About

Dr. Vera Krischik is an Associate Professor and Extension Specialist at the University of Minnesota who performs research and offers extension education focused on pollinator conservation, biocontrols, and integrated pest management (IPM). Her work emphasizes the impact of insecticides on pollinators, including the nontarget effects of microbial insecticides and other pesticides used in landscape, nursery, and greenhouse crops. She is the founder and principal investigator at the Center for Urban Ecology and Sustainability (CUES), which aims to educate landscape professionals and residential landowners about sustainable land management practices that support environmental stewardship. Dr. Krischik's research includes studying soil-inhabiting biocontrol pathogens for managing pests like Japanese beetles, evaluating the effects of pesticides such as chlorantraniliprole, imidacloprid, and clothianidin on butterflies and bees, and developing best management practices for pollinator-friendly landscapes. She has contributed to numerous extension bulletins and resources on pollinator conservation, beneficial insects, and IPM strategies, and has been involved in projects that promote habitat enhancement techniques like beetle banks and stem nesting sites to conserve beneficial insects. Her work integrates scientific research with practical outreach to promote biodiversity and sustainable pest management in various landscapes.

Research topics

• Biology
• Ecology
• Toxicology
• Biotechnology
• Botany
• Zoology

Selected publications

• Improved qPCR diagnosis of <i>Ovavesicula popilliae</i> (Microsporidia) infection of Japanese beetles (Coleoptera: Scarabaeidae) for monitoring pathogen establishment

  Journal of Economic Entomology · 2025-09-04 · 3 citations

  articleOpen accessSenior author

  Based on reports of Japanese beetle (JB), Popillia japonica (Coleoptera: Scarabaeidae), population decline in Michigan following establishment of Ovavesicula popilliae Andreadis and Hanula (Microsporidia: Ovavesiculidae), USDA APHIS initiated a project to inoculate runway fields at major Midwest USA airports with O. popilliae, as part of a long-term plan to decrease JB populations at airports and thereby minimize its spread by cargo aircraft to quarantined states. The initial step is to evaluate the presence or absence of O. popilliae at major cargo airports. To accomplish this, improvements are needed in a previously validated qPCR diagnosis of O. popilliae infections of JB. In this study, the accuracy of qPCR diagnosis, which can be used for pooled samples of JB, is improved by minimizing PCR inhibition, then determining the Ct value for O. popilliae DNA that best distinguishes infected from healthy individuals based on microscopic diagnosis of the same individuals. This approach is validated in a second way by correlating the Ct value for O. popilliae DNA to the concentration of O. popilliae spore vesicles in the same samples of blended and filtered JB. Time efficiency of qPCR diagnosis is improved by combining rough homogenate from a pooled sample of 8 JB before DNA purification and qPCR analysis. Pooled samples can be used to accurately estimate percent infection at inoculated sites where less than 15% of the JB are infected. These new methods are used to detect O. popilliae infections of JB at a major airport in each of 8 different states.

  PublisherOA PDFDOI

• Augmented establishment of <i>Ovavesicula popilliae</i> (Microsporidia) for biocontrol of Japanese beetle (Coleoptera: Scarabaeidae) in Colorado

  Journal of Economic Entomology · 2025-11-20

  articleOpen accessSenior author

  Ovavesicula popilliae (Microsporidia: Ovavesiculidae) is a host specific, obligate pathogen of Japanese beetle (Coleoptera: Scarabaeidae, JB) that causes chronic disease and mortality of larvae, and reduced fecundity of surviving females. Ten sites in Colorado along the leading edge of the westward spread of JB across North America were inoculated in 2015 or 2018 by drenching a small area (200 m2) of turfgrass with solutions of O. popilliae spore vesicles made from macerated infected beetles. This paper reports infection rates in 2021 and 2022 at these sites plus 6 control sites added in 2020 or 2021 to evaluate the impact of inoculations. Infections were diagnosed by extracting DNA from 96 JB per site for qPCR analysis of O. popilliae DNA. A 4-fold greater infection rate in 2022 at inoculated sites compared with control sites is evidence that inoculations augment establishment of O. popilliae. Infection rates of JB at inoculation sites did not reach 1.0% for 3 to 6 yr following inoculations, most likely because the area inoculated is small (200 m2) while JB traps baited with pheromone plus feeding lure attract JB from a large surrounding area.

