RESUMO
Overwintering success is an important determinant of arthropod populations that must be considered as climate change continues to influence the spatiotemporal population dynamics of agricultural pests. Using a long-term monitoring database and biologically relevant overwintering zones, we modeled the annual and seasonal population dynamics of a common pest, Helicoverpa zea (Boddie), based on three overwintering suitability zones throughout North America using four decades of soil temperatures: the southern range (able to persist through winter), transitional zone (uncertain overwintering survivorship), and northern limits (unable to survive winter). Our model indicates H. zea population dynamics are hierarchically structured with continental-level effects that are partitioned into three geographic zones. Seasonal populations were initially detected in the southern range, where they experienced multiple large population peaks. All three zones experienced a final peak between late July (southern range) and mid-August to mid-September (transitional zone and northern limits). The southern range expanded by 3% since 1981 and is projected to increase by twofold by 2099 but the areas of other zones are expected to decrease in the future. These changes suggest larger populations may persist at higher latitudes in the future due to reduced low-temperature lethal events during winter. Because H. zea is a highly migratory pest, predicting when populations accumulate in one region can inform synchronous or lagged population development in other regions. We show the value of combining long-term datasets, remotely sensed data, and laboratory findings to inform forecasting of insect pests.
Assuntos
Mudança Climática , Mariposas , Estações do Ano , Animais , Dinâmica Populacional , TemperaturaRESUMO
Stink bugs (Hemiptera: Pentatomidae) are ubiquitous, cryptic, phytophagous pests that are found in many crops. In agroecosystems, individuals disperse from adjacent noncrop hosts and tend to aggregate or cluster within fields. In this study, we characterized the distribution of Euschistus servus (Say) and Euschistus tristigmus (Say) (Hemiptera: Pentatomidae) over 2 yr at three southeastern United States farmscapes. Stink bugs were captured in pheromone-baited traps, and Spatial Analysis by Distance Indices (SADIE) used to identify the location of significant aggregations by habitat type and season. Euschistus servus adults were more likely to be captured in pecan orchards, cotton, other crops, or unmanaged habitats than in woodland habitats. Significant aggregations of E. servus were detected in a variety of habitats including pecan, corn, cotton, peanut, and tobacco, as well as fallow and hay fields, pastures, and hedgerows. Fewer adult E. tristigmus were captured than E. servus adults, and E. tristigmus adults were typically trapped and aggregated in woodland habitats. The resulting data provide an important understanding regarding the seasonal movement and relative abundance levels of stink bug populations, which are critical to the development of integrated pest management strategies.
Assuntos
Distribuição Animal , Heterópteros , Animais , Arachis , Produtos Agrícolas , Estações do Ano , Sudeste dos Estados Unidos , Análise Espaço-Temporal , Zea maysRESUMO
Most oviposition by Helicoverpa zea (Boddie) occurs near the top of the canopy in soybean, Glycine max (L.) Merr, and larval abundance is influenced by the growth habit of plants. However, the vertical distribution of larvae within the canopy is not as well known. We evaluated the vertical distribution of H. zea larvae in determinate and indeterminate varieties, hypothesizing that larval distribution in the canopy would vary between these two growth habits and over time. We tested this hypothesis in a naturally infested replicated field experiment and two experimentally manipulated cage experiments. In the field experiment, flowering time was synchronized between the varieties by manipulating planting date, while infestation timing was manipulated in the cage experiments. Larvae were recovered using destructive sampling of individual soybean plants, and their vertical distribution by instar was recorded from three sampling points over time in each experiment. While larval population growth and development varied between the determinate and indeterminate varieties within and among experiments, we found little evidence that larvae have preference for different vertical locations in the canopy. This study lends support to the hypothesis that larval movement and location within soybean canopies do not result entirely from oviposition location and nutritional requirements.
