Project Summaries

07-942GA  Project Manager: P. F. O'Leary


John R. Ruberson, University of Georgia

Studies were conducted a second year to characterize which predators in cotton and soybeans attack Southern green and Brown stink bugs. It is relatively easy to demonstrate loss (whether from mortality or emigration is unclear) of stink bugs in cotton and other crops, but it is far more complex to determine who or what is responsible for the loss so that the appropriate natural enemies can be conserved. If we can determine particular natural enemy species that are especially active in consuming stink bugs, then we can target those natural enemies for conservation or enhancement. We applied molecular methods to address this issue. DNA primers were developed at the University of Kentucky to allow us to assay the gut contents of predators for the presence of stink bug DNA. This provides positive evidence for predation, and allows us to determine which predator species are feeding on stink bugs in the field. Three primers were developed - one for Southern green stink bug, Nezara viridula, one for Brown stink bug, Euschistus servus, and one for Green stink bug, Chinavia hilaris. We evaluated stink bugs and predators in three crops: 1) cotton (B2RF), 2) soybeans MG5 and 3) soybeans MG7. All three crops were  planted  at  three locations:  the Belflower  Farm,  Tifton,  GA;  the Attapulgus Research and Education Center, Attapulgus, GA; and the Southwest Research and Education Center, Plains, GA. All crops were sampled by sweep net and all arthropods taken in the samples were counted. Predators and stink bugs were placed in 100% ethanol in preparation for DNA testing and were sent to the University of Kentucky for processing. Due to the high number of specimens needing to be processed (5,342 potential predator specimens were collected), we are still running DNA analyses and, therefore, we can only present partial conclusions here. Thus far, 1,174 predators have been screened for Southern green stink bug DNA, 492 for Brown stink bug DNA, and 595 for Green stink bug DNA. So far, three predator species have tested positive for Southern green stink bug DNA - big-eyed bugs Geocoris spp. (the vast majority collected are G. punctipes; 7.2% of all big-eyed bugs screened), the pirate bug Orius insidiosus (10.4% of all screened), and the hooded beetle Notoxus monodon (5.5% of all screened). Two species (big-eyed bugs - 1.1%; and pirate bugs - 1.6%) also tested positive for Brown stink bug. None tested positive for Green stink bug DNA. All of these predator species were also recorded as stink bug predators in studies in 2011, underscoring their activity. No spiders have thus far tested positive for any stink bug DNA, despite spiders collectively being the most abundant predators in the fields. Big-eyed bugs and pirate bugs also were very abundant in sample locations, though not as abundant as spiders. Hooded beetles were somewhat less common. Our data indicate that predation of stink bugs is occurring, perhaps at low rates, and that rates of predation  may  differ  with stink bug species  (Southern green  higher than Brown and Green). Completion of the assays will provide us more insight into the role of predation and which predator species are most important for stink bug suppression.


Project Year: 2012

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