Seed wilt
It mainly occurs in the seedling stage of sorghum, especially in the fields with more water and excessive humidity, especially after transplanting sorghum, when it encounters continuous rainfall. Its symptom is that sorghum can get sick when it grows to 4-5 leaves. It starts from the lower blade and then expands upward. The infected leaves grow purple stripes and gradually unite, causing the leaves to die from the top and the seeds to turn brown.
This disease is caused by Fusarium moniliforme of Hemiptera. The pathogen overwinters on diseased tissues or diseased residues in fallen soil with mycelium and chlamydospores. Conidia are produced in the following year, which are spread by rainwater sputtering and invade from plant wounds to cause disease. Continuous rainfall in early spring and early summer, warm days and cool nights are conducive to the onset. Low-lying water accumulation in planting areas, closed fields and high humidity, or application of incomplete decomposed soil and miscellaneous fertilizers will aggravate the disease.
Control mode: (1) rotation for more than 3 years; (2) Reasonable close planting, adopting high ridge or high border cultivation; (3) When transplanting seedlings, damage the seedlings as little as possible to avoid causing wounds and allowing germs to invade; (4) Apply fully decomposed organic fertilizer, drain in time after rain, and flood irrigation is strictly prohibited; (5) Use Weibao or Sanbao Qihua to prevent once in the seedbed, and then transplant.
anthrax
Important fungal diseases of sorghum can occur from seedling stage to adult stage. Seedling diseases harm leaves and leaf sheaths, resulting in leaf withering and seedling death; In the middle and late stage, it harms the stem base and ear, causing stem rot and ear rot. The symptoms of leaves and leaf sheaths are the most obvious. Most of the diseased plants started from the lower leaves and gradually developed to the upper leaves, resulting in the death of leaves layer by layer. The diseased leaves mostly start from the leaf tip and extend to the leaf bottom. Leaf lesions are small, nearly round or oval, 2 ~ 4 mm long and 1 ~ 2 mm wide, with dark brown or yellowish brown in the center, purplish red, yellowish brown or brown in the edge, and small black prickles at the top. In severe cases, most of the diseased spots converge, causing the big leaves to turn brown and die. Leaf sheath lesions are large, oval to oblong, red, purple or dark brown, and there are also small black spots with bristles on them. Stem rot occurred in the near maturity, and the internodes at the base of the stem were initially discolored by water, and then formed reddish-brown spots with purple edges in the middle. In severe cases, the base of the stem is cracked, and the inside of the stem is discolored and rotted. Pathogens can also infect ear neck, spikelet stalk and grain, making them rot and discolor.
This disease is caused by Colletotrichum gloeosporioides. Pathogens can not only harm sorghum, but also parasitize many gramineous plants such as wheat, oats and corn, causing anthracnose. Pathogens overwinter in the form of mycelium or conidia in the body or inside and outside the seeds, becoming the source of infection at the beginning of the following year. After the disease occurred in the field, conidia produced on the diseased spot were reinfected by wind, rain or airflow for many times, and continued to spread or cause epidemic. Rainy years or low-lying and high-humidity fields generally occur, and high-temperature and high-humidity and rainy weather is conducive to the disease.
Prevention and control methods: (1) After harvesting, the sick and disabled are treated in time, composted and fermented, and sterilized at high temperature; (2) Digging deep into the soil, transferring the residual sick and disabled bodies in the soil to the depth of the soil layer, and reducing the source of primary infection; (3) implement rotation for more than 3 years and apply fully decomposed organic fertilizer; (4) Top dressing in time to ensure no fertilizer removal in the later period and enhance the disease resistance. (5) timely removing the old diseased leaves at the base of the plant; (6) Strictly carry out seed treatment to prevent and control anthracnose spread by seeds at seedling stage; (7) In epidemic years or individual seriously ill fields, the pesticide can be applied from the booting stage, and Weibao or Sanbao Qihua can be selected.
Sorghum purple spot
It occurs in the middle and late growth period of sorghum, mainly damaging leaves and leaf sheaths. The lower leaves come on first, and gradually expand upward. In severe cases, sorghum leaves die early from bottom to top. Leaf lesions are purple-red, oval or oblong, with inconspicuous edges, mostly confined between parallel veins, and sometimes pale purple halo. When the humidity is high, a gray mold layer grows on the back of the lesion. Leaf sheath lesions are large, oval, purplish red, the edge is not obvious, and mold layer is rarely produced.
The disease belongs to the air-borne repeated infection disease caused by fungi of Cercospora of Hemiptera. Pathogens overwinter in the remains of diseased plants in the form of hyphae or conidia, and become the main source of infection in the following year. After the disease occurred in the field, the conidia produced were spread by airflow and repeatedly infected, so that the pathogen continued to spread. The development of the disease is closely related to the climate, and it is usually more serious in high temperature and rainy years.
Prevention and control methods: (1) Dig the ground in time after autumn, and bury the sick and disabled; (2) Topdressing in time at the late growth stage of sorghum to enhance plant disease resistance. (3) Remove the 1-2 old leaves at the lower part of the diseased plant as soon as possible, so as to enhance ventilation and light transmission and reduce the infection of germs. (4) Prevention and treatment with drugs at the initial stage.