Assuntos
Comportamento Alimentar , Glycine max/crescimento & desenvolvimento , Mariposas/fisiologia , Animais , Larva/fisiologia , Oviposição , Densidade DemográficaRESUMO
A 4-yr study was conducted to determine the degree of aggregation of thrips and injury in cotton, Gossypium hirsutum L., and their spatial association with a multispectral vegetation index (normalized difference vegetation index [NDVI]) and soil apparent electrical conductivity (ECa). Using the Spatial Analysis by Distance IndicEs analyses (SADIE), adult thrips were significantly (P < 0.05) aggregated in 4 out of 24 analyses for adult thrips (17%), 4 out of 24 analyses for immature thrips (17%), and 2 out of 15 analyses for injury (13%). The SADIE association tool showed that NDVI values were associated with adult thrips in 2 out of 20 paired datasets (10%), with immature thrips in 3 out of 20 paired datasets (15%), and with thrips injury in 1 out of 14 paired datasets (7.1%). Soil ECa values were generally more associated with thrips variables than NDVI, with shallow ECa positively associated with adult thrips in 6 out of 21 paired datasets (28.6%), with immature thrips in 8 out of 21 paired datasets (40.0%), and with thrips injury in 8 out of 14 paired datasets (57.1%). The greater frequency of positive associations between thrips variables and soil ECa suggests a greater potential for site-specific management, particularly in the Coastal Plain of the southeastern United States, where soil types are highly variable.
Assuntos
Distribuição Animal , Gossypium , Tisanópteros , AnimaisRESUMO
Native and invasive stink bugs (Hemiptera: Pentatomidae) and the closely related invasive Megacopta cribraria (Hemiptera: Plataspidae) are agricultural pests in the southeastern United States. Natural enemies, from various phyla, parasitize these pests and contribute to population regulation. We specifically investigated Nematoda infections in pentatomid and plataspid pests in one soybean field in South Carolina in 2015. Nematodes were identified through molecular and morphological methods and assigned to family Mermithidae, genus Agamermis. This study reports mermithid nematode infection in immature M. cribraria for the first time and provides the first mermithid host record for the stink bugs Chinavia hilaris, Euschistus servus, and another Euschistus species, and a grasshopper (Orthoptera: Acrididae) in South Carolina. The same Agamermis species infected all hosts. The broad host range and prevalence suggests that Agamermis may be an important contributor to natural mortality of pentatomid and plataspid pests. Previous mermithid host records for the Pentatomidae and Plataspidae worldwide are summarized. Further work is needed to assess the impact of infection on populations over a broader range of agricultural fields and geographic localities.
RESUMO
The kudzu bug, Megacopta cribraria (F.), first discovered in the United States in 2009, has rapidly become a pest of commercial soybean, Glycine max (L.) Merrill, throughout much of the southeast. Because of its recent arrival, management practices and recommendations are not well established. To develop action thresholds, we evaluated insecticide applications targeted at different densities of adults and nymphs determined using the standard 38-cm diameter sweep net sampling method in 12 soybean field trials conducted in Georgia, North Carolina, and South Carolina from 2011 to 2013. Average peak densities of M. cribraria in the untreated controls reached as high as 63.5 ± 11.0 adults per sweep and 34.7 ± 8.0 nymphs per sweep. Insecticide applications triggered at densities of one adult or nymph of M. cribraria per sweep, two adults or nymphs per sweep, and one adult or nymph per sweep, with nymphs present, resulted in no yield reductions in most cases compared with plots that were aggressively protected with multiple insecticide applications. A single insecticide application timed at the R3 or R4 soybean growth stages also resulted in yields that were equivalent to the aggressively protected plots. Typically, treatments (excluding the untreated control) that resulted in fewer applications were more cost-effective. These results suggest that a single insecticide application targeting nymphs was sufficient to prevent soybean yield reduction at the densities of M. cribraria that we observed.
