About

Kathy Demchak is a Senior Extension Associate in the Department of Plant Science at Pennsylvania State University. She holds a B.S. in Horticulture from The Pennsylvania State University (1980) and an M.S. in Horticulture from Virginia Polytechnic Institute and State University (1983). Her responsibilities include conducting applied research to support Pennsylvania berry growers and providing them with current information on production technologies through presentations, articles, and publications. Her research focuses on improving the sustainability of berry production by reducing environmental impacts while maximizing crop productivity. She has been actively involved in studying the behavior and management of the spotted wing drosophila, a devastating insect pest that arrived in Pennsylvania. Additionally, her work includes evaluating new cultivars and types of strawberries, raspberries, and blackberries, developing recommendations for growing day-neutral strawberries, and assessing season extension technologies such as high tunnels and low tunnels. She also researches water treatments aimed at enhancing the food safety of strawberries. Kathy Demchak serves as the coordinator of the 'Mid-Atlantic Berry Guide,' a publication for commercial growers covering six states.

Research topics

• Biology
• Botany
• Horticulture
• Agronomy
• Environmental science
• Ecology
• Genetics
• Zoology

Selected publications

• Occurrence of the Stubby Root Nematode, <i>Nanidorus renifer</i> , in Cultivated and Wild Blueberry ( <i>Vaccinium</i> spp.) Plants in Pennsylvania, U.S.A.

  Plant Health Progress · 2026-01-01

  article

  Stubby root nematodes (SRN) are plant-parasitic nematodes known to cause damage to a wide range of crops, including blueberries. However, while blueberries are native to the eastern and northern regions of the United States, no information is available regarding the presence or distribution of SRN in blueberry production systems in Pennsylvania. To address this gap, between 2023 to 2025, a statewide survey was conducted to assess plant-parasitic nematode populations in commercial blueberry fields in the state. The survey detected the SRN Nanidorus renifer (syn. Paratrichodorus renifer) in 50% of the surveyed counties, at densities of 4 to 56 SRN/100 cm 3 of soil. Subsequent sampling also confirmed the occurrence of this species in wild blueberry plants within the state. These findings represent the first report of N. renifer in the rhizosphere of both cultivated and wild blueberry plants in Pennsylvania.

  PublisherDOI

• Advancing organic amendment-based soil management approaches: a paradigm shift from soil disinfestation to nourishing soil health

  Acta Horticulturae · 2024-11-01 · 2 citations

  article
  PublisherDOI

• Optimizing anaerobic soil disinfestation for high tunnel specialty crop production systems in the U.S. Mid-Atlantic region

  Acta Horticulturae · 2024-11-01 · 1 citations

  article
  PublisherDOI

• Establishment of key Asian larval parasitoids of <i>Drosophila suzukii</i> (Diptera: Drosophilidae) in the US Mid-Atlantic states

  Journal of Economic Entomology · 2024-08-23 · 1 citations

  articleOpen access

  The widespread establishment of Drosophila suzukii (Matsumura) has instigated a classical biological program in the United States and Europe for this invasive pest of soft-skinned fruits. This study reports the first release of an introduced key Asian larval parasitoid, Ganaspis kimorum Buffington (Hymenoptera: Figitidae), in 3 Mid-Atlantic states (Delaware, Maryland, and Pennsylvania), where a total of 26,950 wasps were released in 6 counties during the 2022 and 2023 fruit seasons. Pre-release monitoring in 2023 and 2024 recovered G. kimorum individuals, indicating successful overwintering of parasitoids released in 2022 and 2023. A total of 617 pre- and post-release fruit collections were conducted in a temporal sequence of ripening fruits of 30 different fruit species throughout the 2022 and 2023 fruit seasons at all release locations. G. kimorum were recovered in 40 post-release samples from 9 different host plants at all release locations. However, the overall levels of mean parasitism by G. kimorum were <2% at this early stage of release. At the same time, adventive populations of an unreleased key Asian larval parasitoid, Leptopilina japonica Novković & Kimura (Hymenoptera: Figitidae) were found from 16 sampled host plants throughout the fruit season. Mean parasitism of D. suzukii (primarily by L. japonica) ranged from 0% to 20.0%, which varied by season and host plant but peaked with fruiting of the most D. suzukii-infested wild hosts. We discuss potential ecological mechanisms that may affect the establishment and impacts of these key parasitoids on D. suzukii in this region and future release strategies for G. kimorum.

