EUONYMUS SCALE
Unaspis
euonymi (Comstock), Diaspididae, HOMOPTERA Euonymus scale female armor is dark and oyster-shaped and 1/16 inch long. Mature males are tiny two-winged insects that emerge from their armor to mate with the females (Females do not leave the protective covering).
Eggs are tiny, yellow, oval and are only found beneath the mother's armor.
Young crawlers are yellow and very small before they secrete the protective scale covering (armour).
The armor of male nymphs is narrow (1/32 in. long) and white whereas the armor of female nymphs is dark and oyster shaped (up to 1/16 in. long). Males are usually more numerous than females, and with dense infestations, clusters of the white male armor on the leaves and twigs is noticeable from a distance.
Euonymus
scale is found throughout North Carolina wherever its host plants grow.
Euonymus scale is the most commonly reported insect pest of euonymus, pachysandra and celastrus in North Carolina.
Yellow spots first appear on the leaves. Leaves and stems may become encrusted with the scales to such an extent that whole branches or the entire plant may die.
This scale usually has two or three generations per year. The males emerge and mate with the females. The females lay eggs under their protective shell, and the tiny crawlers hatch and emerge from the mother's shell in April, May and June. They crawl along the leaves and stems before inserting their microscopic, threadlike mouthparts.
Another brood hatches in late summer, and a partial third brood may appear even later so that all stages of development are present during most of the year. Although this scale is small, infestations are often dense and plainly visible particularly with dense populations where males usually greatly outnumber female scales.
Euonymus
scale is difficult to control, but the removal of heavily infested branches
will help. Then spray the plant thoroughly. It will probably be necessary
to spray several times in one season for complete control. The first treatments
should be applied no earlier than mid-April. For best results, spray once
and wait two weeks and spray again.
Do not spray the tender new growth of euonymus, spray before bud break or wait until the new growth has hardened-off somewhat. Water the plant well before spraying or spray after adequate rainfall. If the shrub is under moisture stress, the pesticide (especially oils) may damage the foliage.
The lady beetle, Chilocorus
kuwanae, has been shown to be highly
effective in controling euonymus scale, but it difficult to find commercially
and has been hard to locate in natural settings in NC.
Also, give serious consideration to planting varieties of euonymous that are
less susceptible and even disposing of euonymus specimens that require heavy
maintenance for this pest. Auburn University indicates that spreading
euonymus, (Euonymus kiautschovicus), dwarf winged euonymus (Euonymus alatus 'Compactus'),
and winter creeper euonymus (Euonymus fortunei 'Acutus'), are more resistant
to this pest than other varieties. The University of Georgia
lists several less susceptible species .
Pesticide |
(Trade Name) |
Formulation |
|---|---|---|
| *malathion | 56% emulsifiable concentrate or 25% wettable powder |
|
| *horticultural oils | (various names) | 98 to 99% emulsifiable conc. |
acephate |
(Orthene) (*Orthene) |
75% soluble powder 9.4% emulsifiable concentrate |
| *carbaryl (some homeowner garden sprays also available) | (Sevin) | 50% wettable powder |
| cyfluthrin (*some homeowner garden sprays also available) | (Decathlon) |
20% wettable powder |
| dinotefuran | (Safari) |
* Suitable for home use.
Published by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
ENT/ort-15
July 1994 (Revised) Feb. 2001
Web page last reviewed January, 2008 by webperson.
