Detailed Methods for Controlling the Chinese Rice Grasshopper in Rice

Scientific name Oxya chinensis (Thunberg), belonging to the order Orthoptera, family Acrididae. It is distributed across the rice-growing regions of both northern and southern China.

Host plants include rice, wild rice stem (Zizania latifolia), and other grasses, as well as various plants in the Fabaceae, Convolvulaceae, Malvaceae, and Solanaceae families.

Damage characteristics: adults and nymphs feed on leaves, causing notches; in severe cases the entire leaf is eaten away, leaving only the veins.

Morphological features: adult male body length 15-33 mm, female 19-40 mm, yellow-green, brown-green, or green; the front margin of the forewing is green, the rest light brown; head is broad and large, oval; the vertex extends forward; the facial ridge is broad, with the two lateral margins nearly parallel and bearing a longitudinal groove. Compound eyes are oval; antennae are filiform; the posterior transverse sulcus of the pronotum is located behind the middle; the prosternal process is conical and slightly inclined backward; the wings extend beyond the end of the hind femur. The male's tail end is nearly conical; the supra-anal plate is short and triangular, smooth without lateral grooves, with an acute apex. On the female, the posterior lower corner of the lateral side of the 2nd-3rd abdominal tergites is spine-shaped, sometimes indistinct on the 3rd. The ovipositor valves are long, the upper and lower valves large, with fine teeth on the outer margin. The egg is about 3.5 mm long and 1 mm wide, oblong-cylindrical, slightly curved in the middle, dark yellow; the gelatinous egg pod is brown and envelops the eggs; the pod contains 10-100 eggs, mostly around 30, arranged obliquely in 2 longitudinal rows. Nymphs have 5-6 instars, occasionally 7. The 1st instar is gray-green, with a large head held high, no wing buds, and 13 antennal segments; the 2nd instar is green, with dark brown longitudinal stripes beginning to appear on the sides of the head and thorax, and 14-17 antennal segments; the 3rd instar is light green, with the dark brown longitudinal stripes on both sides of the head and thorax distinct and a pale median band along the dorsal midline obvious, 18-19 antennal segments, and wing buds slightly visible; the 4th instar has triangular wing buds not reaching the first abdominal segment, with 20-22 antennal segments; the final instar has wing buds extending beyond the 3rd abdominal segment, with 23-29 antennal segments.

Life habits: North of Zhejiang and Hunan there is 1 generation per year, and to the south 2 generations; in all areas it overwinters as egg pods in the soil at a depth of 1.5-4 cm in field ridges, waste flats, embankments, etc., or at the roots of weeds and among rice stubble. In Guangzhou, overwintering eggs hatch from late March to early April; in Nanchang, from early to mid-May; in Hanchuan, Hubei, from mid to late May; in Beijing, in early June; and in Gongzhuling, Jilin Province, from early to mid-July. In Guangzhou, emergence occurs in early to mid-June; in Nanchang, in early to mid-July; in Hanchuan, in mid to late July; in Beijing, in early to mid-August; and in Gongzhuling, emergence occurs in mid to late August. In two-generation areas, second-generation adults mostly emerge in September, roughly the same everywhere. Adult lifespan is 59-113 days, the pre-oviposition period is 25-65 days, the egg stage in one-generation areas is 6 months, in two-generation areas the first generation is 3-5 months and the second generation nearly 1 month, and the nymph stage is 42-55 days, up to 80 days in long cases. They prefer to emerge in the morning; mating begins 15-45 days after emergence, and they can mate many times in a lifetime; on stuffy hot nights they have the habit of flying to lights. Eggs are laid in pods underground, mostly on field ridges, with each female laying 1-3 pods. Newly hatched nymphs first feed on weeds, and after the 3rd instar they disperse to damage wild rice stem, rice, beans, and so on. Natural enemies include dragonflies, mantises, frogs, spiders, and birds.

Control methods: (1) Rice grasshoppers like to lay eggs on field ridges, field edges, and beside ditches. In heavily infested areas, organize labor to scrape and turn over the ridges to kill the grasshopper eggs, which has a clear effect. (2) Protecting frogs and toads can effectively suppress the occurrence of this insect. (3) Take advantage of the fact that before the 3rd instar the rice grasshoppers gather on field ridges, field edges, and beside ditches to feed on tender weed leaves, and carry out concentrated control; after entering the 3rd-4th instar they often move into the main fields, and when there are more than 10 insects per 100 plants, promptly spray 50% phoxim emulsifiable concentrate or 50% malathion emulsifiable concentrate or 20% fenvalerate emulsifiable concentrate, 2.5% cyhalothrin emulsifiable concentrate at 2000-3000 times dilution, 40% dimethoate emulsifiable concentrate at 1000 times dilution, or 2.5% beta-cypermethrin emulsifiable concentrate at 1000-2000 times dilution. All can achieve relatively good control results. (4) When a large-scale outbreak occurs, aerial control should be used.