Thomas Kuhar | Virginia Tech (original) (raw)

Papers by Thomas Kuhar

ABSTRACT Farmscaping is a holistic ecologically-based approach to pest management that emphasizes... more ABSTRACT Farmscaping is a holistic ecologically-based approach to pest management that emphasizes the arrangement or configuration of plants that promote biological pest management by attracting and sustaining beneficial organisms. Ideal farmscape plantings provide habitat for beneficial insects, suppress weeds, and grow in close proximity to the cash crop without competing for light, water and nutrients. Research has shown that maintaining high levels of species diversity is a key characteristic of a proper functioning agroecosystem. Unfortunately, intensive farming operations including growing large monocultures, regular cultivation, and excessive use of insecticides often leads to a dramatic reduction in arthropod diversity, especially natural enemies that often keep many pest insects below damaging levels. Farmscaping is a technique designed to add diversity back to the system and minimize disturbance leading to increases in natural enemy populations by providing insectary plants as food and shelter resources. Successful conservation of natural enemies involves manipulation of the environment to favor natural enemies, either by eliminating adverse factors or by providing improved conditions for colonization and survival. In addition to acting as a reservoir for natural enemies, the use of farmscaping may increase alternative prey or insect hosts when other food resources are scarce. Farmscape plantings can also serve as an overwintering habitat for natural enemies to ensure carryover of beneficial insects from year to year.

Arthropod Management Tests, 2013

Journal of Integrated Pest Management, Sep 1, 2014

New pest management programs must strive to achieve sustained, improved crop production and profi... more New pest management programs must strive to achieve sustained, improved crop production and profitable agriculture, while simultaneously conserving natural resources and protecting the environment. Redesigning farms to take advantage of natural biological control can improve the sustainability of integrated pest management programs. A technique common in this approach to pest management is farmscaping, which refers to the arrangement or configuration of plants that promote biological pest management by attracting and sustaining beneficial organisms. Farmscaping is an ecologically based, whole-farm approach to enhancing the efficacy and local abundance of arthropod natural enemies through modification of the environment. However, by adding these resources back to simplified agriculture systems, they provide numerous other ecosystem services such as erosion control, reduced runoff, esthetic benefits, increased revenue, nutrient management, pollination services, soil health, as well as improved pest suppression. Herein, we discuss the strategy of farmscaping, review the theory of how it can improve pest management, and discuss the practicalities and risks involved in incorporating farmscapes into integrated pest management programs.

Environmental Entomology, Aug 1, 2012

To improve cereal leaf beetle scouting efÞciency and encourage the use of thresholds, temperature... more To improve cereal leaf beetle scouting efÞciency and encourage the use of thresholds, temperature-based degree-day models were developed and tested to determine their accuracy to predict the date of egg and larval peaks. Previously published cereal leaf beetle temperature development data were used to create the degree-day model. This model of 182 DD using a base development temperature of 8ЊC was validated using cereal leaf beetle sampling data from four locations in Virginia and North Carolina in 2010, and six locations in 2011. In both years, the degree-day model predicted the average egg peak within 3 d of the observed calendar date. There was also a consistent period between egg and larval peaks averaging 17.5 d. Given the accuracy of this model, historical high and low temperature data were used to create a predictive map of the calendar week that different areas of Virginia and North Carolina would exceed 182 DD, and was validated using survey data from 60 Þeld sites in 2010 and 65 sites in 2011 throughout Virginia and North Carolina. Finally, correlation and linear regression analyses were performed using data from all cereal leaf beetle study populations in 2010 and 2011, as well as previously collected data to determine if the number of eggs at peak could be used to predict larval peak numbers. There was a signiÞcant positive linear relationship between egg peak density and larval peak density, explaining 94% of the variation seen in larval peaks, indicating that egg peaks could reliably predict larval infestation levels.

