S. Malone

Fifty Years of Cereal Leaf Beetle in the U.S.: An Update on Its Biology, Management, and Current Research

Cereal leaf beetle, Oulema melanopus L., is an introduced insect pest of small grains first recorded in the United States in the early 1960s. Since its introduction from Europe or Asia into Michigan, cereal leaf beetle has rapidly spread and can now be found in most states. Cereal leaf beetle feeds on numerous species of grasses and is considered a major pest of oats, barley, and wheat. Although several studies have investigated cereal leaf beetle biology and population dynamics, numerous gaps remain in understanding the mechanisms that influence its spread and distribution, which makes predicting pest outbreaks difficult. Because of the difficulty in predicting when and where pest outbreaks will occur many growers in the southeast apply insecticides on a calendar basis rather than using a threshold-based integrated pest management approach. Our challenge is to develop new information and procedures that will encourage growers to reevaluate the way they are approaching spring-time insect control in wheat, and consider adoption of the integrated pest management approach. This article is a review of cereal leaf beetle biology, past and present management practices, and current research being conducted.

Efficacy of insecticides against Acrosternum hilare and Euschistus servus (Hemiptera: Pentatomidae) in Virginia and North Carolina.

Laboratory bioassays and field trials were conducted to evaluate the efficacy of selected organophosphate, pyrethroid, and neonicotinoid insecticides, as well as a chitin inhibitor, novaluron, against 2 common stink bug pests in Virginia, the green stink bug, Acrosternum hilare (Say), and the brown stink bug, Euschistus servus (Say). Green bean dip bioassays revealed differences in insecticide susceptibility between the 2 species. Acrosternum hilare adults were highly susceptible to all pyrethroids tested, the organophosphates except acephate, and the neonicotinoids except acetamiprid. Acrosternum hilare nymphs were also susceptible to all pyrethroids tested. In general, the neonicotinoids, dinotefuran and clothianidin, were toxic to A. hilare, whereas thiamethoxam and acetamiprid were toxic to E. servus. In field trials in soybean, the neonicotinoids, dinotefuran, imidacloprid, and thiamethoxam were efficacious at controlling stink bugs and, in general, performed comparably to the organophosphates and py...

Impact of Neonicotinoid Seed Treatments on Thrips (Thysanoptera: Thripidae) and Soybean Yield in Virginia and North Carolina

ABSTRACT Currently there are several neonicotinoid insecticide seed treatments registered for use on soybean (Glycine max L.), with disparity in adoption rates in the eastern United States. A complex of seedling insect pests is found in mid-south soybean, but thrips are the primary early season pest of soybean in Virginia and North Carolina. Published knowledge regarding their impact on soybean yield is minimal, as is the impact of thrips on soybean yield; thrips species composition is also understudied. In 2008 through 2010, nine field experiments in Virginia and North Carolina were conducted to evaluate the impact on thrips population dynamics; the influence on yield of neonicotinoid seed treatments, imidacloprid and thiamethoxam, was reported from nine of these experiments. Moreover, thrips species abundance was recorded in three of these experiments. Both imidacloprid and thiamethoxam reduced thrips densities compared with untreated soybean. Thiamethoxam was more effective than imidacloprid in reducing adult thrips densities at 5 wk after planting. Adult densities peaked at 3 wk after planting, followed by larval densities, which peaked at 4 wk after planting. The most abundant thrips species was Frankliniella fusca (Hinds), followed by Neohydatothrips variabilis (Beach). Other common species included F. occidentalis (Pergande) and F. tritici (Fitch). In general, F. fusca was more common earlier in the season, while N. variabilis was more common later in the season. There were no significant differences in yield among any of the treatments or in the untreated controls. Although neonicotinoid insecticides reduced thrips abundance, data collected in these studies demonstrated that there was no positive yield response.

Efficacy of Selected Insecticides Against Eggs of Euschistus servus and Acrosternum hilare (Hemiptera: Pentatomidae) and the Egg Parasitoid Telenomus podisi (Hymenoptera: Scelionidae)

