Intercropped rye strips constrain the within-field foraging behavior of wild and managed bees on watermelon flowers

Abstract Pollinator-dependent crops are typically uniform habitats but the presence of an interplanted cover crop can increase field heterogeneity, potentially affecting pollinator foraging patterns. Particularly, tall grass species like rye can act as physical barriers, constraining movement between crop rows and reducing flower visitation. In this study, we investigated the effects of rye cover crop on pollinator foraging behavior in seedless watermelon. We used 27 commercial fields between 2022 and 2025, which had either no rye (0% rye), one rye strip to every three watermelon rows (25% rye) or one rye strip every other watermelon row (50% rye). Across years, we conducted 20 observational surveys per rye level during watermelon bloom, recording multiple aspects of foraging behavior. We categorized bees in four guilds: honey bees, bumble bees, large solitary bees and small solitary bees. Overall, the number of flower visits per watermelon row was greatest with higher rye level (0% rye: 1.8, 25% rye: 2.0, 50% rye: 3.3). Rye level affected the number of row changes differently for each pollinator guild. Honey bees and small solitary bees were more affected by rye compared to bumble bees and large solitary bees; they visited more flowers per row but moved between rows less frequently. Large solitary bees exhibited the highest probability of crossing over rye. Our study shows that rye created a barrier effect by funneling bee movement, which may lead to uneven yields. To minimize potential nonuniform pollination, we recommend practices that enhance pollinator distribution and biodiversity for more resilient pollination services.