Weed Manipulation and E. servus Densities in Corn. Brown stink bug, Euschistus servus (Say), is a damaging pest of corn, Zea mays L., in the southeastern United States. In the agroecosystem, weeds serve as a bridge host for overwintered E. servus populations until they move to corn. Our objective was to reduce E. servus densities in corn by manipulating the weedy field borders with mowing and dicamba herbicide applications. In this farmscape, E. servus was the predominant stink bug species in the corn and E. servus adult density in the unmanaged weed plots started declining around the second week of May, followed by an increase in density in adjacent corn plots. This movement coincided with the seedling growth of corn. In 2016, dicamba application in the weedy field border resulted in a lower E. servus density in herbicidetreated weed plots compared to untreated plots. Despite this difference, weed manipulations in did not lead to any significant changes in their density in corn. Further evidence suggests that a prominent external source of E. servus, other than field border weeds, in this farmscape is likely driving densities in corn.
Flight Capacity of Adult E. servus. In addition to crops, both weedy field borders and the wooded areas of a typical farmscape in the southeastern United States harbor E. servus host plants, many of which are temporally and spatially limiting in availability or nutritional suitability. Therefore, local dispersion of E. servus is required so that individuals efficiently track and utilize host resources. This research sought to establish the baseline flight capacity of adult E. servus across the season in relation to body weight, sex, overwintering status, nutritional status, and plant host using a computer-monitored flight mill system. Across all the flight sessions, 90.7% of individuals tested flew in a range of 0-1 km, with an individual maximum flight distance of 6.4 km in 22-h. The mean total distance flown, mean flight speed and mean total time spent on actual flight varied across the season. The highest mean flight potential was observed soon after overwintering emergence and a relatively low flight potential was observed during the cropping season. The baseline dispersal potential information generated from this study will help to develop, plan and implement E. servus management programs.
Within-Plant E. servus Distribution in Corn. A 2-year study was conducted to quantify the within-plant vertical distribution of adult E. servus in field corn, to examine potential plant phenological characteristics associated with their observed distribution, and to select an efficient partial plant sampling method for adult E. servus population estimation. Within-plant distribution of adult E. servus was influenced by corn phenology. Based on the multiple selection criteria, during V4-V6 corn growth stages, either the corn stalk below the lowest green leaf or basal stratum method could be employed for efficient E. servus sampling. Similarly, on reproductive corn growth stages (R1-R4), the plant parts between two leaves above and three leaves below the primary ear leaf were found to be areas to provide the most precise and cost-efficient sampling sites.
Sampling E. servus in Corn. Developing a reliable and practical sampling plan for population monitoring of E. servus in corn is essential for implementing integrated pest management measures. E. servus was sampled from commercial corn fields (n=14) in North Carolina in 2016 and 2017. Both the adults and nymphs had a predominantly aggregated spatial distribution. For early vegetative stage corn (V4-V6), using whole plant visual sampling and an economic threshold density of 2 adult stink bugs per 20 plants, 27 sample units were required to estimate population density within 30% of the mean. At the same growth stage, using partial plant sampling and an economic threshold density of 1.73 adult stink bugs per 20 plants, 28 sample units were required to estimate population density with the same level of reliability. Reproductive stage corn (R1-R4) required eight sample units for whole plant sampling and nine sample units for partial plant sampling (Dx=0.3). For E. servus adults, the partial plant sampling method was equally or more cost-reliable than the whole-plant sampling method for pest management in all corn growth stages tested.
|Commitee:||Everman, Wesley, Heiniger, Ronnie, Walgenbach, James|
|School:||North Carolina State University|
|School Location:||United States -- North Carolina|
|Source:||DAI-B 80/03(E), Dissertation Abstracts International|
|Subjects:||Ecology, Entomology, Agriculture|
|Keywords:||Flight potential, Seqential sampling, Spatial distribution|
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