Cottonwood Leafcurl Mite (Aculus lobulifera)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- The mite feeds on terminal foliage and stems, causing stunting; malformation of leaves, terminal tips, and buds; and loss of immature foliage. Heavy attacks can reduce growth and vigor of young Populus in nurseries and plantations.

Look For: Leaves missing on terminal shoot. Stunted crinkled leaves with red veins and purplish-green brittle blades; scaley, brown petioles. Minute four-legged straw-colored mites that resemble dust flecks on the leaves. Use a hand lens to see the mites.

Foliage damaged by cottonwood leafcurl mite Photo by Theodor D. Leininger, USDA Forest Service

Biology- Most leafcurl mites perish with leaf fall. However, some mites find hibernation shelters in bark crevices, branch scars, and at the base of infested trees. In spring, these mites leave their shelters, feed, and lay eggs on the new foliage. Large populations develop rapidly during hot, dry spells.

Monitoring- Inspect young nursery and plantation stock for mites from June to October. Treat if 5 percent of the stock becomes infested in nurseries. Consider control in plantations only if more than half of the trees are infested.

Control:

• Use frequent overhead irrigation in nurseries.
• Drench trees in infested area with a recommended miticide between June and October to kill adults. Apply a follow-up treatment within 2 weeks to control newly hatched mites.