Abundance of Halyomorpha halys (Hemiptera: Pentatomidae) and Megacopta cribraria (Hemiptera: Plataspidae) in Soybean in Areas with Few Previous Sightings in Tennessee.

Halyomorpha halys (Stål) and Megacopta cribraria (Fabricius) are two exotic invasive pests that have invaded the United States in recent years. Halyomorpha halys can damage various fruits, vegetables, and field crops, such as soybean and corn, while Megacopta cribraria only attacks soybean and kudzu, a weed species. They are currently found in southeastern states and threaten soybean and other crops grown in the region. This study evaluated the seasonal abundance of H. halys and M. cribraria in soybeans in 2016 and 2017 in two counties in the central region of Tennessee, where both species had either a few sightings or none that were recorded when this research was being planned. Lures and sweep sampling were used to monitor H. halys, and sweep sampling was used to monitor M. cribraria. Halyomorpha halys was first detected in samples in late July. Their numbers increased in early to mid-September, reached the economic threshold in late Sept, and then started to decline. Megacopta cribraria was first detected in mid to late July, increased their populations in September, but did not reach the economic threshold and declined mid-October. Our results showed the seasonal abundances of H. halys and M. cribraria and their establishment in the central region of Tennessee.

Susceptibility of Different Life Stages of Kudzu Bug Megacopta cribraria (F.) (Hemiptera: Plataspidae) to Two Different Native Strains of Beauveria bassiana.

This is the first study that examined and compared the survival, LC50, and RR50 estimates of Megacopta cribraria F. (Hemiptera: Plataspidae) nymphs and adults that were exposed to two native Beauveria bassiana isolates (Previously codified as NI8 and KUDSC strains) at four concentrations. The greatest reduction in survival and mortality was observed primarily on or after 10 d post-exposure to B. bassiana isolates. Survival of early instars (2nd, 3rd) were not affected by either strains or concentration at 3 d and 5 d post-exposure. Survival of later instars (5th) and adults was significantly reduced when exposed to the KUDSC strain at all concentrations. Comparison of dose−mortality values (LC50) using resistance ratios (RR50) were significantly different between life stages of the kudzu bug for both strains of B. bassiana. The LC50 values showed that kudzu bug adults are more susceptible than any other life stage when exposed to either strain. The KUDSC strain was more pathogenic than NI8 10 d after exposure, but NI8 exhibited significantly higher pathogenicity than KUDSC 20 d after exposure. Our results suggest potential field application of B. bassiana for kudzu bug control and their integration into pest management strategies to suppress them before they cause economic damage to soybean crops.

Use of Pyriproxyfen to Induce Oogenesis in Diapausing Megacopta cribraria (Heteroptera: Plataspidae), and Evaluation of Pyriproxyfen-Induced Eggs for Rearing the Parasitoid Paratelenomus saccharalis (Hymenoptera: Scelionidae).

The mass rearing of hymenopteran egg parasitoids requires an abundant supply of host eggs. The onset of reproductive diapause and subsequent decline in egg production poses a challenge for parasitoid rearing when using host colonies augmented by field-collected insects. We investigated the application of pyriproxyfen, a juvenile hormone analog, to induce oviposition in diapausing adult kudzu bugs, Megacopta cribraria (Fabricius) (Heteroptera: Plataspidae), and the use of eggs produced by pyriproxyfen-treated kudzu bugs to rear the egg parasitoid, Paratelenomus saccharalis (Dodd) (Hymenoptera: Scelionidae). The effects of pyriproxyfen and photoperiod treatments on host mortality, egg production, and rates of parasitoid eclosion from the eggs were used to calculate the parasitoid yield for the different treatment regimes. A combination of pyriproxyfen and a long-day photoperiod increased the parasitoid yield by 87% compared to acetone and a long-day photoperiod. The general applicability of JH-analog mediated egg production for parasitoid rearing is discussed.

