Effect of Planting Date and Maturity Group on Soybean Yield Response to Injury by Megacopta cribraria (Hemiptera: Plataspidae).

The kudzu bug, Megacopta cribraria (F.), is an invasive member of the family Plataspidae originating from Asia. Since its discovery in Georgia in 2009, its distribution has increased to 13 southern and eastern states. In the United States, M. cribraria is bivoltine and has two primary developmental hosts, kudzu and soybean. Here, we evaluated the yield response of soybean to M. cribraria feeding injury in relation to planting date and soybean maturity group. The study contained four replicated trials in Griffin, Tifton, and Midville, GA, in 2012 and 2013. Four planting dates from April to July, served as the whole plot of a split-plot design with maturity group five and seven soybean and insecticide (lambda-cyhalothrin) randomized within planting date. Egg masses, nymphs, and adults were enumerated weekly to biweekly until soybean reached maturity. Two generations were observed in April and May plantings, but only one generation was evident in June and July soybean plantings. Insecticide-protected plots had consistently higher yields than unprotected plots. Grain yield was greatest in the May planting and lowest in the July planting. Season-long feeding by M. cribraria reduced grain yield in April, May, and June plantings but not in the July planting. Maturity group and planting date had significant effects on yield components in most comparisons. This study indicated that early-planted soybean are at greater risk of yield loss from M. cribraria injury compared with later-planted soybean.

Differential expression of candidate salivary effector proteins in field collections of Hessian fly, Mayetiola destructor.

Evidence is emerging that some proteins secreted by gall-forming parasites of plants act as effectors responsible for systemic changes in the host plant, such as galling and nutrient tissue formation. A large number of secreted salivary gland proteins (SSGPs) that are the putative effectors responsible for the physiological changes elicited in susceptible seedling wheat by Hessian fly, Mayetiola destructor (Say), larvae have been documented. However, how the genes encoding these candidate effectors might respond under field conditions is unknown. The goal of this study was to use microarray analysis to investigate variation in SSGP transcript abundance amongst field collections from different geographical regions (southeastern USA, central USA, and the Middle East). Results revealed significant variation in SSGP transcript abundance amongst the field collections studied. The field collections separated into three distinct groups that corresponded to the wheat classes grown in the different geographical regions as well as to recently described Hessian fly populations. These data support previous reports correlating Hessian fly population structure with micropopulation differences owing to agro-ecosystem parameters such as cultivation of regionally adapted wheat varieties, deployment of resistance genes and variation in climatic conditions.

Host Preference of Megacopta cribraria (Hemiptera: Plataspidae) on Selected Edible Beans and Soybean.

Megacopta cribraria (F.) (Hemiptera: Plataspidae) is an Old World pest of legumes in Asia. Since its 2009 discovery in Georgia, it has become an economic pest of soybeans in the southeastern United States. The objective of this study was to determine the host preference of M. cribraria on edible legumes that might incur economic damage from injury of this pest. From 2012 to 2013 choice, no-choice, and field trials were conducted to evaluate the host suitability of several beans of commercial interest including pinto bean, lima bean, winter pea, and black-eyed pea. Choice and no-choice studies were conducted under greenhouse conditions. Plants in greenhouse trials were infested with adults and egg masses collected from kudzu and soybean and monitored for ∼2 wk. Field trials were allowed to be infested by naturally occurring M. cribraria populations. Sweep and whole plant counts of adults, egg masses, and nymphs were used to quantify field infestations. The legume crops found to be suitable developmental hosts are soybean, edamame, and pigeon pea. Low levels of development were seen on fava bean and none on the remaining entries.

Evaluation of corn hybrids expressing Cry1F, cry1A.105, Cry2Ab2, Cry34Ab1/Cry35Ab1, and Cry3Bb1 against southern United States insect pests.

