According to today, Henan Provincial Plant Protection Station invited the Provincial Meteorological Bureau, the Provincial Academy of Agricultural Sciences, Henan Agricultural University and other units of experts and city and county monitoring and reporting technicians to hold a meeting on the occurrence trend of wheat scab, according to the current comprehensive analysis of the development of field fungus, climate trend, field microclimate, wheat growth period, disease resistance of the main varieties, combined with the national trend forecast and the results of Henan Provincial Consultation, it is predicted that wheat scab in Huanghuai wheat area will occur more seriously, and the risk of pandemic is extremely high, mainly in mid-late maturing semi-winter wheat.
The main forecast basis
1. The source of bacteria in the field is sufficient. The corn planting area in Huanghuai wheat area is large, the straw returning is generally implemented, the amount of straw residue in the field is large, the survey in late February, the amount of corn root stubble is 0.2/m2, close to last year and the perennial; the three rainfall in March is large, so that the field humidity in the area continues to be larger, the temperature is higher, which is conducive to the development of gibberella pathogen. According to a recent survey by the agricultural technology and plant protection department, the rate of corn root stubble was 15.1% on March 29, 30 times that of March 20, 12 times that of March 25, and 22.4% higher than the average of the past seven years.
2、 According to the forecast of Henan Provincial Climate Center and Municipal Meteorological Observatory, the precipitation in April is 60-80mm, more than 0-2 percent, the temperature is 16.5-17.5 °C, 0~1 °C higher, there are 5 precipitation processes: light to moderate rain on the 1st-3rd, light rain on the 8th-9th, light to moderate rain on the 16th-17th, light to moderate rain on the 20th-22nd, light to moderate rain on the 25th-26th, and light to moderate rain on the 16th-17th, light rain on the 20th-22nd, and light to moderate rain on the 25th-26th coincided with the flowering period of wheat. High temperature and rain in April, rain during flowering period, is very beneficial to the infection of scab, precipitation in May is more than 0-2 percent, the temperature is higher 0~1 °C, and the climatic conditions in April and May are very favorable to the occurrence and development of wheat scab.
3. The heading and flowering period of wheat was basically consistent with rainfall and spore release. According to the observation of wheat growth period, the current wheat is mostly in the 3-4 elongation period, and the growth period is 3-5 days later than that in recent years, close to the normal year, and it is predicted that the flowering period of weak spring wheat is mostly in April 8-14, and the flowering period of semi-winter wheat is mostly in April 14-20, which can last until April 25. In late March, the climate of our county is warm and humid, the ascomycetes of the scab fungus develop rapidly, a large number of ascomycetes are formed, under the conditions of temperature of 15-25 °C and soil moisture of more than 60%, ascomycetes are formed in 2-3 days, and the ascomycetes can be matured and released after about 15 days, and the spore release period is predicted to be on April 12-25. The flowering period of semi-winter wheat coincided with the release of pathogen spores and the rainfall in mid to late April.
4. The main cultivars have poor resistance to scab. At present, the wheat seedling condition is generally good, the main wheat varieties are mainly susceptible and high-susceptible, the high-susceptible varieties account for about 90%, the resistance to scab is poor, the semi-winter varieties account for about 70%, and the area of suitable wheat is large.
The main symptoms of scab
Wheat scab is also known as red miasma, rotten wheat and so on. The seedling rot buds turn brown, and then the root crown gradually rots, which leads to the yellowing and thinning of the stems and leaves of the wheat seedlings, which can lead to the death of the wheat seedlings in severe cases, and the pink mold will appear on the dead seedlings when the humidity is high. The base of the wheat plant is infected and turns brown and occurs at the base of the neck, first on the leaf sheath there is a water-stained green spot, and then expands into a light brown to reddish-brown irregular spot, and expands to the stem, when the disease is serious, it can cause the plant to be yellow above the diseased part, so that the wheat can not be tasseled or withdrawn from the yellow ear, when the humidity is high, the pink mold layer can be seen on the surface of the diseased part. Wheat flowering stage infection will cause panicle rot, grain filling stage manifestation, maturity stage disaster, usually by the spikelet on the wheat ear first disease, and then rapidly expand to the cob, and then make the upper part of the other spikelets quickly lose water and die, in the later stage of the disease in the base of the spikelet appeared pink colloidal mold layer, the affected part and above the spikelet grains are shriveled, forming a withered white spike.
Conditions and causes of scab
Rainfall during the flowering period of wheat, excessive application of nitrogen fertilizer, overly dense growth of wheat, poor ventilation, etc., will cause high humidity in the field, which is conducive to the occurrence of scab. In the field where the previous crop is maize and the surrounding fields have the accumulation of pathogens when the straw is returned to the field, the probability of scab is also greater. In spring, when the temperature is above 7 °C, the soil moisture content is greater than 50% to form ascospores, and the temperature is higher than 12 °C to form ascospores, and the ascospores are mature and scattered on the anthers, and the spikelets are infected by filaments.
Patterns of occurrence
The pathogenic bacteria of wheat scab are Fusarium graminearum, Fusarium oats, Fusarium acuminate, Fusarium trisepta, Fusarium beads, etc., which oversummer and overwinter on various plant residues such as straw left in the field in a saprophytic state, and germinate under certain temperature and humidity conditions every spring, and spread with wind and rain in the air, and can be infected from wheat flowering to grain filling stage, especially in the flowering stage. When the average temperature is above 9 °C, lasts for 3-5 days of rainy weather, and the rainfall reaches more than 12 mm, if it coincides with the wheat flowering stage, it can cause the occurrence and epidemic of wheat scab.
Response
Wheat scab can be prevented but not cured, must be sprayed in the early stage of flowering prevention, disaster prevention is to increase production, loss is to increase income, start early, prepare sufficient prevention and control substances, adhere to the "take the initiative, see the flowers and spray" unswervingly, professional unified control and group prevention and treatment combined, cross development, staggered peak application, in the early stage of full ear to flowering universal application, focus on winning the battle of wheat scab prevention and control, and strive to reduce the risk of scab epidemic.
Agricultural measures: select improved seeds, scientific farming, and select disease-resistant varieties for planting. Straw treatment, reduce the amount of bacteria, according to the study of wheat stubble average strain with bacteria rate of more than 1%, it reached the base of the epidemic of bacteria, with the straw returned to the field year after year, the bacteria accumulate year after year, there are field rice stumps with bacteria rate even 10%, once the climate is suitable, it is inevitable to do a big occurrence. Cooperate with timely sowing, precision strip sowing, ditch cleaning and moisture management, drought can enter water, waterlogging can drain, and scientific fertilizer. Just like people, if you eat healthy, you will naturally have strong resistance.
Chemical control: From early to mid-April, the first prevention was carried out on wheat at the heading and flowering stage. In case of continuous rain, 5-7 days after the end of the first control, the second prevention and control will be carried out on a sunny day. The agent can be prochloraz, tebuconazole prochloraz, pyraclostrobin, oxime tebuconazole, etc.
Gibberella is one of the epidemic diseases of wheat, wheat infected with scab after the grain is shriveled, not only causes wheat yield reduction, quality reduction, at the same time, wheat scab bacteria will also secrete toxins on the infected grains, and then harm the upper end of the food chain, if the wheat infected with scab disease wheat rate content reaches more than 4%, it will not be edible, so that wheat completely loses its commodity value, therefore, the prevention and control of wheat scab every year is the top priority, and must not be negligent.