The latest control measures of wheat scab

Wheat scab also known as wheat ear dry, rotten wheat head, red wheat head. It mainly causes seedling wither, ear rot, stem base rot and stalk rot, which can be suffered from seedling to heading. Among them, ear rot is the most serious.

Symptom classification

1. Seedling rot

It is caused by infection of seed bacteria or diseased bodies in soil. The buds turn brown first, then the root cap decays, the light ones are yellow and thin, the heavy ones die, and the dead seedlings produce pink mold (conidia and sporozoites) when the humidity is high.

2. Ear rot

When wheat blossoms, the slit produces water-soaked light brown spots on spikelets and glumes, gradually expands to the whole spikelets, and the spikelets are withered. When the humidity is high, pink colloidal mold layer is produced at the diseased spot. At the later stage, dense blue-black particles (ascocarp) were produced on it. Touch with hand, have protuberant feeling, cannot erase, grain shrivel and accompany white to pink mildew. After spikelet disease expands to cob axis, disease part withered brown, make damaged part above spikelet, form withered white ear.

3. Root rot

It can occur from seedling emergence to maturity. The basal tissue of wheat plant becomes brown and decays after being damaged, resulting in death of whole plant.

4. Stalk rot

Most of them occur in the first and second nodes under the ear. At the beginning, water-stained chlorotic spots appear on the leaf sheath, and then expand into light brown to reddish brown irregular spots or expand into the stem. When the disease is serious, it causes the disease to be more than yellow, sometimes unable to heading or take out yellow ears. When the climate is wet, pink mold layer can be seen in the diseased part.

induced pathogen

The disease is caused by a variety of Fusarium, mainly Fusarium graminearum, Fusarium avenae, Fusarium flavum, Fusarium moniliforme and Fusarium taxicum, all of which belong to the subphylum Semi-fungi. The dominant species is Fusarium graminearum, whose large conidia are sickle-shaped, with 3-7 septa, obtuse apex, obvious basal podocytes, colorless single spore, and pink sticky when aggregated together. Microspores are rarely produced. The sexual state is Gibberella zeae, which belongs to Ascomycetes. Ascocarp scattered or gathered on the surface of host tissue, slightly wrapped in the seed seat, pear-shaped, with an orifice, the top was verrucose, purple or purple blue to purple black. Ascospores are colorless, club-shaped, 100-250×15-150(μm) in size, containing 8 ascospores. Ascospores are colorless, spindle-shaped, obtuse at both ends, mostly 3 septa, 16-33×3-6(μm) in size.

Transmission routes and conditions

In the rice-wheat double cropping regions of central and southern China, the pathogen overwinters in the diseased plants of rice, maize and cotton, as well as in the diseased plants of rice, maize and cotton. Asthecium formed on these diseased bodies in the following year was the main source of infection. Ascospores mature at the flowering stage of wheat. Spread by air flow and wind and rain, splash on the withered anthers of flowers, germinate, first survive and then infect spikelets, and produce a large number of pink mold layers (conidia) after a few days. The infection rate was highest from flowering to full bloom. Conidiospores formed from ear rot had little effect on reinfection of the first wheat, but had a greater effect on infection of adjacent late wheat. The fungus can also spend summer and winter in infected seeds as mycelium.

In the wheat regions of northern and northeastern China, the pathogen can overwinter as mycelium or ascocarp on wheat plant residues, diseased seeds and other plant residues such as barnyardgrass, maize and polygonum sojae. In winter wheat area in north China, the mycelium overwinters on cob of wheat and maize in summer, and when the conditions are suitable in the next year, it produces ascocarp and emits ascospores for infection. Scab is mainly transmitted by wind and rain, and rain has a greater effect. In spring, when the temperature is above 7℃, the soil moisture content is greater than 50%, and the ascospores are formed when the temperature is higher than 12℃. Under rainfall or humid air conditions, ascospores mature and scatter on anthers, infecting spikelets through filaments. Late ripening, thick glume shell, fertilizer intolerance varieties more serious disease; field disease caused by large number of diseased bacteria; low-lying, poor drainage, sticky soil, partial application of nitrogen fertilizer, high density, field closed disease.

control methods

1. Selection of disease-resistant (resistant) varieties

Although there are no immune varieties, there are some resistant varieties with good agronomic characters, such as Sumai 3, Sumai 2, Xiangmai 1, Yangmai 4, Wanya 2, Yangmai 5, 158, Liaochun 4, Zaomai 5, Xingmai 17, Xinong 88, Xinong 881, Zhoumai 9-Aiyou 688, Xinbaofeng (7228) Mianmai 26, Wanmai 27, Wannian 2, Zhengyin 1, 2133, Ning 8026, Ning 8017, etc. Dingfeng 3 and Ningchun 24 are spring wheat varieties. All localities can choose according to local conditions.

2. Agricultural control

Reasonable irrigation and drainage, wetland to ditch drainage. After harvest, deep ploughing and stubble cleaning should be carried out to reduce the source of bacteria. Sow seeds at the right time and avoid rain during flowering. It is recommended to apply compost made of enzyme bacteria, adopt formula fertilization technology, apply fertilizer at right time, avoid partial application of nitrogen fertilizer, and improve plant disease resistance.

3. Soak seeds with lime water before sowing. See wheat smut for methods.

4. Chemical control

① seed dressing with yield-increasing bacteria. Every 6672 seeds are sprayed with 100- 150g of solid inoculant or 50ml of liquid inoculant, mixed evenly, dried and planted.

(2) Prevention of ear rot during flowering stage was the key point. spray 800 times solution of 50% carbendazim wettable powder or 1000 times solution of 60% carbendazim hydrochloride wettable powder, 1000 times solution of 505 methyl thiophanate-methyl wettable powder, 800-1000 times solution of 50% carbendazim wettable powder and 1000 times solution of 605 methylmefophanate-methyl wettable powder at initial flowering stage, and control once every 5-7 days. A motorized mist sprayer can also be used. In addition, in the middle and late growth stage of wheat, the control effect of chlorpyrifos 40% 30ml or 10% aprimicarb 10g plus 40% kuling 100g or 60% mildew-proof 70g plus potassium dihydrogen phosphate 150g or urea and probiotics 667m2 was excellent in the mixed area of scab, wheat aphid and armyworm.