Japanese Maple Scale Diagnostic Guide
Japanese maple scale (Lopholeucaspis japonica) is a challenging scale to manage. In the United States, it was first found on the east coast, but is rapidly expanding its range. Japanese maple scales small size, ability to blend in, and long crawler emergence period make it difficult to control. It is a pest primarily of nurseries and is often on hollies. Holly’s tight shrub-like habit makes sprays difficult to accomplish properly.
Trees at Risk
Many – maples, service berry, camellia, hawthorn, red bud, yellowwood, dogwoods, cotoneaster, euonymous, ash, locust, holly, sweetspires, privet, magnolia, crabapples, plum, pyracantha, pears, willow, stewartia, styrax, olives, lindens, elms, zelkova and others.
Signs of Damage
- Branch dieback.
- White, waxy coverings are visible on trunks and limbs.
- Waxy scales are about 1 mm in length.
- Immature scales and eggs are purplish.
- Females are white when wax-covered, dark brown when not.
- Eggs are laid in April/May.
- Crawlers emerge in May/August (806 GDD – 33037 GDD).
- Peak first generation is 1144 GDD, second generation peak is 3037 GDD.
- Within hours the crawlers settle down and create covers.
- Overwintering occurs as mated females.
This is a challenging scale to control. Japanese maple scale’s crawler emergence takes place over several months, making application timing a challenge. Sprayed insecticides may have to be applied as many as three times to get good control. Soil applied options make timing less challenging, but may not provide as effective a control as sprayed applications. It is likely that a combination of the two practices will provide the best results. Do not over fertilize, as it can lead to increased scale populations. Often the scales reside inside of foliage, such as in holly. Maintain close monitoring to detect the scale as soon as possible.
Foliar Spray using RTSA Horticultural Oil
Dosage: 1 - 2.5 oz/gal water Timing: After leaf drop but before bud break. See peak GDD under Biology. Re-Treatment: As neededRTSA Horticultural Oil$39.00
Foliar Spray using Transtect
Dosage: 1.7 oz/100 gal water Timing: Apply as crawlers emerge in May/June Re-Treatment: AnnuallyTranstect$326.00
A Diagnostic Guide is designed to help you identify a pest issue and management solutions. Always refer to product label for all rates and approved uses. Some images courtesy forestryimages.org. Use of the images does not imply endorsement of treatments by forestryimages.org