Phillip M. Roberts

Discovery and distribution of Megacopta cribraria (Hemiptera: Heteroptera: Plataspidae) in northeast Georgia

In October 2009, large aggregations of Megacopta cribraria (F.) (Heteroptera: Plataspidae) were discovered on outside, perimeter walls of houses in northeast Georgia, prompting homeowners to contact county Extension agents and pest management professionals to learn more about the insect and to rid the premises of the nuisance. The insect was flying from nearby patches of kudzu ( Pueraria spp .) onto houses, presumably in an attempt to locate overwintering sites. In its native Asia, one of its preferred hosts is kudzu, an invasive, leguminous vine that now grows throughout the southeastern U.S. Before discovery in Georgia, M. cribraria was unknown from the New World. In addition to its emergence as a nuisance pest, M. cribraria has been reported as a pest of numerous legume crops in Asia, including soybean, Glycine max Merrill . As of August 9, 2010, M. cribraria was known from 48 counties in northeast Georgia and 13 counties in northwest South Carolina. In late June and early July 2010, M. cribraria was found on soybeans in 20 of the 48 Georgia counties and five counties in South Carolina.

From Asian curiosity to eruptive American pest: Megacopta cribraria (Hemiptera: Plataspidae) and prospects for its biological control

The kudzu bug or bean plataspid, Megacopta cribraria (Fabricius), is native to Asia where it appears to be widely distributed (although the taxonomy is not entirely clear), but is infrequently a pest of legumes. This bug appeared in 2009 in the southeastern United States, where it is closely associated with kudzu, Pueraria montana Lour. [Merr.] variety lobata [Willd.] Maesen & S. Almeida. However, the insect has become a consistent economic pest of soybeans, Glycine max (L.) Merr., and some other leguminous crops in areas where large numbers can build in kudzu, in addition to being a considerable nuisance in urban landscapes where kudzu occurs. The insect has remarkable capacity for movement and has spread rapidly from nine Georgia counties in 2009 to seven states in 2012. Despite being a nuisance in urban areas and a crop pest, high populations of the bug also reduce the biomass of kudzu, which is itself a seriously problematic invasive weed, complicating the status of M. cribraria in its expanded range. Extant predators and a pathogen in the US have been observed attacking kudzu bugs in the laboratory and field, but no parasitism of eggs or nymphs has been observed to date. A single record of parasitism of an adult kudzu bug by a tachinid fly is known from the US, but no other adult parasitism has been observed in the US or elsewhere. Extant enemies may eventually significantly reduce the bug’s populations, but at present native enemies appear to be insufficient for the task, and exotic enemies from the kudzu bug’s native range may offer the best possibility for effective biological control in the US. Based on the available literature, the best option for an importation biological control program appears to be the platygastrid egg parasitoid Paratelenomus saccharalis (Dodd) because of its apparent host specificity, intimate biological linkages with M. cribraria, and wide geographic distribution in the Eastern Hemisphere. Other natural enemies may eventually emerge as good candidates for importation, but at present P. saccharalis appears to be the most promising.

Weed Control and Crop Response to Glufosinate Applied to ‘PHY 485 WRF’ Cotton

Abstract Field experiments were conducted in Georgia to evaluate weed control and crop tolerance with glufosinate applied to ‘PHY 485 WRF®’ cotton. This glyphosate-resistant cotton also contains a gene, used as a selectable marker, for glufosinate resistance. Three experiments were maintained weed-free and focused on crop tolerance; a fourth experiment focused on control of pitted morningglory and glyphosate-resistant Palmer amaranth. In two experiments, PHY 485 WRF cotton was visibly injured 15 and 20% or less by glufosinate ammonium salt at 430 and 860 g ae/ha, respectively, applied POST two or three times. In a third experiment, glufosinate at 550 g/ha injured cotton up to 36%. Pyrithiobac or glyphosate mixed with glufosinate did not increase injury compared to glufosinate applied alone; S-metolachlor mixed with glufosinate increased injury by six to seven percentage points. Cotton injury was not detectable 14 to 21 d after glufosinate application, and cotton yields were not reduced by glufosinate or glufosinate mixtures. A program of pendimethalin PRE, glyphosate applied POST twice, and diuron plus MSMA POST-directed controlled glyphosate-resistant Palmer amaranth only 17% late in the season. S-metolachlor included with the initial glyphosate application did not increase control, and pyrithiobac increased late-season control by only 13 percentage points. Palmer amaranth was controlled 90% or more when glufosinate replaced glyphosate in the aforementioned system. Pitted morningglory was controlled 99% by all glufosinate programs and mixtures of glyphosate plus pyrithiobac. Seed cotton yields with glufosinate-based systems were at least 3.3 times greater than yields with glyphosate-based systems because of differences in control of glyphosate-resistant Palmer amaranth. Nomenclature: Diuron; glufosinate; glyphosate; MSMA; pendimethalin; pyrithiobac sodium; S-metolachlor; Palmer amaranth, Amaranthus palmeri S. Wats AMAPA; pitted morningglory, Ipomoea lacunosa L. IPOLA; cotton, Gossypium hirsutum L.

