@article{blinka_herbert_malone_van duyn_roberts_bradley_bacheler_2010, title={Relationship Between External Stink Bug (Hemiptera: Pentatomidae) Boll-Feeding Symptoms and Internal Boll Damage With Respect to Cotton Lint Gin-Out and Fiber Quality}, volume={103}, ISSN={["0022-0493"]}, DOI={10.1603/ec10122}, abstractNote={ABSTRACT 
 Cotton, Gossypium hirsutum L., bolls from 17 field locations in northeastern North Carolina and southeastern Virginia, having 20% or greater internal boll damage, were studied to determine the relationship between external feeding symptoms and internal damage caused by stink bug (Hemiptera: Pentatomidae) feeding. In 2006 and 2007, two cohorts of 100 bolls each were sampled at all field locations. The first cohort was removed as bolls reached approximately quarter size in diameter (2.4 cm). External and internal symptoms of stink bug feeding were assessed and tabulated. Concurrent to when the first cohort was collected, a second cohort of quarter-size-diameter bolls was identified, tagged, examined in situ for external feeding symptoms (sunken lesions), and harvested at the black seed coat stage. Harvested bolls were assessed for internal damage and locks were categorized (undamaged, minor damage, or major damage), dried, and ginned. Lint samples from each damage category were submitted for high volume instrument and advanced fiber information system quality analyses. Significant, moderately strong Pearson correlation coefficients existed between number of external stink bug feeding lesions and internal damage. Pearson correlation of total external lesions with total internal damage was stronger than any correlation among the other single components compared. Predictability plots indicated a rapid increase in relationship strength when relating external stink bug lesions to internal damage as the number of external lesions increased. Approximately 90% predictability of internal damage was achieved with four (2006) or six (2007) external lesions per boll. Gin-turnout and fiber quality decreased with increasing intensity of internal stink bug damage.}, number={6}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Blinka, Eric L. and Herbert, Ames and Malone, Sean and Van Duyn, John W. and Roberts, Phillip and Bradley, J. R. and Bacheler, Jack S.}, year={2010}, month={Dec}, pages={2236–2241} }
 @article{head_jackson_adamczyk_bradley_van duyn_gore_hardee_leonard_luttrell_ruberson_et al._2010, title={Spatial and temporal variability in host use by Helicoverpa zea as measured by analyses of stable carbon isotope ratios and gossypol residues}, volume={47}, ISSN={["0021-8901"]}, DOI={10.1111/j.1365-2664.2010.01796.x}, abstractNote={Summary 1. A high dose ⁄ refuge strategy has been adopted in the USA to manage the risk of Bacillus thuringiensis (Bt) resistance in target pests such as the cotton bollworm (CBW), Helicoverpa zea (Boddie) in transgenic Bt cotton Gossypium hirsutum L. Structured refuges, consisting of non-Bt cotton, have been a mandated part of this strategy to produce non-selected insects that are temporally and spatially synchronous with insects from the Bt crop, diluting Bt resistance alleles through mating. However, the bollworm is highly polyphagous and exploits a large number of crop and weedy hosts concurrently with Bt cotton.}, number={3}, journal={JOURNAL OF APPLIED ECOLOGY}, author={Head, Graham and Jackson, Ryan E. and Adamczyk, John and Bradley, Julius R. and Van Duyn, John and Gore, Jeff and Hardee, Dick D. and Leonard, B. Rogers and Luttrell, Randall and Ruberson, John and et al.}, year={2010}, month={Jun}, pages={583–592} }
 @article{toews_blinka_van duyn_herbert_bacheler_roberts_greene_2009, title={Fidelity of External Boll Feeding Lesions to Internal Damage for Assessing Stink Bug Damage in Cotton}, volume={102}, ISSN={["1938-291X"]}, DOI={10.1603/029.102.0362}, abstractNote={ABSTRACT Previous research showed that the most precise estimates of stink bug damage in developing cotton bolls are obtained by collecting soft quarter-sized bolls and dissecting them for signs of internal feeding damage, such as internal boll wall warts and/or stained lint. However, this method requires considerable time and effort; therefore, scouts and growers are unwilling to invest adequate resources to make sound pest management decisions. Here, the authors evaluated enumeration of external feeding lesions on groups of 10, 15, 20, or 25 bolls per sample as an alternative sampling procedure. Results relate the similarity of external boll feeding lesions to internal damage as a function of boll sample size and external lesion tally. Inverse prediction confidence intervals (CIs) were also calculated to predict internal boll damage on a new sample based only on external feeding lesions. Results show that linear regression model fit increased when examining at least 20 bolls per sample, and only one external lesion per boll provided as good of model fit as using a minimum of two, three, or four lesions per boll. Inverse prediction CIs suggested that more than one sample (20 bolls per sample) will be required to make external lesions an acceptable method for making reasonably accurate management decisions. F-test lack of fit and significant regression models suggest that examination of external lesions is a promising a method for estimating stink bug damage in cotton.}, number={3}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Toews, Michael D. and Blinka, Eric L. and Van Duyn, John W. and Herbert, David A., Jr. and Bacheler, Jack S. and Roberts, Phillip M. and Greene, Jeremy K.}, year={2009}, month={Jun}, pages={1344–1351} }
