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.

Economic Injury Level of the Neotropical Brown Stink Bug Euschistus heros (F.) on Cotton Plants.

In Brazil, the Neotropical brown stink bug, Euschistus heros (F.) (Hemiptera: Pentatomidae), commonly disperses from soybeans to cotton fields. The establishment of an economic treatment threshold for this pest on cotton crops is required. Infestation levels of adults of E. heros were evaluated on cotton plants at preflowering, early flowering, boll filling, and full maturity by assessing external and internal symptoms of injury on bolls, seed cotton/lint production, and fiber quality parameters. A completely randomized experiment was designed to infest cotton plants in a greenhouse with 0, 2, 4, 6, and 8 bugs/plant, except at the full-maturity stage in which only infestation with 8 bugs/plant and uninfested plants were evaluated. Results indicated that the preflowering, early-flowering, and full-maturity stages were not affected by E. heros. A linear regression model showed a significant increase in the number of internal punctures and warts in the boll-filling stage as the population of bugs increased. The average number of loci with mottled immature fibers was significantly higher at 4, 6, and 8 bugs compared with uninfested plants with data following a quadratic regression model. The seed and lint cotton was reduced by 18 and 25% at the maximum level of infestation (ca. 8 bugs/plant) in the boll-filling stage. The micronaire and yellowing indexes were, respectively, reduced and increased with the increase of the infestation levels. The economic injury level of E. heros on cotton plants at the boll-filling stage was determined as 0.5 adult/plant. Based on that, a treatment threshold of 0.1 adult/plant can be recommended to avoid economic losses.

Feeding preference and movement of Nezara viridula and Euschistus serous (Hemiptera: Pentatomidae) on individual cotton plants.

Experiments were conducted in an environmental growth chamber to determine the movement and feeding preferences of Nezara viridula (L.) and Euschistus serous (Say) on individual cotton plants. Fifth instars were caged by species on a single cotton plant (FM 9063 B2F) containing four discrete boll sizes ranging from 1.1 to 3.0 cm in diameter over a period of 5 d per replication. Two digital video cameras were simultaneously focused on each of the four bolls per plant to visually confirm stink bug resting and movement. During the study, a total of 4,080 h of video footage was recorded and analyzed. Results showed that N. viridula and E. serous did not prefer the exact same boll sizes. In a trial with eight stink bugs per plant, N. viridula spent more time on the three larger boll classes, 1.6-2.0, 2.1-2.5, and 2.6-3.0 cm. In a separate trial with one stink bug per plant, N. viridula spent more time on the larger boll classes while E. serous exhibited the strongest preference for 1.1-1.5 and 2.1-2.5 cm bolls. N. viridula moved more often than E. serous and both species moved more often during photophase compared with scotophase. Regardless of species or number of bugs released, bolls in the smallest boll size class fell off the plant about 3 d after the bugs were released. These results confirm that scouts who are estimating stink bug damage should select bolls in the 2.1-2.5 cm diameter boll size class.

Spatial dynamics of stink bugs (Hemiptera: Pentatomidae) and associated boll injury in southeastern cotton fields.

Grid sampling (one sample per 0.40 ha) in 12 cotton (Gossypium hirsutum L.) fields for stink bugs and boll injury caused by stink bug feeding was conducted in 2007 and 2008 in South Carolina and Georgia. The main species collected using the beat cloth method were the green stink bug, Acrosternum hilare (Say) (69%); brown stink bug, Euschistus servus (Say) (18%); and the southern green stink bug, Nezara viridula (L.) (14%), respectively. The inverted distance weighted interpolation method and Spatial Analysis by Distance IndicEs analyses showed spatial variability in both boll injury and stink bug densities. Four of five fields with field-average boll injury exceeding 15% had a combination of either soybean or peanut adjacent to the cotton field of interest. The Spatial Analysis by Distance IndicEs index of dispersion for stink bug densities and boll injury averaged over the season indicated significant aggregation at the 5% error rate in only one and four analyses (combinations of fields, species, and life stages) of a total of 54 in 2007 and 2008, respectively. By sampling date, overall indices of dispersion for boll injury data indicated significant aggregation in four of the 63 date-field combinations at the 5% error rate. Across years, overall indices of spatial association between boll injury and stink bug densities were significant in 17 of 69 analyses, with positive associations detected in seven of 12 fields; these data suggest that spatial distribution of stink bugs in cotton fields does not always coincide with boll injury.

Development of sampling plans for cotton bolls injured by stink bugs (Hemiptera: Pentatomidae).

Cotton, Gossypium hirsutum L., bolls were sampled in commercial fields for stink bug (Hemiptera: Pentatomidae) injury during 2007 and 2008 in South Carolina and Georgia. Across both years of this study, boll-injury percentages averaged 14.8 +/- 0.3 (SEM). At average boll injury treatment levels of 10, 20, 30, and 50%, the percentage of samples with at least one injured boll was 82, 97, 100, and 100%, respectively. Percentage of field-sampling date combinations with average injury < 10, 20, 30, and 50% was 35, 80, 95, and 99%, respectively. At the average of 14.8% boll injury or 2.9 injured bolls per 20-boll sample, 112 samples at Dx = 0.1 (within 10% of the mean) were required for population estimation, compared with only 15 samples at Dx = 0.3. Using a sample size of 20 bolls, our study indicated that, at the 10% threshold and alpha = beta = 0.2 (with 80% confidence), control was not needed when <1.03 bolls were injured. The sampling plan required continued sampling for a range of 1.03-3.8 injured bolls per 20-boll sample. Only when injury was > 3.8 injured bolls per 20-boll sample was a control measure needed. Sequential sampling plans were also determined for thresholds of 20, 30, and 50% injured bolls. Sample sizes for sequential sampling plans were significantly reduced when compared with a fixed sampling plan (n=10) for all thresholds and error rates.