Soybean Host Plant Resistance to Megacopta cribraria (Hemiptera: Plataspidae) and the Potential Role of Leaf Trichome Density.

Megacopta cribraria (F.) (Hemiptera: Plataspidae) is an invasive pest of soybean that has spread across the southeastern United States since its initial discovery in 2009 in Georgia. Previous studies in the southeastern states have documented both the population dynamics of this pest and host plant resistance (HPR) among soybean varieties, although the specific mechanisms of HPR remain unknown. The objectives of this study were, therefore, to 1) quantify field resistance to M. cribraria in multiple soybean varieties in two states previously affected by severe M. cribraria infestations, North Carolina (NC) and South Carolina (SC); and 2) study the role of soybean trichome density in imparting resistance against M. cribraria. Soybean variety 'Camp' was least attractive to M. cribraria, through time and locations, suggesting consistent resistance. Other varieties showed variable performance among the locations and sampling dates. A significant difference in trichome density was evident. However, there was no correlation between trichome density and M. cribraria infestation. Compared to a previously published study in the same location, when M. cribraria adults emerging from overwintering dispersed into soybeans, in our study only first-generation adults dispersed into soybeans. Considering the current trend of significantly lower M. cribraria infestation rates in North and South Carolina, this pest may be finally succumbing to indigenous natural enemies and should be managed by incorporating integrated pest management tactics, such as HPR, that help conserve natural enemy populations.

Even obligate symbioses show signs of ecological contingency: Impacts of symbiosis for an invasive stinkbug are mediated by host plant context.

ABSTRACT: Many species interactions are dependent on environmental context, yet the benefits of obligate, mutualistic microbial symbioses to their hosts are typically assumed to be universal across environments. We directly tested this assumption, focusing on the symbiosis between the sap-feeding insect Megacopta cribraria and its primary bacterial symbiont Candidatus Ishikawaella capsulata. We assessed host development time, survival, and body size in the presence and absence of the symbiont on two alternative host plants and in the insects' new invasive range. We found that association with the symbiont was critical for host survival to adulthood when reared on either host plant, with few individuals surviving in the absence of symbiosis. Developmental differences between hosts with and without microbial symbionts, however, were mediated by the host plants on which the insects were reared. Our results support the hypothesis that benefits associated with this host-microbe interaction are environmentally contingent, though given that few individuals survive to adulthood without their symbionts, this may have minimal impact on ecological dynamics and current evolutionary trajectories of these partners. OPEN RESEARCH BADGES: This article has earned an Open Data Badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.kg4bc56.

Electrophysiological and Behavioral Responses of the Kudzu Bug, Megacopta cribraria (Hemiptera: Plataspidae), to Volatile Compounds from Kudzu and Soybean Plants.

The kudzu bug, Megacopta cribraria, is a key pest of soybean in the United States. Electrophysiological and behavioral responses of adult M. cribraria to kudzu and soybean volatile compounds were examined to identify semiochemicals used for host location. Headspace volatiles collected from undamaged potted plants were analyzed by gas chromatography with electroantennographic detection (GC-EAD). Subsequently, six GC-EAD-active compounds were identified by gas chromatography-mass spectrometry (GC-MS). These six compounds, along with some previously reported insect attractants, were selected for electroantennogram (EAG) assays. The four chemicals that elicited the strongest EAG responses, 1-octen-3-ol, nonanal, benzaldehyde, and ocimene, were selected for evaluation in olfactometer bioassays. Both benzaldehyde and 1-octen-3-ol exhibited dose-dependent responses at higher concentration. Our results provide insight into host location compounds used by adult M. cribraria. These results may be evaluated in future field tests and ultimately useful to develop a semiochemical-based monitoring technique and integrated pest management program for M. cribraria.

Cold Tolerance of Megacopta cribraria (Hemiptera: Plataspidae): An Invasive Pest of Soybeans.

