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Author ORCID Identifier

https://orcid.org/0009-0007-8984-4312

Date Available

10-20-2026

Year of Publication

2026

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College

Agriculture, Food and Environment

Department/School/Program

Entomology

Faculty

David Gonthier

Faculty

Charles Fox

Abstract

Feeding damage from insect pests is a leading challenge for specialty crop growers who follow organic practices. Past research has shown that fine-mesh row covers installed over mesotunnel structures, which form a physical barrier between plants and insects, often reduce insect pest abundance and increase yield compared to open field conditions. However, there are several challenges associated with this practice. Exclusion efficacy varies across a spectrum of insect body sizes and mesh sizes, and effects on yield vary across crops. Additionally, pollination management for pollinator-dependent crops introduces labor requirements and may result in reduced pest exclusion efficacy. Mechanical weed management is a significant challenge in mesotunnel systems because row covers typically must be removed to access crops, adding labor requirements. Adoption of this practice by specialty crop growers in Kentucky remains low.

In chapter 2, I compared organic-compliant pest management strategies in brassica crop production to determine the effects of treatment on insect pest abundance, flea beetle feeding damage, and yield. Across four experimental seasons of spring bok choy and fall napa cabbage production, I compared two fine-mesh row cover products (ExcludeNet and ProtekNet) and a rotation of the organic insecticides spinosad and pyrethrins against an uncovered control. ExcludeNet has a mesh size of 0.95x0.95-mm and is more durable than ProtekNet, which has a mesh size of 0.35x0.35-mm. Flea beetles were able to infiltrate the mesh of ExcludeNet but were excluded by the ProtekNet row cover. Compared to the control, ProtekNet always significantly reduced flea beetle abundance as measured through weekly visual surveys, while a significant reduction was observed in three out of five ExcludeNet treatment-experiment combinations. Row covers always reduced flea beetle feeding damage compared to the control. While harlequin bug pressure was low across treatments in 2024, in 2025, row cover treatments significantly reduced abundance as measured through visual surveys compared to both the control and organic insecticide treatments.. Marketable yield was significantly higher in all ProtekNet and three out of five ExcludeNet treatment-experiment combinations than in the corresponding control.

In chapter 3, I compared two ExcludeNet row cover treatments with different pollination management regimes to a rotation of organic insecticides and an uncovered control in organic eggplant production. Securing the ends of row covers open at anthesis (open-ends) resulted in the greatest yield improvements, but it never significantly differed from a row cover treatment completely removed at flowering (on-off) in measurements of flea beetle abundance, suggesting that yield may have benefited in part from the microclimate effects provided by coverage with the row cover. These findings are combined with results from fieldwork carried out by previous graduate students between 2019 and 2021, which included treatments of ProtekNet fine-mesh row covers, spunbonded row covers, organic insecticides, and untreated controls (2019-2021); reflective plastic mulch (2019); various essential oils (2019-2020); and conventional insecticide. In all three prior experiments, ProtekNet row cover reduced flea beetle abundance at flowering (prior to row cover opening or removal) compared to a control. In previous experimental years, marketable yield was increased compared to a control by a ProtekNet row cover treatment managed with the open-ends strategy (2021) but not by ProtekNet row covers managed with the on-off strategy (2019 and 2020).

In chapter 4, I compared three strategies to manage weeds in the furrows between plastic-mulch-covered beds of crops in triple-bed mesotunnels across three experimental seasons to determine optimal solutions for weed management under row covers. Treatments included a bare ground control, landscape fabric, and a cover crop (perennial ryegrass in spring-bok choy and teff in summer-eggplant and fall-napa cabbage). The landscape fabric treatment always effectively suppressed weeds. The treatments did not differ across any metrics in spring-bok choy, when germination of both weeds and cover crops was low. In summer eggplant, the cover crop treatment had significantly reduced weeds compared to the control in some, but not all, measurements. Eggplant marketable yield in the landscape fabric treatment was triple that of the control and cover crop treatments. In the fall-napa cabbage experiment, the cover crop treatment reduced grass weeds, but not broadleaf or total weed biomass compared to the control. There was no effect of treatment on marketable yield in fall-napa cabbage.

In chapter 5, I collaborated with Kentucky farmers and community and home gardeners to conduct on-farm research at 21 growing sites. Study participants compared a mesotunnel treatment and uncovered control treatment for one or more crops of their choice. Participants were surveyed before and after the growing season and interviewed to assess their perceptions of fine-mesh row covers. Additionally, I surveyed crops for insect pests and collected yield data from participants. Across the entire dataset, there were significantly more aphids in the mesotunnel treatments than the corresponding controls, but when aphids were excluded, there were significantly fewer total insect pests in mesotunnels. For brassica crops, there were significantly fewer caterpillars in mesotunnels. Significant effects of treatment on yield were detected across the entire dataset and on brassica crops; however, there was no significant effect on cucurbits. Across the dataset, average yield per plant was 67% greater in mesotunnel treatments than the control; furthermore, it was always greater in mesotunnel treatments of brassica crops than the corresponding control. However, yield per plant was higher in the control for 25% of all plantings, and yield effects were highly variable for cucurbit crops. Participants highlighted challenges and obstacles to adoption of mesotunnels, but perceptions were generally favorable and 95% of participants indicated their intention to continue using fine-mesh row covers.

The findings of this thesis indicate that fine-mesh row covers tend to reduce insect pest abundance and increase yield compared to an uncovered control. In particular, fine-mesh row covers consistently increased yield for brassica crops in field experiments at the University of Kentucky Horticulture Research Farm and in on-farm trials at sites across the state. However, integration with organic insecticides may be necessary. Yield effects were less consistent for pollinator-dependent crops, including eggplant and cucurbits. Within mesotunnel-plasticulture systems, cover crops planted as a living mulch between raised beds did not penalize yield compared to landscape fabric in cool-season brassica crop production. The outcomes of the on-farm research study suggest that adoption of fine-mesh row covers by Kentucky specialty crop growers may increase, given increased exposure to the practice.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2026.93

Archival?

Archival

Funding Information

This research was funded by the National Institute of Food and Agriculture, U.S. Department of Agriculture Organic Agriculture Research and Extension Initiative Grant (no.: 2023-51300-40855) in 2024-2026, by the National Institute of Food and Agriculture, U.S. Department of Agriculture National Needs Graduate Fellowship Grant (no.: 2021-38420-34057) in 2024-2025, and the Gatton Foundation (no.: 1215528580) in 2025.

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Available for download on Tuesday, October 20, 2026

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