Sweet sorghum pests and diseases and their control

Sweet sorghum pests and diseases are one of the important factors affecting the development of sweet sorghum industry. In order to prevent this from happening, the pests and diseases and potential pests and diseases that occur in sweet sorghum are described below.
1 Disease 1.1 Silk smut mainly occurs in the ear, commonly known as "Umi." Generally, the damaged plants are short. The symptoms were obvious during the flag-picking period. The flag leaves were tightly covered with diseased ears, and the diseased ears were bulging in the middle. The initial stripping of the leaves was a silky white-covered filament. After heading, the upper white skin was slightly reddish, and black after rupture. The powder then exposes a strand of residual filamentous vascular bundle tissue. Winter spores are spread through soil and seeds. When the sweet sorghum seed is from 1 to 1.5 cm in length from the tip of the white bud, it is the most suitable growth period for the pathogen.
Control method: select the seed in the disease-free field or the field with few diseases; select the disease-resistant variety; find the diseased plant to cut down in time, and master the diseased plant before the ash rupture and cut it to the ground for destruction. If the diseased ears are used to feed livestock or sputum, the manure must be fertilized before use to reduce the source of the bacteria; the seeds are screened, the air is selected and the impurities are removed, and the granules are treated with chemicals; the planting structure is carried out for more than 3 years. To reduce soil bacteria and reduce their harm.
1.2 Leaf anthracnose can occur from the seedling stage to the heading stage. Small brown spots appear on the tip of the leaf at the beginning, then expand into oval or merge into irregular lesions, with purple-red or purple-black edges, central light brown, and small black spots on both sides of the leaves are conidia, in soil moisture and atmosphere. When the humidity is high, the disease is serious. When the disease occurs, the leaf function is reduced, which affects the yield of the stem and the grain.
Control method: remove the residue of the diseased plant, burn it or bury it deeply; soak it with appropriate bactericidal agent, rinsing it after rinsing; use the bactericidal agent to prevent it at the beginning of the disease;
1.3 Rust Disease can occur at the seedling stage, producing summer spore heap. The edge of the spore heap is purple-red, and it is mostly born on the back of the leaf. The spores are spread by the airflow, which can infect the plant again. It has a pale yellow spot at the beginning, and then gradually forms an elliptical, slightly raised small spot, which is rust-like after rupture. Auburn and dark brown powders, namely summer spores and teliospores. Winter spores overwinter in the field of diseased plants, and the plants are too dense, poor drainage, and partial application of nitrogen fertilizers will aggravate the disease.
Control methods: clear the residues of field diseased plants in the late autumn to reduce the spread of pathogenic bacteria; timely apply nitrogen fertilizer, pay attention to drainage and flood control during the growth period, strengthen field management;
1.4 Scattered smut disease is obvious after heading. The damaged plants are later, shorter, thinner and less numbered than the healthy plants. The stamens and inner and outer gems of each spikelet on the diseased ear become black powder due to the damage. There is a grayish white film on the outside, which turns into an oval gray bag. It protrudes from the glume and, after the outer membrane ruptures, it emits dark brown powdery chlamydospores, revealing the long central axis, which is formed by the host tissue. The guardian of the diseased ear is also slightly longer than the healthy spike. The disease is mainly caused by seed infection. After the diseased seeds are sown, the germs and seeds are simultaneously germinated, invade the host tissue, develop to the growth point, and finally invade the ear to form the diseased ear. The medicinal treatment of the same smut, the sclerotial ear and the sputum should be destroyed in a concentrated manner to reduce the bacterial source.
1.5 Sorghum large spot disease leaves have long fusiform shape, central light brown, purple fringe edge, irregular irregular wheel pattern in early stage, large lesions, generally about 20 ~ 60 × 4 ~ 10mm, black mold on both sides of the lesion A sub-entity of a pathogen. Usually, the lower part of the plant gradually develops upwards. In the case of moisture, the lesions develop rapidly and merge with each other, causing the leaves to dry up. The disease occurred earlier, and the damage was serious in July. It was the main cause of sorghum stalks in normal temperature and rainy years.