Kudzu bug, Megacopta cribraria Fabricius (Hemiptera: Plataspidae), first discovered in the United States in 2009, is an invasive pest of soybeans. From 2013 to 2016, Maryland has been the northern limit of its distribution in the United States. We sought to determine the physiological cold temperature limits, timing of movement to overwintering locations, and to characterize overwintering microhabitat temperature. We measured supercooling point (SCP) on three populations from distinct USDA plant hardiness zones in Maryland and Virginia between October and December of 2015. The average SCP across all sample months and populations was -12.6°C and no consistent trend of month or population location were observed. Additionally, we assessed the lower lethal temperature to kill 50% of the population (LLT50) at the same population locations in October and November 2015. The average LLT50 over both months and all three population locations was -5.1°C. Again, no consistent trend based on population location was observed but we did find a modest depression in the LLT50 values between October and November. We observed that kudzu bug overwinters in leaf litter and begins to move into the litter in late November to early December. Leaf litter moderates day to night temperature differences and was warmer than ambient temperature by an average of 0.7°C. Evidence suggests that the cold tolerance of the kudzu bug limits its distribution north of Maryland.

Seasonal Occurrence and Interspecific Interactions of Egg Parasitoids of Megacopta cribraria (Heteroptera: Plataspidae) in Japan.

We conducted a field study to determine seasonal egg parasitism rates of the kudzu bug Megacopta cribraria (F.) on the kudzu plant, Pueraria montana (Lour.) Merr. var. lobata (Willd.) Maesen et Almeida ex Sanjappa and Pradeep, in Tokyo, Japan, during the period from May 2014 to September 2014. The eggs of M. cribraria per 1 m2 of kudzu at four locations in Tokyo were collected weekly and parasitism rates were assessed. Eggs of M. cribraria were laid on the kudzu plant from May to September. Megacopta cribraria eggs were parasitized by two parasitoid species, Paratelenomus saccharalis (Dodd) and Ooencyrtus nezarae Ishii. Paratelenomus saccharalis first appeared in May, and its parasitism rates peaked in July and September. Ooencyrtus nezarae first appeared in June and its parasitism rates peaked in July. Except for one location which could not be statistically analyzed because of the small sample size, occurrence of parasitism by P. saccharalis and O. nezarae in M. cribraria egg masses was independent at one location and positively associated at two locations, suggesting that the use of host egg masses by P. saccharalis and O. nezarae is not mutually exclusive. Parasitism rates by P. saccharalis and O. nezarae were significantly lower for egg masses parasitized by both species than for those parasitized by a single species. The proportion of males among O. nezarae progeny was significantly higher for egg masses parasitized by O. nezarae together with P. saccharalis than for those parasitized by O. nezarae alone. These results suggest that parasitism of host egg masses by the two species is influenced by their interspecific interactions.

Seasonal Population Dynamics of Megacopta cribraria (Hemiptera: Plataspidae) in Kudzu and Soybean, and Implication for Insecticidal Management in Soybean.

Megacopta cribraria (F.), an invasive species introduced from Asia in 2009, is now prolific in the southeastern United States. Megacopta cribraria develops primarily on kudzu and soybean completing two generations. It is not well understood how this economic pest is affected by changes in geographic distribution in the United States or how population levels have changed since its establishment. The effect of insecticide application timing on field populations of M. cribraria is not well documented. These studies seek to understand how population dynamics of M. cribraria vary with geographic regions in Georgia. Effect of application timing on populations throughout the growing season was also examined. Weekly from 2012 to 2013, all life stages were enumerated from kudzu and soybean environments at several locations throughout Georgia from sweeps samples and flight intercept captures. Coordinates were recorded for locations, and classified as belonging to the Piedmont or Coastal Plain region of the state. Single spray trials were conducted from 2011-2014, and applications were made to soybean at intervals throughout the season. From 2012 to 2015, two kudzu patches near Griffin, GA, were monitored to detect population changes. Differences in population dynamics from locations around the state were found, but no clear effect of latitude, longitude, or region was observed. Insecticide applications applied in July suppressed nymph populations significantly better than treatments made earlier or later. Megacopta cribraria populations declined in 2014 and 2015 compared with 2012 and 2013. These studies provide the critical information for M. cribraria management in soybean in the southeastern United States.