Effects of adjacent habitat on populations of stink bugs (Heteroptera: Pentatomidae) in cotton as part of a variable agricultural landscape in South Carolina.

The distribution of phytophagous stink bugs and associated boll injury in margins of cotton fields bordering various agronomic crops and woodlands were studied in 2007 and 2008. Two commercial cotton fields, ranging in size from 7.8 to 12.1 ha in Barnwell and Lee Counties, SC, were sampled weekly each year along predetermined transects at 0, 5, 10, and 25 m from the outside margin into the cotton field. Stink bugs were sampled using a ground cloth (0.91 by 0.91 m), and quarter-sized bolls (≈ 2.5 cm in diameter) were collected and examined for internal damage. Density (bugs/row-m) of total stink bugs (adults plus nymphs) was greatest in cotton adjacent to peanut. Boll injury was significantly greater in cotton adjacent to soybean and peanut than in cotton next to other habitats, including corn, cotton, and woodlands, during midseason. Density of nymphs was greatest in cotton adjacent to peanut during mid and late season. Densities of total stink bugs and adults were greatest in cotton immediately adjacent (0 m) to all bordering crops and decreased as distance from the margin increased. Boll injury was greatest in cotton immediately adjacent (0 m) to the bordering crop in mid and late season. Because densities of stink bugs and boll injury vary spatially and temporally along field margins of cotton and can vary significantly based on the adjacent crop, such factors should be considered when developing integrated pest management strategies in cotton.

Sampling stink bugs (Hemiptera: Pentatomidae) for population estimation and pest management in southeastern cotton production.

Stink bugs (Hemiptera: Pentatomidae) were sampled in commercial cotton, Gossypium hirsutum L., fields in 2007 and 2008 in South Carolina and Georgia. The main species collected with the beat cloth and sweep net methods were green stink bug, Acrosternum hilare (Say) (63 and 57%, respectively); brown stink bug, Euschistus servus (Say) (23 and 18%, respectively); and southern green stink bug, Nezara viridula (L.) (14 and 22%, respectively). Average stink bug densities were 0.145 +/- 0.010 (mean +/- SEM) for adults and 0.250 +/- 0.027 for nymphs per 3.7 m of row by using the beat cloth method. Average stink bug densities were 0.291 +/- 0.016 for all adults and 0.137 +/- 0.018 for all nymphs per 50 sweeps. A density of two southern green stink bugs per 3.7 m of row by using the beat cloth method required 43 samples (reliability or precision, Dx = 0.3) for population estimation, whereas 88 samples were necessary for a density of two southern green stink bugs per 50 sweeps. At low densities, the sweep net was a more cost-reliable sampling method for all species and life stages. For adult stink bugs, the beat cloth method became more reliable at densities of 1.0, 3.2, and 5.8 stink bugs per 3.7 m of cotton row for southern green stink bug, brown stink bug, and green stink bug, respectively. Sequential sampling consistently reduced sample size for all insects compared with a fixed sampling plan.

Monitoring Tribolium castaneum (Herbst) in pilot-scale warehouses treated with beta-cyfluthrin: are residual insecticides and trapping compatible?

Integrated pest management strategies for cereal processing facilities often include both pheromone-baited pitfall traps and crack and crevice applications of a residual insecticide such as the pyrethroid cyfluthrin. In replicated pilot-scale warehouses, a 15-week-long experiment was conducted comparing population trends suggested by insect captures in pheromone-baited traps to direct estimates obtained by sampling the food patches in untreated and cyfluthrin-treated warehouses. Warehouses were treated, provisioned with food patches and then infested with all life stages of Tribolium castaneum (Herbst). Food patches, both those initially infested and additional uninfested, were surrounded by cyfluthrin bands to evaluate if insects would cross the bands. Results show that insect captures correlated with population trends determined by direct product samples in the untreated warehouses, but not the cyfluthrin-treated warehouses. However, dead insects recovered from the floor correlated with the insect densities observed with direct samples in the cyfluthrin-treated warehouses. Initially, uninfested food patches were exploited immediately and after six weeks harbored similar infestation densities to the initially infested food patches. These data show that pest management professionals relying on insect captures in pheromone-baited traps in cyfluthrin-treated structures could be deceived into believing that a residual insecticide application was suppressing population growth, when the population was actually increasing at the same rate as an untreated population.

Factors affecting capture of Cryptolestes ferrugineus (Coleoptera: Laemophloeidae) in traps placed in stored wheat.

Cryptolestes ferrugineus (Stephens), the rusty grain beetle, infests grain externally and is a common pest of stored wheat throughout the world. Detection and population estimation of this insect are important in avoiding discounts at the point of sale. Laboratory experiments compared number of insect captures in the WNB II probe and PC trap in stored grain with a known insect density. Capture rates were strongly related to insect densities in wheat. In a simultaneous test of insect density, ranging from one to three insects per kilogram, and temperatures between 20 and 40 degrees C, insect captures in WB II probe traps increased linearly with insect density in the grain but had a quadratic response to temperature. Hole density, ranging from 40 to 120 holes along a 15-cm stretch of the trap body, was unrelated to number of insect captures. Probe trap diameters ranging from 26 to 60 mm were also unrelated to insect captures. Finally, dead rusty grain beetles were recovered in probe traps. The recovery of dead insects increased with insect density when insects were found in an aggregated dispersal pattern, such as would be found following phosphine fumigation of grain. Experiments discussed here will help grain managers understand how probe traps may be used in C. ferrugineus population estimation.