Cottony Maple Scale

Taxonomy

Kingdom:

Animalia

Phylum:

Arthropoda

Class:

Hexapoda (including Insecta)

Order:

Hemiptera

Family:

Coccidae

Genus:

Pulvinaria

Species:

P. innumerabilis

Subspecies:

P. innumerabilis

Scientific Name

Pulvinaria innumerabilis
(Rathvon)

Common Names

cottony maple scale

Compiled by Whitney Cranshaw, Colorado State University:

COTTONY MAPLE SCALE

Pulvinaria innumerabilis (Rathvon)

Homoptera: Coccidae

Hosts:

Silver maple, honeylocust, hackberry, linden and other hardwoods.

Damage and Diagnosis:

Cottony maple scale is one of the largest and the most conspicuous scale insect that occurs in the region. Adult females may swell to over 1/4 inch diameter when producing a large cottony egg sack. Adults and nymphs feed on plant sap of twigs and leaves, respectively. Sustained outbreaks can reduce plant vigor and even cause dieback. However, natural controls are abundant for this species and outbreaks are usually terminated following a single season.

Cottony maple scale also excretes honeydew as it feeds. When high populations are present this can allow sooty mold to grow on trunks and branches and may attract nuisance wasps and bees.

Life History and Habits:

Cottony maple scale adults.

The cottony maple scale spends the winter as adult, mated females on twigs and branches. During winter they appear as small, indistinguished dark lumps but begin to grow rapidly when they resume feeding in spring. A very large, wax-covered egg sack is ultimately produced by late spring, somewhat of the appearance of a marshmallow, and may contain over a thousand eggs. Eggs hatch from late June through July and the newly hatched crawlers settle on the undersides of leaves, usually near the midrib. During this leaf-feeding stage the nymphs are flattened with oval form and nearly translucent.

Nymphs feed on leaves until late summer, migrating to twigs and small branches before leaves drop. They then molt for the last time, after which the females remain in place for the rest of their lives. Males are produced at this time which are mobile and mate with the females, dying afterwards. There is one generation per year.

Management:

Abundant natural controls appear to be able to control cottony maple scale in most locations. Several parasitic wasps, predatory plant bugs (Dereaocoris nebulosus) and other general predators are particularly important. As the result of these biological controls infestations of cottony maple scale typically are short lived even without applied controls.

Oil sprays applied during the dormant season can help control overwintering cottony maple scale; mid-summer foliar oil applications can control stages on leaves. Crawler sprays should be first applied during mid to late June and may need reapplication because of the extended egg hatch period. Systemic applications of imidacloprid should be effective against summer stages that occur on leaves.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.