitoids and predators that feed on it and other citrus pests. In short, ecologically sustainable, integrated management tactics that are less reliant on area-wide insecticide applications are warranted for long term pest control. One such environmentally benign control tactic that fits into an integrated pest management program is biological control of GWSS. To date, a significant amount of research has been dedicated toward evaluating the efficacy of GWSS egg parasitoids. However, very little research has been conducted on the evaluation of its naturally occurring predators. As such, a two-year study was conducted in a citrus orchard to determine predation rates on GWSS. A total of 1,578 arthropod predators, representing 18 taxa, were collected and assayed for the presence of GWSS remains using two types of molecular gut content assays. The gut content analyses revealed the presence of GWSS remains in the gut of 2.3% of the total arthropod predator population, with 3.1% of the spiders and 0.6% of the insect predators testing positive. Low frequencies of GWSS detection in the gut of predators indicated that GWSS life stages were not the primary prey and that predators may contribute little to pest suppression in citrus.

Technical Abstract: A two-year study was conducted in a citrus orchard, Citrus sinensis L., to determine predation rates on glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar). A total of 1,578 arthropod predators, representing 18 taxa, were collected and assayed for the presence of GWSS egg protein by an enzyme-linked immunosorbent assay (ELISA) using a Homalodisca-species and egg-specific monoclonal antibody (mAb) and then by polymerase chain reaction (PCR) using a H. vitripennis-specific DNA marker. The gut content analyses revealed the presence of GWSS remains in the gut of 2.28% of the total arthropod predator population, with 3.09% of the spiders and 0.59% of the insect predators testing positive. Moreover, a comparison of the two assays indicated that they were not equally effective at detecting GWSS remains in predator guts. Low frequencies of GWSS detection in the gut of predators indicated that GWSS life stages were not the primary prey and that predators may contribute little to pest suppression in citrus.