 @article{siebert_nolting_leonard_braxton_all_van duyn_bradley_bacheler_huckaba_2008, title={Efficacy of Transgenic Cotton Expressing Cry1Ac and Cry1F Insecticidal Protein Against Heliothines (Lepidoptera: Noctuidae)}, volume={101}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493-101.6.1950}, abstractNote={Abstract Cotton, Gossypium hirsutum L, plants expressing Cry1Ac and Cry1F (Phytogen 440W) insecticidal crystal proteins of Bacillus thuringiensis (Bt) Berliner, were evaluated against natural populations of tobacco budworm, Heliothis virescens (F.), and bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), across 13 southern U.S. locations that sustained low, moderate, and high infestations. The intrinsic activity of Phytogen 440W was compared with nontreated non-Bt cotton (PSC355) and with management strategies in which supplemental insecticides targeting heliothines were applied to Phytogen 440W and to PSC355 cotton. Infestations were composed primarily of bollworm, which is the least sensitive of the heliothine complex to Cry toxins. Therefore, damage recorded in these studies was primarily due to bollworm. Greater than 75% of all test sites sustained heliothine infestations categorized as moderate to high (10.6–64.0% peak damaged bolls in nontreated PSC355). Phytogen 440W, alone or managed with supplemental insecticide applications, reduced heliothine-damaged plant terminals, squares (flower buds), flowers, and bolls equal to or better (1.0–79.0-fold) than managing a non-Bt cotton variety with foliar insecticides across all infestation environments. Rarely (frequency of ≤11% averaged across structures), sprayed Phytogen 440W reduced damaged structures compared with nontreated Phytogen 440W. Protection against heliothine-induced plant damage was similar across the three levels of infestation for each viable management strategy, with exception to damaged squares for nontreated Phytogen 440W. In situations of moderate to high heliothine infestations, cotton plants expressing Cry1Ac and Cry1F may sustain higher levels of damage compared with that same variety in low infestations. No significant difference in yield was observed among heliothine management strategies within each infestation level, indicating cotton plants may compensate for those levels of plant damage. These findings indicate Phytogen 440W containing Cry1Ac and Cry1F provided consistent control of heliothines across a range of environments and infestation levels.}, number={6}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Siebert, M. Willrich and Nolting, S. and Leonard, B. R. and Braxton, L. B. and All, J. N. and Van Duyn, J. W. and Bradley, J. R. and Bacheler, J. and Huckaba, R. M.}, year={2008}, month={Dec}, pages={1950–1959} }
 @article{siebert_tindal_leonard_van duyn_babcock_2008, title={Evaluation of corn hybrids expressing Cry1F (Herculex (R) I insect protection) against fall armyworm (Lepidoptera : Noctuidae) in the southern United States}, volume={43}, ISSN={["0749-8004"]}, DOI={10.18474/0749-8004-43.1.41}, abstractNote={Efficacy of two insect-resistant corn hybrids expressing the Cry1 F insecticidal crystal protein of Bacillus thuringiensis var. aizawai Berliner (transformation event TC1507) was evaluated against fall armyworm, Spodoptera frugiperda (J.E. Smith), in three southern U.S. locations. Larval susceptibility was evaluated on CrylF and nonBt field corn, Zea mays L., plants (V3–V12 and R1–R2 stages) in field plots and laboratory studies. Leaf-feeding injury was significantly less and plant height was significantly greater for hybrids containing Cry1 F as compared with nonBt corn hybrids when exposed to natural or artificial fall armyworm infestations. In addition, larval mortality was significantly greater on CrylF corn hybrids compared with that on nonBt hybrids. These results demonstrate that corn hybrids containing CrylF represent an effective plant incorporated insecticidal protein management option for fall armyworm. In environments where fall armyworm may exceed damage thresholds and have to be carefully managed with foliar sprays, utilization of CrylF corn hybrids will allow growers flexibility in planting and an efficient means for managing infestations.}, number={1}, journal={JOURNAL OF ENTOMOLOGICAL SCIENCE}, author={Siebert, Melissa Willrich and Tindal, Kelly V. and Leonard, B. Rogers and Van Duyn, John W. and Babcock, Jonathan M.}, year={2008}, month={Jan}, pages={41–51} }
 @article{jackson_bradley_van duyn_leonard_allen_luttrell_ruberson_adamczyk_gore_hardee_et al._2008, title={Regional assessment of Helicoverpa zea populations on cotton and non-cotton crop hosts}, volume={126}, ISSN={["1570-7458"]}, DOI={10.1111/j.1570-7458.2007.00653.x}, abstractNote={Abstract}, number={2}, journal={ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA}, author={Jackson, R. E. and Bradley, J. R. and Van Duyn, J. and Leonard, B. R. and Allen, K. C. and Luttrell, R. and Ruberson, J. and Adamczyk, J. and Gore, J. and Hardee, D. D. and et al.}, year={2008}, month={Feb}, pages={89–106} }