  PublisherDOI

• Qpcr Tracking of Japanese Beetles (Popilliae Japonica Newman) Infected by Ovavesicula Popilliae at Introduction Sites in Colorado, United States

  SSRN Electronic Journal · 2024-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Adult monarch butterflies show high tolerance to neonicotinoid insecticides

  Ecological Entomology · 2023 · 16 citations

  • Biology
  • Toxicology
  • Botany

  Abstract Numerous studies have documented the negative effects of neonicotinoids on bees; it remains crucial to examine how neonicotinoids affect other non‐target nectar‐feeding insects, such as the monarch butterfly, Danaus plexippus . Wildflowers growing near agricultural areas can be contaminated with neonicotinoids that affect survival or cause sublethal changes to behaviours of nectar‐feeding insects. Nectar residues of imidacloprid and clothianidin found in milkweeds and wildflowers adjacent to agricultural field range from 0 to 72.8 ng/mL. At field‐relevant doses, two neonicotinoids (imidacloprid and clothianidin) were studied for their effects on adult monarch survival, reproduction, flight and behaviour. First, we fed adult monarchs artificial nectar solutions ranging from 15 to 386 ng/mL of imidacloprid and 19 to 531 ng/mL of clothianidin. Neonicotinoid ingestion slightly reduced monarch reproduction but had no significant effects on survival, weight change, or activity levels. Second, we fed monarchs higher clothianidin doses (909 and 4030 ng/mL), that exceed field‐relevant levels by 22 and 99 times. These higher doses reduced monarch nectar consumption, survival, flight performance and reaction time in response to a drop test. Results show that adult monarchs tolerate field‐relevant doses as high as 54 ng/mL for imidacloprid and 75 ng/mL for clothianidin, with minimal lethal or sub‐lethal effects until much higher doses are supplied. We conclude that adult monarchs are more tolerant of ingested clothianidin and imidacloprid than indicated by previous research.

  PublisherOA PDFDOI

• The Current State and Future Potential of Microbial Control of Scarab Pests

  Applied Sciences · 2023 · 17 citations

  Senior authorCorresponding
  • Biology
  • Biotechnology
  • Toxicology

  Injury and control costs for the invasive scarab Japanese beetle (Family Scarabeidae, Popillla japonica) alone is estimated at $450 million per year in the U.S. Chemical controls are commonly used to control scarab pests, but concerns about human safety and negative impacts on beneficial and non-target organisms, such as pollinators, are increasingly driving the market towards less toxic and more environmentally friendly management options. Microbial entomopathogens are excellent candidates for biopesticides and biocontrol agents. Although microbial pesticides currently make up only 1–2% of the insecticide market, the discovery and development of new microbes are increasing. Microbial products are non-toxic to humans and most are species-specific, reducing non-target effects. While some are slow-acting, others provide rapid control and some can be as efficacious as chemical insecticides, particularly when used in combination. Another major advantage of microbial controls is that many can persist in the environment, and become biocontrol agents, providing long-term control and reducing costs. This article provides a summary of the microbial entomopathogens that are known to infect scarab beetle species including bacterial, fungal, viral, microsporidian, and protozoan taxa, as well as the existing formulations and their efficacy. Lesser-known microbial species are also discussed as potential future controls. We also discuss the development of new techniques for improving efficacy, such as genetic engineering, synergistic interactions, auto-dissemination strategies, and improved formulations.

  PublisherOA PDFDOI

• Host Plant Species Mediates Impact of Neonicotinoid Exposure to Monarch Butterflies

  Insects · 2021 · 13 citations

  • Biology
  • Ecology
  • Zoology

  showed no significant reductions in any variable measured. Our results indicate that monarchs are tolerant to low doses of neonicotinoid, and that negative impacts of neonicotinoids depend on host plant type. Plant toxins may confer protective effects or leaf physical properties may affect chemical retention. Although neonicotinoid residues are ubiquitous on milkweeds in agricultural and ornamental settings, commonly encountered doses below 50 ng/g are unlikely to cause substantial declines in monarch survival or migratory performance.

  PublisherOA PDFDOI

• Ten-Year Performance of the United States National Elm Trial

  Arboriculture & Urban Forestry · 2017-05-01 · 13 citations

  articleOpen access

  Ulmus americana (American elm) was an important urban tree in North America prior to the introduction of the Dutch elm disease pathogen in 1930. Subsequently, urban and community forests were devastated by the loss of large canopies. Tree improvement programs produced disease tolerant American and Eurasian elm cultivars and introduced them into the nursery industry. However, consumer acceptance was slow. The National Elm Trial was established to evaluate commercially available taxa of elm across the United States. Established at 16 locations, these plantings monitored survival and growth, as well as disease and insect pressure for 7 to 10 years. ‘Morton’ elm had &gt;90% survival, while 13 cultivars averaged 70% to 90%, and five cultivars ranged from 25% to 69% survival. Trunk diameter growth by location ranged from 0.5 cm/year (Colorado, U.S.) to more than 2.0 cm/year (Iowa, U.S.). By taxa, trunk diameter growth ranged from a low, by ‘JFS Bieberich’ elm (0.7 cm/year), to a high by ‘New Horizon’ elm (1.7 cm/year). Scale insects were minor issues at most trial locations, except Colorado, where scales contributed to the death of several cultivars. Performance ratings (scale 1 to 5) ranged from 2.7 for ‘JFS Bieberich’ elm to 4.5 for ‘New Horizon’ elm. Based on the ratings, the preferred cultivars of American elm were ‘New Harmony’ and ‘Princeton’, and the preferred cultivars of Asian elm were The Morton Arboretum introductions and ‘New Horizon’. These findings will help green-industry professionals determine what elm cultivars will perform the best in different regions.