Control methods: use resistant varieties; timely ploughing, the diseased plant debris buried deep in the soil, special attention should be paid to the sorghum late growth period can not be lack of fertilizer to reduce the incidence.
2 Pests There are many pests that harm sweet sorghum. The main pests are as follows:
2.1 Underground pests 2.1.1 蝼蛄 There are mainly African cockroaches and North China cockroaches in China, North China cockroaches are mainly distributed in the north of China, and African cockroaches are distributed throughout the country. Longer life history, 1 year or more years. Nocturnal, strong phototaxis, hobby sweet substances, endangering the roots of sweet sorghum, causing seedling death.
Control method: Apply pesticides in the planting ditch before sowing or sowing; mix the seeds with the pesticide; in the sorghum field, dig a small pit every 20m, then put the horse manure or fresh grass with water into the pit, After the insects are lured in, they are concentrated and killed during the day. Or put bait in the pit; in the spring, you can dig the pit to kill the insects, and dig the eggs in the summer to kill the eggs.
2.1.2 蛴螬 (chafer) There are mainly Korean chafers and oriental chafers. Its life history is longer, with adult or larvae wintering in the soil, adult insects crouching at night or crouching, and the latter are mostly. The types of night out are often phototaxis, and usually have a false death habit. Harm the roots of seedlings, resulting in lack of seedlings.
Control method: apply an appropriate amount of insecticide per acre of planting ditch; artificially kill or lightly trap adult insects; use fertilized manure when fertilizing, otherwise it is easy to produce cockroaches; intercropping ramie, attracting and poisoning against various chafers Killing effect; artificial light trapping during the emergence period; the use of bacterial insecticides to control cockroaches also has a certain effect, mainly using Bacillus thuringiensis.
2.2 Seedling pests There are mainly sorghum long scorpions, which are concentrated in the stems of seedlings, sucking seedling sap, affecting seedling growth, and causing seedling death in severe cases.
Control method: When the adult cluster is overwintering, the stone blocks and the grass are collected to catch the wintering larvae; when the humidity is high, the Beauveria bassiana can be used for prevention and control.
2.3 Leaf-eating pests 2.3.1 Aphids There are many aphids that harm sweet sorghum, but the most serious damage is sugar cane. It can occur in large quantities when it is hot, dry and rainy. The worm has a short generation and rapid reproduction. The egg is overwintered on the grass. After the spring temperature reaches 10 °C, it hatches, feeds at the root of the grass, and then moves up to the tender stem to feed. The winged parthenogenetic and wingless parthenogenes produced after the second generation, when the sorghum emerged in June, moved to the sorghum, parasitized in the back of the leaf to feed the nutrients, and the initial stage was more harmful to the lower leaves, gradually reaching the upper part of the plant. The leaves spread, so that the back of the leaf is covered with insects, and a large amount of honeydew is secreted and dripped on the lower leaves and stems. The oil shines brightly, so it is called “oil-bearing strain”, which affects photosynthesis and normal growth of the plants, causing the leaves to turn red. "Bald neck", "瞎 tip", less spikes, increased tannin content in the grain, and high quality of rice, seriously affecting its yield and quality.
Control method: At the beginning of the occurrence, the leaves with aphids are gently laid down, and the deep burial in the field is carried out, which has a certain effect on controlling the spread of mites; it can be controlled with chemicals, but it is necessary to pay attention to some varieties allergic to organophosphate insecticides. It should not be used; it can also be used to improve the microclimate in the field by means of soybean intercropping; in the case of large occurrences, low-volume spraying with insecticides can be used.
2.3.2 One year of the genus Moth in the north of China, the wintering in the depth of 6~10cm in the soil, the emergence in the late June of the next year, the adult in the middle of July, the maternal ovulation on the back of the sorghum leaf, the egg single Scattered. After the larva hatches, the leaves are taken, and the hazard period is about 1 month. Adults crouched out at night, have phototaxis, like wet, dark, often on the back of the leaves. If the rain is continuous and the climate is cool in July, it will easily occur. Viscous soils are heavier than sandy soils.