  PublisherOA PDFDOI

• Widespread establishment of adventive populations of Leptopilina japonica (Hymenoptera, Figitidae) in North America and development of a multiplex PCR assay to identify key parasitoids of Drosophila suzukii (Diptera, Drosophilidae)

  NeoBiota · 2024 · 40 citations

  • Biology
  • Ecology
  • Botany

  In recent years, there has been an increase in the adventive establishment and spread of parasitoid wasps outside of their native range. However, lack of taxonomic tools can hinder the efficient screening of field-collected samples to document the establishment and range expansion of parasitoids on continent-wide geographic scales. Here we report that Leptopilina japonica (Hymenoptera, Figitidae), a parasitoid of the globally invasive fruit pest Drosophila suzukii (Diptera, Drosophilidae), is now widespread in much of North America despite not having been intentionally introduced. Surveys in 2022 using a variety of methods detected L. japonica in 10 of 11 surveyed USA States and one Canadian Province where it was not previously known to occur. In most surveys, L. japonica was the most common species of D. suzukii parasitoid found. The surveys also resulted in the detection of Ganaspis cf. brasiliensis (Hymenoptera, Figitidae), the recently-released biological control agent of D. suzukii , in six USA States where it had not previously been found. These new detections are likely a result of intentional biological control introductions rather than spread of adventive populations. A species-specific multiplex PCR assay was developed as a rapid, accurate and cost-effective method to distinguish L. japonica , G. cf. brasiliensis, the closely-related cosmopolitan parasitoid Leptopilina heterotoma (Hymenoptera, Figitidae) and other native parasitoid species. This dataset and the associated molecular tools will facilitate future studies of the spread and ecological impacts of these introduced parasitoids on multiple continents.

  PublisherOA PDFDOI

• Soilless-Grown Green and Purple Basil Response to High Tunnel Photo-Selective Covering Films

  Horticulturae · 2023-12-28 · 4 citations

  articleOpen access

  Protected cultivation systems, such as high tunnels, have gained popularity for their ability to enhance growth conditions and extend the growing season of horticultural crops. The choice of the covering film in these systems can significantly impact crop productivity and quality while influencing pest and pathogen incidence. This study aimed to evaluate the yield, physiological responses, and nutritional quality of green and purple basil grown in high tunnels using different plastic film covers. The study was conducted in Central Pennsylvania using twelve research high tunnels covered with four alternative polyethylene films with varying light diffusion and ultraviolet (UV) radiation transparency levels: TuffLite IV (TIV), KoolLite Plus (KLP), UV-transparent (UVT), and UV-opaque (UVO). Green ‘Genovese Compact Improved’ and purple ‘Amethyst Improved’ basil (Ocimum basilicum L.) cultivars were grown as test crops. The plastic covering film had a significant effect on the growth of both basil cultivars, with a significant interaction between the film and basil genotype. Green basil generally exhibited higher fresh and dry biomass compared to purple basil, and the film effect varied with the basil genotype. Leaf area, stem, leaf, and total plant biomass were influenced by the plastic cover, with UVO and UVT films resulting in higher biomass production. The plastic covering films showed varying effects on the mineral content, total chlorophyll, carotenoids, total phenolic compounds, and antioxidant activity, with UVO and UVT films often resulting in improved nutritional quality compared to traditional films. Furthermore, covering films influenced the downy mildew severity on both cultivars and the UVT film consistently limited the severity of the foliar disease in both genotypes. Overall, this study highlights the importance of selecting appropriate plastic covering films with varying levels of UV transparency in high tunnel production systems.

  PublisherOA PDFDOI

• Seasonal Population of Drosophila suzukii (Diptera: Drosophilidae) and Pesticide Use Pattern after Its Invasion in Caneberry Crops in Pennsylvania (USA)

  Arthropoda · 2022-11-17 · 3 citations

  articleOpen access

  Drosophila suzukii (Diptera: Drosophilidae) is a major invasive pest of caneberries (e.g., blackberries and raspberries) and other thin-skinned fruit crops. In recent years, it has been reported as an economically important fruit pest in many countries. In caneberries, the timely detection and management of invasive insect pests such as D. suzukii is important to maintain profitability and avoid fruit export restriction. Invasions by such new pest species in commercial crop production often changes pesticide use patterns and frequency as growers try to control pest populations on their farms. In this study, we examined the seasonal population of D. suzukii and pesticide use patterns before and after D. suzukii invasion in primocane-fruiting raspberry and floricane-fruiting blackberry crop production in Pennsylvania. The results of seasonal monitoring conducted over two years showed higher populations of D. suzukii fruit flies during the settle period. The evaluation of crop-specific pesticide programs showed an increase in pesticide use frequency compared to the crop season before D. suzukii invasion in the blackberry planting. Similarly, over a five-fold increase in pesticide application was recorded in the raspberry planting in the year following invasion. The implications of increased pesticide use patterns in blackberry and raspberry production are discussed.