Arthropod Management Tests, 2011

Arthropod Management Tests, 2016

Corn (hybrid, maize, sweet) j Zea mays bollworm/corn earworm/tomato fruitworm j Helicoverpa zea E... more Corn (hybrid, maize, sweet) j Zea mays bollworm/corn earworm/tomato fruitworm j Helicoverpa zea European corn borer j Ostrinia nubilalis fall armyworm j Spodoptera frugiperda Corn earworm (CEW): Helicoverpa zea (Boddie) European corn borer (ECB): Ostrinia nubilalis (H€ ubner) Fall armyworm (FAW): Spodoptera frugiperda (J.E. Smith) The objective of this experiment was to assess the efficacy of insecticides for the control of lepidopteran pests of sweet corn in eastern Virginia. The experiment consisted of eight treatments arranged in an RCB design with four replicates. "Merit" sweet corn was planted on 12 Jul 2015 at the Virginia Tech Eastern Shore Agricultural Research and Extension Center in Painter, VA. Plots were two rows wide and 20-ft (6.1 m) long with no guard rows. Rows were planted on a 3 ft row center (0.9 m) in a 6 tier field design, 8 ft (2.4 m) alleys between tiers. Insecticide treatments were applied at 100% tasseling on 24 Aug and were repeated on 26, 28, 31 Aug and 2, 4 Sep (six total applications A, B, C, D, E, F). Each spray was applied at 36 gpa with a 1-nozzle boom equipped with a D3 spray tip and 45 core and powered by a CO 2 backpack sprayer at 40 psi.

Arthropod Management Tests, 2014

In Virginia and other Mid-Atlantic states, the invasive brown marmorated stink bug (BMSB) has bec... more In Virginia and other Mid-Atlantic states, the invasive brown marmorated stink bug (BMSB) has become a serious nuisance pest (Rice et al. 2014). Each fall, these insects aggregate on buildings seeking shelters in which to spend the winter months. A licensed pest control professional can treat buildings for stink bugs in the late summer or fall just prior to bug congregation. A number of insecticides are registered for structural pest control, but the relative effectiveness of these products is not completely known. It is also not known how long these chemicals remain effective after application. We conducted an experiment to evaluate the residual efficacy of several commercial pesticides registered for use on buildings (Table 1).

Arthropod Management Tests, 2009

Arthropod Management Tests, 2016

Arthropod Management Tests, 2009

Arthropod Management Tests, 2016

Colorado potato beetle | Leptinotarsa decemlineata * This research was supported by industry gift... more Colorado potato beetle | Leptinotarsa decemlineata * This research was supported by industry gifts of insecticidal material from Certis USA.

Crop Protection

The carbamate insecticide methomyl is sometimes used to control slugs in field corn and soybean b... more The carbamate insecticide methomyl is sometimes used to control slugs in field corn and soybean by foliar applications, but control outcomes in research trials and commercial operations have been mixed. In this study, laboratory bioassays were conducted on dusky slug, Arion subfuscus Müller, a common pest of corn and soybean in the Mid-Atlantic United States, to evaluate residual toxicity of Lannate LV (methomyl) at low and high concentrations corresponding to label recommended field rates, and if toxicity may be affected by ambient moisture or repellency to treated plants. Without wetting events, methomyl residues on corn plants caused 90-100% mortality of A. subfuscus for two days and 70-90% mortality for six days. When corn plants were briefly misted with ca. 0.3 cm of water 6 h after methomyl application, mortality was 36% 12 h after treatment, and 0 to 5% 24 h after treatment for both low and high rates. Repellency of A. subfuscus to corn plants treated with the high rate of methomyl was narrowly significant (P = 0.04) and low rate was not significant. These results suggest that high ambient moisture needed to elicit slug activity in the field also abates toxicity of methomyl residues, explaining why field control is usually poor despite high mortality in the lab.

Arthropod Management Tests, 2013

Virginia Cooperative Extension programs and employment are open to all, regardless of race, color... more Virginia Cooperative Extension programs and employment are open to all, regardless of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Mark A. McCann, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Alma C. Hobbs, Administrator, 1890 Extension Program, Virginia State, Petersburg. Potato Aphid on Tomatoes

Journal of Economic Entomology, 2019

Flea beetles, are common pests of cabbage Brassica oleracea L. (Brassicales: Brassicaceae) and eg... more Flea beetles, are common pests of cabbage Brassica oleracea L. (Brassicales: Brassicaceae) and eggplant Solanum melongena L. (Solanales: Solanaceae), but little is known about the flea beetle populations in Virginia, their impact on yield, or the most effective control methods. This research investigates flea beetle populations and the impact of their feeding injury on cabbage and eggplant in Southwest Virginia and determines the most efficacious control methods. In Whitethorne, VA, cabbage and eggplant crops were vacuum sampled weekly throughout two summers (2015, 2016). Crucifer flea beetle, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), and striped flea beetle, Phyllotreta striolata Fabr. (Coleoptera: Chrysomelidae) were found on cabbage; whereas, eggplant flea beetle, Epitrix fucula (Crotch) (Coleoptera: Chrysomelidae), and the tobacco flea beetle, Epitrix hirtipennis (Melsheimer) (Coleoptera: Chrysomelidae) were found on eggplant. To evaluate the impact of flea bee...

