Weed host interactions with spider mites in intermountain west corn production

With climate change, it is predicted that more frequent high temperatures and drought severity will lead to an increase in damage caused by pests that thrive under these conditions. Spider mite outbreaks, for example, are associated with plant water-stress and there is evidence that some weeds are more resilient to drought than crops, leading to major concerns for the management of these two pest types. Weeds compete with crops for limited resources, but what is unclear is which weeds harbor spider mites and whether they exacerbate the impact of spider mites on corn. Survey was conducted to identify weeds at the edges of corn fields and their host association with spider mites. Fifteen corn fields were surveyed from northern Utah. We also conducted parallel field study to investigate how varied irrigation levels impact spider mite infestations from weeds and whether the selection of drought-tolerant corn hybrids alters interactions. We paired either redroot pigweed and two-spotted spider mite or green foxtail and Banks grass mite, and then randomly assigned these pairs to field cages receiving optimal or suboptimal irrigation. Results showed that field bindweed and nightshade were the most common weeds hosting two spotted spider mites and banks grass mites, respectively. Further results showed that mite populations were higher under reduced irrigation than under optimal irrigation, while populations were increased on drought susceptible corn. This information may assist in developing strategies for managing these pests and contribute to the development of integrated pest management for corn production systems in water-stressed environments.