Assuntos
Heterópteros , Controle de Insetos/métodos , Inseticidas , Animais , Georgia , North Carolina , Ninfa , Densidade Demográfica , South Carolina , Glycine max/crescimento & desenvolvimentoRESUMO
In 1999, crop consultants scouting for stink bugs (Hemiptera spp.) in South Carolina discovered a formerly unobserved seed rot of cotton that caused yield losses ranging from 10 to 15% in certain fields. The disease has subsequently been reported in fields throughout the southeastern Cotton Belt. Externally, diseased bolls appeared undamaged; internally, green fruit contain pink to dark brown, damp, deformed lint, and necrotic seeds. In greenhouse experiments, we demonstrated transmission of the opportunistic bacterium Pantoea agglomerans by the southern green stink bug, Nezara viridula (L.). Here, green bolls were sampled from stink bug management plots (insecticide protected or nontreated) from four South Atlantic coast states (North Carolina, South Carolina, Georgia, and Florida) to determine disease incidence in the field and its association with piercing-sucking insects feeding. A logistic regression analysis of the boll damage data revealed that disease was 24 times more likely to occur (P = 0.004) in bolls collected from plots in Florida, where evidence of pest pressure was highest, than in bolls harvested in NC with the lowest detected insect pressure. Fruit from plots treated with insecticide, a treatment which reduced transmission agent numbers, were 4 times less likely to be diseased than bolls from unprotected sites (P = 0.002). Overall, punctured bolls were 125 times more likely to also have disease symptoms than nonpunctured bolls, irrespective of whether or not plots were protected with insecticides (P = 0.0001). Much of the damage to cotton bolls that is commonly attributed to stink bug feeding is likely the resulting effect of vectored pathogens.
Assuntos
Herbivoria , Heterópteros/fisiologia , Controle de Insetos , Insetos Vetores/microbiologia , Pantoea/fisiologia , Doenças das Plantas/microbiologia , Animais , Frutas/microbiologia , Gossypium , Modelos Biológicos , Sementes/microbiologia , Sudeste dos Estados UnidosRESUMO
A 3-yr study (2009-2011) was conducted to examine the spatial and temporal dynamics of stink bugs in three commercial farmscapes. Study locations were replicated in South Carolina and Georgia, in an agriculturally diverse region known as the southeastern coastal plain. Crops included wheat, Triticum aestivum (L.), corn, Zea mays (L.), soybean, Glycine max (L.), cotton, Gossypium hirsutum (L.), and peanut, Arachis hypogaea (L.). Farmscapes were sampled weekly using whole-plant examinations for corn, with all other crops sampled using sweep nets. The predominant pest species of phytophagous stink bugs were the brown stink bug, Euschistus servus (Say), the green stink bug, Chinavia hilaris (Say), and the southern green stink bug, Nezara viridula (L.). Chi-square tests indicated a departure from a normal distribution in 77% of analyses of the variance to mean ratio, with 37% of slopes of Taylor's power law and 30% of coefficient ß of Iwao's patchiness regression significantly greater than one, indicating aggregated distributions. Spatial Analyses by Distance IndicEs (SADIE) indicated aggregated patterns of stink bugs in 18% of year-end totals and 42% of weekly counts, with 80% of adults and nymphs positively associated using the SADIE association tool. Maximum stink bug densities in each crop occurred when the plants were producing fruit. Stink bugs exhibited greater densities in crops adjacent to soybean in Barnwell and Lee Counties compared with crops adjacent to corn or fallow areas. The diversity of crops and relatively small size of fields in the Southeast leads to colonization of patches within a farmscape. The ecological and management implications of the spatial and temporal distribution of stink bugs within farmscapes are discussed.