Environmental Entomology, 2017

Thiamethoxam is a neonicotinoid insecticide commonly applied directly to the seeds (seed-treatmen... more Thiamethoxam is a neonicotinoid insecticide commonly applied directly to the seeds (seed-treatment) of commercial snap beans, Phaseolus vulgaris L. While previous studies have examined target and nontarget effects of thiamethoxam seed-treatments in snap beans and other crops, to our knowledge, none have been conducted in agroecosystems predominated by the pest Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae). This study examined the effects of thiamethoxam-treated snap beans on E. varivestis, other arthropods, and crop performance in southwestern Virginia. Greenhouse experiments were conducted to evaluate residual toxicity of treated snap beans to E. varivestis and a key predator, Podisus maculiventris (Say) (Hemiptera: Pentatomidae). Treated plants were highly toxic to E. varivestis at 13 d, moderately toxic from 16 to 20 d, and minimally toxic at 24 d. P. maculiventris was unaffected by exposure to treated plants or by feeding on E. varivestis that consumed treated plants. Small plot field experiments in 2014 and 2015 showed no significant effects of thiamethoxam seed-treatments on E. varivestis densities, other arthropods, crop injury, or yield. In 2016, planting was delayed by persistent rain, resulting in early E. varivestis colonization. In this year, thiamethoxam-treated plants had significantly lower densities and feeding injury from E. varivestis, followed by significantly higher yields. Natural enemies were unaffected by seed-treatments in all field experiments. These experiments demonstrated that thiamethoxam seed-treatments provide control of E. varivestis when beetles infest fields within 2 to 3 wk after planting; but otherwise provide negligible advantages. Negative effects from thiamethoxam seed-treatments on nontarget arthropods appear minimal for snap beans in this region.

ABSTRACT Farmscaping is a holistic ecologically-based approach to pest management that emphasizes... more ABSTRACT Farmscaping is a holistic ecologically-based approach to pest management that emphasizes the arrangement or configuration of plants that promote biological pest management by attracting and sustaining beneficial organisms. Ideal farmscape plantings provide habitat for beneficial insects, suppress weeds, and grow in close proximity to the cash crop without competing for light, water and nutrients. Research has shown that maintaining high levels of species diversity is a key characteristic of a proper functioning agroecosystem. Unfortunately, intensive farming operations including growing large monocultures, regular cultivation, and excessive use of insecticides often leads to a dramatic reduction in arthropod diversity, especially natural enemies that often keep many pest insects below damaging levels. Farmscaping is a technique designed to add diversity back to the system and minimize disturbance leading to increases in natural enemy populations by providing insectary plants as food and shelter resources. Successful conservation of natural enemies involves manipulation of the environment to favor natural enemies, either by eliminating adverse factors or by providing improved conditions for colonization and survival. In addition to acting as a reservoir for natural enemies, the use of farmscaping may increase alternative prey or insect hosts when other food resources are scarce. Farmscape plantings can also serve as an overwintering habitat for natural enemies to ensure carryover of beneficial insects from year to year.

Arthropod Management Tests, 2013

Journal of Integrated Pest Management, Sep 1, 2014

New pest management programs must strive to achieve sustained, improved crop production and profi... more New pest management programs must strive to achieve sustained, improved crop production and profitable agriculture, while simultaneously conserving natural resources and protecting the environment. Redesigning farms to take advantage of natural biological control can improve the sustainability of integrated pest management programs. A technique common in this approach to pest management is farmscaping, which refers to the arrangement or configuration of plants that promote biological pest management by attracting and sustaining beneficial organisms. Farmscaping is an ecologically based, whole-farm approach to enhancing the efficacy and local abundance of arthropod natural enemies through modification of the environment. However, by adding these resources back to simplified agriculture systems, they provide numerous other ecosystem services such as erosion control, reduced runoff, esthetic benefits, increased revenue, nutrient management, pollination services, soil health, as well as improved pest suppression. Herein, we discuss the strategy of farmscaping, review the theory of how it can improve pest management, and discuss the practicalities and risks involved in incorporating farmscapes into integrated pest management programs.

