Azalea (Rhododendron)-Azalea leafminer

Caloptilia azaleella

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Pest description and crop damage The adult insect is a golden yellow moth about 0.5 inch long. The larvae are small, pale yellow to green caterpillars, 0.125 to 0.25 inch long. The larvae mine leaves during the early part of their development. During later stages of their development, they are also responsible for rolling leaves and chewing holes in them.

Biology and life history The insect overwinters as a pupa in rolled leaves, or possibly as a larva in a mined leaf. After the adult moth emerges, eggs are laid singly on the underside of leaves. The larvae emerge and mine into the leaf, causing the mined tissue to turn brown. Then they emerge from the leaf and roll it over their bodies with silk to feed. Later, they select an undamaged leaf, roll it up, and pupate in it. The adult moth emerges about a week later. There may be two to three generations per year.

Scouting and thresholds Observe new early-spring growth for rolled leaves and feeding damage.

Management-biological control

Very low temperatures in winter significantly reduce overwintering populations. Spiders and parasitic/predatory insects greatly reduce populations throughout the year.

Management-cultural control

Hand-pick larvae if found. Removal of overwintering sites, such as rolled leaves on the ground or plastered to plants, can reduce next year's population.

Management-chemical control

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Apply first just after blooming. Apply again at 2 to 3 week intervals until control is complete. Applications in late summer and early fall have given exceptional cleanup for the following season.

For more information

Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 202).