What are the common pests of rice? Main species and identification methods

During rice cultivation, many pests are often encountered; they feed on the roots and stems of the plants, harming the growth and development of the plants. What are the common pests of rice? How should they be controlled?

Common rice pests and their control

1. Rice leaf roller

(1) Introduction: The rice leaf roller, commonly known as the leaf-rolling worm, leaf-bud worm, or white-leaf worm, is a major rice pest that occurs frequently in rice-growing regions of our country. It generally reduces rice yield by 10-20%, and in severe cases by more than 50%, or even causes total crop loss.

The adult rice leaf roller is a small yellow moth, 8 mm long, with black stripes on its wings. The larva is a pale green, elongated, fleshy worm. The larva spins silk to roll rice leaves longitudinally into a leaf tube, hiding inside the tube to eat the leaf mesophyll, causing the leaf tube to turn dead white. When outbreaks occur, the rice field turns a dead white, causing great losses. Rice leaf roller larvae move nimbly; when disturbed, they immediately shrink back or drop to the ground.

(2) Control methods: Strengthen fertilizer and water management, and fertilize reasonably; carry out biological control by using Trichogramma dendrolimi and Trichogramma australicum during the peak moth emergence period, and apply pesticides at the right time, 5-7 days after the moth peak day or at the peak of the 2nd-instar larvae. Commonly used agents include: abamectin, and a compound of abamectin and hexaflumuron, 2.8% abamectin + 3% hexaflumuron (Jinbiao). The best application times are morning and evening; on cloudy days it can be applied all day. If applied in light rain, the pesticide concentration should be increased.

2. Rice planthopper

(1) Introduction: The main species occurring in rice fields are the white-backed planthopper and the brown planthopper. Generally, the white-backed planthopper dominates in the early stage of rice, and the brown planthopper dominates in the later stage. That is, the white-backed planthopper mainly damages from tillering to jointing stage.

In affected fields, rice leaves turn yellow and tillering decreases; in severe cases, rice plants collapse in patches and “lodging pond” die. The brown planthopper mainly damages from booting to maturity stage; when the damage is severe, the base of the rice clump turns dark brown and gradually the whole plant dies. Affected fields often show “yellow pond”; in severe cases the whole field turns yellow and withered, as if burned by fire.

(2) Control methods: Reasonable close planting, and attention to the rational use of nitrogen, phosphorus, and potassium fertilizers. The agents used include: at the beginning of the peak period of young nymphs, choose 25% buprofezin wettable powder at 25-30 g per mu, mixed with 50-60 kg of water for spraying; or use 10% MIPC wettable powder at 200-250 g per mu, or 25% metolcarb wettable powder at 100-150 g per mu, or 40% omethoate emulsifiable concentrate at 100-150 g per mu, mixed with 50-60 kg of water and sprayed evenly.

3. Stem borers

(1) Introduction: Stem borers include the greater wax moth, the striped stem borer, and the yellow stem borer, 3 species. They overwinter as mature larvae in rice stubble. All 3 species bore into rice as larvae to feed. At different growth stages of rice, damaged plants can form dead hearts, dead sheaths, injured plants, dead booting ears, and white ears. The larvae of the greater wax moth are reddish brown; the larvae of the striped stem borer are dark brown with 5 longitudinal lines on the back; the larvae of the yellow stem borer are pale yellow-green.

(2) Control methods: After rice harvest, pick out the rice straw and keep it away from the rice field, and expose it to the sun for several days to kill the borers inside the straw. For pesticide use, per mu use 25% dimehypo aqueous solution 200-250 ml, 80% monosultap powder 35-40 g, 90% crystal trichlorfon 100-200 g, 40% dimethoate emulsifiable concentrate 100 g, 20% triazophos emulsifiable concentrate 100 ml, 5% fipronil gel suspension 30 ml, etc. Choose any one and add 50-60 kg of water for spraying. Alternatively, use 25% dimehypo aqueous solution 200-250 ml or 5% dimehypo granules 1-1.5 kg; choose either one and mix with 20 kg of moist fine soil to make medicated soil, spread it in the rice field, and maintain a shallow water layer of 3-5 cm for 3-5 days.

4. Rice thrips

(1) Introduction: Commonly known as gray worms. Adults and nymphs use their mouthparts to rasp the leaf surface, forming fine yellowish-white spots. Both sides of the leaf tip curl inward, gradually causing the whole leaf to curl, shrink, and turn yellow. In rice fields severely affected at the early tillering stage, seedlings do not grow, roots do not develop, there is no tillering, and they may even die in clumps.

