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Background Fall armyworm, Spodoptera frugiperda, is a target pest of the Vip3A protein used in pyramided Bt corn and cotton in the USA. In this study, we provide the first documentation of a resistance allele conferring Vip3A resistance in a field-derived population of S. frugiperda from the USA, and characterize its inheritance and cross-resistance. Results An F2 screen with 104 two-parent families generated from a field collection of S. frugiperda in Louisiana, USA, resulted in one family carrying a Vip3A resistance allele. The Vip3A-resistant strain (RR) derived from the two-parent family showed a high level of resistance to Vip3A in both diet and whole-plant bioassays, with a resistance ratio of >632.0-fold relative to a susceptible population (SS) based on diet-overlay bioassays. The inheritance of Vip3A resistance was monogenic, autosomal and recessive. Furthermore, the Vip3A resistance conferred no cross-resistance to Cry1F, Cry2Ab2 or Cry2Ae purified proteins, with resistance ratios of 3.5, 5.0 and 1.1, respectively. Conclusion These findings provide valuable information for characterizing Vip3A resistance, resistance monitoring, and developing effective resistance management strategies for the sustainable use of the Vip3A technology. © 2017 Society of Chemical Industry.

Fall armyworm, Spodoptera frugiperda, is a target pest of the Vip3A protein used in pyramided Bt corn and cotton in the USA. In this study, we provide the first documentation of a resistance allele conferring Vip3A resistance in a field-derived population of S. frugiperda from the USA, and characterize its inheritance and cross-resistance.An FThese findings provide valuable information for characterizing Vip3A resistance, resistance monitoring, and developing effective resistance management strategies for the sustainable use of the Vip3A technology. © 2017 Society of Chemical Industry.

The cotton fleahopper, Pseudatomoscelis seriatus (Reuter) (Hemiptera: Miridae) is an economically important insect pest of cotton in the United States. However, reports of cotton fleahopper infestation and its management in cotton fields are restricted primarily to Texas, Oklahoma, and Arkansas. The objective of this study was to understand the genetic diversity of cotton fleahopper populations infesting cotton in the cotton-growing areas of the United States. Amplified fragment length polymorphism markers were used to detect genetic diversity and to characterize geographic genotypes across the distribution of the cotton fleahopper in the United States. We used 172 individuals and 559 amplified fragment length polymorphism loci in this study and found significant, but low, level of genetic differentiation among geographic populations (F(ST) = 0.02; P < 0.0001). Molecular fingerprints of cotton fleahopper populations were partitioned into three broad regional genetic populations with a western, central, and eastern distribution. The western (Arizona) and eastern (Florida, Georgia, South Carolina, and North Carolina) populations are genetically distinct, whereas the central (Texas, Oklahoma, Arkansas, Mississippi, Louisiana, and Alabama) population represents an admixed population, which include both western and eastern populations. These results suggest considerable gene flow among the populations within regions but restricted gene flow among populations from eastern and western region.

Given rapid changes in agricultural practice, it is critical to understand how alterations in ecological, technological, and economic conditions over time and space impact ecosystem services in agroecosystems. Here, we present a benefit transfer approach to quantify cotton pest-control services provided by a generalist predator, the Mexican free-tailed bat (Tadarida brasiliensis mexicana), in the southwestern United States. We show that pest-control estimates derived using (1) a compound spatial–temporal model – which incorporates spatial and temporal variability in crop pest-control service values – are likely to exhibit less error than those derived using (2) a simple-spatial model (i.e., a model that extrapolates values derived for one area directly, without adjustment, to other areas) or (3) a simple-temporal model (i.e., a model that extrapolates data from a few points in time over longer time periods). Using our compound spatial–temporal approach, the annualized pest-control value was $12.2 million, in contrast to an estimate of $70.1 million (5.7 times greater), obtained from the simple-spatial approach. Using estimates from one year (simple-temporal approach) revealed large value differences (0.4 times smaller to 2 times greater). Finally, we present a detailed protocol for valuing pest-control services, which can be used to develop robust pest-control transfer functions for generalist predators in agroecosystems.EDITED BY Neville Crossman EDITED BY Neville Crossman