 @article{jackson_marcus_gould_bradley_van duyn_2007, title={Cross-resistance responses of Cry1Ac-selected Heliothis virescens (Lepidoptera : Noctuidae) to the Bacillus thuringiensis protein Vip3A}, volume={100}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493(2007)100[180:CROCHV]2.0.CO;2}, abstractNote={Abstract One susceptible and three Cry1Ac-resistant strains of tobacco budworm, Heliothis virescens (F.) (Lepidoptera: Noctuidae), were used in laboratory studies to determine the level of cross-resistance between the Bacillus thuringiensis (Berliner) toxins Cry1Ac and Vip3A by using concentration–mortality and leaf tissue experiments. Concentration–mortality data demonstrated that the three Cry1Ac-resistant H. virescens strains, YHD2, KCBhyb, and CxC, were at least 215- to 316-fold resistant to Cry1Ac compared with the susceptible strain, YDK. Results from Vip3A concentration–mortality tests indicated that mortality was similar among all four H. virescens strains. Relative larval growth on Cry1Ac reflected concentration–mortality test results, because YHD2 larval growth was mostly unaffected by the Cry1Ac concentrations tested. Growth ratios for KCBhyb and CXC indicated that they had a more moderate level of resistance to Cry1Ac than did YHD2. Relative larval growth on Vip3A was highly variable at lower concentrations, but it was more consistent on concentrations of Vip3A above 25 &mgr;g/ml. Differences in larval growth among strains on Vip3A were not as pronounced as seen in Cry1Ac experiments. Mortality and larval growth also was assessed in leaf tissue bioassays in which YDK, CxC, and KCBhyb neonates were placed onto leaf disks from non-Bt and Bt cotton, Gossypium hirsutum L., for 5 d. Three Bt lines were used in an initial bioassay and consisted of two Vip3A-containing lines, COT203 and COT102, and a Cry1Ac-producing line. Mortality of KCBhyb and CXC was lower than that of YDK larvae in the presence of leaf tissue from the Cry1Ac-producing line. Additionally, increased larval growth and leaf tissue consumption on Cry1Ac-containing leaf disks was observed for KCBhyb and CXC. Mortality and larval weights were similar among strains when larvae were fed leaf tissue of either non-Bt, COT203, or COT102. A subsequent leaf tissue bioassay was conducted that evaluated four cotton lines: non-Bt, Cry1Ab-expressing, Vip3A-expressing, and pyramided-toxin plants that produced both Cry1Ab and Vip3A. Mortality levels were similar among strains when fed non-Bt, Vip3A-expressing, or pyramided-toxin leaf tissues. Mortality was higher for YDK than for KCBhyb or CXC on Cry1Ab-expressing leaf tissues. No differences in larval weights were observed among strains for any genotype tested. Results of these experiments demonstrate that cross-resistance is nonexistent between Cry1Ac and Vip3A in H. virescens. Thus, the introduction of Vip3A-producing lines could delay Cry1Ac-resistance evolution in H. virescens, if these lines gain a significant share of the market.}, number={1}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Jackson, R. E. and Marcus, M. A. and Gould, F. and Bradley, J. R., Jr. and Van Duyn, J. W.}, year={2007}, month={Feb}, pages={180–186} }
 @article{jackson_gould_bradley_duyn_2006, title={Genetic variation for resistance to Bacillus thuringiensis toxins in Helicoverpa zea (Lepidoptera : Noctuidae) in eastern North Carolina}, volume={99}, DOI={10.1603/0022-0493-99.5.1790}, abstractNote={Abstract To evaluate resistance to Bacillus thuringiensis Berliner (Bt) toxins, adult female bollworms, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), were collected from four light trap locations in two eastern North Carolina counties from August to October during 2001 and 2002. Females were allowed to oviposit, and upon hatching, 24 neonates from each female (F1 lines) were screened for survival and growth rate on each of three diets: non-Bt diet, diet containing 5.0 &mgr;g/ml Cry1Ac toxin, or diet containing 5.0 &mgr;g/ml Cry2Ab toxin. These screens were designed to identify nonrecessive Bt resistance alleles present in field populations of bollworm. Of 561 and 691 families screened with both Cry1Ac- and Cry2Ab-containing diets in 2001 and 2002, respectively, no F1 lines were identified that seemed to carry a gene conferring substantial resistance to either Cry1Ac or Cry2Ab. Adults from F1 lines with growth scores in the highest (R) and lowest (S) quartiles were mated in four combinations, RxR, SxR, RxS, and SxS. Differences in growth rates of larvae from these crosses demonstrated that there is substantial quantitative genetic variation in eastern North Carolina populations for resistance to both Cry1Ac and Cry2Ab toxins. These findings, in addition to results suggesting partially dominant inheritance of resistance to Cry1Ac and Cry2Ab, are critically important for determining appropriate resistance management strategies that impact the sustainability of transgenic cotton, Gossypium hirsutum (L.).}, number={5}, journal={Journal of Economic Entomology}, author={Jackson, R. E. and Gould, Fred and Bradley, J. R. and Duyn, J. W. Van}, year={2006}, pages={1790–1797} }
 @article{gould_cohen_bentur_kennedy_duyn_2006, title={Impact of small fitness costs on pest adaptation to crop varieties with multiple toxins: A heuristic model}, volume={99}, DOI={10.1603/0022-0493-99.6.2091}, abstractNote={Abstract A deterministic two-locus model was used to examine how small fitness costs to individuals carrying resistance alleles could impact the risk of panmictic insect pest populations adapting to crop varieties that produced two distinct toxins. Parameters examined were 1) level of toxicity of each toxin, 2) initial frequencies of alleles for adaptation to the toxins, 3) percentage of population feeding on nontoxic plants, and 4) level of fitness cost associated with adaptation to each of the two toxins. Resistance to each toxin was assumed to be biochemically independent, controlled by a resistance coding allele at a single locus, and inherited as a partially recessive trait in the