Environmental Entomology, Aug 1, 2012

To improve cereal leaf beetle scouting efÞciency and encourage the use of thresholds, temperature... more To improve cereal leaf beetle scouting efÞciency and encourage the use of thresholds, temperature-based degree-day models were developed and tested to determine their accuracy to predict the date of egg and larval peaks. Previously published cereal leaf beetle temperature development data were used to create the degree-day model. This model of 182 DD using a base development temperature of 8ЊC was validated using cereal leaf beetle sampling data from four locations in Virginia and North Carolina in 2010, and six locations in 2011. In both years, the degree-day model predicted the average egg peak within 3 d of the observed calendar date. There was also a consistent period between egg and larval peaks averaging 17.5 d. Given the accuracy of this model, historical high and low temperature data were used to create a predictive map of the calendar week that different areas of Virginia and North Carolina would exceed 182 DD, and was validated using survey data from 60 Þeld sites in 2010 and 65 sites in 2011 throughout Virginia and North Carolina. Finally, correlation and linear regression analyses were performed using data from all cereal leaf beetle study populations in 2010 and 2011, as well as previously collected data to determine if the number of eggs at peak could be used to predict larval peak numbers. There was a signiÞcant positive linear relationship between egg peak density and larval peak density, explaining 94% of the variation seen in larval peaks, indicating that egg peaks could reliably predict larval infestation levels.

Arthropod Management Tests, 2011

Arthropod Management Tests, 2016

Corn (hybrid, maize, sweet) j Zea mays bollworm/corn earworm/tomato fruitworm j Helicoverpa zea E... more Corn (hybrid, maize, sweet) j Zea mays bollworm/corn earworm/tomato fruitworm j Helicoverpa zea European corn borer j Ostrinia nubilalis fall armyworm j Spodoptera frugiperda Corn earworm (CEW): Helicoverpa zea (Boddie) European corn borer (ECB): Ostrinia nubilalis (H€ ubner) Fall armyworm (FAW): Spodoptera frugiperda (J.E. Smith) The objective of this experiment was to assess the efficacy of insecticides for the control of lepidopteran pests of sweet corn in eastern Virginia. The experiment consisted of eight treatments arranged in an RCB design with four replicates. "Merit" sweet corn was planted on 12 Jul 2015 at the Virginia Tech Eastern Shore Agricultural Research and Extension Center in Painter, VA. Plots were two rows wide and 20-ft (6.1 m) long with no guard rows. Rows were planted on a 3 ft row center (0.9 m) in a 6 tier field design, 8 ft (2.4 m) alleys between tiers. Insecticide treatments were applied at 100% tasseling on 24 Aug and were repeated on 26, 28, 31 Aug and 2, 4 Sep (six total applications A, B, C, D, E, F). Each spray was applied at 36 gpa with a 1-nozzle boom equipped with a D3 spray tip and 45 core and powered by a CO 2 backpack sprayer at 40 psi.

Arthropod Management Tests, 2014

In Virginia and other Mid-Atlantic states, the invasive brown marmorated stink bug (BMSB) has bec... more In Virginia and other Mid-Atlantic states, the invasive brown marmorated stink bug (BMSB) has become a serious nuisance pest (Rice et al. 2014). Each fall, these insects aggregate on buildings seeking shelters in which to spend the winter months. A licensed pest control professional can treat buildings for stink bugs in the late summer or fall just prior to bug congregation. A number of insecticides are registered for structural pest control, but the relative effectiveness of these products is not completely known. It is also not known how long these chemicals remain effective after application. We conducted an experiment to evaluate the residual efficacy of several commercial pesticides registered for use on buildings (Table 1).

Arthropod Management Tests, 2009

Arthropod Management Tests, 2016

Arthropod Management Tests, 2009

Arthropod Management Tests, 2016

Colorado potato beetle | Leptinotarsa decemlineata * This research was supported by industry gift... more Colorado potato beetle | Leptinotarsa decemlineata * This research was supported by industry gifts of insecticidal material from Certis USA.

