Landscape effects on Solenopsis invicta (Hymenoptera: Formicidae) and Geocoris spp. (Hemiptera: Geocoridae), two important omnivorous arthropod taxa in field crops

Authors: Olson, Dawn; ZEILINGER, ADAM - University Of California; PRESCOTT, KRISTINA - University Of Minnesota; Coffin, Alisa; RUBERSON, JOHN - University Of Georgia; ANDOW, DAVID - University Of Minnesota

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/29/2018
Publication Date: 7/10/2018
Citation: Olson, D.M., Zeilinger, A., Prescott, K., Coffin, A.W., Ruberson, J., Andow, D. 2018. Landscape effects on Solinopsis invicta (Hymenoptera: Formicidae) and Geocoris spp. (Hemiptera: Geocoridae), two important omnivorous arthropod taxa in field crops. Environmental Entomology. 47:1057-1063. https://doi.org/10.1093/ee/nvy104.
DOI: https://doi.org/10.1093/ee/nvy104

Interpretive Summary: The economically important brown stink bug, Euschistus servus, is a native pest of many crops in southeastern USA and insecticide applications is the prevailing method of population suppression. To facilitate biological control of E. servus populations, we investigated two egg predators’ response to both local and landscape factors that may influence their distribution and ability to cause immature E. servus mortality. We estimated the densities of fire ants and Geocoris spp. in 181 fields in 16 landscapes on four major crop hosts—maize, peanut, cotton and soybean—over three years in the coastal plain of Georgia USA. We used a geographic information system (GIS) to characterize the surrounding landscape structure (proportion of land-use types, connectivity of host cropland). We also characterized the within field or local scale complexity using the distance from the sampling site to field margin vegetation. For Geocoris spp., the landscape factors most related to Geocoris spp. increased numbers were the proportion of cotton and soybean in the landscape, whereas fire ant numbers was mainly negatively associated with the proportion of maize, soybean and all crops combined in the landscape. Local scale factors most associated with their density were the identity of specific crops. The proportion of non-crop habitat (woodland and pasture) in the landscape had a positive relationship with fire ant density, whereas it had a negative relationship with Geocoris spp. density. Our results suggest that these omnivorous arthropod species can be differentially distributed among specific crops in the landscape likely because of the relative quality of the crop and non-crop habitats to these species.

Technical Abstract: We selected two areas, one located in the southwest and the other located in the east-central Coastal Plain of Georgia with a total of 16 landscapes and sampled E. servus host crops (intensively produced maize, peanut, cotton and soybean) over 3 years. Each field was sampled using two permanent parallel transects (spaced 30.5 m apart) running perpendicular to the edge of the field. All sampled field edges were adjacent to woodland. For each landscape, we determined the proportion of the landscape that contained E. servus host crops maize, peanut, cotton and soybean, proportion of semi-natural and natural habitat (woodland, pasture and non-crop stink bug hosts in woodland edges) and the number of crop fields within 100 m, 500 m and 1000 m radii from the sampled fields as a measure of cropland connectivity. We determined the set of landscape and local scale variables that best explained variation in Geocoris spp. and fire ant density using the elastic net method of variable selection. We have found that fire ant and Geocoris spp. counts were more strongly associated with landscape factors involving the proportion of specific crops in the landscape than with local scale factors such as crop identity and within field distances to the field edge. However, crop identity was also associated with these species numbers; Geocoris spp. numbers were positively associated with soybean and maize whereas S. invicta numbers were positively associated with peanut and negatively associated with maize and soybean, indicating that both landscape and local scale factors can be important in structuring populations of these generalist predator species.