Project Title : Insect Responses to Induced Apple

Significant Findings: 1. Apple leaf quality deteriorates with the season. We confirmed in multiple seasons that L. subjuncta larval development is prolonged and pupal weight is decreased on apple foliage as the season progresses. These data indicate the apple leaves are a relatively good food material for Lacanobia larvae early in the season but deteriorate in quality later in the season. Similar results were obtained for Pandemis leafroller larvae on apple leaves. Poor leaf quality may cause more damage to fruit by leaf-eating caterpillars. 2. Sources of variance for apple leaf quality. The quality of apple leaves as caterpillar food was not strongly tied to leaf relative age (as leaf position on a branch). Leaf quality was not reduced with methyl jasmonate treatments (to induce chemical defenses), or with prior feeding on the leaves by other caterpillars (also should induce chemical defenses). Leaf quality did vary with apple variety, with fastest development on Red Delicious leaves. 3. Potato is a superb host of Lacanobia larvae, compared to many weeds, annual crops, and foliage of tree fruits evaluated. Also, in 2003, Lacanobia larvae, mixed with cutworms and armyworms, were found defoliating areas of commercial potato plantings near Othello and near Ephrata. 4. Pandemis leafroller and Lacanobia fruitworm larvae prefer apple foliage over fruit and Lacanobia fruitworm larvae preference for foliage was greatest with Spring foliage. These findings support the hypothesis that damage to apple fruit may be exacerbated by deterioration in foliage quality.