1. Harmful symptoms
Citrus aphids are widely distributed in China, and occur in all planting areas, including orange aphids, cotton aphids, meadowsweets and orange dipters. Aphids often cluster on the young citrus shoots and young leaves to suck sap, after the young tissue is damaged, forming uneven wrinkles, causing the leaves to shrink and curl, severe young shoots wither, poor growth of new shoots of the tree body; its excreted honeydew often leads to soot disease, affecting fruit quality and yield.
Prevention and control programmes
(1) Agricultural control: prune the branches of the affected branches and the branches of insects and eggs in winter, especially the late autumn shoots of the victims, and reduce the population base of the overwintering insects. During the citrus growing season, each new shoot should be controlled consistently.
(2) Biological control: protection and utilization of natural enemies. Such as four-spotted ladybird, six-spotted ladybird, ten-spotted ladybird, red-shouldered ladybird, aphid-eating fly, aphid cocoon bee and jumping wasp.
(3) Chemical control: it can be jointly controlled with pests at the shoot stage such as pyllids and leafminer moths; 26% chlorofluoride cyanopyridine 1000 times, 30% thiamethoxazine 1500 times, 20% carnoprofen amine 2000 times, 22% thiacediasis • perchlorofluoride 1500 times for prevention.
3. Morphological characteristics
Adult aphids are small and soft. The wingless female aphid is 1.3 mm long, pitch black, reddish-brown with antennae, 6 antennae, gray-brown; winged female aphids are similar to wingless, with two pairs of wings, white and transparent; wingless males are similar to females, with dark brown and particularly enlarged hind feet. Wingless female adult aphids are 1.5–1.9 mm long, mostly dark green, brown or black in spring and yellow-green in summer; winged female adult aphids are 1.2–1.9 mm long, yellow, light green or dark green, and both wingless and winged bodies are covered with a thin layer of white wax powder, and the tail flakes are cyan and papillary. The wingless female aphid is 1.6–1.8 mm long and is all yellow, green, or yellowish green; the head is black with papillae on both sides of the body; the winged female aphid is 1.7 mm long and has a black head and thorax; the abdomen is yellow or yellow-green, with 1 pair of black spots on each side of the back of the second to fourth segment of the abdomen; if the aphid is bright yellow, the abdominal tube is short, and the abdomen is hypertrophied. Winged aphids have a more developed thorax and winged buds. The wingless parthenope aphid is 2.0 mm long, ovoid, black or black-brown, shiny, with wrinkled head, reticulated on the back of the chest, and a pronounced reticulate on the ventral surface; winged solitary female aphid is 1.8 mm long, long ovate, black-brown, shiny; antennae are 1.5 mm long; the midrib of the forewing is bifurcated; the nymph is 0.2-0.5 mm long, the wingless aphid is light brown or pale yellow, the winged aphid tan, and the wing buds are milky white.
Fourth, the law of occurrence
The high incidence of citrus aphids is from May to June and august to October, which are the most harmful periods for mixed aphid species. Orange aphids occur for more than 20 generations a year, overwintering on the branches with eggs, overwintering as adults in the south, and hatching into wingless aphids in March of the following year, and each wingless female can give birth to up to 68 aphids in a lifetime. Meadowsweets occur for more than 20 generations a year, overwintering with eggs in the cracks or buds of the host branches; the overwintering eggs begin to hatch in early March, with the first peak of reproduction in April and May, and the second peak in September and October. Cotton aphids occur 10 to 20 generations a year, up to 30 generations in the south, with eggs overwintering in the roots of dandelions and other weeds, and can also overwinter among the axillary of small shoots such as hibiscus; south of the Yangtze River, eggs and wingless adults and nymphs overwinter, and the first peak occurs in the spring shoot ticing period, and the second time is harmful to autumn shoots in August and September. Orange diptera also occurs in more than 20 generations a year, often in winter and spring.
5. Hazards
Causes wounds, curls leaves, leaves lose green, spreads the virus