Assuntos
Distribuição Animal , Hemípteros/fisiologia , Agricultura , Animais , Cadeia Alimentar , Georgia , Hemípteros/crescimento & desenvolvimento , Ninfa/crescimento & desenvolvimento , Ninfa/fisiologia , Dinâmica Populacional , Estações do Ano , South CarolinaRESUMO
Since its discovery in the southeastern United States, the invasive plataspid Megacopta cribraria (F.) (Hemiptera: Plataspidae) has infested soybean (Glycine max (L.) Merrill) fields in often very high numbers. To optimize sampling plans, sweep-net and beat-cloth sampling was conducted in soybean fields in South Carolina during 2012 and 2013. Across all fields, densities averaged 7.2 ± 0.5 (SEM) adults and 4.5 ± 0.4 nymphs per 20 sweeps and 5.5 ± 0.3 adults and 4.5 ± 0.3 nymphs per 1.83 m of row. Coefficients of Taylor's power law were used to generate sampling plans for population estimates and sequential sampling plans for pest management decision making. At an economic threshold of one nymph per sweep, optimum sample sizes were 184, 48, and 22 within 10, 20, and 30% of the mean with the sweep-net method. At the corresponding threshold for the beat cloth (24.7 nymphs per 1.83 m of row), optimum sample sizes were 239, 62, and 29 within 10, 20 and 30% of the mean, respectively. At all adult and nymph densities, fewer sweep-net samples were required for population estimations compared with the number of beat-cloth samples. Sequential sampling reduced the sample size required to reach a management decision for the sweep net and beat cloth compared with a fixed sampling plan. The sweep-net method was more cost reliable for population estimation at low densities of both life stages, with the beat cloth becoming more cost reliable as populations increased. The beat-cloth method was more cost reliable than sweep-net sampling across all densities and life stages for pest management practices. These results may be used by researchers, county Extension agents, consultants, and farm managers to both facilitate sampling and improve reliability of M. cribraria estimates for research purposes and for pest management.
Assuntos
Proteção de Cultivos/métodos , Glycine max , Hemípteros , Animais , Proteção de Cultivos/economia , Ninfa , Densidade Demográfica , South CarolinaRESUMO
Interspecific competition is an important ecological concept which can play a major role in insect population dynamics. In the southeastern United States, a complex of stink bugs (Hemiptera: Pentatomidae), primarily the brown stink bug, Euschistus servus (Say), and corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), are the 2 most common pests of field corn, Zea mays L. (Poales: Poaceae). Stink bugs have the greatest potential for economic injury during the late stages of vegetative corn development when feeding can result in deformed or "banana-shaped" ears and reduced grain yield. Corn earworm moths lay eggs on corn silks during the first stages of reproductive development. A 2-year field study was conducted to determine the impact of feeding by the brown stink bug during late-vegetative stages on subsequent corn earworm oviposition, larval infestations, and grain yield. Brown stink bug feeding prior to tasseling caused deformed ears and reduced overall grain yield by up to 92%. Across all trials, varying levels of brown stink bug density and injury reduced the number of corn earworm larvae by 29-100% and larval feeding by 46-85%. Averaged across brown stink bug densities, later planted corn experienced a 9-fold increase in number of corn earworm larvae. This is the first study demonstrating a competitive interaction between these major pests in a field corn setting, and these results have potential implications for insect resistance management.
RESUMO
The majority of field corn, Zea mays L., in the southeastern United States has been genetically engineered to express insecticidal toxins produced by the soil bacterium, Bacillus thuringiensis (Bt). Field corn is the most important mid-season host for corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), which has developed resistance to all Cry toxins in Bt corn. From 2020 to 2023, corn earworm pupae were collected from early- and late-planted pyramided hybrids expressing Bt toxins and non-Bt near-isolines in North and South Carolina (16 trials). A total of 5,856 pupae were collected across all trials, with 55 and 88% more pupae collected in later-planted trials relative to early plantings in North and South Carolina, respectively. Only 20 pupae were collected from hybrids expressing Cry1Fâ +â Cry1Abâ +â Vip3A20 across all trials. Averaged across trials, Cry1A.105â +â Cry2Ab2 hybrids reduced pupal weight by 6 and 9% in North and South Carolina, respectively, relative to the non-Bt near-isoline. Cry1Fâ +â Cry1Ab hybrids reduced pupal weight on average by 3 and 8% in North and South Carolina, respectively, relative to the non-Bt near-isoline. The impact of the Bt toxins on pupal weight varied among trials. When combined with data from 2014 to 2019 from previous studies, a significant decline in the percent reduction in pupal weight over time was found in both states and hybrid families. This study demonstrates a continued decline in the sublethal impacts of Bt toxins on corn earworm, emphasizing the importance of insect resistance management practices.