field. When plants are extremely toxic to the pest, effective refuge size is 10%, and there is a fitness cost to resistance alleles only when in homozygous form (5%), the pest population is never predicted to adapt to either toxin as long as the initial frequencies of the resistance alleles are below 0.05. Even if the initial frequency of the allele for adapting to one toxin is 0.95 when a two-toxin cultivar completely replaces a one-toxin cultivar, the model predicts that a low equilibrium allelic frequency will develop for both resistance alleles, as long as the frequency of the allele for adapting to the second toxin is initially 0.001 or less. If cultivars with one and two toxins are planted, the model predicts that resistance will develop. Nonrandom mating and stochastic variation within subpopulations also could lead to evolution of resistance.}, number={6}, journal={Journal of Economic Entomology}, author={Gould, F. and Cohen, M. B. and Bentur, J. S. and Kennedy, George and Duyn, J. Van}, year={2006}, pages={2091–2099} }
 @article{jackson_mahaffey_bradley_van duyn_sorenson_2005, title={The impact of transgenic cottons expressing one or two proteins from Bacillus thuringiensis on survival and damage potential of first and second instars of Ostrinia nubilalis (Lepidoptera: Crambidae)}, volume={9}, ISBN={1524-3303}, number={4}, journal={Journal of Cotton Science (Online)}, author={Jackson, R. E. and Mahaffey, J. S. and Bradley, J. R., Jr. and Van Duyn, J. W. and Sorenson, C. E.}, year={2005}, pages={199} }
 @article{jackson_bradley_van duyn_gould_2004, title={Comparative production of Helicoverpa zea (Lepidoptera : Noctuidae) from transgenic cotton expressing either one or two Bacillus thuringiensis proteins with and without insecticide oversprays}, volume={97}, ISSN={["1938-291X"]}, DOI={10.1603/0022-0493-97.5.1719}, abstractNote={Abstract Transgenic cotton, Gossypium hirsutum (L.), expressing either one or two Bacillus thuringiensis ssp. kurstaki Berliner (Bt) proteins was compared with the conventional sister line in field experiments with regard to production of bollworm, Helicoverpa zea (Boddie), and bolls damaged by bollworm. The relative numbers of bollworms that developed on Bollgard (Monsanto Co., St. Louis, MO), Bollgard II (Monsanto Co.), and conventional cotton were estimated under nontreated conditions in 2000 and both insecticide-treated and nontreated conditions in 2001–2002 in North Carolina tests. Averaged across seven field studies under nontreated conditions, Bollgard cotton generated statistically similar numbers of large (L4–L5) bollworm larvae compared with the conventional variety; however, Bollgard cotton produced significantly fewer damaged bolls and bollworm adults than the conventional variety. Production of large larvae, damaged bolls, and adults was decreased dramatically by Bollgard II cotton as compared with Bollgard and conventional varieties. When comparing insecticide-treated and nontreated cotton genotypes, both Bt cotton sustained less boll damage than the conventional variety averaged across insecticide regimes; furthermore, Bollgard II cotton had fewer damaged bolls than the Bollgard variety. When averaged across cotton genotypes, pyrethroid oversprays reduced the numbers of damaged bolls compared with the nontreated cotton. Insecticide-treated Bollgard cotton, along with insecticide-treated and nontreated Bollgard II cotton reduced production of bollworm larvae, pupae, and adults. However, the addition of pyrethroid oversprays to Bollgard II cotton seemed to be the best resistance management strategy available for bollworm because no bollworms were capable of completing development under these conditions.}, number={5}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Jackson, RE and Bradley, JR and Van Duyn, JW and Gould, F}, year={2004}, month={Oct}, pages={1719–1725} }
 @article{jackson_bradley_van duyn_2004, title={Performance of feral and Cry1Ac-selected Helicoverpa zea (Lepidoptera : Noctuidae) strains on transgenic cottons expressing one or two Bacillus thuringiensis ssp kurstaki proteins under greenhouse conditions}, volume={39}, ISSN={["0749-8004"]}, DOI={10.18474/0749-8004-39.1.46}, abstractNote={Efficacy of Bollgard (DP50B) and Bollgard II (DP50BX) cottons that express either one or two Bacillus thuringiensis Berliner proteins, respectively, along with the conventional sister genotype (DP50), was determined for a feral strain of bollworm, Helicoverpa zea (Boddie), and a Cry1Ac-selected bollworm strain in 1999. In 2000, a greenhouse study was designed to compare the efficacy of three transgenic cottons expressing either the Cry1Ac endotoxin alone (DP50B), the Cry2Ab endotoxin alone (DP50X), or both the CrylAc and Cry2Ab endotoxins (DP50BX) against a feral and a Cry1Ac-selected bollworm strain. Results from the 1999 greenhouse study evaluating both a feral and a Cry1Ac-selected bollworm strain demonstrated that when averaged across bollworm strains, the Bollgard II genotype significantly reduced larval survival and fruit penetration by bollworm compared to the Bollgard variety. Also, the Cry1Ac-selected bollworm strain displayed increased larval survival, superficial fruit damage, and fruit penetration compared to the feral strain when averaged across genotypes. In the 2000 study, the Bollgard II genotype significantly reduced fruit penetration by bollworm below that of the Bollgard variety when averaged across strains; however, the single Cry2Ab-producing genotype performed similarly to both Bollgard and Bollgard II with respect to fruit penetration. The Cry1Ac-selected bollworm strain exhibited significantly greater larval survival and superficial fruit damage on the Bollgard variety compared to the feral strain, but no differences among larval strains were evident for other genotypes. Also, when averaged across genotypes, the Cry1Ac-selected bollworm strain penetrated a higher proportion of cotton fruit compared to the feral strain. These results suggest that commercialization of Bollgard II cottons would significantly reduce bollworm survival and damage compared to that experienced by current Bollgard varieties. Bollgard II plantings also should have a positive impact on Bt resistance management of bollworm.}, number={1}, journal={JOURNAL OF ENTOMOLOGICAL SCIENCE}, author={Jackson, RE and Bradley, JR and Van Duyn, JW}, year={2004}, month={Jan}, pages={46–55} }
