Temperature alters the interaction between a herbivore and a resistant host plant

Temperature and other environmental factors can strongly influence arthropods and their interactions with host plants. However, such effects are usually studied while keeping the suitability of host plants as constant as possible, thereby removing the possibility of interactions between temperature and host plant resistance. We performed experiments to determine whether temperature interacts with plant resistance to alter the density, movement, and distribution of wingless soybean aphids on resistant and susceptible soybeans. In individual plant tests, temperature influenced aphids differently depending on the plant they were on; aphids in the warmer temperature did better than aphids in the cooler temperature when on susceptible plants, but when on resistant plants aphids did worse in the warmer temperature. This pattern was, in part, due to markedly increased aphid fecundity on susceptible plants in warmer temperatures which was not the case on resistant plants. A follow-up experiment showed that higher temperature meant lower adult survival for aphids on a nutrient-poor diet, further suggesting how higher temperatures may be difficult for aphids when on resistant host plants. We also saw that both higher temperature and resistance increased within-plant movement in an additive fashion. Altering temperature and host plant resistance can each influence the demographic and movement responses of herbivores; however, this study indicates that the two factors may interact to influence herbivores in potentially unexpected ways.