During the past 12 000 years agricultural systems have transitioned from natural habitats to conventional agricultural regions and recently to large areas of genetically engineered (GE) croplands. This GE revolution occurred for cotton in a span of slightly more than a decade during which a switch occurred in major cotton production areas from growing 100% conventional cotton to an environment in which 95% transgenics are grown. Ecological interactions between GE targeted insects and other insectivorous insects have been investigated. However, the relationships between ecological functions (such as herbivory and ecosystem transport) and agronomic benefits of avian or mammalian insectivores in the transgenic environment generally remain unclear, although the importance of some agricultural pest management services provided by insectivorous species such as the Brazilian free-tailed bat, Tadarida brasiliensis, have been recognized. We developed a dynamic model to predict regional-scale ecological functions in agricultural food webs by using the indicators of insect pest herbivory measured by cotton boll damage and insect emigration from cotton. In the south-central Texas Winter Garden agricultural region we find that the process of insectivory by bats has a considerable impact on both the ecology and valuation of harvest in Bacillus thuringiensis (Bt) transgenic and non- transgenic cotton crops. Predation on agricultural pests by insectivorous bats may enhance the economic value of agricultural systems by reducing the frequency of required spraying and delaying the ultimate need for new pesticides. In the Winter Garden region, the presence of large numbers of insectivorous bats yields a regional summer dispersion of adult pest insects from Bt cotton that is considerably reduced from the moth emigration when bats are absent in either transgenic or non-transgenic crops. This regional decrease of pest numbers impacts insect herbivory on a transcontinental scale. With a few exceptions, we find that the agronomics of both Bt and conventional cotton production is more profitable when large numbers of insectivorous bats are present.

Brazilian free-tailed bats (Tadarida brasiliensis) form enormous summer breeding colonies, mostly in caves and under bridges, in south-central Texas and northern Mexico. Their prey includes several species of adult insects whose larvae are known to be important agricultural pests, including the corn earworm or cotton bollworm (Helicoverpa zea). We estimate the bats' value as pest control for cotton production in an eight-county region in south-central Texas. Our calculations show an annual value of $741 000 per year, with a range of $121 000–$1 725 000, compared to a $4.6–$6.4 million per year annual cotton harvest.

Previous studies suggest grain sorghum, Sorghum bicolor (L.) Moench, acts as an early-season predator source for nearby cotton, Gossypium hirsutum L., in areas where their growing seasons overlap. However, few data exist on predator movement in this system, and proposed causes of movement have not been tested. Field studies in 2001 and 2002 addressed both issues. Predator marking with rubidium was employed to measure predator movement between equal-sized areas of cotton and grain sorghum at three stages of grain sorghum phenology. Concurrent manipulative experiments in field cages tested for effects of phenology and aphid levels on movement by Hippodamia convergens Guerin-Meneville, a common predator in this system. Results from 2001 showed cotton gained 2.7 predators for every one lost to adjacent grain sorghum but that the collective movement of predators was similar among the three periods examined. The coccinellids H. convergens and Scymnus loweii Mulsant moved preferentially into cotton and seemed responsible for the overall pattern of predator movement between crops. For predators moving from grain sorghum into cotton, estimated rates of dispersal (15.8–19.9 m/d) were found to be similar among all taxa studied. Cage experiments suggested both crop phenology and abundance of aphid prey in cotton and grain sorghum cause predator movement, but only the effect of phenology was consistent between years. These results support the idea that grain sorghum is a source of predators during cotton’s early growth stages and suggest that grain sorghum may continue to contribute to natural enemy populations during later stages of cotton growth.

Applications of two doses of an internal physiological marker, rubidium, were applied as foliar solutions of rubidium chloride (RbCl) to field plots of cotton, Gossypium hirsutum L., and grain sorghum, Sorghum bicolor (L.) Moench, to determine the potential of this technique for detecting intercrop movement of generalist predators. Because artificially elevated rubidium levels of marked plants and insects decline with time, three applications were made at distinct phenological stages of grain sorghum to test if multiple mark-recapture experiments could be conducted at the same sites. Samples of predators and plant tissues were made at the onset of each sampling period and every 2 d through 6 d after RbCl application. Results showed that both crops, as well as all arthropod predators tested, exhibited significant elevation of rubidium levels over field-collected controls. Further, the effectiveness of the mark did not differ between crops, indicating that one set of protocols is sufficient for mar...

A prey-specific gut content enzyme-linked immunosorbent assay (ELISA) was used to identify predation of eggs of bollworm, Helicoverpa zea (Boddie), by Orius spp. in commercial cotton fields in Texas. Degradation of the egg protein began immediately after O. insidiosus fed on an egg. However, the protein antigen was detectable in the predator for approximately 10 h after feeding. The antigen retention time provided a conservative estimate of predation and insured that when predation was detected it occurred on the day predators were collected. The percentage of individual of Orius spp. that was positive by ELISA for the egg antigen varied throughout each growing season. The highest frequency of positive responses occurred before cotton bloom and after peak bloom.

