Pest description and crop damage Adult moths are about 0.12 inch long. The wings are held roof-like over the body and are golden bronze with white bands. Eggs are flat, translucent, and laid on the undersides of leaves. The larvae vary in appearance depending on their age, as they progress through five instars. Young larvae are legless and cream-colored. Older instars have legs and are cylindrical in shape, cream-colored and about 0.12 inch long. Mature larvae are yellow and about 0.18 inch long. The larvae feed within the leaf tissue creating discolored areas on the leaf. If feeding is sufficiently extensive, fruit quality and yield are reduced. This pest is primarily a problem in apples and, secondarily, in cherries and rarely causes significant damage in pears.
Biology and life history This insect overwinters as pupae in leaf litter. The adults emerge early in the season and lay eggs on the undersides of leaves around the pink stage of flower bud development. Eggs are flat and translucent. The first three larval instar stages feed on spongy soft tissue inside the leaves, creating blotches visible only on the undersurface of the leaves. Later instars develop by early to mid-May. These feed on the upper surface of the leaf beneath the epidermis, spinning silken webs to tie the mine together, giving it the characteristic "tentiform" appearance. Larvae then pupate inside the leaf. There are three to four overlapping generations per year.
Pest monitoring Eggs and mines can be observed on the leaves but no thresholds have been established for this pest in pears.
Parasitic wasps, especially Pnigalio flavipes, can provide substantial natural control of this pest. Leafminer problems may be induced by loss of biological control due to broad spectrum insecticides.
Management-chemical control: HOME USE
- azadirachtin (neem oil)-Products containing neem extract may be phytotoxic to some pear cultivars. Some formulations are OMRI-listed for organic use.
- bifenthrin-Highly toxic to bees.
- carbaryl-Highly toxic to bees.
- gamma-cyhalothrin-Highly toxic to bees.
- imidacloprid-Highly toxic to bees. Soil drenches may have residual activity in woody plants lasting for 12 or more months. If short-term management is the goal, consider other approaches.
- insecticidal soap-Some formulations are OMRI-listed for organic use.
- kaolin-Applied as a spray to leaves, stems, and fruit, it acts as a repellant to some insect pests. Some formulations are OMRI-listed for organic use.
- lambda-cyhalothrin-Highly toxic to bees.
- malathion-Highly toxic to bees.
- permethrin-Highly toxic to bees.
- pyrethrins (often as a mix with other ingredients) -Highly toxic to bees. Some formulations are OMRI-listed for organic use.
- spinosad-Some formulations are OMRI-listed for organic use.
- zeta-cypermethrin-Highly toxic to bees.
Management-chemical control: COMMERCIAL USE
Chemical control for western tentiform leafminer is generally not required in commercial pear orchards.