Cottony Maple Scale

Pulvinaria innumerabilis

Cottony maple scale, Pulvinaria innumerabilis, is a soft scale insect that attacks a large variety of woody plants. Its favored host is maple trees, although it has been found on a number of other species as well. 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, and can become a nuisance as it coats patios, decks, and vehicles.

Download Cottony Maple Scale Fact Sheet

Treatment Strategy

Cottony maple scale will not harm the tree in small numbers. However, in large numbers large amounts of sap will be sucked from the tree. This weakens the tree and causes dieback of branches, making it more susceptible to additional insect or disease issues.

Cottony maple scale is easily treated with soil-applied products such as Xytect and Transtect. Both are systemic products that are applied to the soil at the base of the tree and are taken up by the root system, to work from the inside of the plant. A contact insecticide such as Up-Star® Gold can be sprayed on the scales, but this is rarely done as the timing must coincide with egg hatch and crawler emergence to be effective. Improperly timed applications will come into contact with only the waxy shell created by maturing scales and will provide little control.

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Cottony Maple Scale Treatment Option 1

Transtect is applied to the soil in the late spring or early summer and will provide a quick knockdown (within 2 weeks). It has a residual of at least 90 days, so one application will control scale feeding for the season.

Application Type - Soil drench

DIY Product/Equipment Needed:

• Transtect

Soil Drench Kit

• Measuring or diameter tape

• Bucket or watering can

• Gloves

Cottony Maple Scale Treatment Option 2

Xytect is applied to the soil and has a long residual (1 year), however it usually will take 30 – 60 days for the product to reach the leaves. Professional arborists will often apply Xytect in the fall of the year for control the whole next season. Early spring application is also very effective.

Application Type - Soil drench

DIY Product/Equipment Needed:

• Xytect

• Soil Drench Kit

• Measuring or diameter tape

• Bucket or watering can

• Gloves

Cottony Maple Scale Treatment Option 3

Up-Star® Gold – Spray products such as Up-Star® Gold are not used very often anymore for larger trees due to issues with drift and contact with beneficial insects. But smaller plants can be treated easily with a hand sprayer. These products typically have a residual of 10 – 14 days, so applications should be done in the early summer, and again if necessary.

Application Type - Foliar spray

DIY Product/Equipment Needed:

 • Up-Star® Gold

• Hand pump sprayer with wand

• Gloves

• Safety glasses

Cottony Maple Scale DIY Kit

Option 1

Application Type Soil drench

DIY Product/Equipment Needed:

• Transtect

• Soil Drench Kit

• Measuring or diameter tape

• Bucket or watering can

• Gloves

Option 2

Application Type Soil drench

DIY Product/Equipment Needed:

• Xytect

• Soil Drench Kit

• Measuring or diameter tape

• Bucket or watering can

• Gloves

Option 3

Application Type Foliar spray

DIY Product/Equipment Needed:

 • Up-Star® Gold

• Hand pump sprayer with wand

• Gloves

• Safety glasses

How Is It Spread?

Cottony maple scale has one generation per year. Emerging in the early spring, adults mate and then lay eggs. In early summer eggs hatch and young scales migrate towards the leaves for feeding. Attached to the leaf and immobile, crawlers mature by the end of summer.

Susceptible Trees

Silver maple, red maple, boxelder, alder, hackberry, dogwood, hawthorn, beech, osage orange, apple, mulberry, sycamore, poplar, peach, plum, pear, oak, black locust, willow, linden and elm

Symptoms

• Small white cottony looking balls attached to branches about ¼ – 1/2 of an inch diameter.

• Looks like popcorn strung along the twigs.

• Stunted, yellowing leaves leading to premature leaf drop and dieback.

Lookalikes

None

Related/Similar Problems

Drought

Timing

Fall or Spring, Summer

Urgency

Moderate

Risk of Spreading

High

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