Spider mite (Acari: Tetranychidae) outbreaks are common on corn grown in the arid West. Hot and dry conditions reduce mite development time, increase fecundity, and accelerate egg hatch. Climate change is predicted to increase drought incidents and produce more intense temperature patterns. Together, these environmental shifts may cause more frequent and severe spider mite infestations. Spider mite management is difficult as many commercially-available acaricides are ineffective due to the development of resistance traits in field mite populations. Therefore, alternative approaches to suppress outbreaks are critically needed. Drought-tolerant plant hybrids alleviate the challenges of growing crops in water-limited environments; yet, it is unclear if drought-tolerant hybrids exposed to water-stress affects mite outbreaks under these conditions. We conducted a greenhouse experiment to evaluate the effect of drought-tolerant corn hybrids on Banks grass mite, a primary pest of corn, under optimal irrigation and water-stress irrigation. This was followed by a 2-year field study investigating the effect of drought-tolerant corn hybrids exposed to the same irrigation treatments on Banks grass mite artificially infested on hybrids and resident spider mite populations. Results showed that water-stressed drought-tolerant hybrids had significantly lower Banks grass mite and resident spider mite populations than water-stressed drought-susceptible hybrids. Interestingly, water-stressed drought-tolerant hybrids had equal Banks grass mite populations to drought-susceptible and drought-tolerant hybrids under optimal irrigation. We posit that planting drought-tolerant hybrids may suppress spider mite outbreaks in water-challenged areas.

Banks grass mite egg and motile densities in the greenhouse experiment were Log_x transformed before analyses to correct for heterogeneous variances and non-normal distribution. For the field experiment, resident spider mite motiles, and egg densities were    transformed before analyses. Conversely, densities of Banks grass mite motiles, and eggs, as well as leaf temperature were Log_x transformed before analyses to correct for heterogeneous variances and non-normal distribution. Data for testing differences between hybrids within each seed company were Log_x transformed to correct for heterogeneous variances and non-normal distribution. Data were analyzed using JMP (version 9.3; SAS Institute Inc., Cary, NC, USA).