  PublisherOA PDFDOI

• Neonicotinoid residues in ornamentals alter behavior and survival of bees and beneficials

  2016 International Congress of Entomology · 2016-01-01

  article1st authorCorresponding
  PublisherDOI

• Soil-Applied Imidacloprid Translocates to Ornamental Flowers and Reduces Survival of Adult Coleomegilla maculata, Harmonia axyridis, and Hippodamia convergens Lady Beetles, and Larval Danaus plexippus and Vanessa cardui Butterflies

  PLoS ONE · 2015-03-23 · 79 citations

  articleOpen access1st authorCorresponding

  Integrated Pest Management (IPM) is a decision making process used to manage pests that relies on many tactics, including cultural and biological control, which are practices that conserve beneficial insects and mites, and when needed, the use of conventional insecticides. However, systemic, soil-applied neonicotinoid insecticides are translocated to pollen and nectar of flowers, often for months, and may reduce survival of flower-feeding beneficial insects. Imidacloprid seed-treated crops (0.05 mg AI (active ingredient) /canola seed and 1.2 mg AI/corn seed) translocate less than 10 ppb to pollen and nectar. However, higher rates of soil-applied imidacloprid are used in nurseries and urban landscapes, such as 300 mg AI/10 L (3 gallon) pot and 69 g AI applied to the soil under a 61 (24 in) cm diam. tree. Translocation of imidacloprid from soil (300 mg AI) to flowers of Asclepias curassavica resulted in 6,030 ppb in 1X and 10,400 ppb in 2X treatments, which are similar to imidacloprid residues found in another plant species we studied. A second imidacloprid soil application 7 months later resulted in 21,000 ppb in 1X and 45,000 ppb in 2X treatments. Consequently, greenhouse/nursery use of imidacloprid applied to flowering plants can result in 793 to 1,368 times higher concentration compared to an imidacloprid seed treatment (7.6 ppb pollen in seed- treated canola), where most research has focused. These higher imidacloprid levels caused significant mortality in both 1X and 2X treatments in 3 lady beetle species, Coleomegilla maculata, Harmonia axyridis, and Hippodamia convergens, but not a fourth species, Coccinella septempunctata. Adult survival were not reduced for monarch, Danaus plexippus and painted lady, Vanessa cardui, butterflies, but larval survival was significantly reduced. The use of the neonicotinoid imidacloprid at greenhouse/nursery rates reduced survival of beneficial insects feeding on pollen and nectar and is incompatible with the principles of IPM.

  PublisherOA PDFDOI

• Chronic Exposure of Imidacloprid and Clothianidin Reduce Queen Survival, Foraging, and Nectar Storing in Colonies of Bombus impatiens

  PLoS ONE · 2014-03-18 · 82 citations

  articleOpen accessSenior authorCorresponding

  In an 11-week greenhouse study, caged queenright colonies of Bombus impatiens Cresson, were fed treatments of 0 (0 ppb actual residue I, imidacloprid; C, clothianidin), 10 (14 I, 9 C), 20 (16 I, 17C), 50 (71 I, 39 C) and 100 (127 I, 76 C) ppb imidacloprid or clothianidin in sugar syrup (50%). These treatments overlapped the residue levels found in pollen and nectar of many crops and landscape plants, which have higher residue levels than seed-treated crops (less than 10 ppb, corn, canola and sunflower). At 6 weeks, queen mortality was significantly higher in 50 ppb and 100 ppb and by 11 weeks in 20 ppb-100 ppb neonicotinyl-treated colonies. The largest impact for both neonicotinyls starting at 20 (16 I, 17 C) ppb was the statistically significant reduction in queen survival (37% I, 56% C) ppb, worker movement, colony consumption, and colony weight compared to 0 ppb treatments. Bees at feeders flew back to the nest box so it appears that only a few workers were collecting syrup in the flight box and returning the syrup to the nest. The majority of the workers sat immobilized for weeks on the floor of the flight box without moving to fed at sugar syrup feeders. Neonicotinyl residues were lower in wax pots in the nest than in the sugar syrup that was provided. At 10 (14) ppb I and 50 (39) ppb C, fewer males were produced by the workers, but queens continued to invest in queen production which was similar among treatments. Feeding on imidacloprid and clothianidin can cause changes in behavior (reduced worker movement, consumption, wax pot production, and nectar storage) that result in detrimental effects on colonies (queen survival and colony weight). Wild bumblebees depending on foraging workers can be negatively impacted by chronic neonicotinyl exposure at 20 ppb.

  PublisherOA PDFDOI

Frequent coauthors

• Pedro Barbosa

  5 shared

• Emily G. Tenczar

  University of Minnesota

  5 shared

• Robert F. Denno

  3 shared

• Clive G. Jones

  Cary Institute of Ecosystem Studies

  3 shared

• Sonia Altizer

  University of Georgia

  2 shared

• R. W. Goth

  Agricultural Research Service

  2 shared

• Eric McCloud

  Wake Forest University

  2 shared

• D. R. Smitley

  Michigan State University

  2 shared

Labs

• Krischik LabPI

Awards & honors

• Ralph E Powe Jr Faculty Awards