ABSTRACT Brown stink bug, Euschistus servus (Say), and green stink bug, Acrosternum hilare (Say) (Hemiptera: Pentatomidae), are major agricultural pests. Although various insecticides are used to control nymphs and adults, little is known about how they affect eggs. Laboratory bioassays and field trials were conducted to determine the efficacy of common field rates of acephate, &lgr;-cyhalothrin, spinosad, and thiamethoxam on developing E. servus and A. hilare eggs, as well as Telenomus podisi Ashmead (Hymenoptera: Scelionidae) parasitoids developing in E. servus eggs. In laboratory bioassays, egg masses were dipped into insecticide and water solutions and assessed for mortality after 2 wk. In the field trials, egg masses on a cloth section were pinned to leaves in each plot of a randomized complete block and returned to the laboratory 24 h after exposure to insecticide sprays. Mortality was assessed after 2 wk. In dip bioassays, there was a significant effect of insecticide treatment on A. hilare eggs with all insecticides resulting in greater mortality than the water control. However, no effect of treatment occurred in the field with A. hilare or for E. servus eggs in both the laboratory bioassays and the field trials. In contrast, developing T. podisi parasitoids showed significant mortality when exposed to all insecticide treatments, when dipped or field-treated. Spinosad and &lgr;-cyhalothrin treatments resulted in 100% mortality of T. podisi, and acephate resulted in greater mortality than thiamethoxam. Our results suggest that there is relatively little efficacy from insecticide sprays on stink bugs developing in eggs but that mortality of egg parasitoids may be significant.

Toxicity, Feeding Preference, and Repellency Associated with Selected Organic Insecticides Against Acrosternum hilare, and Euschistus servus, (Hemiptera: Pentatomidae)

ARSTRACT Experiments were conducted to evaluate the toxicity, feeding preference, repellency, and field efficacy associated with the organic insecticides azadirachtin, pyrethrins, and spinosad against two stink bug species, Acrosternum hilare, (Say) and Euschistus servus, (Say) (Hemiptera: Pentatomidae). Laboratory toxicity bioassays were conducted using treated green bean pods. The conventional pyrethroid &lgr;-cyhalothrin was included for comparison. A. hilare, adults and nymphs were most susceptible to &lgr;-cyhalothrin and to tank mixes of pyrethrins + spinosad. E. servus, adults were susceptible to &lgr;-cyhalothrin, spinosad, and all tank mixes, whereas E. servus, nymphs were susceptible to &lgr;-cyhalothrin only. Feeding preference tests were conducted using insecticide-treated tomatoes and counting the number of feeding stylet sheaths on fruit after 24 h. All tomatoes treated with either azadirachtin, pyrethrins, or tank mixes resulted in fewer numbers of stylet sheaths than the untreated control, whereas treatment with spinosad alone did not. In filter paper repellency tests, both E. servus, and A. hilare, were repelled by pyrethrins and exhibited no response to azadirachtin. E. servus, was attracted to spinosad in comparison with a water-treated control; however, A. hilare, displayed no response. In field efficacy trials, each of the organic insecticides reduced the number of stink bugs in soybean, Glycine max, (L.) Merr., for up to 2 d after treatment; however, none of the insecticides reduced stink bug damage to fruit in tomatoes even after multiple applications. Implications for organic growers and integrated pest management programs are discussed.

Role of Insecticides in Reducing Thrips Injury to Plants and Incidence of Tomato Spotted Wilt Virus in Virginia Market-Type Peanut

Abstract Tomato spotted wilt virus (family Bunyaviridae, genus Tospovirus, TSWV), transmitted by many thrips species, is a devastating pathogen of peanut, Arachis hypogaea L. TSWV has become a serious problem in the Virginia/Carolina peanut-growing region of the United States. During 2002, TSWV was present in 47% of the North Carolina hectarage and caused a 5% yield reduction in Virginia. Factors influencing levels of TSWV in runner market-type peanut cultivars, which are primarily grown in Alabama, Flordia, Georgia, and Texas, have been integrated into an advisory to help those peanut growers reduce losses. An advisory based on the southeast runner market-type version is currently under development for virginia market-type peanut cultivars that are grown primarily in the Virginia/Carolina region. A version based on preliminary field experiments was released in 2003. One factor used in both advisories relates to insecticide use to reduce the vector populations and disease incidence. This research elucidated the influence of insecticides on thrips populations, thrips plant injury, incidence of TSWV, and pod yield in virginia market-type peanut. Eight field trials from 2003 to 2005 were conducted at two locations. In-furrow application of aldicarb and phorate resulted in significant levels of thrips control, significant reductions in thrips injury to seedlings, reduced incidence of TSWV, and significant increases in pod yield. Foliar application of acephate after aldicarb or phorate applied in the seed furrow further reduced thrips plant injury and incidence of TSWV and improved yield. These findings will be used to improve the current virginia market-type TSWV advisory.

