Tracking flight activity of potato leafhopper (Hemiptera: Cicadellidae) with the Midwest Suction Trap Network.

Potato leafhopper (PLH), Empoasca fabae Harris (Hemiptera: Cicadellidae), is an economic pest of a variety of crops that migrates between overwintering sites in the southern United States and northern breeding grounds. Since 2005, the Midwest Suction Trap Network (STN) has monitored the magnitude and timing of aerially dispersing aphids' activity, but the potential of the network to monitor other taxa is only beginning to be explored. Here, we use the Midwest STN to examine how the magnitude and timing of PLH activity vary with weather, cropland cover, and time of year. We found that weekly PLH activity increased early in the season (May-June) with increasing degree day accumulation and decreased mid-season (July-August) with increasing occurrence of rain. The first detections occurred earlier in southern latitudes, while the last detections occurred sooner, when there was more surrounding potato land cover, and later over time between 2018 and 2021 and in southern latitudes. PLH activity was thus longer in duration in southern latitudes and has continued to extend later into the year overall. Resolving uncertainty about how well the Midwest STN captures migratory activity and how closely suction trap detections reflect local population densities in crop fields remain important research priorities before the potential of the Midwest STN for PLH monitoring can be realized. Still, observed patterns suggest that PLH could increase in economic importance as insects disperse over larger portions of the growing season in the warming, agriculturally productive US Midwest and that the STN can become a useful tool to monitor these changes.

Extended Sentinel Monitoring of Helicoverpa zea Resistance to Cry and Vip3Aa Toxins in Bt Sweet Corn: Assessing Changes in Phenotypic and Allele Frequencies of Resistance.

Transgenic corn and cotton that produce Cry and Vip3Aa toxins derived from Bacillus thuringiensis (Bt) are widely planted in the United States to control lepidopteran pests. The sustainability of these Bt crops is threatened because the corn earworm/bollworm, Helicoverpa zea (Boddie), is evolving a resistance to these toxins. Using Bt sweet corn as a sentinel plant to monitor the evolution of resistance, collaborators established 146 trials in twenty-five states and five Canadian provinces during 2020-2022. The study evaluated overall changes in the phenotypic frequency of resistance (the ratio of larval densities in Bt ears relative to densities in non-Bt ears) in H. zea populations and the range of resistance allele frequencies for Cry1Ab and Vip3Aa. The results revealed a widespread resistance to Cry1Ab, Cry2Ab2, and Cry1A.105 Cry toxins, with higher numbers of larvae surviving in Bt ears than in non-Bt ears at many trial locations. Depending on assumptions about the inheritance of resistance, allele frequencies for Cry1Ab ranged from 0.465 (dominant resistance) to 0.995 (recessive resistance). Although Vip3Aa provided high control efficacy against H. zea, the results show a notable increase in ear damage and a number of surviving older larvae, particularly at southern locations. Assuming recessive resistance, the estimated resistance allele frequencies for Vip3Aa ranged from 0.115 in the Gulf states to 0.032 at more northern locations. These findings indicate that better resistance management practices are urgently needed to sustain efficacy the of corn and cotton that produce Vip3Aa.

Efficacy of Helicoverpa Armigera Nucleopolyhedrovirus on Soybean for Control of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) in Arkansas Agriculture.

Helicoverpa armigera nucleopolyhedrovirus (HearNPV) is a naturally occurring virus commercially produced for control of Heliothines, including Helicoverpa zea. One drawback with using this virus for control has been the slower time to mortality compared with synthetic insecticides. However, a new formulation (Heligen®) has anecdotally been thought to result in quicker mortality than previously observed. The objective of this study was to evaluate percent defoliation, the efficacy of HearNPV on mortality for each H. zea larval instar, and the potential for control of a second infestation. Fourteen days after the first infestation, all plants were re-infested with a second instar larva to simulate a second infestation. Helicoverpa armigera nucleopolyhedrovirus was effective at killing 1st-3rd instars, resulting in 99% mortality over 4-6 days. However, 4th and 5th instar mortality only reached 35%. Second infestation larvae died between 3.4 and 3.8 days, significantly faster than the 1st infestation of 2nd instars, which had a mean time to mortality of 4.9 days. An increase in mortality rate is probably due to increasing viral concentrations after viral replication within the first hosts. Final defoliation percentages were significantly smaller in the treated plants versus the untreated plants. Only 3rd and 4th instar larvae caused percent defoliation to exceed the current Arkansas action threshold of 40%. Helicoverpa armigera nucleopolyhedrovirus in the Heligen formulation can control 1st-3rd instars within 4-6 days, while keeping defoliation below the action threshold of 40%.