Confirmed Distribution and Occurrence of Megacopta cribraria (F.) (Hemiptera: Heteroptera: Plataspidae) in the Southeastern United States

Abstract Megacopta cribraria (F) (Hemiptera: Heteroptera: Plataspidae) was first discovered in North America in 9 counties in northeastern Georgia (USA) in October 2009. By the end of 2012, surveys conducted in Georgia and neighboring states confirmed that the insect had spread into 383 additional counties in the southeastern U.S., including the states of Alabama, Florida, Georgia, Mississippi, North Carolina, South Carolina, Tennessee and Virginia. It was reported from 33 species of plants representing 15 taxonomic families in these surveys, with 17 of those from the family Fabaceae (legumes). Kudzu (Pueraria montana Lour. [Merr.] variety lobata [Willd.] Maesen & S. Almeida) was the most frequently reported host. All life stages of the insect were observed only on kudzu and soybean (Glycine max [L.] Merrill) which, to date, are the only confirmed reproductive host plants of M. cribraria in its expanded North American range.

Frankliniella fusca resistance to neonicotinoid insecticides: an emerging challenge for cotton pest management in the eastern United States

BACKGROUND Over the past two decades, neonicotinoid seed treatments have become the primary method to manage tobacco thrips, Frankliniella fusca Hinds, on seedling cotton. Because this insect is highly polyphagous and the window of insecticide exposure is short, neonicotinoid resistance was expected to pose a minimal risk. However, reports of higher than expected F. fusca seedling damage in seed-treated cotton fields throughout the Mid-South and Southeast US production regions suggested neonicotinoid resistance had developed. To document this change, F. fusca populations from 86 different locations in the eastern United States were assayed in 2014 and 2015 for imidacloprid and thiamethoxam resistance to determine the extent of the issue in the region. RESULTS Approximately 57 and 65% of the F. fusca populations surveyed had reduced imidacloprid and thiamethoxam sensitivity respectively. Survivorship in diagnostic bioassays was significantly different at both the state and regional scales. Multiple-dose bioassays conducted on 37 of the populations documented up to 55- and 39-fold resistance ratios for imidacloprid and thiamethoxam respectively. CONCLUSION Estimates of neonicotinoid resistance indicate an emerging issue for management of F. fusca in the eastern United States. Significant variation in survivorship within states and regions indicated that finer-scale surveys were needed to determine factors (genetic, insecticide use) driving resistance evolution.

Assessing Stink Bug Resistance in Soybean Breeding Lines Containing Genes from Germplasm IAC-100

Abstract Sixty-five soybean, Glycine max (L.) Merr., breeding lines containing the stink bug resistant ‘IAC-100′ in their pedigrees were evaluated for their resistance to stink bug, primarily southern green stink bug, Nezara viridula L., feeding in replicated field trials from 2001 to 2005. Plots were sampled throughout the season for stink bug abundance, and, at harvest, seed samples were rated for stink bug-induced kernel damage. Individual seeds were categorized as having none, light, moderate, or heavy damage plus 100-seed wt and plot yields were determined. Both ground cloth and sweep net sampling procedures were used to compare stink bug densities between the soybean entries. Stink bug densities varied between years; however, in the years when populations exceeded four per row-meter or six per 25 sweeps, there were more damaged soybean seeds (>25%) in the entries with higher stink bug numbers. During the first 2 yr of evaluations, the mean stink bug-damaged soybean seeds ranged from 10.0 to 38.2%. From these differential responses, 28 entries were selected for continued study in 2003–2004. In 2003, stink bug-damaged soybean seeds were low, with damage ranging from 2.9 to 18.2%. In 2004, stink bug damage ranged from 8.8 to 53.2%. From these 28 lines, 12 entries were selected for an advanced field screening trial in 2005, including the IAC-100 and ‘Hutcheson’. Damaged soybean seeds ranged from 18.5 to 54.1% among these 12 entries in 2005, under heavy stink bug pressure. From these evaluations, four breeding lines with either Hutcheson × IAC-100 or IAC-100 × ‘V71-370′ in their genealogy were identified as possible breeding material for future soybean stink bug resistance cultivar development.

