Water available for agriculture is anticipated to become increasingly constrained as a consequence of climate change. Water-stress can promote herbivorous arthropod outbreaks in agricultural systems, due in part to increasing the concentration of nutrients in plant tissues. The Banks grass mite (Acari: Tetranychidae) is a major pest specializing on corn, which is an economically important crop in the Intermountain West. Consequently, there has been increased investment in the development of crops capable of tolerating water-stress for sustaining the growing human population. We tested if drought tolerant and drought susceptible corn hybrids in either optimal or water-stressed conditions increased mite populations. We evaluated the growth of Banks grass mite in the greenhouse setting and resident mite populations over a 2-year field study in northern Utah. Both the greenhouse and field experiments were conducted using a randomized 2 x 2 factorial design (two levels of corn drought tolerance x two irrigation levels). We used five drought tolerant and five drought susceptible commercially available corn hybrids. We measured leaf area and temperature, mite density, and corn yield.
Results/Conclusions
We found that water-stress resulted in reduced leaf area and increased leaf temperature in the greenhouse. Mite densities were similar on drought tolerant and drought susceptible corn hybrids under optimal watering. However, mites were more reduced on drought tolerant corn under water stress. This pattern was consistent across seed companies. In the field experiment, we found greater densities of mites under water-stressed conditions than optimal watering. However, in the second year mite populations were reduced on the drought tolerant corn hybrids compared to the drought susceptible hybrids. Similar to the greenhouse study, leaf area was lower and leaf temperature was higher in both field seasons. Further, we found that drought susceptible corn hybrids produced lower yield in water-stress but there were no differences between the drought susceptible and tolerant corn hybrids under optimal watering in the field. Given the prediction that the frequency and intensity of water-stress will become more severe in the western United States, we anticipate that drought tolerant traits will become increasingly important for sustaining agriculture production. Further, we recommend that future efforts in pest management integrate plant traits and irrigation practices for more comprehensively understanding pest outbreaks.