Development of Economic Thresholds Toward Bollworm (Lepidoptera: Noctuidae), Management in Bt Cotton, and Assessment of the Benefits From Treating Bt Cotton With Insecticide.

Widespread field-evolved resistance of bollworm [Helicoverpa zea (Boddie)] to Cry1 and Cry2 Bt proteins has threatened the utility of Bt cotton for managing bollworm. Consequently, foliar insecticide applications have been widely adopted to provide necessary additional control. Field experiments were conducted across the Mid-South and in Texas to devise economic thresholds for foliar insecticide applications targeting bollworm in cotton. Bt cotton technologies including TwinLink (TL; Cry1Ab+Cry2Ae), TwinLink Plus (TLP; Cry1Ab+Cry2Ae+Vip3Aa), Bollgard II (BG2; Cry1Ac+Cry2Ab), Bollgard 3 (BG3; Cry1Ac+Cry2Ab+Vip3Aa), WideStrike (WS; Cry1Ac+Cry1F), WideStrike 3 (WS3; Cry1Ac+Cry1F+Vip3Aa), and a non-Bt (NBT) variety were evaluated. Gain threshold, economic injury level, and economic thresholds were determined. A 6% fruiting form injury threshold was selected and compared with preventive treatments utilizing chlorantraniliprole. Additionally, the differences in yield from spraying bollworms was compared among Bt cotton technologies. The 6% fruiting form injury threshold resulted in a 25 and 75% reduction in insecticide applications relative to preventive sprays for WS and BG2, respectively. All Bt technologies tested in the current study exhibited a positive increase in yield from insecticide application. The frequency of yield increase from spraying WS was comparable to that of NBT. Significant yield increases due to insecticide application occurred less frequently in triple-gene Bt cotton. However, their frequencies were close to the dual-gene Bt cotton, except for WS. The results of our study suggest that 6% fruiting form injury is a viable threshold, and incorporating a vetted economic threshold into an Integrated Pest Management program targeting bollworm should improve the sustainability of cotton production.

Metabolic Pathways for S-Metolachlor Detoxification Differ Between Tolerant Corn and Multiple-Resistant Waterhemp.

Herbicide resistance in weeds can be conferred by target-site and/or non-target-site mechanisms, such as rapid metabolic detoxification. Resistance to the very-long-chain fatty acid-inhibiting herbicide, S-metolachlor, in multiple herbicide-resistant populations (CHR and SIR) of waterhemp (Amaranthus tuberculatus) is conferred by rapid metabolism compared with sensitive populations. However, enzymatic pathways for S-metolachlor metabolism in waterhemp are unknown. Enzyme assays using S-metolachlor were developed to determine the specific activities of glutathione S-transferases (GSTs) and cytochrome P450 monooxygenases (P450s) from CHR and SIR seedlings to compare with tolerant corn and sensitive waterhemp (WUS). GST activities were greater (∼2-fold) in CHR and SIR compared to WUS but much less than corn. In contrast, P450s in microsomal extracts from CHR and SIR formed O-demethylated S-metolachlor, and their NADPH-dependent specific activities were greater (>20-fold) than corn or WUS. Metabolite profiles of S-metolachlor generated via untargeted and targeted liquid chromatography-mass spectrometry from CHR and SIR differed from WUS, with greater relative abundances of O-demethylated S-metolachlor and O-demethylated S-metolachlor-glutathione conjugates formed by CHR and SIR. In summary, our results demonstrate that S-metolachlor metabolism in resistant waterhemp involves Phase I and Phase II metabolic activities acting in concert, but the initial O-demethylation reaction confers resistance.