The population dynamics of the bollworm, Helicoverpa zea (Boddie), and its associated natural enemies were studied in insecticide-free, commercial, short-season cotton fields from 1991 to 1995 in the southern Blacklands of Texas. Bollworm had one discernable generation per season in cotton. Partial ecological life tables constructed for each annual generation indicated that 71–95% mortality could be consistently expected in the egg and first-instar life stages. Intrageneration mortality ranged from 93 to 99%. Unexplained mortality was the leading cause of mortality in 1991–1993, but not in 1994 and 1995 when predation due to Orius spp. was partitioned. Unexplained mortality included abiotic as well as biotic factors. Parasite activity was consistently low. Egg parasitization by Trichogramma spp. averaged 3.4%. Larval parasitization rarely exceeded 5% and no larval parasitization was found in 1993. Microplitis croceipes (Cresson) was the most common larval parasite collected. Predation of bollworm eggs by Orius insidiosus (Say), the numerically dominant predator in the system, was estimated using ELISA in 1994 and 1995. O. insidiosus was the most important mortality factor when measured consuming 84 and 71% of the eggs in 1994 and 1995, respectively.

Recombinant baculoviruses have been genetically engineered to reduce the time to kill infected pests, thus reducing crop damage. In this study, wild-type viruses and recombinant viruses expressing a scorpion toxin were applied to cotton in response to larval infestations of Helicoverpa zea and Heliothis virescens in 1997 and 1998. A chemical standard and an untreated control acted as comparison treatments. The goals of this field study were to (1) assess the efficacy of recombinant baculoviruses in protecting cotton from larval feeding damage; (2) assess the impact of recombinant virus introductions on predator densities and diversity; and (3) determine if cotton predators acquire baculovirus by consuming infected heliothines. When applications were timed at larval emergence, certain recombinant virus treatments protected cotton from damage better than wild-type virus treatments and as well as the chemical standard. Differences in efficacy between recombinant and wild-type baculoviruses were not apparent if treatments were applied 3 to 4 days after peak larval emergence. Predator densities and diversity were similar among recombinant and wild-type baculovirus treatments, whereas plots treated with the chemical standard had consistently smaller predator populations. From polymerase chain reaction analyses of predators in 1997 and 1998, 1.7 and 0.2%, respectively, of predators had consumed a virus-infected heliothine. Nine of the 26 predators carrying viral DNA were positive for recombinant virus. Additionally, 13 of the 26 predators were found to disperse 13.5 to 105 m 2 to 5 days after initial virus applications. Five of these dispersing predators (0.2% of all predators evaluated) carried recombinant viral DNA. These results suggest that the potential for the inadvertent spread of recombinant viral DNA via dispersing predators is low.

Adjacent plots of cotton, Gossypium hirsutum L., and grain sorghum, Sorghum bicolor (L.) Moench, were established in 1997 and 1998 to study the movement of generalist predators in this system. Previous authors have suggested that sorghum acts as a source of generalist insect predators for cotton pests but several questions about the dynamics of insect movement remain unanswered. Mark–recapture methods were used to determine the timing of predator movement and to measure the net gains, if any, for cotton in terms of predators. Destructive sampling of cotton and grain sorghum plants was used to determine which environmental factors might cause predator movement in this system. Results showed that several generalist predators move between cotton and sorghum, most frequently Orius spp. and Hippodamia convergens Guerin-Meneville. Movement of predators into cotton peaked during the hard-dough and soft-dough stages of sorghum phenology in 1997 and 1998, respectively. Although cotton received a net gain in total predators, the number of insects leaving cotton once exceeded the number entering from sorghum, indicating that predator movement is not unidirectional in this system. Further, data on predator dispersal rates suggest that predators possess the necessary mobility for their use in field-scale conservation (as opposed to strip cropping). Results of destructive sampling show that predator movement was positively correlated with ambient temperatures and negatively correlated with local aphid levels. These results support the use of sorghum as a predator conservation tool in cotton and are particularly relevant as the boll weevil eradication programs increase the feasibility of pesticide reductions and conservation in cotton.

The purpose of this study was to assess the susceptibility of the bollworm, Helicoverpa zea (Boddie), to the pyrethroid cypermethrin in the primary crop production areas of Texas. Pyrethroid insecticides are widely used in cotton and in other production systems, such as grain sorghum and corn. The statewide monitoring program that evaluated resistance in male H. zea was conducted from April to September 2005, surveying nine Texas counties with a total of 5,041 moths from all areas used for analysis. Data from all areas were sent to Texas A&M University Toxicology Laboratory for analysis. Considerable variability in response to cypermethrin was detected in H. zea across the state. Based on LC50 data, the most resistant populations were from Nueces, Uvalde, and Williamson counties while the most susceptible populations were from Ellis, Fisher and Mitchell, Hockley, and Swisher counties. Accepted for publication 2 October 2006. Published 19 July 2007.