What are the main species of scale insects that harm Michelia alba and what are the control methods?

The mainscale insectsthat harm Michelia alba are mainly the chaff scale (Parlatoria pergandii), the Japanese wax scale (Ceroplastes japonicus), and the ivy round scale (Aspidiotus nerii). Their adults and nymphs gather on the undersides of leaves and on branches, piercing and sucking sap, causing leaves to turn yellow and wilt, sometimes accompanied by sooty mold, affecting the plant's normal growth and reducing its ornamental value.

(1) Chaff scale: also known as chaff shield scale or gray spot scale, named for its grayish-white scale covering that resembles a flake of chaff. The female adult is nearly pear-shaped or oval, light purple with a slight yellow tinge, about 0.8 mm long; the female scale is oblong, about 1.5-2 mm long, with a white, grayish-white or light brown wax layer, slightly raised in the middle and sloping at the outer edge. The male adult is light purple, with 1 pair of wings and 3 pairs of legs, and a needle-like copulatory organ at the end of the abdomen; the male scale is slender, grayish-white, with nearly parallel sides. Newly hatched nymphs are flat, oval, light purplish-red, with no wax on the body surface. The chaff scale is widely distributed in northern regions, generally producing 2-3 generations per year, overwintering as fertilized female adults or as eggs under the scale on branches and leaves, with the first-generation nymphs emerging successively in late April of the following year. The chaff scale has a wide range of hosts and is harmful to jasmine, Michelia figo, camellia, and others.

(2) Japanese wax scale: also known as the Japanese wax scale insect. It is widely distributed in East China and North China, and causes considerable damage to Michelia alba, camellia, Michelia figo, and Gardenia jasminoides. The female of the Japanese wax scale is oval and light brown; the scale is white or grayish-white, about 4 mm long, with a tortoiseshell-like depression on the surface, raised in the center, and surrounded by 8 rough protrusions. The male adult is long oval, brown, about 1 mm long, with a pair of membranous, semi-transparent white wings. The development of the Japanese wax scale goes through 4 stages: egg, nymph, pupa, and adult. Newly hatched nymphs are flat, oval, light yellow, and 0.5 mm long.

The Japanese wax scale generally produces 1 generation per year, overwintering as fertilized female adults on branches and leaves, with the peak hatching period from mid-June to mid-July of the following year.