Past Research Projects

Research in our lab integrates basic studies on the biology, ecology and behavior of vegetable insect pests and pathogens with applied studies utilizing both novel and traditional pest management approaches.

The projects listed below have all been concluded and their descriptions are presented here as an archive. Please note, they have not been updated and may or may not still be accurate.

See also: Current Research Projects, Refereed Publications.

Overwintering habitats of the Colorado potato beetle in Wisconsin’s Central Sands production area

Documenting localized Colorado potato beetle movement improves our understanding of how this pest interacts with landscapes beyond the crop. Identification of preferred overwintering sites will provide fundamental research-based information needed to more feasibly and economically apply various cultural management tools (e.g. rotation, trap crops, perimeter sprays, etc).

In temperate potato production regions, preferred CPB overwintering, or diapause, sites, are thought to be outside production fields and along field margins. Late season movement of CPB towards prominent dark, vertical landscape features, such as windbreaks and adjacent forested edges, is hypothesized to occur in many systems.

Understanding behavioral tendencies of adult CPB dispersion from the field will make management practices such as large scale, focused trap crops, trenches, and specific applications of adulticides more efficient and effective. To address these questions, this project has documented and quantified differing bordering landscape elements, consistent with the Natural Resource Initiatives, Managed Ecosystems Project, serving as potential overwintering habitats and has attempted to document the movement and dispersal patterns of overwintered, adult CPB from these areas.

A realization of what, if any, specific non-crop community is preferentially selected by CPB in the Central Sands would be advantageous for several reasons. 1) Unmanaged fallow areas may not provide services and additionally create quality overwintering conditions for beetles. 2) Important native plant communities of particular interest have been identified in the potato growing region through the efforts by the USDA’s Natural Resource Initiatives program. These communities may provide positive ecosystem services such as biological control of pests. 3) Characterization of landscapes which are consistently associated with CPB will promote more effective management solutions.

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New insecticide technology for control in potato insect pest management

cpbThe Colorado potato beetle continues to be the most serious insect pest found on commercially produced potatoes in Central Sands region of Wisconsin, largely as a result of its resistance to several registered insecticides. The Colorado potato beetle causes damage as a defoliator in both the adult and larval stages. Non-chemical control options for Colorado potato beetle are often limited in scope. Cultural manipulations such as crop rotation, to avoid over wintered populations, can be effective in delaying infestations and decreasing their severity, and trap crops or physical barriers (trenches) have also been employed successfully in other growing regions to delay infestation. Following infestation, however, biological regulation by beneficial insects (predators, parasitoids, etc.) is usually ineffective and growers must relay on chemical control to prevent economic damage.

Thus, although cultural and biological controls can provide some level of population reduction, the Colorado potato beetle must be managed primarily with insecticides. Chemical management programs should be designed to keep Colorado potato beetle populations below damaging levels while avoiding potential problems associated with resistance, non-target toxicity, environmental degradation, and worker safety. This project tests different chemical management programs with registered and experimental insecticides.

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Vine crop pest management

A key limiting factor for all cucurbit farmers includes cucumber beetles (Acalymma vittatum) and subsequent transmission of the bacterial wilt pathogen, Erwinia tracheiphila. This project focuses on the development of enhanced IPM practices for cucurbit production employing a combination of novel cultural and pest management practices. A special focus has been to emphasize practices that limit impacts on
domestic and native pollinators. To date, we have documented significant reductions in both populations of cucumber beetles and the bacterial pathogen they transmit in susceptible vine crops using these tactics. Specifically, mean incidence of bacterial wilt was 2-3 X less prevalent among grower cooperators who implemented a combination of IPM-based practices when compared to both commercial and organic farm operators. The seasonal abundance and species composition of insect pollinators did vary among farms locations with Apis and Bombus spp. occurring most frequently. We have demonstrated the ability to significantly reduce the reliance on broad spectrum insecticides by incorporating IPM-based, cultural practices that prevent damaging beetle feeding.

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2008 Wisconsin surveys of Colorado potato beetle insensitivity to neonicotinoids

This project is directed at further enhancing our present integrated pest management strategies for key insect pests in potato with a focus on the development of integrated chemical, biological, and cultural management practices. A primary focus of the proposed work has been to accurately identify pest management strategies that reduce the total number of insecticide applications, limit the onset or development of insecticide resistance, and provide novel or refined management tactics for the sequence of insect control measures implemented. An emphasis of this project is to document the occurrence and increase(s) in neonicotinoid resistance among populations of Colorado potato beetle while also providing practical guidance towards implementing an appropriate insecticide resistance management program. Objectives of this project have been designed to address knowledge gaps that must be filled if we are to devise both short and long-term, sustainable management plans to address the key insect pests in potato.

