White Peach Scale
Aculus ligustri (Keifer) Eriophyidae PROSTIGMATA


DESCRIPTION

Adult -The female scale is 1 to 2.25 mm in diameter, circular, convex, and thickened. It is white, yellowish white, or grayish white with a yellow or reddish spot (the cast skin of the nymph). The male adult scale is a small, two-winged insect that looks like a gnat but has two tail filaments.

Egg -The female egg is coral colored, and the male egg is pinkish white. The tiny eggs are found beneath the female scale.

Nymph -The female nymphal scale looks like the adult but is smaller and lacks the spot on the scale. The male nymph is elongate oval, white or dirty white, and about 1 mm long. Crowding and particular host plants can affect the shape and color of the scale considerably.


BIOLOGY

Distribution -The white peach scale is found throughout the southern part of the United States and as far north as Connecticut.

Host Plants -As its name implies, the white peach scale is a pest of peach. However, this insect feeds on many other plants of economic and ornamental value. Some of the most frequently infested ornamentals are chinaberry, flowering peach, French mulberry, and persimmon; but other hosts include catalpa, lilac, privet, and walnut.

Damage -The white peach scale feeds on the bark, fruit, or leaves of the host plant. Its feeding can cause stunting, leaf drop, and death of entire branches.

Life History -Overwintering as adult females, white peach scales become active in the spring and begin depositing eggs about April 1 in the Southeast. The insects continue laying eggs for approximately 30 days. Female eggs are produced before male eggs during the sequence of egg-laying. In 3 or 4 days, the eggs hatch into young nymphs or crawlers. Female crawlers are more active than their male counterparts. The crawlers settle and begin feeding within 2 days. The first nymphal stadium lasts 7 or 8 days. The second female nymphal stadium lasts about 12 days. The adult emerges after the second molt. Secondinstar male nymphs molt about 5 days after their first molt and then emerge from their scales in 7 or 8 days as adults. The emergence of the male scale and the final molt of the female scale coincide. After molting, male scales die within 24 hours. Fourteen to 16 days after mating, the females begin to lay eggs. At 25C, a generation is completed in 35 to 40 days. There are three generations per year in the Southeast. Because mortality of the first and second generations is high, the movement of the scale to other plants occurs mostly during the third generation in September and October.


CONTROL

Because the insect may be found on the undersurfaces of branches, it is important to treat all infested areas on the plant. For specific chemical controls, see the current state extension service recommendations.

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