Cover crop, rye residue and in-furrow treatment effects on thrips

Abstract:  Thrips and thrips damage to cotton and peanut plants were compared in plots with in‐furrow treatments of aldicarb, phorate and diammonium phosphate (DAP) fertilizer under two tillage regimes with a winter cover of crimson clover and under different levels of rye residue ground cover. Adult and larval thrips numbers were significantly lower in cotton plots following winter crimson clover cultivation compared with no‐cover plots in all 3 years. Thrips numbers did not differ with respect to the in‐furrow treatments in the clover plots, but in the no‐cover plots, they were significantly higher in the untreated control and DAP treatments compared with the aldicarb treatment. Thrips damage was higher in the no‐cover than the clover plots except in the aldicarb treatments. Within the cover crop plots, thrips damage was highest in the control and phorate treatments and similar in the DAP and aldicarb treatments. There was an inverse relationship between the amount of rye residue ground cover and thrips density and thrips damage in cotton and peanuts. There was also an inverse relationship between the density of rye residue and damage to peanuts from Bunyaviridae tospovirus. Cotton yield was reduced in the cover crop plots and was not measured in the rye residue and peanut plots. These results suggest that ground cover alone decreases thrips numbers and thrips damage in both cotton and peanuts and that a winter crimson clover cover and an in‐furrow treatment of DAP enhanced plant protection from thrips in cotton.

Rise and Fall of Cotton Aphid (Hemiptera: Aphididae) Populations in Southeastern Cotton Production Systems

Abstract The impact of natural enemies on cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), populations in cotton, Gossypium hirsutum L., production systems in the southeastern United States was evaluated over 3 yr in irrigated commercial cotton fields. Fungal epizootics caused by the entomopathogen Neozygites fresenii (Nowakowski) Batko reduced aphid numbers to subthreshold levels in 1999, 2000, and 2001 and occurred consistently in early to mid-July in all 3 yr. Scymnus spp. were the most abundant aphidophagous predators, although other coccinellid species and generalist predators such as spiders, fire ants, heteropterans, and neuropterans also were present. Studies using arthropod exclusion cages demonstrated little impact of predators or parasitoids on aphid populations before fungal epizootics. Arthropod natural enemies were most abundant after epizootics and may have suppressed aphid populations late in the season. Seed cotton yield, and lint quality were not affected by aphicide applications in any year of the study. Implications of these findings for aphid management in the southeastern United States are discussed.

Fidelity of External Boll Feeding Lesions to Internal Damage for Assessing Stink Bug Damage in Cotton

ABSTRACT Previous research showed that the most precise estimates of stink bug damage in developing cotton bolls are obtained by collecting soft quarter-sized bolls and dissecting them for signs of internal feeding damage, such as internal boll wall warts and/or stained lint. However, this method requires considerable time and effort; therefore, scouts and growers are unwilling to invest adequate resources to make sound pest management decisions. Here, the authors evaluated enumeration of external feeding lesions on groups of 10, 15, 20, or 25 bolls per sample as an alternative sampling procedure. Results relate the similarity of external boll feeding lesions to internal damage as a function of boll sample size and external lesion tally. Inverse prediction confidence intervals (CIs) were also calculated to predict internal boll damage on a new sample based only on external feeding lesions. Results show that linear regression model fit increased when examining at least 20 bolls per sample, and only one external lesion per boll provided as good of model fit as using a minimum of two, three, or four lesions per boll. Inverse prediction CIs suggested that more than one sample (20 bolls per sample) will be required to make external lesions an acceptable method for making reasonably accurate management decisions. F-test lack of fit and significant regression models suggest that examination of external lesions is a promising a method for estimating stink bug damage in cotton.

Insecticidal Control of Megacopta cribraria (Hemiptera: Plataspidae) in Soybean

Abstract  The invasive kudzu bug, Megacopta cribraria (F.) (Hemiptera: Plataspidae), has become an economic pest of soybean, Glycine max (L.) Merrill, in the southeastern United States since its initial discovery in Georgia. Information on management practices, including insecticides, is limited due to its uncertain pest status in its native range and recent introduction to the United States. We evaluated the efficacy in controlling M. cribraria and economic benefits of a variety of insecticides labeled for use in soybean from different chemical classes in field trials in South Carolina and Georgia from 2010 through 2012. Several pyrethroids were among the most effective insecticides for control of M. cribraria. The pyrethroid bifenthrin had an immediate (2–6 d after treatment application) percentage of control of 97.5 ± 0.2% (SEM), which was the highest of the active ingredients tested. Likewise, net marginal benefits were typically greatest for pyrethroids, either alone or tank-mixed with other materials. Our results confirm that chemical control of M. cribraria in commercial soybean production is economically viable, but the number of effective chemical classes is limited.