Western Tentiform Leafminer
Western tentiform leafminer (Phyllonorycter elmaella) is an indirect pest that mines the leaves of apple and cherry trees, it can reduce photosynthesis, and thus fruit size and quality. Biological control by numerous, naturally occuring wasps is common. Successful managgement requires a good sampling program and knowledge of treatment thresholds.
Pupa are 1/8 to 1/5 inch long, yellow-brown changing to dark brown, and cylindrical, tapering sharply at the rear end.
Adults are 1/8 to 1/5 inch long, small, slender moths with forewings that are golden brown and have white bands edged with black. Their hindwings are gray with long hairs on the edges. The wings are held roof-like over the body when at rest.
Eggs are extremely small and difficult to see without magnification. They are round and flat, and transparent when first laid, turning yellowish green.
- Reduced photosynthetic capability of leaves
- Reduced fruit quality
- Leaf drop, premature ripening, and fruit drop
Chemical control is most effective against sapfeeding larvae in mines and adult moths flying in orchards. Insecticide sprays should only be applied when leafminer treatment thresholds are exceeded during the second or third generation. Pre-bloom applications targeting first generation sapfeeders are only recommended if large numbers of adult moths are observed in the orchard during April or May, or egg counts exceed three per leaf during tight cluster to pink stage of apple.
There are at least six species of parastic wasps that attack leafminers in the Northwest, and at least several species are common in Utah orchards. Leafminer parasitism can be as high as 90% and can eliminate the need for chemical control of even a formerly high population. The wasps lay their eggs inside the mines on the outside of leafminer larvae. Wasp larvae hatch from the eggs and devour the developing leafminer larva.