Date of Award

12-1-2025

Degree Name

Master of Science

Department

Plant, Soil, and Agricultural Systems

First Advisor

Walters, Alan

Abstract

Pumpkins (Cucurbita spp.) are a highly valued crop produced in all 50 states, with Illinois holding the top position for pumpkin acreage. Pumpkins depend on insect-mediated pollination services and rank among the most pollinator-dependent crops worldwide. If sufficient pollination by insects is not achieved, fruit production can decrease by 95% or more, resulting in significant crop loss. Bees are effective pollinators of pumpkins and are well-suited to transfer the pollen required for fruit set. Many pumpkin growers in southern Illinois rely entirely on wild bee populations to provide the pollination services required for commercial pumpkin production. Therefore, two field studies were conducted in 2023 and 2024 to assess wild bee population abundance and determine if pollination deficits are present in southern Illinois pumpkin fields. In the first study, five fields were evaluated for pollinator activity in pumpkin pistillate and staminate flowers between the hours of 6:00 AM and 10:00 AM. Results from this study indicated that three bee species, squash bees (Peponapis pruinosa), bumblebees (Bombus spp.), and honeybees (Apis mellifera), are involved in providing pollination services in southern Illinois pumpkin fields. However, pollinator abundance and species composition differed by field location and surrounding landscape. Differences were detected (P≤ 0.05) in pollinator populations across locations and indicated that total pollinator visits differed between agronomic and horticultural landscapes in staminate flowers. In contrast, no differences were detected in pistillate flowers regarding pollinator composition and landscape type. In both pistillate and staminate flowers, bumblebees, honeybees, and squash bees provided the majority of visits, respectively. However, at both locations surrounded by a horticulturally diverse landscape, honeybee visitations were higher than bumblebee visits in pistillate flowers. In the second study, three field locations were evaluated for pollination deficits by comparing hand-pollinated and open-pollinated pumpkins for fruit and seed set and yield. Two fields were located at the Belleville Research Center (BRC), with ‘Kratos’ and ‘Magic Wand’ pumpkins assessed. The third field was in Fults, IL, at a grower location that contained ‘Magic Lantern’ pumpkins. Pollination deficits differed among field locations for percent fruit-set with only the ‘Kratos’ field at BRC not exhibiting a pollination deficit for percent fruit set. However, pumpkins were not pollen-limited for fruit or seed yield characteristics. The presence of a fruit-set pollination deficit in most of the fields evaluated indicates that, in some southern Illinois pumpkin fields, wild pollinators are not providing the required pollination services for fruit set.

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