Tolerance and compensatory ability after invertebrate damage are important components of plant defense and are affected by various endogenous and exogenous factors. Here, we examine the impact of feeding damage caused by different densities of the redlegged earth mite (Halotydeus destructor Tucker) on the performance and recovery of canola and wheat seedlings at different plant developmental stages, and when grown under three levels of moisture stress. Both canola and wheat were susceptible to feeding damage caused by H. destructor at early growth development stages (canola—cotyledon, first and second true leaf stage; wheat—GS10 and GS12), but tolerated damage at the later growth stages (canola—third true leaf stage; wheat—GS14). Wheat plants compensated completely for mite feeding damage, while canola plants showed partial compensation when feeding occurred at the cotyledon and first true leaf stages. Canola was susceptible to immediate feeding damage from H. destructor under all levels of moisture stress and did not compensate for this damage over time when grown in the unstressed and moderately stressed treatments. Under severe moisture stress conditions, plant performance traits and mite density often showed a nonlinear relationship, with growth initially increasing as mite density increased, but then decreasing markedly as densities exceeded 30 mites/100 cm2. Wheat seedlings were susceptible to immediate feeding damage when grown in the unstressed and severe stress conditions, but were generally able to compensate for this damage regardless of moisture conditions. The implications of these results for the management of H. destructor are discussed.
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Vol. 42 • No. 5