The cottony maple scale, Pulvinaria innumerabilis, is one of the largest and most conspicuous scale insects in this country.  Its favored host is maple trees, although it has been found on a number of other species as well.  Females are inconspicuous and overwinter on twigs, and in the spring they rapidly grow and produce their characteristic white egg sac. 

Damage comes from crawlers that appear in June and July when they migrate to the undersides of leaves, insert their mouthparts in or near the veins, and withdraw sap from the plant.  Heavy infestations may kill weakened trees and cause branch dieback in healthy trees. 

Large amounts of honeydew are produced which eventually cause the leaves to be covered with grayish/black colored sooty mold.  The sooty mold reduces the aesthetic features of maples and honeydew can become a nuisance as it coats patios, decks, and vehicles.

Susceptible Hosts
Silver maple – preferred host (Acer saccharinum), red maple (A. rubrum), boxelder  (A. negundo), Alder (Alnus), Hackberry (Celtis), Dogwood (Cornus), Hawthorn (Crataegus), Beech (Fagus), Osage orange (Maclura pomifera), Apple (Malus), Mulberry (Morus), Sycamore (Platanus), Poplar (Populus), Peach, plum (Prunus), Pear (Pyrus), Oak (Quercus), Black locust (Robinia pseudoacacia), Willow (Salix), Linden (Tilia), Elm (Ulmus)

Pest
Pulvinaria innumerabilis

Symptoms
* Cottony maple scale can produce large amounts of honeydew which can eventually be covered with sooty mold
* Premature loss of foliage may occur with heavy infestations
* Branch dieback may occur with heavy infestations

Signs
* Mature females can be found on undersides of leaves near veins, and may reach 5mm in length
* Mature females look like popcorn strung along the twigs.  White egg sacs may be ¼” to 1/2” in length and are visible in late spring to early summer

Life Cycle
* Females grow rapidly in spring and produce hundreds of eggs
* Adults emerge and mate as the leaves begin expansion in the spring
* Eggs hatch in early summer and young scales migrate to the leaves
* Scales mature in late summer
* One generation per year

Distinguish from Look-alikes
* The cottony maple scale may be most likely confused with the cottony maple leaf scale which it resembles.  The cottony maple leaf scale produces its egg sacs on the leaves, not the twigs.

Females grow rapidly in spring and produce hundreds of eggs. Eggs hatch in early summer and young scales migrate to the leaves.  Xytect and Transtect soil applications must be timed to ensure high titer levels are within the tree at the time of the first generation crawler hatch and feeding. 

Arborists should use foliar sprays for immediate activity against crawlers or for management of overwintering females on twigs with dormant sprays.

Expectations:
Xytect and Transtect will provide a high level of control of all soft scales.  Arborists should use foliar sprays for immediate activity against crawlers or for management of overwintering females on twigs with dormant sprays.  Properly timed soil applications of Xytect or Safari will work extremely well for most soft scales.
Females grow rapidly in spring and produce hundreds of eggs. Eggs hatch in early summer and young scales migrate to the leaves. 

Scales mature in late summer and after mating females return to twigs and branches for the winter making dormant oil applications a good option, especially if soil applications of Xytect or Transtect have not been previously applied.

Other Treatment Practices:
Promote health and vigor with proper irrigation, mulching, proper pruning and prescription based fertilization practices.

Ohio State University