Associate Professor Utah State University Logan, Utah
Climate variability has major implications for agriculture due to the increase in the frequency and intensity of simultaneous abiotic, namely water-stress, and biotic stresses to crops. Plant water-stress alone harms crops but can attract outbreaks of herbivores with varied host specialization, and plants succumb to further yield losses dealing with multiple stressors. Host-plant resistance provides a route to lessen yield losses from herbivory; however, our knowledge of the interactions between water-stress and pest resistance is limited, especially for mite herbivores of maize including the generalist twospotted spider mite (Tetranychus urticae; TSM) and the specialist Banks grass mite (Oligonychus pratensis; BGM). Using lab and field studies, host plant resistant traits for spider mites are identified. Specifically, maize resistance appears to be driven by benzoxazinoid plant defenses and only affects the generalist TSM, while the specialist BGM is not affected. Moreover, the interactions between water-stress and host plant resistance show that spider mite resistance is maintained even with plant water-stress. Despite the lack of resistance toward BGM, drought tolerant corn hybrids not only alleviate plant water-stress but also reduce BGM populations when plants have reduced irrigation compared to non-drought tolerant corn hybrids exposed to the same abiotic stress. These findings highlight the importance of including the nuances of multiple stressors within the framework of host plant resistance.