Studies were conducted across the southern United States to characterize the efficacy of multiple Bacillus thuringiensis (Bt) events in a field corn, Zea mays L., hybrid for control of common lepidopteran and coleopteran pests. Cry1F protein in event TC1507 and Cry1A.105 + Cry2Ab2 proteins in event MON 89034 were evaluated against pests infesting corn on above-ground plant tissue including foliage, stalks, and ears. Cry34Ab1/Cry35Ab1 proteins in event DAS-59122-7 and Cry3Bb1 in event MON 88017 were evaluated against the larvae of Mexican corn rootworm, Diabrotica virgifera zeae Krysan and Smith, which occur below-ground. Field corn hybrids containing Cry1F, Cry1A.105 + Cry2Ab2, Cry34Ab1/Cry35Ab1, and Cry3Bb1 insecticidal proteins (SmartStax) consistently demonstrated reductions in plant injury and/or reduced larval survivorship as compared with a non-Bt field corn hybrid. Efficacy provided by a field corn hybrid with multiple Bt proteins was statistically equal to or significantly better than corn hybrids containing a single event active against target pests. Single event field corn hybrids provided very high levels of control of southwestern corn borer, Diatraea grandiosella (Dyar), lesser cornstalk borer, Elasmopalpus lignosellus (Zeller), and fall armyworm, Spodoptera frugiperda (J.E. Smith), and were not significantly different than field corn hybrids with multiple events. Significant increases in efficacy were observed for a field corn hybrid with multiple Bt events for sugarcane borer, Diatraea saccharalis (F.), beet armyworm, Spodoptera exigua (Hübner), corn earworm, Helicoverpa zea (Boddie), and Mexican corn rootworm. Utilization of field corn hybrids containing multiple Bt events provides a means for managing insect resistance to Bt proteins and reduces non-Bt corn refuge requirements.

Quantifying the Contribution of Seed Blended Refugia in Field Corn to Helicoverpa zea (Lepidoptera: Noctuidae) Populations.

Helicoverpa zea (Boddie), a pest of cotton that also occurs in field corn, is commonly controlled through the use of foliar-applied insecticides or transgenic crops expressing Bacillus thuringiensis (Berliner) (Bt) genes. To minimize the risk of Bt resistance in pest populations, refuge systems have been implemented for sustainable agroecosystem management. Historically, structured refuge compliance among growers has been low, leading to the commercialization of seed blended refugia. To test the viability of seed blended refugia in southern U.S. field corn, field studies were conducted in Mississippi and Georgia during 2016, 2017, and 2018 growing seasons. To quantify adult H. zea emergence from structured (non-Bt corn) and seed blended refuge options, emergence traps were utilized. Kernel damage among seed blended refuge and structured refuge corn ears were recorded and compared. The timing of moth emergence was recorded. When compared to a structured refuge, H. zea adult moth emergence from seed blended refugia did not significantly differ. Kernel damage of non-Bt plants in the seed blended treatments was not significantly different than non-Bt plants in the structured refuge treatments. Moth emergence timing was not significantly delayed between the structured refuge and seed blended refuge treatments. Results of this study suggest that a seed blended refuge may provide an effective insecticide resistance management alternative for H. zea in areas where structured refuge compliance is low.

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.

Alfalfa weevil (Coleoptera:Curculionidae) management in alfalfa by spring grazing with cattle.

The effect of continuous, intensive grazing by cattle in the 1st alfalfa growth cycle on larval densities of the alfalfa weevil, Hyera postica (Gyllenhal), was evaluated in "Alfagraze' and "Apollo' alfalfa, which are tolerant and not tolerant to grazing, respectively. In small-cage exclusion trials, grazing reduced larval numbers in 1991 by 65% in Alfagraze and by 32% in Apollo. Larval numbers in 1992 were low (< or = 0.6 larvae per stem) and were not reduced significantly by grazing. Grazing and use of early insecticide treatments of permethrin or carbofuran at low rates with < or = 7-d grazing restrictions to suppress larval numbers before grazing also were examined in large-plot exclusion trails in 1993 and 1994. Grazing reduced larval densities by 60% in 1993 and 45% in 1994 during a 3-wk period beginning 3 wk after grazing was initiated. However, alfalfa weevil larvae caused moderate leaf injury in 1993 and severe injury in 1994 before grazing reduced larval numbers. Use of permethrin at 0.11 kg (AI)/ha or carbofuran or chlorpyrifos at 0.28 kg (AI)/ha effectively reduced larval numbers and prevented leaf injury before grazing began. Therefore, a combination of an early application of an insecticide treatment with a short grazing restriction followed by continuous grazing will control alfalfa weevil larvae while allowing cattle to graze and directly use forage of grazing-tolerant alfalfa.

Evaluating grower, landscape manager, and consumer perceptions of azalea lace bug (Heteroptera: Tingidae) feeding injury.