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Onion thrips control using foliar insecticides in dry bulb onion production

Common thrips species
Photo: Mississippi State University

Effective, economical, and efficient long term management of onion thrips continues to be a challenge in the production of dry bulb onion. This insect pest continues to be a high pest priority for Wisconsin onion growers. Many of the currently registered products for control of onion thrips are not equally effective against the insect. As a result, thrips management is a top priority and an improved understanding of the ecology and management of this pest is essential towards the development of long-term control methods. The objective of this project is to evaluate currently registered and new, potentially efficacious insecticide foliar treatments to target problematic populations of onion thrips, and also to develop efficacy data in support of future registration of novel insecticides with unique modes of action.

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Mint bud mite management in Wisconsin peppermint production: application timing and new tools

Effective, economical, and efficient long term management of mint bud mite continues to be a challenge for specific field locations and the production of black peppermint. In addition to effective crop rotation, bud mites are managed almost exclusively using acaricides. Some acaricides used for control perform adequately, while others continue to perform poorly. Several reasons to explain poor performance include an inappropriate choice of active ingredient, a short residual activity, an application made too late, inadequate application coverage, or a resistant population. Wisconsin mint growers, unlike mint producers in other portions of the US, have a limited number of acaricide management tools for use in controlling mint bud mites. Currently, propargite (Comite® / Omite®) and more recently fenpyroximate (Fujimite) are the only registered acaricides for use in Wisconsin against mint bud mite. Some insensitivity of mint bud mite to propargite combined with concerns regarding environmental persistence, cost, and its listing as a B2 carcinogen make this an increasingly non-viable control option. Spiromesifen (Oberon®) is a relatively new mode of action with both insecticide and acaricide activity which is currently under review with the Federal IR-4 Program. Additional new compounds which may show promise in controlling mint
bud mite include Abamectin, (Temprano™), bifenazate (Acramite® 4SC), and diflubenzuron, (Dimilin® 2L) under optimized spray conditions. The use of these new tools has not been well defined in Wisconsin production systems. The goal of this research will be to refine the use of Fujimite and Comite, and document the potential for Acramite, Dimilin, Oberon, and Temprano as feasible, future control options.

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Non crop sources of CMV and implications for management

CMV_250wRecently snap bean (Phaseolus vulgaris L.) and pepper (Capsicum annuum L.) crops in Wisconsin have experienced significant increases in incidence and crop losses associated with infection of cucumber mosaic virus. This increase has anecdotally been linked to the recent introduction and establishment of the soybean aphid (Aphis glycines Matsumura) in the upper Midwest region. Presumably, the unique population biology and dispersal of this species has changed both the spatial arrangement and temporal movement patters previously observed with respect to CMV in the region.

Although significant new information has been developed recently to describe soybean aphid seasonal dispersal, its competence as a virus vector, and the timing of virus increase in susceptible, processing snap bean crops, limited information exists to document the primary inoculum sources where these viruses are acquired. Knowledge of which vector(s) species transmit these viruses to processing snap beans in Wisconsin, where they acquire the viral pathogens, when they move into fields, and when they spread the pathogen to snap beans is critical to understanding and managing the spread of these viral diseases. This project is directed at further enhancing our present understanding of the epidemiology of problematic bean viruses in affected areas of Wisconsin with a focus on factors that influence virus geographical distribution and spread. The objectives are (1) to identify and characterize the seasonal abundance of the primary aphid vectors of CMV and AMV among perennial crops in the agricultural landscape, and (2) to compare the genetic structure of the population of CMV and AMV isolates collected from virus-affected, susceptible succulent bean plantings, dispersing insect vectors, and potential reservoir hosts.

