@article{eckel_cho_walgenbach_kennedy_moyer_1996, title={Variation in thrips species composition in field crops and implications for tomato spotted wilt epidemiology in North Carolina}, volume={78}, ISSN={0013-8703 1570-7458}, url={http://dx.doi.org/10.1111/j.1570-7458.1996.tb00761.x}, DOI={10.1111/j.1570-7458.1996.tb00761.x}, abstractNote={AbstractThrips were surveyed in tomato spotted wilt‐susceptible crops in five areas across North Carolina. Tomato, pepper, and tobacco plants in commercial fields were sampled and 30 species of thrips were collected over a 3‐year period. The most common species overall was Frankliniella tritici (Fitch). The most common thrips species that are known to vector Tomato Spotted Wilt Virus (TSWV) were F. fusca (Hinds), and F. occidentalis (Pergande). Relatively low numbers of Thrips tabaci Lindeman, another reported vector, were collected. The spatial and temporal occurrence of vectors varied with sampling method, crop species, region of North Carolina, and localized areas within each region. In a laboratory experiment, no difference was detected between the ability of F. fusca and F. occidentalis to acquire and transmit a local isolate of TSWV. Based on vector efficiency and occurrence, F. fusca is considered the most important vector of TSWV in tobacco, whereas both F. fusca and F. occidentalis are important vectors of TSWV in tomato and pepper.}, number={1}, journal={Entomologia Experimentalis et Applicata}, publisher={Wiley}, author={Eckel, Craig S. and Cho, Kijong and Walgenbach, James F. and Kennedy, George G. and Moyer, James W.}, year={1996}, month={Jan}, pages={19–29} }
 @article{eckel_bradley_vanduyn_1993, title={CHANGES IN INSECTICIDE EFFICACY AGAINST HELICOVERPA-ZEA (BODDIE) ON SOYBEAN DUE TO LARVAL SIZE AND PLANT PHENOLOGY}, volume={12}, ISSN={["0261-2194"]}, DOI={10.1016/0261-2194(93)90018-E}, abstractNote={The within-plant distribution of corn earworm, Helicoverpa zea (Boddie), on soybean, Glycine max (L.) Merrill, changes with larval size and plant phenological stage. Small (instars 1 and 2) larvae on H. zea are often found within rolled leaves and flowers when each plant part is available (vegetative and flowering stages). Medium (instars 3 and 4) and large (instars 5 and 6) larvae at all plant reproductive growth stages, and small larvae when rolled leaves and flowers are not available, are found primarily on open leaves. Because both rolled leaves and flowers may protect small larvae from exposure, insecticide efficacy may be reduced in soybean fields during the vegetative or flowering stages. To ensure that any differences observed in field experiments were not due to differences in susceptibility, the relative mortality of small, medium, and large H. zea larvae fed on soybean foliage treated with insecticides was assessed in the laboratory. No significant difference between small, and medium plus large larvae (combined) was detected in one test, but mortality of small larvae was significantly higher in another test. In the field, the number of H. zea larvae on insecticide-treated and untreated soybeans was compared 1 and 7 days after application, with separate experimental designs. The relative number of small, medium, and large larvae in each treatment varied with soybean growth stage. Differences between insecticide treatments were greater for large larvae than for small larvae when soybeans were flowering. When soybeans were in the pod-forming stages, few larvae of any size were found in the insecticide-treated plots one day after application. One week after application, greater differences in larval numbers were observed for small and medium larvae on soybeans in early reproductive growth stages than for large larvae in early stages or all sizes in later stages. It was concluded that insecticide efficacy for small H. zea larvae is low on soybeans in vegetative or early flowering growth stages. Because mortality of small larvae was higher at later plant growth stages, and as mortality of small larvae fed on insecticide-treated foliage was as high as, or higher than, mortality of larger larvae, the low efficacy may be attributed to lower exposure to insecticides.}, number={1}, journal={CROP PROTECTION}, author={ECKEL, CS and BRADLEY, JR and VANDUYN, JW}, year={1993}, month={Feb}, pages={45–50} }
 @article{eckel_bradley_vanduyn_1993, title={SOYBEAN YIELD INTERACTION BETWEEN HELICOVERPA-ZEA INFESTATION AND SIMULATED FROST INJURY}, volume={85}, ISSN={["0002-1962"]}, DOI={10.2134/agronj1993.00021962008500020013x}, abstractNote={AbstractSoybean, Glycine max (L.) Merr., yields may be reduced by corn earworm, Helicoverpa zea (Boddie), feeding and by early frosts. One consequence of H. zea feeding can be a delay in pod development. A consequence of frost injury can be shortening of the seed fill duration. The objective of 12 experiments conducted at multiple locations from 1984 to 1987 was to evaluate the potential for an interaction between H. zea feeding damage and early frost. Insecticides were used to establish varying levels of H. zea populations in soybean and paraquat (1,1′.dimethyl‐4,4′‐bipyridinium dichloride) was used to simulate frost injury. Significant yield differences between levels of H. zea populations were detected in eight experiments, and paraquat treatments significantly reduced yields in 11 experiments. A significant interaction between H. zea population level and paraquat treatment time occurred in three experiments. In these experiments, yield reduction due to paraquat was greater where H. zea populations were larger. Although soybean can compensate for a delay in pod set caused by H. zea feeding in most years, when seed fill period is shortened, as would occur with early frost, a delay in pod set can contribute to yield loss. Identifying one of the many factors that lead to variation in yield loss from a particular level of H. zea infestation, is a step towards more effective management of this pest.}, number={2}, journal={AGRONOMY JOURNAL}, author={ECKEL, CS and BRADLEY, JR and VANDUYN, JW}, year={1993}, pages={232–235} }
