Attraction of insect pests to stressed-out trees

Stressed trees may suffer from physical, physiological, phytochemical, or a combination of responses that can alter their susceptibility to insect pests. The type of stress the tree experiences may influence its physiological responses, resulting in differential susceptibility of a tree to specific herbivores. In this study, we investigated the induced responses of red maple trees (Acer rubrum ‘Brandywine’ and ‘Franksred’) to four stress treatments  and their resulting susceptibility to common maple insect pests. . The treatments included a) herbicide damage, b) complete defoliation, c) 50% girdling around the base of the tree, and d) control (i.e., no induced stressor). These treatments mimic damage commonly seen in nursery production systems due to herbicide drift, herbivore defoliation, and mechanical damage. Treatments were applied in May following first flush of spring foliage. After re-flush, we recorded the presence and quantity of common-insect pests of maple, including mites, leafhoppers, flatheaded borers, and maple leaftiers. Additionally, we measured physical, physiological, and phytochemical characteristics of the trees to determine if pest pressures correlated with specific stress responses.  We will present how these pest pressures varied among the different induced stressors. We will also present possible reasons for differential responses of pests (i.e., correlations between insect pests and physical, physiological, and phytochemical responses). Understanding how various stressors effect the susceptibility of trees to certain pests will help improve pest-management strategies. These improved strategies should allow nurseries and growers to apply appropriate, preventative measures based on the cause of plant injury.