Control method: artificially capture larvae. The moth larvae are large, inactive, easy to catch, can be captured and killed according to the catastrophic; digging during the winter, or removing the egg during the egg; light trapping.
2.3.3 armyworms There is no diapause phenomenon in the process of growth and development. When conditions are suitable, it can be propagated all year round. Therefore, the generations in different parts of China vary according to the latitude of the region, and the higher the latitude, the fewer generations occur. It is nocturnal and has a strong tendency to black light. It is a common pest of grass crops, larvae bite leaves, and even bite the ears.
Control method: starting from the initial stage of adult spawning, the wheat field will insert 150 small grasses per hectare to induce spawning, change every 2 days, burn the grain grass, or pick eggs in the field during spawning; At the time of 0.13 to 0.20 hectares, set a sweet and sour wine to trap the pot or set 30 to 45 poplars or cereals per hectare, and kill them day by day, which can significantly reduce the amount of eggs in the field and the density of larvae; A small lethal agent is used for drug control.
2.4 Stem pests 2.4.1 Corn borer Corn borer is harmful in the sorghum production areas of northwest, north, northeast and east China. The occurrence of alfalfa in the corn borer varies with the climatic conditions of each place, and can occur from 1 to 6 generations per year. Prevention and treatment methods: when the corn borer harms the heart leaf, spray the insecticide (the organophosphorus allergy variety is used with caution); the egg hatching period is used Insecticides for heart leaf control.
2.4.2 In the north China, Henan, Jiangsu and other provinces, 2 generations occur in the first year. The young larvae feed on the mesophyll in the heart leaves, leaving only the epidermis, which is window-like. When the age increases, it bites into irregular holes or sputum. Feeding the stem into the hazard, and some bite the growth point, so that the sorghum forms a heart-shaped, easy to fold the stem. The mature larvae overwinter in the sorghum stalks, mainly damaging the summer sowing sorghum or its late-maturing varieties.
Control method: similar to corn borer, if it occurs simultaneously with corn borer, it can be controlled at the same time. If it is different for a period of time (more than 10 days), it must be sprayed once more; the wintering larvae of the strip are more in the upper part of the stalk, when harvesting The method of long tassel can be taken to reduce the amount of wintering larvae.
2.5 Ear pests 2.5.1 Myzus persicae In the green rice stage, the larvae eat grain, and after 3 years of age, they climb out of the net and condense the spikelets. The larvae are filled with feces at the pupil, which is easy to cause mildew and lower the quality of sorghum. In North China, two to three generations occurred in the first year, and the Yangtze River Basin was in the fourth to fifth generations. The last generation of mature larvae overwintered in the gaps of sorghum, corn, ramie and sunflower disk and warehouse. Adults have strong chemotaxis, and adults after emergence must feed on supplemental nutrients to lay eggs.
Control method: remove the wintering insects in the wintering place, and eliminate the overwintering insects on the rice stalks and ears before degranulation. The wintering larvae of the warehouse gap and orchard bark should also be killed; the number of eggs and larvae should be investigated at the beginning of sorghum heading, and when the rate of worms (egg) reaches 20% or more, chemical control is required.
2.5.2 The ash mites occur in 2 to 3 generations in 1 year, and the mature larvae overwinter in the gluten. The wintering larvae in the northeast and northwestern regions are degraded in about the end of May. The hazard period is from June to September, and the field overlaps. The larvae of 1~2 generations endanger the seedlings, causing heartlessness, and overwintering with mature larvae or pupa.
Control method: Turn the field in autumn, expose the root lice to the ground, kill the overwintering larvae under low temperature and dry conditions; manually remove the dead heart seedlings, concentrate on burning; master the insects, carry out chemical control if necessary;
The above-mentioned pests and diseases are only the main types that occur on sweet sorghum. As the planting area continues to expand, new pests and diseases will continue to emerge. We must take comprehensive measures to control pests and diseases in accordance with the requirements of the plant protection policy and to protect the environment, so as to minimize the harm. If blindly pursuing the high yield of sweet sorghum and destroying the environmental conditions on which human beings depend, it will be worth the effort!
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