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Seasonal infectivity of aster leafhoppers in carrot

Each year, Wisconsin growers produce carrots on an average of 4200 acres grossing over $6 million dollars in revenues (USDA-NASS, 2007 annual bulletin). Unfortunately, carrot fields are threatened annually by the occurrence of aster yellows phytoplasma (AYp), which is obligately transmitted by the aster leafhopper (Macrosteles quadrilineatus Forbes). Current control practices strictly utilize insecticide sprays that target the aster leafhopper. Spray timing is guided by an aster yellows index that is based on the proportion of infective leafhoppers present in a field at a given point in time. Crop scouting and molecular diagnostic tools have decreased the inherent lag between finding inoculative leafhoppers and prescribed sprays. However, yield losses of 5-20% resulting from AYp are still commonplace (1). A more comprehensive and sustainable, multi-tactic control strategy is warranted to lower inoculum pressure in the areas surrounding susceptible crops. The management of off-crop habitats in ways that minimize the persistence and decrease the accumulation of AYp inoculum in the local environment has the potential to contribute to the sustainability of carrot production primarily through reductions in pesticide.

Aster leafhopper nymph, first instarThe primary focus of this research is to improve our knowledge of where leafhoppers acquire the pathogen, when they move into susceptible fields, and when they spread the pathogen to crops. Specifically, our focus has been to 1) accurately identify primary inoculum sources of AYp of greatest epidemiological significance in non-crop habitats surrounding carrot fields and 2) to compare the genetic structure of the population of AYp from reservoir hosts to that within carrot and to determine if genotype variability relates to either prevalence or infectivity potential of the pathogen. Ultimately, this project will provide accurate, new information about the relative importance of AYp sources in the habitat surrounding carrot fields. This information can then be used to evaluate the local AYp risk and, in turn, management practices can be developed to decrease the accumulation and local persistence of the pathogen.

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Long-term storability of potato virus Y infected tubers

PVY_symptoms2In recent years, Potato Virus Y has reemerged as a serious disease problem in many potato production areas in the northern United States and eastern Canada. Asymptomatic cultivars which express mild or no symptoms when infected with PVY combined with an increase in recombinant strains of this virus prevent accurate field identification and rouging of infected plants. There is a lack of effective strategies to reduce the incidence of PVY infected plants and tubers, and there is a need to improve cost-effective methods of determining PVY levels in seed lots and further understanding the impact of current season virus infection on tuber storage and quality attributes.

Limited information currently exists to document the impact of PVY infection on quality aspects tuber storage performance. In the first year of preliminary research, we have documented significant reductions in storage quality parameters including percent solids and shrinkage. This area of investigation seems extremely important towards limiting continued storage losses and further assessing the impact of plant disease (PVY infection) on seed tuber physiological age.

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Seasonal flight dynamic of aphid species in occurrence with potato virus Y infection in commercial potato fields

green-peach-aphidPotato virus Y (PVY), once managed effectively by strict seed certification practices, has re-emerged as a serious disease problem in the seed potato crop in many areas of the United States and Canada. New variants of PVY that cause tuber necrosis further threaten tuber quality in both seed and commercial crops. Managing levels of PVY in seed and eliminating the tuber necrotic strains will require an adjustment of seed certification practices and a more aggressive use of on-farm management strategies by both seed and commercial potato growers.

The goal of this project has been to document the seasonal phenology of aphid vector species and their relationship to PVY incidence in the field. Replicated field plots were set up in Wisconsin using green tile pan traps and sentinel potato plants. Sentinel plants were left in the field for a week, then held in an aphid-proof greenhouse for PVY disease development and detection. Membrane ELISA was used to test for the presence of PVY. Over a similar sample interval, aphids were collected from green tile pan traps and identified to species. Correlating aphid movement with PVY disease progress will help to define the relative importance of specific aphid vectors in driving recent PVY disease cycles. Moreover, we hope to define the periods of greatest risk for PVY transmission and the necessity for deployment of targeted, best management practices to limit PVY spread.

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Native bees in cucurbits

bee_250wThe contribution by native pollinators towards pollination has been studied in several crops requiring insect-mediated pollination including watermelon, pumpkin, and sunflower. However, there is a scarcity of research regarding the level of wild bee visitation to open cucumber flowers. We will sample the native bee communities in
pickling cucumber in the Central Sands and Driftless Region of Wisconsin. This study will determine if the landscape surrounding a field impacts the species diversity and abundance of native bees. It is expected that a greater level of natural habitat near cucumber fields can offer alternative floral resources and undisturbed nesting sites for wild pollinators. Additionally, this project will examine if the species assemblage of native pollinators varies based on the date of planting and the distance from field edges.

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