Impacts of Tillage, Maturity Group, and Insecticide Use on Megacopta cribraria (Hemiptera: Plataspidae) Populations in Double-Cropped Soybean.

Megacopta cribraria (F.), also known as the kudzu bug, is a soybean pest in the United States, and it can cause up to a 60% yield reduction if not controlled. Insecticides are commonly used to manage this pest in commercial soybean fields. However, other soybean production practices may also affect kudzu bug populations. This study investigated the effect of soil tillage, maturity group selection, and insecticide use on kudzu bug densities in soybean. During 2012 and 2013, at two locations each year in North Carolina, four varieties of soybean maturity groups were planted in June into conventionally tilled plots and into plots with cereal crop residue under reduced tillage conditions (mimicking double-crop production). Plots were further split as insecticide-protected and untreated. Four times more kudzu bugs were found in conventionally tilled than reduced till plots throughout the growing season. Selection of the maturity group influenced the attractiveness of the kudzu bug to oviposit on soybean. A 56% reduction of kudzu bug densities was achieved through insecticide treatment, with an ∼6% increase in yield. Information on how production practices, including soil tillage, affect kudzu bug populations in soybean may help growers select practices to minimize kudzu bug injury and protect yield.

Ecology and Management of Kudzu Bug (Hemiptera: Plataspidae) in Southeastern Soybeans.

Kudzu bug, Megacopta cribraria Fabricius (Hemiptera: Plataspidae), is an invasive exotic pest of soybeans that has been present in the southeastern United States since 2009 and has been rapidly spreading through soybean-producing states. Their primary reproductive hosts in the United States are soybean, kudzu, pigeon pea, black eye pea, lima bean, pinto bean, wisteria, white sweet clover, white clover, red clover, alfalfa, perennial peanut, and American joint vetch. In soybeans, the kudzu bug feeds on vascular fluids at the stem, petiole, and nodes, causing yield losses of up to 60%. The current management recommendation for this pest includes spraying of pyrethroids such as bifenthrin, but this method is not environmentally friendly, as this negatively impacts beneficial insect populations. Sustainable management tactics, including the development of economic thresholds for insecticide sprays, assessing the spatial and temporal distribution of this pest, manipulating cultivation practices, use of biological control, and host plant resistance, are currently being explored. We present an overview of the ecology of the kudzu bug in soybeans and available management tactics to assist with the management of this potentially devastating pest of soybeans as it spreads westward.

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 .

Host Plant Resistance to Megacopta cribraria (Hemiptera: Plataspidae) in Diverse Soybean Germplasm Maturity Groups V Through VIII.

Initially discovered in Georgia in 2009, the exotic invasive plataspid, Megacopta cribraria (F.), has become a serious pest of soybean ( Glycine max (L.) Merrill). Managing M. cribraria in soybean typically involves the application of broad-spectrum insecticides. Soybean host plant resistance is an attractive alternative approach; however, no commercial soybean cultivars have been identified as resistant. During 2013 and 2014, we compared 40 and 44 soybean genotypes, respectively, for resistance to M. cribraria in a split-plot design under natural insect infestation in small-plot experiments. Soybean genotypes were selected to maximize diversity with respect to maturity group, pubescence type, leaf shape, seed size, nitrogen fixation, drought tolerance, seed protein content, and pest resistance. Megacopta cribraria egg masses, nymphs, and adults were counted during the growing season to identify potentially resistant soybean genotypes. Soybean seed yield was measured in insecticide-protected and unprotected conditions to determine tolerance to M. cribraria feeding. In both years, a range of host plant resistance was observed. The fewest M. cribraria adults and nymphs were found on narrow-leaf, small-seeded cultivars 'N7103' and 'Vance,' as well as the nonnodulating cultivar 'Nitrasoy.' Additionally, N7103 and Vance were among the least susceptible genotypes to M. cribraria oviposition in the field. Most 'Benning' cultivar insect-resistant near-isogenic breeding lines also displayed moderate levels of resistance to M. cribraria . Seed yields of Vance and N7103 were less affected by M. cribraria in 2013 than most other soybean genotypes. These results may be useful to soybean breeders to develop cultivars with resistance to 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.