RESUMO
ABSTRACT Since its discovery in the United States, the invasive plataspid Megacopta cribraria (F.) (Hemiptera: Plataspidae) has infested soybean [Glycine max (L.) Merrill] fields in often alarming numbers in parts of the southeastern United States. Although a known feeder on soybean, reports of its pest status in its native Asian range are conflicting, and little information exists documenting its impact on soybean yields. Our objective was to examine the relationship between M. cribraria density and soybean yield loss. M. cribraria adults and nymphs were confined to small soybean plots by using walk-in field cages from late vegetative stage to harvest in 2011 and 2012. Adults (0, 5, or 25 per plant) were added at late vegetative stages, and their progeny were allowed to complete a full generation within the caged plots. Densities reached as high as 182.5 +/- 23.1 (SEM) nymphs and adults per plant, and soybean yield was reduced by as much as 59.6% at the highest density treatment. The yield components seeds per pod and individual seed weight were reduced as M. cribraria densities increased, but pods per plant and protein and oil content were not affected. Preliminary economic injury level curves for a range of grain prices and management costs were calculated based on 2012 yield loss data combined with population monitoring. M. cribraria is capable of causing severe reductions in soybean yields at densities that are relevant within its invasive U.S. range.
Assuntos
Glycine max/crescimento & desenvolvimento , Heterópteros/fisiologia , Animais , Produtos Agrícolas/economia , Produtos Agrícolas/crescimento & desenvolvimento , Comportamento Alimentar , Cadeia Alimentar , Heterópteros/crescimento & desenvolvimento , Ninfa/crescimento & desenvolvimento , Ninfa/fisiologia , Densidade Demográfica , South Carolina , Glycine max/economiaRESUMO
The plataspid Megacopta cribraria (F.), which was recently introduced to the United States, forms nuisance aggregations on the exteriors of homes when it seeks overwintering sites in the fall. Little to no published information is available on the efficacy of insecticides labeled for professional use and exterior applications on homes and other structures against this insect. In a series of three experiments, we evaluated the residual efficacy of nine insecticides incorporating pyrethroid, neonicotinoid, and oxadiazine active ingredients on surfaces composed of five exterior building materials (vinyl soffit, brick, painted and unfinished plywood, and metal) at rates labeled for use in structural perimeter applications. Pyrethroids and pyrethroid-neonicotinoid mixes were broadly effective, resulting in 100% mortality or knockdown within 24 h in most cases. The neonicotinoid dinotefuran performed similarly on metal and vinyl surfaces, but its residual efficacy was reduced on more porous brick and wood surfaces. The oxadiazine indoxacarb acted more slowly than the other materials, but its performance was maintained on porous surfaces. Overwintering adults of M. cribraria were generally susceptible to the broad-spectrum insecticides most commonly used for exterior applications to homes and other structures.
Assuntos
Heterópteros/efeitos dos fármacos , Inseticidas/toxicidade , Resíduos de Praguicidas/toxicidade , Animais , Materiais de Construção , Controle de Insetos , Espécies Introduzidas , South Carolina , Fatores de TempoRESUMO
The corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), is a cosmopolitan pest in the field crop landscape in the southeastern United States. Field corn (Zea mays L.) is the most important midseason host for H. zea where intensive selection pressure occurs for resistance to insecticidal toxins from Bacillus thuringiensis (Bt). Because spatial patterns of H. zea in field corn have not been extensively studied, field corn was sampled for H. zea larvae and injury in 2021 and 2022. Patterns of spatial aggregation were identified in a number of fields in both larval populations and injury. Aggregation of H. zea larvae was less common at R5 than at R2. Associations between the spatial patterns of H. zea and the variability in crop phenology were identified in some fields, with positive associations between plant height and H. zea larvae, indicating that ovipositing H. zea moths avoid areas with reduced plant height and delayed reproductive maturity. Additionally, negative spatial associations between stink bug ear injury and H. zea larvae and their injury were found in a small number of cases, indicating some spatial interactions between the two pest complexes and their injury. Results from these studies provide valuable insight into the spatial patterns of H. zea in field corn. An understanding of the local dispersal and population dynamics of H. zea can be used to help further improve integrated pest management and insect resistance management programs for this major polyphagous pest.