Field Assessment of Aphid Doubling Time and Yield of Sorghum Susceptible and Partially Resistant to Sugarcane Aphid (Hemiptera: Aphididae).

Since outbreaks were first detected in grain sorghum, Sorghum bicolor (L.) Moench (Cyperales: Poaceae), in 2013, sugarcane aphid, Melanaphis sacchari Zehntner has become a major annual pest in grain sorghum-producing regions of North America. Economic thresholds have been recommended for susceptible hybrids, but these recommendations may not be suitable for grain sorghum hybrids partially resistant to sugarcane aphid. The objectives were to evaluate the grain yield-aphid density relationship and field-based population growth rates of the aphid on sorghum hybrids susceptible and partially resistant to sugarcane aphid across multiple years, locations, and hybrids. These data verified previously established economic injury levels for susceptible hybrids. The observed maximum aphid density ranged from 6 to 451 aphids per leaf for resistant hybrids and from 67 to 1,025 for susceptible hybrids. Across 50 location-year combinations, the maximum aphid density observed on resistant hybrids decreased by 0-99%, compared to a susceptible hybrid at the same location (mean reduction = 80%). Doubling time for sugarcane aphid populations on partially resistant hybrids was up to 6.4-fold higher than on known susceptible hybrids. For 48 of the 50 location-years, yield loss attributable to sugarcane aphid was not detected on the partially resistant hybrids; therefore, an economic injury level was unable to be estimated. If an economic injury level exists for resistant hybrids, it is likely at an aphid population level that exceeds the levels experienced in this study. It remains prudent to monitor resistant hybrids for unusual leaf decay associated with aphid densities that exceed current economic injury levels used for susceptible hybrids.

Presence-Absence Sampling Plans for Stink Bugs (Hemiptera: Pentatomidae) in the Midwest Region of the United States.

Stink bugs represent an increasing risk to soybean production in the Midwest region of the United States. The current sampling protocol for stink bugs in this region is tailored for population density estimation and thus is more relevant to research purposes. A practical decision-making framework with more efficient sampling effort for management of herbivorous stink bugs is needed. Therefore, a binomial sequential sampling plan was developed for herbivorous stink bugs in the Midwest region. A total of 146 soybean fields were sampled across 11 states using sweep nets in 2016, 2017, and 2018. The binomial sequential sampling plans were developed using combinations of five tally thresholds at two proportion infested action thresholds to identify those that provided the best sampling outcomes. Final assessment of the operating characteristic curves for each plan indicated that a tally threshold of 3 stink bugs per 25 sweeps, and proportion infested action thresholds of 0.75 and 0.95 corresponding to the action thresholds of 5 and 10 stink bugs per 25 sweeps, provided the optimal balance between highest probability of correct decisions (≥ 99%) and lowest probability of incorrect decisions (≤ 1%). In addition, the average sample size for both plans (18 and 12 sets of 25 sweeps, respectively) was lower than that for the other proposed plans. The binomial sequential sampling plan can reduce the number of sample units required to achieve a management decision, which is important because it can potentially reduce risk/cost of management for stink bugs in soybean in this region.

Evaluation of Two-Leaf Sampling Units to Estimate Sugarcane Aphid (Hemiptera: Aphididae) Economic Thresholds in Commercial Grain Sorghum.

Sugarcane aphid Melanaphis sacchari Zehntner is a significant economic pest of grain sorghum in the United States. Effective monitoring and early detection are cornerstones for managing invasive pests. The recently developed binomial sequential sampling plan estimates sugarcane aphid economic thresholds (ETs) based on classification whether a 2-leaf sample unit has ≤ or ≥ 50 M. sacchari. In this study, we evaluated eight 2-leaf sampling units for potential use in the sequential sampling plan. From 2016 through 2017, whole plant counts of M. sacchari were recorded non-destructively in situ on sorghum plants from 140 fields located in five states. Plant canopies were stratified into three categories. Two leaves from each stratum were used to compare linear relationships between M. sacchari numbers per two-leaf sample unit and total M. sacchari density per plant. Analysis revealed that two randomly selected leaves from the middle stratum accounted more variation for estimating M. sacchari density when compared to two leaves from the other strata. Comparison of eight two-leaf sampling units within plant growth stages were variable in quantifying variation of M. sacchari densities. When growth stages were combined, the standard uppermost + lowermost leaf sample unit and a unit consisting of two randomly selected leaves from the middle stratum revealed little difference in their enumeration of variation in M. sacchari density. Because other sample units were either less predictive and/or more variable in estimating M. sacchari density, we suggest that the (L1+U1) sample unit remain the preferred method for appraising M. sacchari ETs.

