Spatial distribution of stink bugs (hemiptera: pentatomidae) in wheat

A two-year study was conducted in South Carolina wheat (Triticum aestivum L. (Poales: Poaceae)) fields to describe spatial and temporal dynamics of stink bugs (Hemiptera: Pentatomidae), which were sampled weekly with sweep nets. In 2010, the main phytophagous stink bugs caught in a grid sampling plan across two fields were the brown stink bug, Euschistus servus (Say), the rice stink bug, Oebalus pugnax (F.), the southern green stink bug, Nezara viridula (L.), and the red shouldered stink bug, Thyanta custator (F.), for both adults and nymphs. In 2011, the main phytophagous stink bugs were E. servus, O. pugnax, N. viridula, and T. custator across two fields. Adult stink bug counts adjacent to fallow fields were 2.1-fold greater for all species combined compared with counts adjacent to woods. Spatial Analysis by Distance IndicEs (SADIE) indicated significant aggregation for 35% of analyses for adults and nymph stink bugs at each sampling date. As a measure of spatial and temporal stability, positive SADIE association indices among sampling dates recorded 11, 36, 43, and 16% of analyses for adult E. servus and 7, 50, 50, and 14% for adult O. pugnax in fields A, B, C, and D, respectively. Adult and nymph stink bugs were spatially associated within wheat fields based on SADIE association indices. Seasonal counts of stink bugs were spatially associated with spike counts at least once for each species across the four fields. Future work may investigate practices to reduce stink bug buildup on wheat in the spring and movement to susceptible crops such as corn, Zea mays L.

The spatial distribution of the Japanese beetle, Popillia japonica, in soybean fields

The Japanese beetle, Popillia japonica Newman (Coleoptera: Scarabaeidae), is a serious pest of many agricultural and horticultural plants. Relatively little research has investigated the distributions of Japanese beetles in agricultural fields, and this lack of information makes pest management more difficult. In the present study, the spatial distribution of Japanese beetles in soybean fields was examined. Specifically, how the distribution and abundance of beetles was affected by distance from an edge, edge direction, and edge type was examined. An edge effect for density was discovered; beetle numbers decreased significantly with increasing distance from the field edge. The east and south sides averaged higher numbers of beetles than the north and west. Downwind edges, in particular downwind edges adjacent to hedgerows, also had significantly higher beetle densities. In addition, females relatively far from the edge had larger egg loads than those closer to the edge. Differences in aggregation seeking behavior, in combination with movement in relation to wind and obstructions such as hedgerows, are possible explanations for these spatial patterns.

Habitat age increases reproduction and nutritional condition in a generalist arthropod predator

We studied the nutritional and reproductive response of Poecilus cupreus (synonymous with Pterostichus cupreus), one of the most abundant carabid beetles in arable land, to the succession in sixteen 1- to 4-year-old wildflower areas. A total of 390 male and 373 female beetles was examined. Each female was dissected and the number of ripe eggs counted. The nutritional state was expressed by a condition factor, which was calculated for each individual based on the observed weight and elytra length of male and female P. cupreus. Carabids in the 1-year-old wildflower areas contained significantly less ripe eggs than those from the 4-year-old areas. The condition factor of female and male beetles was significantly lower in 1- than 2- to 4-year-old areas. We examined the influence of habitat parameters (vegetation cover, soil water content, coarse and fine sand, pore volume, habitat size and age, surrounding landscape structure) on the reproductive success and nutritional state of P. cupreus in the 16 wildflower areas. The number of eggs was best explained by habitat age, accounting for 53.4% of the variability. The variation in the condition factor of female and male beetles was best explained by habitat age, which accounted for 73% and 71% of the variation, respectively. Moreover, the beetles' reproductive potential and nutritional condition were significantly associated with vegetation cover, and occasionally also with soil water content. The potential of wildflower areas as a reservoir for the generalist predator P. cupreus was shown to increase with successional age.