Assuntos
Bacillus thuringiensis , Heterópteros , Mariposas , Animais , Zea mays/genética , Controle Biológico de Vetores/métodos , Larva , Sudeste dos Estados Unidos , Bacillus thuringiensis/genética , Plantas Geneticamente Modificadas , Proteínas de Bactérias/genética , Endotoxinas , Proteínas Hemolisinas/genéticaRESUMO
A complex of stink bugs, primarily the brown stink bug, Euschistus servus (Say) (Hemiptera: Pentatomidae) , and the southern green stink bug, Nezara viridula (L.) (Hemiptera: Pentatomidae) , are the most damaging insect pests of field corn, Zea mays L., in the southeastern United States. Characterizing the spatial patterns of these highly mobile, polyphagous pests is critical for developing efficient and effective sampling plans. In 2021 and 2022, stink bugs and their injury were assessed biweekly from emergence through R2 in 20 corn fields. The spatial analysis by distance indices (SADIE) showed that aggregation patterns were identified primarily in adult populations of both E. servus and N. viridula, and in nymphal populations of both species to a lesser extent. Aggregation patterns were also identified in early vegetative injury, but not in ear injury assessed at R2. The spatial association of stink bugs and their injury varied with corn phenological stage. A lack of spatial association between stink bug populations early in the season and vegetative injury suggests a need for intensive sampling, particularly in fields with increased residue from cover crops. Results of this study illustrate the variability in spatial patterns of stink bugs in corn, which can help to improve sampling plans for decision-making in IPM programs.
Assuntos
Heterópteros , Zea mays , Animais , Sudeste dos Estados Unidos , Densidade Demográfica , Estações do AnoRESUMO
After resistance is first detected, continued resistance monitoring can inform decisions on how to effectively manage resistant populations. We monitored for resistance to Cry1Ac (2018 and 2019) and Cry2Ab2 (2019) from southeastern USA populations of Helicoverpa zea. We collected larvae from various plant hosts, sib-mated the adults, and tested neonates using diet-overlay bioassays and compared them to susceptible populations for resistance estimates. We also compared LC50 values with larval survival, weight and larval inhibition at the highest dose tested using regression, and found that LC50 values were negatively correlated with survival for both proteins. Finally, we compared resistance rations between Cry1Ac and Cry2Ab2 during 2019. Some populations were resistant to Cry1Ac, and most were resistant to CryAb2; Cry1Ac resistance ratios were lower than Cry2Ab2 during 2019. Survival was positively correlated with larval weight inhibition for Cry2Ab. This contrasts with other studies in both the mid-southern and southeastern USA, where resistance to Cry1Ac, Cry1A.105, and Cry2Ab2 increased over time and was found in a majority of populations. This indicates that cotton expressing Cry proteins in the southeastern USA was at variable risk for damage in this region.
RESUMO
Cotton leafroll dwarf virus (CLRDV) is an emerging aphid-borne pathogen infecting cotton, Gossypium hirsutum L., in the southern United States (U.S.). The cotton aphid, Aphis gossypii Glover, infests cotton annually and is the only known vector to transmit CLRDV to cotton. Seven other species have been reported to feed on, but not often infest, cotton: Protaphis middletonii Thomas, Aphis craccivora Koch, Aphis fabae Scopoli, Macrosiphum euphorbiae Thomas, Myzus persicae Sulzer, Rhopalosiphum rufiabdominale Sasaki, and Smynthurodes betae Westwood. These seven have not been studied in cotton, but due to their potential epidemiological importance, an understanding of the intra- and inter-annual variations of these species is needed. In 2020 and 2021, aphids were monitored from North Carolina to Texas using pan traps around cotton fields. All of the species known to infest cotton, excluding A. fabae, were detected in this study. Protaphis middletonii and A. gossypii were the most abundant species identified. The five other species of aphids captured were consistently low throughout the study and, with the exception of R. rufiabdominale, were not detected at all locations. The abundance, distribution, and seasonal dynamics of cotton-infesting aphids across the southern U.S. are discussed.