Preoverwintering Copulation and Female Ratio Bias: Life History Characteristics Contributing to the Invasiveness and Rapid Spread of Megacopta cribraria (Heteroptera: Plataspidae).

Prewinter copulation, sperm storage, and oocyte development in overwintering adult Megacopta cribraria (F.) was examined in Alabama (Lee Co.). Microscopic examinations of the spermathecae and ovaries were made in females and of the testes in males that were collected approximately weekly from September 2013 through March 2014. The results indicated that approximately 15% of females mated before entering winter dormancy and sperm was stored in their spermatheca for up to seven months, oocytes in mated overwintering females proceeded to postblastoderm stage before the onset of spring feeding and mating in March, all of the overwintering males had sperm in their testes, and the ratio of females gradually increased in populations during overwintering. This study indicates that both males and females are capable of reproductive dormancy. The biological significance of these life cycle aspects is discussed from the viewpoints of invasiveness and adaptation.

First report of a mermithid nematode infecting the invasive Megacopta cribraria (Hemiptera: Plataspidae) in the United States.

Megacopta cribraria (Hemiptera: Plataspidae) has become a pest of soybean, Glycine max (L.), in the United States. While several natural enemies of M. cribraria have been reported, our study is the first to report nematodes beneath the pleural membranes in the abdominal cavities of adults. Morphological and molecular analyses suggest this nematode belongs to the family Mermithidae. This first report of a nematode infection in M. cribraria adds to the current inventory of enemies attacking this insect. Our observations provide a basis for future research to examine the impact of nematodes on M. cribraria mortality and to investigate their capacity to reduce populations.

Development, Survival, and Reproduction of Megacopta cribraria (Heteroptera: Plataspidae) at Different Constant Temperatures.

The plataspid Megacopta cribraria (F.), an economic pest of soybeans, Glycine max (L.) Merrill, in Asia recently invaded North America and has become not only an important pest of soybean but also a nuisance pest. Although much is reported about M. cribraria in its native and invasive range, little information has been documented on the effect of temperatures on its development, longevity, and reproduction. We evaluated the influence of five constant temperatures (17-33°C) on the development, survival, fecundity, and population growth of M. cribraria in the laboratory. The developmental time for egg and nymph stages was shortened significantly with increasing temperature. The developmental time from egg to adult emergence was 114.81, 76.26, 44.54, and 38.54 d at 17, 21, 25, and 29°C, respectively. The nymphs of M. cribraria could not complete full development at a constant 33°C. The developmental threshold temperature estimated for egg to adult was 14.25°C, with a thermal constant of 849.56 degree-days. Females had the longest preoviposition period at 21°C (54.33 d), and the preoviposition period was shortened significantly as the temperature increased. Females had the longest oviposition period (35.33 d) and the highest fecundity (159.67 eggs per female) at 25°C and did not lay any eggs at 17°C. Female longevity was found to be shortest (44.0 d) at 29°C, and similar (75.67-81.50 d) at 17-25°C. The population trend index of M. cribraria was the highest (46.47) at 25°C, followed by 29°C (10.84) and 21°C (6.70). The results will be useful for predicting the phenology and population dynamics of M. cribraria and will provide some biological information on the invasive species in its nonnative range.