Main Species of Scale Insects on White Orchid Tree and Their Control Methods

The scale insects that mainly harm the white orchid tree are the chaff scale, the Japanese wax scale, and the ivy round scale, among others. 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 normal growth of the plant and reducing its ornamental value.

(1) Chaff scale: also known as the chaff shield scale and gray dot scale, named for its grayish-white scale covering that resembles a chaff flake. The female adult is nearly pear-shaped or oval, pale purple with a slight yellow tinge, about 0.8 mm long; the female scale covering 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 pale 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 covering is slender and grayish-white, with nearly parallel sides. Newly hatched nymphs are flat, oval, pale 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 mated female adults or as eggs under the scale covering on branches and leaves, with the first-generation nymphs emerging successively in late April of the second year. The chaff scale has a wide range of hosts and harms jasmine, banana shrub, camellia, and others.

(2) Japanese wax scale: also known as the Japanese scale. It is widely distributed in East China and North China and causes considerable harm to white orchid trees, camellias, banana shrubs, gardenias, and others. The female of the Japanese wax scale is oval and light brown; the scale covering 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, translucent white wings. The development of the Japanese wax scale goes through 4 stages: egg, nymph, pupa, and adult. Newly hatched nymphs are flat, oval, pale yellow, and 0.5 mm long.

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