Date of Graduation

5-2020

Document Type

Thesis

Degree Name

Master of Science in Horticulture (MS)

Degree Level

Graduate

Department

Horticulture

Advisor/Mentor

Garcia, Maria E.

Committee Member

Johnson, Donn T.

Second Committee Member

McWhirt, Amanda L.

Third Committee Member

Joshi, Neelendra K.

Keywords

Arkansas; biopesticides; high tunnels; strawberries; yield

Abstract

This two-year study investigated combinations of biopesticides to determine impacts on strawberry fruit marketable fruit yields, and effectiveness in controlling strawberry pests in a high tunnel production system at the University of Arkansas, Division of Agriculture Research and Extension Center in Fayetteville, Arkansas. Two strawberry cultivars Fragaria × ananassa (Duch.), Camino Real and Sweet Sensation were grown in a high tunnel from early-October to mid-May for two consecutive growing seasons, (2017-18 and 2018-19) with six treatment combinations of biopesticides including an untreated (water) control, nutrient spray and selected biological based fungicides and insecticides, arranged into a split-plot randomized block design. The cost associated with each biopesticide treatment combination was calculated based on the number of times applied to the specific area of the study and the cost of the products. Relative humidity, daily light integral (DLI) and growing degree days (GDD) were also recorded to show differences between the two growing seasons. During the 2018 season, the control (water) treatment numerically had the highest total and marketable fruit weight, but was not significantly different from any biopesticide treatment. No significant effects of biopesticide treatment were observed during the 2019 season on fruit yield or quality, thus indicating that there was no clear advantage to any of the treatments on improving fruit marketability. The biopesticide combination treatments were also evaluated for their impacts of four high tunnel pests of strawberry, powdery mildew (Podosphaera aphanis (Wallr.) U. Braun and S. Takam. (formerly Sphaerotheca macularis (Wall. Ex Fries) Jacz f. sp. Fragariae (Peries))), gray mold (Botrytis cinerea), two-spotted spider mites (Tetranychus urticae (Koch) (Acari: Tetranychidae)), and strawberry aphids (Chaetosiphon fragaefolii (Cockerell) (Homoptera: Aphididae)). Disease incidence for 2018 was less than 16% for powdery mildew and less than 25% for gray mold. Powdery mildew in 2019 had less than 1% of disease incidence and gray mold had less than 2% disease incidence. In 2018, two-spotted spider mite populations were greater than the economic threshold of 5 mites per leaflet, but populations remained below the economic threshold in 2019. Strawberry aphid populations were not present in either harvest season. Overall findings point to the evaluated combinations of biopesticides not having a significant effect on fruit marketability or disease/arthropod control. These findings indicate that the tested combinations should not be used by producers to control pests or improve marketable yield of strawberries in high tunnels.

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