7/2/2013 - By Harrell's

Matt Shultz, Harrell's Horticulture Technical Specialist says, 'Be on the look out.... Cottony Maple Scale is starting to release crawlers in the Mid Atlantic region this week.' Matt provides the following photos. 

Cottony Maple Scale 3rd instar overwintering stage2

Cottony Maple Scale 3rd instar overwintering females

Cottony Maple Scale 3rd instar overwintering stage 2

Cottony Cushion Crawler Mass

According to Stanton Gill, Extension Specialist, IPM and Entomology for Nurseries and Greenhouses at the Central Maryland Research and Education Center University of Maryland Extension, "Trees infested by cottony maple scale are maple, dogwood, boxelder, honeylocust, linden, poplar, basswood and elm and many others. 

Overwintering females complete development in June and lay eggs through late summer. Each cottony white egg mass contains 1,000 to 1,500 eggs. Eggs hatch into crawlers in late June through July. The crawlers are flat, oval, brown insects with two distinct eyes, short antennae, tiny legs and are microscopic, or about the size of a period on this page. They migrate to the underside of leaves and insert their piercing-sucking mouthparts along the midrib and then withdraw sap from the tree’s vascular cells. They spend the remainder of the summer feeding on leaves. Males mature in late summer, emerge as tiny, winged gnatlike insects, mate with immature females and then die. Just before leaf drop, mated females move back to the branches and twigs and reinsert their mouthparts for overwintering. There is one generation a year. 

The insect feeding causes twig dieback. Severe infestations can kill major limbs and occasionally the entire tree, especially if the tree is stressed (drought)." 

Both Matt and Gill recommend the following control measures: 

Distance, Acephate, Talus, or Oils right now and then start applying systemics in 2-3 weeks, products such as Tristar, Safari, and Imidacloprid.