Efficacy and Value of Prophylactic vs. Integrated Pest Management Approaches for Management of Cereal Leaf Beetle (Coleoptera: Chrysomelidae) in Wheat and Ramifications for Adoption by Growers

ABSTRACT Cereal leaf beetle, Oulema melanopus L., can be effectively managed in southeastern U.S. wheat, Triticum aestivum L., with scouting and a single insecticide treatment, applied at the recommended economic threshold. However, many growers eschew this approach for a prophylactic treatment, often tank mixed with a nitrogen application before wheat growth stage 30. The efficacy of a prophylactic and an integrated pest management (IPM) approach was compared for 2 yr using small plot studies in North Carolina and regional surveys across North Carolina and Virginia. Economic analyses were performed, comparing the total cost of management of each approach using the regional survey data. From a cost perspective, the prophylactic approach was riskier, because when cereal leaf beetle densities were high, economic loss was also high. However, fields under the prophylactic approach did not exceed threshold as often as fields using IPM. Total cost of prophylactic management was also

Effects of Diamide Insecticides on Predators in Soybean.

20.72 less per hectare, giving this approach an economic advantage over IPM. The majority of fields under the IPM approach did not exceed the economic threshold. Hence, from an economic perspective, both the prophylactic and IPM approaches have advantages and disadvantages. This helps explains the partial, rather than complete, adoption of IPM by southeastern U.S. wheat growers. Cereal leaf beetle was spatially aggregated across the region in 2010, but not in 2011. As a result, from an economic standpoint, prophylaxis or IPM may have a better fit in localized areas of the region than others. Finally, because IPM adoption is favored when it has a strong economic advantage over alternative management approaches, more emphasis should be placed on research to reduce costs within the IPM approach.

Relationship between external stink bug (Hemiptera: Pentatomidae) boll-feeding symptoms and internal boll damage with respect to cotton lint gin-out and fiber quality.

Abstract Predatory arthropods can be important for preventing insect pests from reaching damaging levels in soybean. However, the predator community can be compromised when pest control strategies include the application of broad-spectrum insecticides. The use of selective insecticides such as diamides could conserve predators while still providing necessary pest control. We evaluated two selective diamide insecticides, chlorantraniliprole and flubendiamide, and a broad-spectrum insecticide, lambda-cyhalothrin in combination with chlorantraniliprole, for impact on predators in soybean. We applied insecticides to field plots and documented predator abundance prior to and up to 3 wk postapplication using sticky card, beat sheet, and sweep net sampling methods. In sweep net samples, total predator abundance in plots treated with the selective insecticides was not significantly different from untreated control plots. For beat sheet samples, there were no significant differences in the abundance of total predators on any day postapplication between the selective diamide insecticides or the untreated control, but abundance decreased after application of lambda-cyhalothrin + chlorantraniliprole and did not recover. For sticky cards, there were no differences in predator abundance among treatments on any day postapplication. Over all, results showed that there were no significant differences in the abundance of total predators, Anthocoridae, Araneae, or Geocoridae after application of flubendiamide or chlorantraniliprole compared with the untreated control for up to 3 wk after application. All insecticides significantly decreased populations of lepidopteran pests compared with the untreated control, but only lambda-cyhalothrin + chlorantraniliprole reduced predatory arthropod abundance.

Contrasting Role of Temperature in Structuring Regional Patterns of Invasive and Native Pestilential Stink Bugs.

ABSTRACT Cotton, Gossypium hirsutum L., bolls from 17 field locations in northeastern North Carolina and southeastern Virginia, having 20% or greater internal boll damage, were studied to determine the relationship between external feeding symptoms and internal damage caused by stink bug (Hemiptera: Pentatomidae) feeding. In 2006 and 2007, two cohorts of 100 bolls each were sampled at all field locations. The first cohort was removed as bolls reached approximately quarter size in diameter (2.4 cm). External and internal symptoms of stink bug feeding were assessed and tabulated. Concurrent to when the first cohort was collected, a second cohort of quarter-size-diameter bolls was identified, tagged, examined in situ for external feeding symptoms (sunken lesions), and harvested at the black seed coat stage. Harvested bolls were assessed for internal damage and locks were categorized (undamaged, minor damage, or major damage), dried, and ginned. Lint samples from each damage category were submitted for high volume instrument and advanced fiber information system quality analyses. Significant, moderately strong Pearson correlation coefficients existed between number of external stink bug feeding lesions and internal damage. Pearson correlation of total external lesions with total internal damage was stronger than any correlation among the other single components compared. Predictability plots indicated a rapid increase in relationship strength when relating external stink bug lesions to internal damage as the number of external lesions increased. Approximately 90% predictability of internal damage was achieved with four (2006) or six (2007) external lesions per boll. Gin-turnout and fiber quality decreased with increasing intensity of internal stink bug damage.