Development of Binomial Sequential Sampling Plans for Sugarcane Aphid (Hemiptera: Aphididae) in Commercial Grain Sorghum.

The sugarcane aphid (Melanaphis sacchari Zehntner) is a significant economic pest of grain sorghum (Sorghum bicolor (L.) Moench) in the Southern United States. Current nominal and research-based economic thresholds are based on estimates of mean aphids per leaf. Because enumerating aphids per leaf is potentially time consuming, binomial sequential sampling plans for M. sacchari were developed that allow users to quickly classify the economic status of field populations and determine when an economic threshold has been exceeded. During 2016 and 2017, counts of M. sacchari were recorded from 281 sampling events in 140 sorghum fields located in six states (Oklahoma, Kansas, Texas, Arkansas, Louisiana, Mississippi) . Regression analysis was used to describe the relationships between the mean M. sacchari density per two-leaf sample and proportion of plants infested with one or more aphids. Tally thresholds of T50 and T100 aphids per two-leaf sample were selected based on goodness of fit and practicality. Stop lines for both tally thresholds were developed for selected economic thresholds using Wald's sequential probability ratio test. Model validations using an additional 48 fields demonstrated that reliable classification decisions could be made with an average of 11 samples regardless of location. This sampling system, when adopted, can allow users to easily and rapidly determine when M. sacchari infestations need to be treated.

Metabolic resistance to S-metolachlor in two waterhemp (Amaranthus tuberculatus) populations from Illinois, USA.

BACKGROUND: Two waterhemp (Amaranthus tuberculatus) populations from Illinois demonstrating multiple-resistance to acetolactate synthase (ALS)-, 4-hydroxyphenylpyruvate dioxygenase, and photosystem II (PSII)-inhibiting herbicides (designated CHR and SIR) also displayed reduced sensitivity to very-long-chain fatty acid-inhibiting herbicides, including S-metolachlor. We hypothesized that a physiological mechanism, such as enhanced metabolism, could be responsible for the reduced efficacy of S-metolachlor. RESULTS: Metabolism experiments indicated that resistant populations degraded S-metolachlor more rapidly than sensitive populations and equally as rapidly as corn 2-24 h after treatment (HAT). Resistant waterhemp and corn metabolized 90% (DT90 ) of absorbed S-metolachlor in less than 3.2 h whereas DT90 values for sensitive waterhemp exceeded 6 h. The glutathione S-transferase inhibitor 4-chloro-7-nitrobenzofurazon and cytochrome P450-inhibitor malathion decreased the amount of S-metolachlor metabolized in resistant waterhemp at 4 HAT but not in sensitive waterhemp or corn, and altered the abundance of certain metabolites in resistant waterhemp. CONCLUSION: Results from this research demonstrate that resistance to S-metolachlor in these waterhemp populations is due to enhanced herbicide metabolism relative to sensitive populations. In addition, our results indicate that resistant waterhemp might utilize metabolic pathway(s) more intricate than either sensitive waterhemp or corn based on their metabolite profiles. © 2020 Society of Chemical Industry.

Impact of Planting Date on Melanaphis sacchari (Hemiptera: Aphididae) Population Dynamics and Grain Sorghum Yield.

The sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), has become a major pest of grain sorghum, Sorghum bicolor (L.) Moench, in the United States in recent years. Feeding by large densities of sugarcane aphids causes severe damage, which can lead to a total loss of yield in extreme cases. Our objective was to determine the effect of grain sorghum planting date on sugarcane aphid population dynamics and their potential to reduce yields. We conducted field experiments from 2015 to 2017 in which an aphid-susceptible grain sorghum hybrid was planted at four different dates, which encompassed the typical range of planting dates used in Arkansas production systems. Plots were either protected from sugarcane aphid feeding using foliar insecticide sprays, or left untreated to allow natural populations of sugarcane aphids to colonize and reproduce freely. Planting date impacted both the magnitude and severity of sugarcane aphid infestations, with the highest population densities (and subsequent reductions in sorghum yield) generally occurring on plots that were planted in May or June. Sugarcane aphid feeding reduced yields in the untreated plots in two of the four planting date categories we tested. Earlier planting generally resulted in less sugarcane aphid damage and improved yields compared with later planting dates. While the effect of planting date on sugarcane aphid populations is likely to vary by region, sorghum producers should consider grain sorghum planting date as a potential cultural tactic to reduce the impact of sugarcane aphid.

Development of Economic Thresholds for Sugarcane Aphid (Hemiptera: Aphididae) in Susceptible Grain Sorghum Hybrids.

Sugarcane aphid, Melanaphis sacchari Zehtner (Hemiptera: Aphididae), outbreaks on grain sorghum were first detected in the United States in 2013. The spread of sugarcane aphid across the sorghum-producing regions of North America necessitated increased insecticide use to mitigate economic loss. A field experiment to develop economic thresholds for sugarcane aphid was conducted 15 times across seven locations across the southern United States during 3 yr (2014-2016). Grain sorghum hybrids were evaluated by measuring yield in response to a range of aphid infestations. Yield-aphid population density relationships were described by linear function, which facilitated calculating economic injury levels and economic thresholds. The slopes of the yield-aphid density regressions were significant, negative, and relatively stable across locations, years, and agronomic conditions. The relationships aggregated into two groups, populations that exhibited relatively slow and fast population growth, and common economic injury levels were determined using control costs and market values of grain. Average economic injury levels of 37 and 102 aphids per leaf were most applicable to the two groupings of sorghum/aphid relationships and aphid population growth. Using field-based sugarcane aphid population doubling time estimated from weekly observations of aphid densities, economic thresholds were calculated, ranging from 19 to 132 aphids per leaf across the 15 locations-years. Without site-specific knowledge of a slow-growing aphid population and given cost and market price variability of the system, a 40 aphid per leaf threshold is most prudent to use across the range of hybrid, environmental, and market conditions experienced in this study.

Field Studies on the Horizontal Transmission Potential by Voluntary and Involuntary Carriers of Helicoverpa armigera nucleopolyhedrovirus (Baculoviridae).

Horizontal transmission of Helicoverpa armigera nucleopolyhedrovirus (HearNPV) has been found to occur through several pathways involving abiotic factors such as soil, wind, and rain, and biotic factors such as predators, parasitoids, and infected hosts. Previous studies examining horizontal transmission through certain biological carriers speculated they were likely not significant in increasing infection rates, however; these studies only focused on a relatively small number of arthropods present within a field setting. This study was conducted to evaluate the horizontal transmission potential of HearNPV by all potential biological carriers when applied as a foliar bioinsecticide or as virus-infected, nonmotile Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) larvae in a soybean field. Soybean plots were either sprayed with HearNPV or infested with late-stage HearNPV-infected larvae, and sample zones were sampled 3, 7, 10, 14, 17, and 21 days after the infestation, and analyzed for viral presence using PCR. We then identified HearNPV carriers through contamination from the application (involuntary) or through contact with a HearNPV-infected larva (voluntary). Both were confirmed through PCR analysis. Regardless of application technique, on average, HearNPV was capable of disseminating up to 61.0 m in 3 d after inoculation and was found within the sampled canopy 13-21 d after inoculation. Several arthropods were identified as novel carriers of HearNPV. Results from this study indicate that many novel HearNPV carriers are likely important in disseminating HearNPV.

Management of Megacopta cribraria (Hemiptera: Plataspidae) at Different Stages of Soybean (Fabales: Fabaceae) Development.