RESUMO
BACKGROUND: Characterizing Helicoverpa zea (Boddie) damage to maize (Zea mays L.) in relation to the spatiotemporal composition of Bt crops is essential to understand how landscape composition affects H. zea abundance. To examine this relationship, paired Bt (expressing Cry1A.105 + Cry2Ab2) and non-Bt maize plots were sampled across North and South Carolina during 2017-2019. Kernel damage and larval exit holes were measured following larval development. To understand how maize abundance surrounding sample sites related to feeding damage and larval development, we quantified maize abundance in a 1 km buffer surrounding the sample site and examined the relationship between local maize abundance and kernel damage and larval exit holes. RESULTS: Across the years and locations, damage in Bt maize was widespread but significantly lower than in non-Bt maize, indicating that despite the widespread occurrence of resistance to Cry toxins in maize, Bt maize still provides a measurable reduction in damage. There were negative relationships between kernel injury and ears with larval exit holes in both Bt and non-Bt maize and the proportion of maize in the landscape during the current year. CONCLUSION: Despite the widespread occurrence of resistance to Cry toxins in maize, this resistance is incomplete, and on average Bt maize continues to provide a measurable reduction in damage. We interpret the negative relationship between abundance of maize within 1 km of the sample location and maize infestation levels, as measured by kernel damage and larval exit holes, to reflect dispersion of the ovipositing moth population over available maize within the local landscape. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
Assuntos
Bacillus thuringiensis , Mariposas , Zea mays , Animais , Bacillus thuringiensis/genética , Proteínas de Bactérias/genética , Endotoxinas/genética , Proteínas Hemolisinas/genética , Resistência a Inseticidas/genética , Larva/genética , Mariposas/genética , Plantas Geneticamente Modificadas/genética , Zea mays/genéticaRESUMO
Tarnished plant bug, Lygus lineolaris (Hemiptera: Miridae), is an economically damaging pest in cotton production systems across the southern United States. We systematically scouted 120 commercial cotton fields across five southeastern states during susceptible growth stages in 2019 and 2020 to investigate sampling optimization and the effect of interface crop and landscape composition on L. lineolaris abundance. Variance component analysis determined field and within-field spatial scales, compared with agricultural district and state, accounted for more variation in L. lineolaris density using sweep net and drop cloth sampling. This result highlights the importance of field-level scouting efforts. Using within-field samples, a fixed-precision sampling plan determined 8 and 23 sampling units were needed to determine L. lineolaris population estimates with 0.25 precision for sweep net (100 sweeps per unit) and drop cloth (1.5 row-m per unit) sampling, respectively. A spatial Bayesian hierarchical model was developed to determine local landscape (<0.5 km from field edges) effects on L. lineolaris in cotton. The proportion of agricultural area and double-crop wheat and soybeans were positively associated with L. lineolaris density, and fields with more contiguous cotton areas negatively predicted L. lineolaris populations. These results will improve L. lineolaris monitoring programs and treatment management decisions in southeastern USA cotton.
RESUMO
Genetically engineered crops expressing Bacillus thuringiensis (Bt) Cry toxins have transformed insect management in maize and cotton, reducing insecticide use and associated off-target effects. To mitigate the risk that pests evolve resistance to Bt crops, the US Environmental Protection Agency requires resistance management measures. The approved resistance management plan for Bt maize in cotton production regions requires a structured refuge of non-Bt maize equal to 20% of the maize planted; that for Bt cotton relies on the presence of an unstructured natural refuge comprising both non-Bt crop and non-crop hosts. We examined how abundance of Bt crops (cotton and maize) and an important non-Bt crop (soybean) component of the natural refuge affect resistance to Bt Cry1Ac toxin in local populations of Helicoverpa zea, an important lepidopteran pest impacted by Bt cotton and maize. We show refuge effectiveness is responsive to local abundances of maize and cotton and non-Bt soybean, and maize, in its role as a source of H. zea infesting cotton and non-Bt hosts, influences refuge effectiveness. These findings have important implications for commercial and regulatory decisions regarding deployment of Bt toxins targeting H. zea in maize, cotton, and other crops and for assumptions regarding efficacy of natural refuges.