 @article{burd_gould_bradley_van duyn_moar_2003, title={Estimated frequency of nonrecessive Bt resistance genes in bollworm, Helicoverpa zea (Boddie) (Lepidoptera : Noctuidae) in eastern North Carolina}, volume={96}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493-96.1.137}, abstractNote={Abstract In summer 2000, adult female bollworm moths, Helicoverpa zea (Boddie), were collected from light-traps at four locations near the Tidewater Research Station, Plymouth, NC. Female moths were allowed to lay eggs, and at hatch, 72 larvae from each female were screened for growth rate on normal artificial diet and on diets containing 5.0 μg of either Cry1Ac or Cry2Aa Bt toxin per milliliter of diet. The growth rate bioassays were performed to isolate nonrecessive Bt resistance genes present in field populations of bollworm. We found one individual out of 583 screened that appeared to carry a major gene for resistance to Cry1Ac. Assuming four alleles per individual, the gene frequency is 1/2332 or 0.00043. Other females appeared to have minor genes for Cry1Ac resistance or major genes with lower levels of dominance. We also found one individual out of 646 screened that appeared to carry a major gene for resistance to Cry2Aa. The gene frequency for Cry2Aa resistance was estimated at 1/2584 or 0.00039. Again, other females seemed to carry additional minor resistance genes. Along with other results that indicate partially dominant inheritance of Cry1Ac resistance in bollworm, these allele frequency estimates are important for determining the rate of resistance evolution in H. zea to specific Bt toxins.}, number={1}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Burd, AD and Gould, F and Bradley, JR and Van Duyn, JW and Moar, WJ}, year={2003}, month={Feb}, pages={137–142} }
 @article{storer_peck_gould_van duyn_kennedy_2003, title={Sensitivity analysis of a spatially-explicit stochastic simulation model of the evolution of resistance in Helicoverpa zea (Lepidoptera : Noctuidae) to Bt transgenic corn and cotton}, volume={96}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493-96.1.173}, abstractNote={Abstract The sensitivities of a model simulating the evolution of resistance in Helicoverpa zea to Bt toxins in transgenic crops were investigated by examining effects of each of the model parameters on the frequency of resistance alleles after 8 yr. The functional dominance of resistance alleles and the initial frequency of those alleles had a major impact on resistance evolution. The survival of susceptible insects on the transgenic crops and the population dynamics of the insect, driven by winter survival and reproductive rates, were also important. In addition, agricultural practices including the proportion of the acreage planted to corn, and the larval threshold for spraying cotton fields affected the R-allele frequency. Many of these important parameters are inherently variable or cannot be measured with accuracy, so model output cannot be interpreted as being a forecast. However, this analysis is useful in focusing empirical research on those aspects of the insects’ life system that have the largest effects on resistance development, and indicates ways in which to improve products and agricultural practices to increase the expected time to resistance. The model can thus be used as a scientific basis for devising a robust resistance management strategy for Bt crops.}, number={1}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Storer, NP and Peck, SL and Gould, F and Van Duyn, JW and Kennedy, GG}, year={2003}, month={Feb}, pages={173–187} }
 @article{storer_peck_gould_van duyn_kennedy_2003, title={Spatial processes in the evolution of resistance in Helicoverpa zea (Lepidoptera : Noctuidae) to Bt transgenic corn and cotton in a mixed agroecosystem: a biology-rich stochastic simulation model}, volume={96}, ISSN={["1938-291X"]}, DOI={10.1603/0022-0493-96.1.156}, abstractNote={Abstract A simulation model is developed to examine the role of spatial processes in the evolution of resistance in Helicoverpa zea populations to Bt corn and Bt cotton. The model is developed from the stochastic spatially explicit Heliothis virescens model described by Peck et al. (1999), to accommodate a spatial mix of two host crops (corn and cotton), and to reflect the agronomic practices, as well as the spatial and temporal population dynamics of H. zea, in eastern North Carolina. The model suggests that selection for resistance is more intense in Bt cotton fields than in Bt corn fields. It further suggests that local gene frequencies are highly dependent on local deployment levels of Bt crops despite the high mobility of the adult insects. Region-wide average gene frequencies depend on the region-wide level of Bt deployment, so incomplete technology adoption slows the rate of resistance evolution. However, on a local scale, H. zea populations in clusters of fields in which Bt use is high undergo far more rapid evolution than populations in neighboring clusters of fields in which Bt use is low. The model suggests that farm-level refuge requirements are important for managing the risk of resistance. The model can be used as an aid in designing plans for monitoring for resistance by suggesting the appropriate distribution of monitoring locations, which should focus on areas of highest Bt crop deployment. The findings need to be placed in the context of the input parameters, many of which are uncertain or highly variable in nature, and therefore, a thorough sensitivity analysis is warranted.