The invasive plataspid Megacopta cribraria (F.) is now distributed throughout much of the southeastern United States. While it readily feeds and develops on the invasive weed kudzu, Puereria montana (Loureiro) Merrill var. lobata (Willdenow), M. cribraria is an economic pest of soybean, Glycine max (L.) Merrill. Differences in the susceptibility of soybean to M. cribraria -induced yield reductions based on plant phenology were assessed using two experimental protocols in Georgia, North Carolina, and South Carolina from 2011 to 2013 in which soybeans were protected from M. cribraria using insecticides during different stages of plant phenology. In the first protocol, where insecticide applications were initiated at progressively later stages in soybean development depending on treatment, yields in the untreated plots were reduced by an average of 13% compared with plots that were protected beginning at full flowering (R2). Soybean plots that were protected beginning at 4 wk after full flowering or earlier did not suffer yield reductions from M. cribraria . In the second protocol, where insecticide applications began at R2 and were discontinued at progressively later stages in soybean development depending on treatment, yields in the untreated plots were reduced by an average of 12% compared with plots that were protected until 8 wk after R2. Plots in which protection was discontinued beginning at 4 wk after full flowering or later did not suffer yield reductions. The period from two to 6 wk after R2 (generally coinciding with pod and seed development - stages R3-R5) was identified as critical for management of M. cribraria .

Megacopta cribraria (Hemiptera: Plataspidae) Population Dynamics in Soybeans as Influenced by Planting Date, Maturity Group, and Insecticide Use.

Since its unintentional introduction during 2009, Megacopta cribraria (F.) has spread rapidly throughout the southeastern United States, mainly feeding and reproducing on kudzu, Pueraria montana Loureiro (Merr.) variety lobata (Willdenow), and soybeans, Glycine max (L.) Merr. Megacopta cribraria has become a serious economic pest in soybeans, forcing growers to rely solely on insecticide applications to control this insect. The main objective of this study was to investigate if variation in planting date and maturity group of soybeans had an impact on management of M. cribraria populations. Three experimental fields were located in North Carolina (2) and South Carolina (1), and the tests replicated during 2012 and 2013. Treatments consisted of three planting dates, four maturity groups, and insecticide treated versus untreated, at each location. More M. cribraria were found in untreated early planted soybeans than late planted soybeans. Generally, maturity group did not influence population densities of M. cribraria. Yield was significantly influenced by the interaction between planting date and maturity group. There was a negative linear relationship between M. cribraria populations and soybean yield. Although early planted soybeans may avoid drought conditions and potentially large populations of defoliators, these fields may be at greater risk for infestation by M. cribraria.

Action Thresholds for Managing Megacopta cribraria (Hemiptera: Plataspidae) in Soybean Based on Sweep-Net Sampling.

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.

Developing Sampling Plans for the Invasive Megacopta cribraria (Hemiptera: Plataspidae) in Soybean.

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.

Within-field spatial distribution of Megacopta cribraria (Hemiptera: Plataspidae) in soybean (Fabales: Fabaceae).

The recently introduced plataspid Megacopta cribraria (F.) can infest fields of soybean (Glycine max (L.) Merrill) in the southeastern United States. Grid sampling in four soybean fields was conducted in 2011 and 2012 to study the spatial distribution of M. cribraria adults, nymphs, and egg masses. Peak oviposition typically occurred in early August, while peak levels of adults occurred in mid-late September. The overall sex ratio was slightly biased at 53.1 ± 0.2% (SEM) male. Sweep samples of nymphs were biased toward late instars. All three life stages exhibited a generally aggregated spatial distribution based on Taylor's power law, Iwao's patchiness regression, and spatial analysis by distance indices (SADIE). Interpolation maps of local SADIE aggregation indices showed clusters of adults and nymphs located at field edges, and mean densities of adults were higher in samples taken from field edges than in those taken from field interiors. Adults and nymphs were often spatially associated based on SADIE, indicating spatial stability across life stages.

Reduction of soybean yield components by Megacopta cribraria (Hemiptera: Plataspidae).

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.

Residual efficacy of insecticides applied to exterior building material surfaces for control of nuisance infestations of Megacopta cribraria (Hemiptera: Plataspidae).

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.