Crop Protection

The carbamate insecticide methomyl is sometimes used to control slugs in field corn and soybean b... more The carbamate insecticide methomyl is sometimes used to control slugs in field corn and soybean by foliar applications, but control outcomes in research trials and commercial operations have been mixed. In this study, laboratory bioassays were conducted on dusky slug, Arion subfuscus Müller, a common pest of corn and soybean in the Mid-Atlantic United States, to evaluate residual toxicity of Lannate LV (methomyl) at low and high concentrations corresponding to label recommended field rates, and if toxicity may be affected by ambient moisture or repellency to treated plants. Without wetting events, methomyl residues on corn plants caused 90-100% mortality of A. subfuscus for two days and 70-90% mortality for six days. When corn plants were briefly misted with ca. 0.3 cm of water 6 h after methomyl application, mortality was 36% 12 h after treatment, and 0 to 5% 24 h after treatment for both low and high rates. Repellency of A. subfuscus to corn plants treated with the high rate of methomyl was narrowly significant (P = 0.04) and low rate was not significant. These results suggest that high ambient moisture needed to elicit slug activity in the field also abates toxicity of methomyl residues, explaining why field control is usually poor despite high mortality in the lab.

Arthropod Management Tests, 2013

Virginia Cooperative Extension programs and employment are open to all, regardless of race, color... more Virginia Cooperative Extension programs and employment are open to all, regardless of race, color, national origin, sex, religion, age, disability, political beliefs, sexual orientation, or marital or family status. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Mark A. McCann, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Alma C. Hobbs, Administrator, 1890 Extension Program, Virginia State, Petersburg. Potato Aphid on Tomatoes

Journal of Economic Entomology, 2019

Flea beetles, are common pests of cabbage Brassica oleracea L. (Brassicales: Brassicaceae) and eg... more Flea beetles, are common pests of cabbage Brassica oleracea L. (Brassicales: Brassicaceae) and eggplant Solanum melongena L. (Solanales: Solanaceae), but little is known about the flea beetle populations in Virginia, their impact on yield, or the most effective control methods. This research investigates flea beetle populations and the impact of their feeding injury on cabbage and eggplant in Southwest Virginia and determines the most efficacious control methods. In Whitethorne, VA, cabbage and eggplant crops were vacuum sampled weekly throughout two summers (2015, 2016). Crucifer flea beetle, Phyllotreta cruciferae (Goeze) (Coleoptera: Chrysomelidae), and striped flea beetle, Phyllotreta striolata Fabr. (Coleoptera: Chrysomelidae) were found on cabbage; whereas, eggplant flea beetle, Epitrix fucula (Crotch) (Coleoptera: Chrysomelidae), and the tobacco flea beetle, Epitrix hirtipennis (Melsheimer) (Coleoptera: Chrysomelidae) were found on eggplant. To evaluate the impact of flea bee...

Environmental Entomology, 2017

Thiamethoxam is a neonicotinoid insecticide commonly applied directly to the seeds (seed-treatmen... more Thiamethoxam is a neonicotinoid insecticide commonly applied directly to the seeds (seed-treatment) of commercial snap beans, Phaseolus vulgaris L. While previous studies have examined target and nontarget effects of thiamethoxam seed-treatments in snap beans and other crops, to our knowledge, none have been conducted in agroecosystems predominated by the pest Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera: Coccinellidae). This study examined the effects of thiamethoxam-treated snap beans on E. varivestis, other arthropods, and crop performance in southwestern Virginia. Greenhouse experiments were conducted to evaluate residual toxicity of treated snap beans to E. varivestis and a key predator, Podisus maculiventris (Say) (Hemiptera: Pentatomidae). Treated plants were highly toxic to E. varivestis at 13 d, moderately toxic from 16 to 20 d, and minimally toxic at 24 d. P. maculiventris was unaffected by exposure to treated plants or by feeding on E. varivestis that consumed treated plants. Small plot field experiments in 2014 and 2015 showed no significant effects of thiamethoxam seed-treatments on E. varivestis densities, other arthropods, crop injury, or yield. In 2016, planting was delayed by persistent rain, resulting in early E. varivestis colonization. In this year, thiamethoxam-treated plants had significantly lower densities and feeding injury from E. varivestis, followed by significantly higher yields. Natural enemies were unaffected by seed-treatments in all field experiments. These experiments demonstrated that thiamethoxam seed-treatments provide control of E. varivestis when beetles infest fields within 2 to 3 wk after planting; but otherwise provide negligible advantages. Negative effects from thiamethoxam seed-treatments on nontarget arthropods appear minimal for snap beans in this region.