}, number={1}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Storer, NP and Peck, SL and Gould, F and Van Duyn, JW and Kennedy, GG}, year={2003}, month={Feb}, pages={156–172} }
 @article{faircloth_bradley_van duyn_2002, title={Effect of insecticide treatments and environmental factors on thrips populations, plant growth and yield of cotton}, volume={37}, ISSN={["0749-8004"]}, DOI={10.18474/0749-8004-37.4.308}, abstractNote={Field experiments were conducted in 1997–1999 in Washington Co., NC, to examine how cotton, Gossypium hirsutum, is affected by thrips species composition and abundance, environmental factors, and insecticide applications. Populations of adult and juvenile thrips were monitored in seedling cotton treated with insecticide applications of either imidacloprid as a seed treatment, acephate as a foliar spray, or aldicarb applied in-furrow. The number of plants per 3.05 row-m, location of the first fruiting branch, number of open bolls per 1.52 row-m, yields, accumulated degree-d 60′s (DD60′s), and accumulated rainfall were recorded each year the studies were conducted. Aldicarb and acephate provided better thrips control than did imidacloprid in all 3 yrs. Thrips species ratios differed among years. In 1997, the aldicarb treatment resulted in a better “earliness profile” (lower fruit set and more early opening bolls) than either acephate or imidacloprid, while in 1998 and 1999 there were few differences in these plant parameters. In 1997, all insecticide treatments resulted in statistically higher yields compared with the untreated check. Accumulated DD60′s were consistently higher in 1998 and 1999 than in 1997 after the first thrips sampling date. Cumulative rainfall appeared to be inversely associated with juvenile thrips populations.}, number={4}, journal={JOURNAL OF ENTOMOLOGICAL SCIENCE}, author={Faircloth, JC and Bradley, JR and Van Duyn, JW}, year={2002}, month={Oct}, pages={308–316} }
 @article{suh_orr_van duyn_borchert_2002, title={Influence of cotton microhabitat on temperature and survival of Trichogramma (Hymenoptera : Trichogrammatidae) within cardboard capsules}, volume={31}, ISSN={["1938-2936"]}, DOI={10.1603/0046-225X-31.2.361}, abstractNote={Abstract Field studies were conducted in 1996 and 1997 to determine the most suitable release sites in cotton for inundatively released encapsulated Trichogramma exiguum Pinto & Platner. Atypical applications of a plant growth regulator, mepiquat chloride (Pix), were used to manipulate cotton plant size and canopy closure to produce a range of plant sizes that might be present in North Carolina when Trichogramma releases for suppression of third-generation (F3) heliothines were made. Pix treatments had a significant effect on canopy closure, which significantly influenced the number of hours soil surface temperatures between rows were ≥35°C. The mean daily number of hours temperatures were ≥35°C was greatest on the soil surface between rows, followed by in the canopy, then soil surface within rows. A significant correlation between the number of hours preimaginal Trichogramma were exposed to temperatures ≥35°C and Trichogramma emergence was found in 1997. Consequently, suitability of the soil surface as a release site for Trichogramma capsules depended significantly on the level of canopy closure, location of capsules relative to the center of rows, and length of time capsules remained in the field before parasitoid emergence. Our results indicate that these factors should be considered when implementing augmentative releases of Trichogramma wasps in cotton.}, number={2}, journal={ENVIRONMENTAL ENTOMOLOGY}, author={Suh, CPC and Orr, DB and Van Duyn, JW and Borchert, DM}, year={2002}, month={Apr}, pages={361–366} }
 @article{storer_van duyn_kennedy_2001, title={Life history traits of Helicoverpa zea (Lepidoptera : Noctuidae) on non-Bt and Bt transgenic corn hybrids in Eastern North Carolina}, volume={94}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493-94.5.1268}, abstractNote={Abstract Transgenic varieties of field corn that express the Cry1Ab B. thuringiensis (Bt) toxin in ear tissue present the potential of reducing ear feeding by the corn earworm, Helicoverpa zea (Lepidoptera: Noctuidae), and for reducing the size of populations of the insect infesting other host crops. Life history parameters of H. zea feeding on ears of conventional and Bt field corn varieties were measured in field plots in eastern North Carolina in 1997 and 1998. Transformation events investigated were Mon-810 and Bt-11. Bt corn was found to cause a steady mortality of larvae during development, but permitted ≈15–40% survival to the prepupal stage compared with non-Bt corn. Mortality of prepupae and pupae from Bt corn was also higher than from non-Bt corn, reducing overall adult production by 65–95%. The larvae that did survive grew more slowly on Bt than on non-Bt corn, and produced pupae that weighed 33% less. Pupation and adult eclosion were delayed by 6–10 d by feeding on Bt corn ears. Corn varieties expressing Bt in ear tissue have the potential to reduce H. zea ear feeding by up to 80%, and the potential to reduce populations emerging from ear-stage corn fields to infest cotton, soybean and other crops by around 75%. To have a measurable effect on area-wide populations, Bt corn varieties would need to be planted in large proportions of corn fields. Extensive planting of varieties such as those tested here, having only moderate effects on H. zea, would raise concerns about rapid evolution of resistance.