The hazard pesticides pose to pollinators are well‐understood from laboratory studies. However, the field‐level response of pollinators to pesticide use in agroecosystems is not well‐established, nor is it clear if synergisms between pesticides affect pollinator visitation to crops. Here, we evaluated if fungicide and insecticide use posed a hazard to wild and honeybees at 87 cucurbit—pumpkin, cucumber, watermelon—farms in the Midwestern United States. We also evaluated if synergisms between local‐ (i.e. focal cucurbit field) and landscape‐level (i.e. surrounding crops) pesticide use influence wild and honeybee visitation to crop flowers. We found that bees were exposed to pesticides above regulatory levels of concern and that synergisms between a few local insecticides and landscape‐level fungicides reduced wild bee visitation to cucurbit flowers. Honey and bumblebee visitation to crops was not strongly influenced by synergisms between pesticides used at the local and landscape level. Synthesis and applications. We found pesticides posed hazards to honey and wild bee species. However, pesticides were less likely to affect short‐term visitation rates of honeybees compared with wild bee species. Thus, there is a need for changes in pesticide use at large spatial scales to reduce reliance on honeybees and maximize wild bee visitation to pollinator‐dependent crops. We suggest that a multifaceted approach, involving collaborations between farmers, consumers and policymakers, will be fruitful to promote changes in pesticide use and wild bee pollinators.

Natural enemies and pollinators require nutritional and habitat resources that are often not found in conventional agricultural fields. The addition of flowering plants within agroecosystems may provide the resources necessary to support beneficial insects at the local scale. We hypothesized that insect pollinator and natural enemy abundance would increase in cucumber (Cucumis sativus) plots containing flower strips and that the effect would be greatest in the crop rows closest to the flower strips. Three flower treatments were tested: 1) buckwheat (Fagopyrum esculentum), 2) yellow mustard (Brassica hirta), 3) sweet alyssum (Lobularia maritima), and cucumbers as a control. Flowers were planted within a commercial cucumber field in 20-m-long strips in a randomized complete block design with six replications in the 2014 and 2015 growing seasons. Some floral treatments successfully attracted more beneficial insects than others, but the beneficials did not disperse out to the cucumber plants. Cucumber yield was unaffected by flowers with one exception: in 2015, cucumber yield in the sweet alyssum plots were greater than those in plots with no flowers. Our research indicates that adding flowers to cucumber fields to increase services from beneficial insects needs to be further investigated to better understand the effect of factors such as relative flowering strip size.

Onion thrips, Thrips tabaci Lindeman, is a primary insect pest of onions (Allium cepa) worldwide. Onion thrips cause feeding damage by destroying epidermal tissue. They are also vectors of Pantoea ananatis (Serrano) Mergaert, the bacteria that causes center rot. Onions with center rot develop white streaks with water-soaked margins along the onion leaves, which turn necrotic and lead to bulb rot during storage. The role of thrips feeding on the establishment and progression of bacterial infection in onions has not been investigated. Onions infested with thrips and inoculated with P. ananatis had more necrotic tissue and symptoms were more severe with increasing thrips density. We conducted a fluorescence microscopy study that examined how P. ananatis (expressing a fluorescence protein gene) colonized a control group of onions without thrips in comparison to a test group of onions with thrips. We found that P. ananatis colonized some onions in the control group because of naturally existing wounds in the epidermal tissue but more colonization was found in the thrips infested group because of the increased presence of entry points caused by thrips feeding. Overall, our results demonstrate that wounds caused by thrips feeding facilitate center rot development by providing entry sites for the bacteria into leaf tissue.