A survey using modified azalea stems was used to establish a "tally threshold value" for assessing azalea lace bug, Stephanitis pyrioides (Scott), feeding injury to azalea shrubs. Consumers and green-industry professionals, represented by ornamental growers, landscape architects, and landscape managers, recognized azalea lace bug injury when injured leaf area exceeded 2%. Purchase and treatment decisions of professionals and consumers were evaluated by surveying responses to Rhododendron indica variety alba 'Delaware Valley White' azaleas representing a range of damage. Survey participants also provided a brief biographical background and answers to questions regarding pesticide use, ability to identify diseases, pests, and beneficial organisms, and willingness to consider pesticide alternatives. Professionals and consumers expressed a strong interest in limiting urban pesticide use. The 2 groups indicated a hypothetically acceptable level of 6-10% plant damage by arthropod pests. A 2% injury threshold was used to determine the level of proportional damage (the percentage of leaves displaying 2% or more lace bug leaf feeding injury) resulting in either the rejection of plant purchase or initiation of treatment. A nonlinear curve was fit to treatment and no-purchase responses of professionals and consumers using a modified 3-parameter Mitscherlich nonlinear growth function. Half of the surveyed professionals and consumers indicated that damage proportions >10% (1.03% actual injury) were sufficient to reject an azalea for purchase. Proportional damage levels >43% (3.3% actual injury) would be necessary to prompt 50% of the respondents to initiate treatment of damaged azaleas to control lace bugs.

Azalea growth in response to azalea lace bug (Heteroptera: Tingidae) feeding.

The effects of azalea lace bug, Stephanitis pyrioides (Scott), feeding injury on azalea growth and development were investigated using 'Girard's Rose' azaleas during a 2-yr field study in Georgia Low, medium, and high injury treatments, which corresponded to 6, 8, and 14% maximum canopy area injury, were compared with control azaleas that received no lace bug infestation. Flower number, whole-shrub leaf and stem dry mass, and dry mass and size of new growth tissues were unaffected by treatments. In contrast, growth index measurements, a general measure of variability frequently used for horticultural differentiation, showed significant reductions for all treatments in comparison to control azaleas after 20 wk. Though not directly quantified, this apparent discrepancy may be explained as an artifact of lace bug feeding-induced leaf abscission. Growth index measurements had considerable variability and may not be the most reliable measurement of size. In July 1998, plant canopy densities among azaleas maintained in the high injury treatments were approximately 15% less full than the canopies of control shrubs. Predaceous insects had a significant negative association with azalea lace bug number during the 2-yr study. Flower and new tissue production, measured destructively during two growing seasons, revealed azalea tolerance to 14% of maximum canopy area lace bug feeding-injury levels.

Using aesthetic assessments of azalea lace bug (Heteroptera: Tingidae) feeding injury to provide thresholds for pest management decisions.

Research on consumer, grower, and landscape manager perception of azalea lace bug, Stephanitis pyrioides (Scott), feeding and on plant productivity parameters, including gas exchange and growth, has increased our understanding of the nature of feeding injury. These studies made it possible to develop decision-making guidelines for cost-effective maintenance of aesthetically pleasing azaleas. Criteria were considered for three management situations: a 0.41-ha (1-acre) nursery production system that may use either insecticidal soap, acephate, or imidacloprid to control lace bugs; a landscape planting of a group of 10 azaleas; or maintenance of a single azalea in the landscape. Lace bug thresholds were calculated using a hybrid economic injury level (EIL) formula. Pesticide application decisions were determined using survey-based data from grower, landscape manager, and consumer perceptions of unacceptably injured azaleas at point-of-purchase for the nursery situation. Additional landscape scenarios incorporated the perceptions of growers, landscape managers, and consumers for those levels of lace bug feeding-injury that prompted the desire for treatment. Hybrid EIL determinations are appropriate for lace bug management in landscape systems where landscape professionals manage large plantings of azaleas and as a component of pest management among nursery production systems. Aesthetic considerations are more appropriate in determining control thresholds among a few or individual azaleas in the landscape.

Whole-plant CO2 exchange measurements on azaleas injured by azalea lace bug (Heteroptea: Tingidae) feeding.

Whole-plant gas exchange was measured continuously for 24 h on rooted cuttings of Girard's 'Pleasant White' azaleas. Azalea treatments were azalea lace bug, Stephanitis pyrioides (Scott), feeding injury levels that averaged 6, 13, or 31% leaf-area injury throughout the plant canopies. Gas exchange parameters, including net photosynthesis, dark respiration, carbon use efficiency, and growth, were compared with undamaged control plants. Responses of Girard's 'Pleasant White' azaleas suggested that azaleas were tolerant of lace bug feeding injury levels above the aesthetic threshold. Azalea tolerance can be incorporated into an integrated management plan to reduce chemical inputs into the urban landscape.