}, number={5}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Storer, NP and Van Duyn, JW and Kennedy, GG}, year={2001}, month={Oct}, pages={1268–1279} }
 @article{agi_burd_bradley_van duyn_2001, title={Planting date effects on hellothine larval numbers, fruit damage, and yield of transgenic B.t. cotton in North Carolina}, volume={36}, ISSN={["0749-8004"]}, DOI={10.18474/0749-8004-36.4.402}, abstractNote={The susceptibility of Bollgard® cotton and non-B.t. cotton to bollworm, Helicoverpa zea (Boddie), was examined under contrasting crop management strategies in northeastern North Carolina in 1995, 1996, and 1998. Specifically, planting date effects were observed in Edgecombe Co. in 1995 and 1996, in Martin Co. in 1996, and in Washington Co. in 1998. The bollworm was the only lepidopterous pest which occurred at damaging levels in these tests. Although no significant differences were detected in mean percent egg deposition, mean percent larval infestation, and mean percent damaged fruit between early-planted and late-planted plots in 1995 and 1996, yields were higher in early-planted cotton than in late-planted cotton. In 1998 mean percent damaged fruit was higher in early-planted cotton than in late-planted cotton, but early-planted cotton had significantly higher yields than late-planted cotton. Early planting may be an effective management strategy for Bollgard® cotton in northeastern North Carolina.}, number={4}, journal={JOURNAL OF ENTOMOLOGICAL SCIENCE}, author={Agi, AL and Burd, A and Bradley, JR and Van Duyn, JW}, year={2001}, month={Oct}, pages={402–410} }
 @article{faircloth_bradley_van duyn_groves_2001, title={Reproductive success and damage potential of tobacco thrips and western flower thrips on cotton seedlings in a greenhouse environment}, volume={18}, number={3}, journal={Journal of Agricultural and Urban Entomology}, author={Faircloth, J. C. and Bradley, J. R. and Van Duyn, J. W. and Groves, R. L.}, year={2001}, pages={179–185} }
 @article{sorenson_ihrig_bradley_van duyn_herbert_2000, title={Comparison of two computer techniques and a visual technique for the estimation of wheat leaf consumption by cereal leaf beetle (Coleoptera : Chrysomelidae)}, volume={35}, ISSN={["0749-8004"]}, DOI={10.18474/0749-8004-35.4.391}, abstractNote={Three techniques for estimating wheat foliage defoliation by cereal leaf beetle, Oulema melanopus (L.), larvae were evaluated. The techniques were visual estimation, computer estimation with image capture through a flatbed scanner (Lanalyze), and a commercially available video computer image analysis system (CIAS). Both computer-assisted techniques exhibited high levels of repeatability. Both consistently produced errors of less than 3 percent, although each system exhibited different error patterns. The Lanalyze system tended to systematically underestimate actual defoliation of mock leaves, while the CIAS system tended to overestimate actual defoliation. Visual estimators exhibited greater variation among estimates and, on average, greater discrepancies from actual defoliation when compared with the computer assisted techniques. The experience of the observer had a bearing on the accuracy and consistency of visual estimates; more experienced observers had the best accuracy.}, number={4}, journal={JOURNAL OF ENTOMOLOGICAL SCIENCE}, author={Sorenson, CE and Ihrig, RA and Bradley, JR and Van Duyn, JW and Herbert, DA}, year={2000}, month={Oct}, pages={391–401} }
 @article{suh_orr_van duyn_2000, title={Effect of insecticides on Trichogramma exiguum (Trichogrammatidae : Hymenoptera) preimaginal development and adult survival}, volume={93}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493-93.3.577}, abstractNote={Abstract The effect of insecticides on Trichogramma exiguum Pinto & Platner emergence, adult survival, and fitness parameters was investigated. Insecticides tested were lambda cyhalothrin, cypermethrin, thiodicarb, profenophos, spinosad, methoxyfenozide, and tebufenozide. All insecticides, with the exception of methoxyfenozide and tebufenozide, adversely affected Trichogramma emergence from Helicoverpa zea (Boddie) host eggs when exposed at different preimaginal stages of development (larval, prepupal, or pupal). Regardless of the developmental stage treated, none of the insecticides tested had a significant effect on the sex ratio or frequency of brachyptery of emerged females. However, the mean life span of emerged T. exiguum females significantly varied among insecticide treatments, and was significantly affected by the developmental stage of parasitoid when treated. Based on LC50 values, spinosad and prophenofos were the most toxic compounds to female T. exiguum adults, followed by lambda cyhalothrin, cypermethrin, and thiodicarb. Insecticides field-weathered for four to 6 d on cotton leaves showed no activity against female T. exiguum adults.}, number={3}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Suh, CPC and Orr, DB and Van Duyn, JW}, year={2000}, month={Jun}, pages={577–583} }