(2) Control methods: In winter and spring, in conjunction with compost collection, remove weeds along field edges and ditches, and clear dead branches and fallen leaves beside field ridges and plots.

Apply pesticide during the peak hatching period. Commonly used agents include: per mu use 40% omethoate emulsifiable concentrate 100 ml, or 50% phoxim emulsifiable concentrate 100 ml, mixed with 50-60 kg of water for spraying; or per mu use 70% imidacloprid water-dispersible granules 0.5-1 g, mixed with 15-30 kg of water for spraying. In the seedling field stage, 3% carbofuran granules can also be applied at 2.5 kg per mu, or the seedling tips can be soaked in 40% omethoate emulsifiable concentrate 1000-fold solution after pulling the seedlings, and transplanted immediately after soaking.

5. Rice stem maggot

(1) Introduction: Also known as the rice stem fly. The rice stem maggot larvae bore into the rice stem to damage the heart leaf, growing point, and young ear of rice.

(2) Control methods: For pesticide use, the peak adult emergence period and peak egg hatching period are the suitable control times, or apply pesticide when there are 3-4 insects per square meter in the seedling field or 1-2 insects per hundred clumps of rice in the main field. Per mu use 90% crystal trichlorfon 100-200 g, 50% fenitrothion emulsifiable concentrate 100 g, 10% imidacloprid wettable powder 10-20 g, 80% dichlorvos emulsifiable concentrate 50 g, 40% dimethoate emulsifiable concentrate 50 g; choose any one and mix with 50-60 kg of water for spraying.

6. Chinese rice locust

(1) Introduction: The adults and nymphs of the rice locust bite leaves into notches, and in severe cases eat the leaves completely. In the later growth stage of rice, the rice locust also bites off rice ears and feeds on grains.

(2) Control methods: Clear ditches and remove weeds, and protect natural enemies of the rice locust such as frogs, spiders, dragonflies, and mantises. For pesticide use, before the locust nymphs reach the 3rd instar, carry out concentrated pesticide application on field ridges, field edges, and beside ditches. After the rice locust enters the rice field, when there are more than 10 rice locusts per hundred rice plants, spray pesticide from the middle of the rice field outward on a clear morning or after 4 p.m. for better effect. Per mu use 90% crystal trichlorfon 100-200 g, 80% dichlorvos emulsifiable concentrate 50-80 g, 40% dimethoate emulsifiable concentrate 30-40 g, 40% phoxim emulsifiable concentrate 40 g, etc.; choose any one and mix with 50-60 kg of water for spraying.

7. Rice skipper

(1) Introduction: Also known as the rice skipper butterfly. The larva is 2-3 cm long, with a pale brownish-yellow head and a “w”-shaped brown mark in the center front of the head. The body is yellow-green, with a dark green line on the back. The larva spins silk to bind several rice leaves together, forming a cylindrical, longitudinally rolled leaf tube, and hides inside the tube to feed and cause damage.

(2) Control methods: In winter and spring, remove weeds along field edges and ditches; when the occurrence is not heavy, manually pick off the leaf tubes to eliminate the larvae. The use of highly toxic pesticides is prohibited, and natural enemies such as parasitic wasps and true bugs should be protected. For pesticide use, when there are 10-15 insects per hundred clumps of rice, apply pesticide at the young larval stage. Per mu use 90% crystal trichlorfon 100 g + washing powder 25 g, 50% fenitrothion emulsifiable concentrate 125 ml, 80% dichlorvos emulsifiable concentrate 75-100 ml; choose any one and mix with 50-60 kg of water for spraying.

8. Rice leaf beetle

(1) Introduction: Commonly known as the dung-carrying worm, pig-dung worm, or red-headed worm. Adults and larvae feed on the mesophyll of rice leaves, causing white stripes to form on the leaves. When the insect population is large, only a transparent epidermis remains on the leaves, and the whole leaf turns white, withered, and scorched; in severe cases the whole plant dies.

(2) Control methods: In winter, remove weeds along field edges, ditches, and other places to eliminate overwintering sources of the insect. Rice fields in mountainous areas are severely affected, so pesticide control should be strengthened. At the 1st-2nd instar larval stage, per mu use 90% crystal trichlorfon 100-200 g, 25% quinalphos emulsifiable concentrate 25-30 g, 40% phoxim emulsifiable concentrate 40 g per mu, 80% dichlorvos emulsifiable concentrate 50-80 ml per mu, etc.; choose any one and mix with 50-60 kg of water for spraying. If the insect population is large, apply again about 10 days after the first application.

The above is a basic introduction to the insect pests that rice may encounter, for reference only, and I hope it is helpful to everyone.