 @article{eckel_terry_bradley_vanduyn_1992, title={CHANGES IN WITHIN-PLANT DISTRIBUTION OF HELICOVERPA-ZEA (BODDIE) (LEPIDOPTERA, NOCTUIDAE) ON SOYBEANS}, volume={21}, ISSN={["0046-225X"]}, DOI={10.1093/ee/21.2.287}, abstractNote={Within-plant distribution of Helicoverpa zea (Boddie) on soybeans, GLycine max (L.) Merrill, was investigated from 1980 to 1986. The distribution of larvae upon plant parts was evaluated based on the number on each plant part and on the number adjusted for the surface area of each plant-part. Distribution of larvae changed with larval size. The proportion of larvae, based on the number per plant part, was highest on rolled leaves for small larvae, but was highest on open leaves for large larvae. Distribution of larvae adjusted for the area of plant parts was most dense on rolled leaves, flowers, and pods. Plant phenology affected larva distribution because flowers and pods were unavailable in some plant growth stages. Larvae were observed feeding on all plant parts, but larvae found on stems were predominantly moving rather than feeding.}, number={2}, journal={ENVIRONMENTAL ENTOMOLOGY}, author={ECKEL, CS and TERRY, LI and BRADLEY, JR and VANDUYN, JW}, year={1992}, month={Apr}, pages={287–293} }
 @article{eckel_bradley_vanduyn_1992, title={REDUCTIONS IN SOYBEAN YIELD AND QUALITY FROM CORN-EARWORM FLOWER FEEDING}, volume={84}, ISSN={["1435-0645"]}, DOI={10.2134/agronj1992.00021962008400030011x}, abstractNote={AbstractSoybean, Glycine max (L.) Merr., defoliation and pod feeding by corn earworm, Helicoverpa zea (Boddie), are often considered types of injury that lead to yield and quality reductions. When infestations coincide with the flowering period, however, density of H. zea larvae is higher on flowers than on other plant parts. Experiments were conducted to assess yield reductions relative to H. zea feeding on flowers, foliage, and pods. Populations of H. zea were manipulated with insecticides at two locations in 1983 and 1984 to achieve varying densities in soybean. Flower numbers, leaf area, and pod numbers were reduced in treatments with larger populations of corn earworm larvae. In addition, fewer flowers were shed from plants with large H. zea populations, and in one trial, pod shed was also decreased. Flower removal by H. zea larvae resulted in a delay in pod set. At harvest, the number of seeds per pod was reduced in three trials that had the largest H. zea populations. Seed weight was increased or decreased by H. zea injury. Injury by H. zea sometimes increased percent soybean seed protein and sometimes reduced harvestable yield. Flower feeding contributed to yield losses by delaying pod set.}, number={3}, journal={AGRONOMY JOURNAL}, author={ECKEL, CS and BRADLEY, JR and VANDUYN, JW}, year={1992}, pages={402–409} }
 @article{eckel_bradley_vanduyn_1992, title={SOYBEAN GROWTH AND DEVELOPMENT ALTERATIONS CAUSED BY HELICOVERPA-ZEA (BODDIE) FEEDING}, volume={84}, ISSN={["0002-1962"]}, DOI={10.2134/agronj1992.00021962008400050011x}, abstractNote={AbstractCorn earworm, Helicoverpa zea (Boddie), injury to soybean, Glycine max (L.) Merr, is characterized primarily by feeding on leaves, pods, and flowers. Although soybean can withstand considerable damage to each plant part individually or in combination without yield loss, corn earworm larvae frequently cause yield reductions. To evaluate alterations in plant growth that determine if yield losses occur, the plant growth and yield response of soybean to corn earworm injury was observed at six experimental sites from 1985 to 1987. Insecticides were used to either promote or suppress corn earworm populations, and population levels were monitored during the period of infestation with ground‐cloth samples. The effect of corn earworm feeding on leaf area index, number of flowers, number of pods, and pod weight was monitored weekly from the time of infestation until harvest. Leaf area index was reduced at each site. Flower and pod feeding resulted in a delay in pod fill and a reduction in final pod number at several sites. The rate of pod fill was increased in treatments with large corn earworm populations at two sites and was decreased at one site. The number of seeds per pod was also reduced by corn earworm feeding at several sites; the weight per pod was decreased at one site and increased at other sites. At harvest, the seed number, weight per seed, percent oil and protein, and harvestable yield were sampled. Yields were reduced at all but one site, and losses were attributed primarily to reduction in pod and seed number. At one site where infestation occurred during the early flowering stage, yield loss was attributed primarily to reduced weight per seed. Since mechanisms of yield reduction were different, different thresholds may be required for soybean in early reproductive stages and soybeans in later stages.}, number={5}, journal={AGRONOMY JOURNAL}, author={ECKEL, CS and BRADLEY, JR and VANDUYN, JW}, year={1992}, pages={813–820} }