Pest description and crop damage Euonymus scale females are dark, 0.0625 inch long, and mussel-shape. The males are narrow, elongative, and white. Crawlers are orange. Euonymus scale are found on both leaves and stems. Infested leaves develop yellow to white spots from scale feeding, and in severe cases significant defoliation can occur. Euonymus scale infests a wide range of ornamental genera that include Camellia, Buxus, Daphne, Hedera, Ilex, Jasminum, Ligustrum, Lonicera, Pachysandra, and Prunus.
Biology and life history The scale overwinters as fertilized females. Crawlers emerge in the spring from beneath the shells of the overwintering females. There may be two to three generations per year.
Evergreen euonymus (E. japonica) is extremely susceptible to scale infestations, as is spindle tree (E. europaeus). Plant resistant species. Euonymus alata (especially 'Compacta') and E. fortunei 'Acutus' are seldom infested. Several other species, including E. kiautschovicus, will tolerate scale feeding. Hand-wipe to help control small infestations, when practical. Prune out heavily infested branches. Apply Tanglefoot, "stickem," or a similar adhesive around infestations of adult scale to catch the crawler stage. As with aphids, avoid excessive nitrogen fertilizer, as this favors population increase.
Apply in May and again in June or July.
For more information
Johnson, W.T. and H.H. Lyon (1991), Insects That Feed on Trees and Shrubs, 2nd ed., Cornell University Press (p. 388).