  PublisherOA PDFDOI

• Albion Strawberry Responds to Mulch Treatments and Low Tunnels Covered with Photoselective Films

  HortScience · 2021 · 9 citations

  • Horticulture
  • Agronomy
  • Environmental science

  The impact of photoselective films on strawberry plants in a low tunnel system has not been well investigated in the northeastern United States, nor have there been studies looking at the effect of mulch color in a plasticulture system. During two separate years (2016 and 2017), we evaluated ‘Albion’ in an annual system with three ground mulch treatments (black plastic, white-on-black plastic, and no plastic) and under six cover treatments. Five of the cover treatments were low tunnel films that varied in their ultraviolet, photosynthetically active, and near-infrared radiation transmission profiles: Tufflite IV TM (TIV), KoolLite Plus (KLP), Trioplast (TRP), and custom-manufactured UV-transparent (UVT) and UV-blocking (UVO) films. The sixth cover treatment was the traditional open bed environment (no low tunnel). ‘Albion’ produced fruit for 18 to 19 continuous weeks during both years until as late as Thanksgiving (24 Nov.) in 2016. Overall, the average marketable yield was greater in 2017 (486 g/plant) than in 2016 (350 g/plant), and it was greater on black mulch than on no mulch (445 vs. 380 g/plant, respectively); white mulch was intermediate (419 g/plant) ( P ≤ 0.05). There was not a significant increase in marketable yield under low tunnels compared with open beds. The average fruit mass was greater under KLP and UVO than open beds (TIV and UVT were intermediate), and greater on beds with no mulch than black mulch (white mulch was intermediate). Across cover treatments, plants on black mulch produced more runners than plants on white or no mulch, and the black mulch/open bed treatment generated the greatest number of runners in both years, more than double most other treatments in 2016. The present study demonstrates that mulch selection is important for maximizing the yield of ‘Albion’ in the Northeast region, and that both mulch and cover impact runnering and fruit size. For plant propagators producing ‘Albion’ tips in a field environment, the results of this study suggest they are likely to maximize runner quantity by cultivating plants on black mulch without low tunnel cover.

  PublisherOA PDFDOI

• Effects of Cane Emergence Time, Bending, and Defoliation on Flowering and Yield in Primocane-Fruiting Blackberry

  Agronomy · 2020 · 2 citations

  Senior authorCorresponding
  • Biology
  • Horticulture
  • Agronomy

  Primocane-fruiting (PF) blackberries are adaptable to different production systems. To increase yields in PF blackberries, their primocanes are typically tipped or topped in summer to encourage branch formation from axillary buds below the cut. In this study, we determined in PF ‘Prime-Ark® Traveler’ whether early emerging primocanes were more productive than those that emerged later in the season, and the effect of primocane bending and defoliation on flowering. The primocanes that emerged in April produced 64% more flower shoots than those that emerged after May. Also, these findings indicate the alternative primocane management practices of selecting the early emerging primocanes and bending to orient primocanes horizontally, and leaf removal to increase budbreak and flower shoot emergence. The present work contributes toward a better understanding of primocane emergence time and orientation–flowering relations, and how these factors mediate crop performance of PF blackberry.

  PublisherOA PDFDOI

• UV-blocking High-tunnel Plastics Reduce Japanese Beetle (Popillia japonica) in Red Raspberry

  HortScience · 2019-05-01 · 15 citations

  articleOpen access

  Insecticides are the primary tool raspberry growers use to control Japanese beetles ( Popillia japonica ), but reliance on pesticides is costly and there are risks to nontarget species. Based on observations that Japanese beetles were less abundant on raspberries in high tunnels than in fields, we investigated the effects of plastic films that transmit different amounts of ultraviolet (UV) light to Japanese beetles. Many insects are sensitive to light in the UV-A range and use it for navigation. High-tunnel plastics that block varying percentages of UV radiation are increasingly available. We grew two primocane-fruiting red raspberry cultivars, Polka and Josephine, in tunnels with six different covering treatments. Five were plastics that blocked the UV range to varying degrees, and one was a no-plastic treatment. In 2016, beetles were counted and removed from the plants by hand daily. In 2017, beetles were removed by hand every 4 to 5 days. Foliage temperature was measured in each tunnel twice in 2017 with an infrared (IR) thermometer. Spectral transmittance characteristics of the plastics were measured with a spectroradiometer in 2015 and 2018. Mean beetle counts by date and for the whole season were compared for the plastics and cultivars. Japanese beetle numbers were significantly greater in the no-cover treatment than in all plastic treatments. The plastic that blocked more than 90% of the UV-A range usually had significantly lower beetle populations than the plastics that blocked the least UV-A. Overall, it appears that using a UV-blocking plastic can reduce Japanese beetle aggregation and feeding damage on raspberries, decreasing the need for other control. This could benefit growers by reducing the cost of insecticides and decreasing exposure risk for nontarget organisms.

  PublisherOA PDFDOI

Frequent coauthors

• Barbara L. Goulart

  33 shared

• Wei Qiang Yang

  18 shared

• Yadong Li

  Yunnan Agricultural University

  9 shared

• C. B. Smith

  Colorado State University

  9 shared

• Gregory M. Loeb

  Cornell University

  7 shared

• Rebecca L. Loughner

  Cornell University

  6 shared

• David J. Biddinger

  Pennsylvania State University

  5 shared

• Richard P. Marini

  Pennsylvania State University

  4 shared

Education

• M.S.

  Virginia Polytechnic Institute and State University

  1983

• B.S.

  The Pennsylvania State University

  1980