Wheat Pest and Disease Control Methods and Key Technical Points
Spider Mites in Wheat [Distribution and Damage] There are mainly two species of spider mites in wheat, the winter grain mite [Penthaleus major (Duges)] and the brown wheat mite [Petrobia latens (Muller)]. The former belongs to the family Penthaleidae, order Acariformes, class Arachnida; the latter belongs to the family Tetranychidae. Both are distributed in wheat-growing regions across the country. In the north, the brown wheat mite predominates, while in the south...
Spider Mites in Wheat
[Distribution and Damage] There are mainly two species of spider mites in wheat, the winter grain mite [Penthaleus major (Duges)] and the brown wheat mite [Petrobia latens (Muller)]. The former belongs to the family Penthaleidae, order Acariformes, class Arachnida; the latter belongs to the family Tetranychidae. Both are distributed in wheat-growing regions across the country. In the north, the brown wheat mite predominates, while in the south, the winter grain mite predominates. The winter grain mite mainly damages wheat, followed by barley, peas, and weeds such as alfalfa and thistle, and is mainly found in wheat fields with low-lying terrain, high groundwater levels, heavy clay soil, and excessively dense plant stands. The brown wheat mite mainly occurs in dry wheat fields on high, dry terrain. In addition to damaging wheat and barley, it also damages crops such as cotton and soybean.
[Morphological Characteristics] The winter grain mite has an oval body, 0.65-0.98 mm long, with red spots on the dorsal surface, and 4 pairs of legs, with the first pair being the longest, the fourth pair next, and the second and third pairs equal in length. The brown wheat mite has a spindle-shaped body, 0.5 mm long, with a red central dorsal stripe and dark brown sides, and 4 pairs of legs, with the first pair being twice as long as the second and third pairs.
[Occurrence Pattern] The winter grain mite has 2-3 generations per year, overwintering as adults, nymphs, and eggs on wheat plants and weeds. Damage is severe from mid-to-late March to early April. Over-summering eggs begin damaging autumn seedlings in October. It prefers moist conditions and is mostly active before 8-9 AM and after 4-5 PM. The brown wheat mite has 3-4 generations per year, overwintering as adults and eggs. It enters its peak damage period from April to May. Over-summering eggs damage autumn seedlings in early-to-mid October. It prefers dry conditions and is active during the day, most actively from 3-4 PM. When rain or heavy dew occurs, it hides motionless in wheat clusters or soil crevices.
[Control Methods]
1. Agricultural measures: Use crop rotation, rational irrigation, and shallow plowing after wheat harvest to reduce pest sources.
2. Chemical control: First, seed treatment by mixing 100-200 mL of 75% 3911 emulsifiable concentrate with 5 kg of water and spraying onto 50 kg of wheat seed; second, field application by spraying with 40% dimethoate emulsifiable concentrate at 2000x dilution, or 40% dicofol emulsifiable concentrate at 1500x dilution, or 50% malathion emulsifiable concentrate at 2000x dilution.
Wheat Aphids
[Distribution and Damage] The main species of wheat aphids include the English grain aphid [Macrosiphum avenae (Fabricius)], the greenbug [Schizaphis graminum (Rondani)], and the bird cherry-oat aphid [Rhopalosiphum padi (Linnaeus)], all belonging to the family Aphididae, order Homoptera. They occur in wheat-growing regions across the country. They mainly damage wheat and other gramineous crops and weeds. Nymphs and adults often gather in large numbers on leaves, stems, and ears to suck sap. The damaged areas initially show small yellow spots, which later become streaks, causing wilting and the entire plant to wither and die.
[Morphological Characteristics] The greenbug has antennae shorter than the body length, cornicles extending beyond the tip of the abdomen, prominent frontal tubercles, and the forewing media vein of the winged form is 2-branched. The English grain aphid has antennae longer than the body length, cornicles extending beyond the tip of the abdomen, prominent frontal tubercles, and the forewing media vein of the winged form is 3-branched. The bird cherry-oat aphid has antennae shorter than the body length, cornicles not extending beyond the tip of the abdomen, and inconspicuous frontal tubercles. The forewing media vein of the winged form is 3-branched.
[Occurrence Pattern] In Henan Province, wheat aphids have 10-20 generations per year. In winter, wingless aphids hide in wheat root crowns or underground roots. After wheat turns green, they begin to reproduce and cause damage in large numbers. Under normal circumstances, wheat aphids often outbreak before winter in October or during February-March of the current year when conditions are warm and precipitation is low. Irrigated fields are generally less affected than dry fields, and wheat fields with fertile soil are generally less affected than fields with poor fertility.
[Control Methods]
1. Agricultural measures: First, select aphid-resistant and high-yielding varieties; second, harrow and press in early spring and clear weeds along field edges.
2. Chemical control: First, seed treatment, which in yellow dwarf disease epidemic areas can achieve both disease prevention and pest control; see yellow dwarf disease control for methods. Second, field application: spray with 50% pirimicarb wettable powder at 5-7 grams per 666.7 sq m, or 40% dimethoate or omethoate emulsifiable concentrate at 50 mL, or 90% methomyl powder at 8-10 grams, or 25% bingchongling emulsifiable concentrate at 50 mL, or 50% phoxim emulsifiable concentrate at 50 mL, or 2.5% deltamethrin emulsifiable concentrate at 10-15 mL, diluted in 50-60 kg of water. Among these, pirimicarb has good control efficacy and does not harm natural enemies, so it can be given priority.