 @article{suh_orr_van duyn_borchert_2000, title={Trichogramma exiguum (Hymenoptera: Trichogrammatidae) releases in North Carolina cotton: Evaluation of heliothine pest suppression}, volume={93}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493-93.4.1127}, abstractNote={Abstract Field studies were conducted in 1996 and 1997 to reevaluate the use of augmentative releases of Trichogramma wasps for heliothine management in cotton. In 1996, nine releases of Trichogramma exiguum Pinto & Platner, spaced 3–4 d apart, were made into three 0.4-ha cotton plots. Six weekly releases were made in 1997, each containing two T. exiguum cohorts developmentally staggered by 45°C degree-days. Field release rates, estimated from laboratory and field quality control data, averaged 108,357 T. exiguum ♀♀ per hectare per cohort per release in 1996 and 193,366 ♀♀ per hectare per cohort per release in 1997. In 1996, mean ± SD adult emergence under laboratory conditions for released cohorts was 92 ± 7%; 62 ± 5% of emerged adults were females, 3 ± 2% of females displayed brachyptery (nonfunctional wings), mean female longevity under laboratory conditions was 15 ± 4 d, and mean ± SD field emergence was 97 ± 2%. Quality control measurements were similar in 1997. In 1996, mean ± SD percent parasitism of heliothine eggs in field plots on the sampled dates ranged from 67 ± 4 to 83 ± 5% in T. exiguum release plots and 25 ± 9 to 55 ± 8% in control plots. In 1997, parasitism levels ranged from 74 ± 4 to 89 ± 5% in T. exiguum release plots and 18 ± 18 to 69 ± 11% in control plots. Despite increased parasitism levels in T. exiguum release plots, there were no significant differences in density of fifth instars, boll damage, or yield between T. exiguum release and control plots. Therefore, it is concluded that Trichogramma augmentation is not an effective heliothine management tool in North Carolina cotton.}, number={4}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Suh, CPC and Orr, DB and Van Duyn, JW and Borchert, DM}, year={2000}, month={Aug}, pages={1127–1136} }
 @article{suh_orr_van duyn_2000, title={Trichogramma releases in North Carolina cotton: Why releases fail to suppress heliothine pests}, volume={93}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493-93.4.1137}, abstractNote={Abstract Field studies were conducted in 1996 and 1997 to determine the fate of naturally oviposited F3 heliothine eggs in cotton plots treated with augmentative releases of Trichogramma exiguum Pinto & Platner and nontreated plots. Four cohorts of newly oviposited eggs (<24 h old) were followed in 1996 and two cohorts in 1997. In 1996, mean ± SD percent parasitism, estimated by in-field studies following the fate of naturally oviposited eggs, ranged from 7 ± 7 to 61 ± 8% in T. exiguum release plots and 0 ± 0 to 35 ± 13% in control plots. The mean ± SD percent of eggs hatched in T. exiguum release plots ranged from 1 ± 2 to 11 ± 4% and 7 ± 4 to 28 ± 10% in control plots. In 1997, mean ± SD percent egg parasitism ranged from 27 ± 4 to 40 ± 3% in T. exiguum release plots and 15 ± 18 to 25 ± 8% in control plots. The mean ± SD percent of eggs hatched in T. exiguum release plots ranged from 7 ± 3 to 12 ± 2% and 18 ± 6 to 28 ± 8% in control plots. Despite increased parasitism and reduced egg hatch in T. exiguum release plots, overall, there was no significant difference in larval density (all instars combined) between T. exiguum release and control plots. Combined analysis of the heliothine larval populations and egg fate data revealed that the additional egg mortality produced by released T. exiguum was offset by lower larval mortality in release plots. Because of the occurrence of compensatory mortality, the egg stage of heliothines is not an appropriate target for biological control using Trichogramma wasp releases.}, number={4}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Suh, CPC and Orr, DB and Van Duyn, JW}, year={2000}, month={Aug}, pages={1137–1145} }
 @article{storer_gould_kennedy_peck_van duyn_1999, title={Evolution of region-wide resistance in cotton bollworm to Bt cotton as influenced by Bt corn: Identification of key factors through computer simulation}, volume={2}, number={1999}, journal={Beltwide Cotton Conferences. Proceedings}, author={Storer, N. P. and Gould, F. and Kennedy, G. G. and Peck, S. L. and Van Duyn, J. W.}, year={1999}, pages={952–956} }
 @article{performance of selected bt cotton genotypes against bollworm in north carolina_1999, volume={2}, number={1999}, journal={Beltwide Cotton Conferences. Proceedings}, year={1999}, pages={931–934} }
 @article{lambert_bradley_gould_van duyn_1998, title={Bollworm (Helicoverpa zea): adaptation to BT toxin?}, volume={2}, number={1998}, journal={Beltwide Cotton Conferences. Proceedings}, author={Lambert, A. L. and Bradley, J. R., Jr. and Gould, F. and Van Duyn, J. W.}, year={1998}, pages={1033–1037} }
 @article{suh_orr_van-duyn_1998, title={Reevaluation of Trichogramma releases for suppression of heliothine pests in cotton}, volume={2}, number={1998}, journal={Beltwide Cotton Conferences. Proceedings}, author={Suh, C. P. C. and Orr, D. B. and Van-Duyn, J. W.}, year={1998}, pages={1098–1101} }
 @article{interactions of helicoverpa zea and bt cotton in north carolina_1997, volume={2}, number={1997}, journal={Beltwide Cotton Conferences. Proceedings}, year={1997}, pages={870–873} }