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Southeastern Apple ProductionENTOMOLOGY |
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Spotted Tentiform Leafminer
Phyllonorycter blancardella
Description
Adult spotted tentiform leafminer (STLM) moths are 1/8 inch long and have brown wings with white transverse stripes margined with black. Larvae are yellowish and 1/8 inch long when fully grown and pupae are brown, tapered, and 1/8 inch long. Eggs are oval, yellowish, dome-shaped, and laid on the undersides of leaves. At roughly 1/10 inch in diameter, they are not easily seen.
 Adult |
 Larva |
 Pupa |
Life History
STLM overwinter as pupae in fallen apples leaves. Adults begin to emerge around the 1/2-inch green stage and continue through bloom. Females fly to leaves and lay about 25 single eggs which hatch in 6 to 10 days. Larvae go through a sap-feeding and a tissue-feeding stage. Sap-feeders are very small, piercing plant cells and sucking sap on one side of the leaf. Tissue-feeders are larger, have well-developed mouthparts, and feed on tissue inside leaves. Each generation requires 35 to 55 days, and STLM are usually active from early spring until leaves drop in the fall.
Damage
STLM injure leaves by internal feeding or 'mining.' Each mature mine reduces the leaf's green tissue by 5 percent, and may buckle the leaf like a small tent. Excessive mining can be damaging, especially when combined with drought, mites, or foliar diseases. Mines remain visible after STLM larvae have emerged or been killed by sprays, so it is necessary to open them and check for larvae to determine if they are active.
 Leaf with tissue mines |
 Mine - top of leaf |
 Degrees of damage |
 Mine opened to show larva |
Monitoring and Control
STLM adults can be monitored with pheromone traps, but a careful field search is necessary to estimate the size of a population. Use the methods and chart below to determine the need for action.
First generation eggs: If an insecticide effective against STLM is not routinely applied at tight cluster to pink, sampling for first generation eggs may be useful to determine the need for control of first generation larvae (though first generation larvae rarely increase to damaging levels). Select 5 terminals per tree and use a hand lens to count the number of eggs on the underside of the second, third, and fourth leaves (in the order they unfold).
First generation larvae: Select 5 terminals per tree and count the number of mines on the underside of the second, third, and fourth leaves (in the order they unfold).
Second and third generation larvae: Select 5 mature leaves per tree from the periphery of the tree and count the total number of sap and tissue mines.
| Generation | Sampling Period | Action Threshold Level |
|---|---|---|
| 1st egg | Pink | 6 eggs / cluster |
| 1st larval | Petal fall - first cover | 1 mine / leaf |
| 2nd larval | 3rd and 4th cover | 2 mines / leaf |
| 3rd larval | July | 5 mines / leaf |
 'Diamond' pheromone trap for STLM |
Insect and Mite Management Overview
Insect and Mite Index
Southeastern Apple Production Mountain Horticultural Crops Research & Extension Center 455 Research Drive Mills River, NC 28759 Phone: 828.684.3562 ~ Fax: 828.684.8715 Email: jim_walgenbach@ncsu.edu |
Web Crafters: Anne S. Napier and
Steve Schoof |
Updated March 12, 2007