|Reay-jones, Francis P.f.|
|Bauer, Philip - Phil|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2016
Publication Date: 7/19/2016
Citation: Reay-Jones, F., Greene, J.K., Bauer, P.J. 2016. Stability of spatial distributions of stink bugs, boll injury, and NDVI in cotton. Environmental Entomology. 45(5):1243-1254. Interpretive Summary: Apparent soil electrical conductivity is often related to the ability of the soil to hold water and thus is related to plant growth and productivity. We conducted this field experiment to investigate if apparent soil conductivity is related to how insect pests of cotton aggregate within cotton fields. We found that thrips numbers and thrips injury to cotton were related to apparent soil electrical conductivity. Thrips tended to aggregate in areas with more vigorously growing plants which were on soils with higher apparent electrical conductivity. Similarly, damage to cotton bolls by stink bugs was also greater in areas with more vigorously growing plants. These results suggest that site-specific management of these two pests has potential for increasing economical and environmental benefits. These results will be used by researchers developing improved ways to scout and treat cotton fields for insect pests.
Technical Abstract: A two-year study was conducted to determine the degree of aggregation of thrips, stink bugs, and aphids in cotton, Gossypium hirsutum L., and their spatial association with soil apparent electrical conductivity (ECa), a multispectral vegetation index (Normalized Difference Vegetation Index [NDVI]), and other plant characteristics. Using the Spatial Analysis by Distance IndicEs analyses (SADIE), thrips adults and nymphs were significantly aggregated in 27% of analyses and 18% for thrips injury. Stink bugs were less frequently aggregated, with 15% for adults, 5% for nymphs, and 29% for boll injury. NDVI values expressed as integers were also significantly aggregated within fields in 17 of 37 analyses, with the majority of significant indices occurring in July and August. Using the SADIE association tool, NDVI values were significantly associated with variables including thrips nymphs (two positive associations out of 10 analyses), thrips injury (one positive association out of 10 analyses) and boll injury (five positive associations out of nine analyses). Soil ECa was significantly associated with thrips adults (six positive associations out of 22 analyses), thrips nymphs (12 positive associations out of 22 analyses), and thrips injury (10 positive and one negative association out of 22 analyses). Our study suggests that management efforts for thrips may need to focus in areas of the field with higher values of soil ECa. Because the proportion of injured bolls increased with NDVI, stink bugs were either attracted to vigorously growing cotton with high NDVI values, or stink bugs were more prone to cause injury to cotton bolls on vigorously growing plants. The degree of aggregation of thrips and stink bugs and their association with soil and plant characteristics, combined with the highly variable soils in the southeastern coastal plains in the United States, suggest that site-specific management of these insect groups in cotton has potential for maximizing economical and environmental benefits and deserves further study.