Red stripe virus disease
Viral diseases will occur throughout the growth period, and plants that develop at seedling stage suffer the most. At the beginning of the disease, there are faded stripes between the veins at the base of the heart leaf, which spread to the whole leaf after being connected in rows intermittently, resulting in light green and yellow stripes. Sometimes the stripes turn red and purple spindle-shaped necrotic spots appear, and the expansion of the lesions is limited by thick veins. In severe cases, the whole leaves are purple and dry. The diseased plants are short, and the plant height of the diseased plants at seedling stage is 1/3 ~ 1/2 of that of the healthy plants, so they can't head and die early. From jointing stage to booting stage, the plant height of infected plants was 1/2 ~ 4/5 of that of healthy plants, and the number of spikes, spike length, number of grains per spike and grain weight decreased. The plant height of susceptible plants after heading is basically normal.
The virus is transmitted by aphids, infected plant juice friction and infected seeds, but it is mainly transmitted by aphids in a non-sustainable way. The control of aphids is mainly based on chemical agents, timely sowing, increased application of organic fertilizer, timely intertillage weeding, soil cultivation and moisture conservation.
stain
There are five kinds of head smut in sorghum: head smut, loose smut, full smut, flower smut and long grain smut, all of which are harmful to ears.
Head smut mainly infects bacteria in soil, which belongs to bud infiltration and spreads once a year. The soaking period of seedlings is from the white shoot stage to the bud length of 2 cm. After the onset, the whole ear became a fungus gall, which did not bear fruit. The diseased plants with 5 ~ 6 leaves are obviously shorter than the healthy plants, and the leaves are dark green. At booting stage, the flag Ye Ting is straight, and white sticks can be seen when the bracts are peeled off, commonly known as "black rice". Ebony was small and finger-shaped in the early stage, and gradually expanded into a cylinder, which was hard and the internal organization changed from white to black. Then ebony sticks out from the bracts with a white film on the surface. After the film burst, black powder was released, leaving bundles of black silk. The diseased plant of loose head smut is also shorter than the healthy plant, and the diseased ear grains are destroyed by pathogenic bacteria and become oval or cylindrical small "gray bags". The small gray bag is slightly larger than the healthy particles, and it is covered with a dark gray film. The film breaks easily, releasing black powder. Generally, the whole ear is diseased, but the original ear shape is still maintained. Only a few diseased ears were damaged by some grains, and the rest of the grains bore fruit as usual. There is no difference between the diseased plants and the healthy plants. After heading, the diseased ear grains turned gray, and the ear shape remained unchanged except the glume shell. The gray package is cylindrical, containing black powdery winter spores and covered with a gray-white film. The film is hard and not easy to break. When it breaks, only the top cracks a small mouth. Only some spikelets are infected with head smut, and the others are healthy. The diseased spikelets are mostly located at the lower part of the spike, close to the flag leaf sheath. The affected ovary is white, and it tends to expand from one side to form convex blister spots (bacterial galls). The outer membrane of bacterial galls is grayish white and irregularly cracked, exposing black powdery winter spores. Long grain smut only occurs on some spikelets. The ovary of infected spikelets becomes slightly curved galls, protruding from the glume and the outer membrane is gray. The top of the gall burst and the black powdery winter spore ball dispersed. After the black powder is dispersed, there is no stele, only 8 ~ 10 black filaments are left, that is, residual vascular bundle tissue.
Control methods: (1) rotation with non-host plants; (2) Straw composting, high-temperature fermentation and full decomposition to prevent the fertilizer from carrying bacteria. Dig deep to clear the stubble and eliminate the sick and disabled. (3) Use fully decomposed organic fertilizer. (4) After the "sea" appears but before it is broken, the diseased plants should be pulled out in time, buried or destroyed. (5) Seed treatment: soak the seeds in warm water of 45-55℃ for 5 minutes, then close the seeds and sow when the seeds just germinate. (6) Improve the sowing quality, shorten the sprouting time, and reduce the embryo soaking time.
Physiological diseases
It is caused by the lack of nutrients in sorghum, and the symptoms vary with the lack of elements.
Nitrogen deficiency: slow growth, thin stems, narrow leaves, yellow leaves, few and thin roots, slow growth, poor quality of millet per ear and low yield. Early nitrogen deficiency is not easy to detect, and it can only be found when the seedlings are light yellow. When sorghum grows to knee height, the symptoms are obvious, showing thin plant type and yellow-green leaves. The lower old leaves turn yellow from the tip of the leaf and then extend along the veins, and the leaf margin is still green. Finally, the whole leaves turn yellow and dry, leading to premature aging of plants. Remedial measures are timely topdressing decomposed manure or biogas slurry outside the roots;
2. Phosphorus deficiency: the leaves are narrow and dark green, the number of flowers is reduced, the flowering and fruiting are delayed, the roots are underdeveloped, the roots are few and short, the plants grow slowly, and they are greedy for green and mature late. The solution is to apply more decomposed farm manure.
3. Potassium deficiency: the central part of the leaf is dark green, the tip and edge of the leaf are yellow or necrotic, the boundary between the yellow and necrotic part and the healthy part is obvious, and the leaf is folded and bent. Control method: increase the application of farmyard manure.
4. Trace element deficiency: Mn-deficient plants grow slowly, showing obvious greenness, with reddish-brown pigment bands between veins; The veins of sulfur-deficient leaves turn yellow, and the base of stem turns red in late autumn, and gradually expands to the whole leaf along the leaf edge; Iron-deficient leaves turn brown, stems and leaf sheaths turn red and purple, and new young leaves turn green.
soil insect
Mainly biting the leaves and young stems of seedlings, resulting in lack of nests and broken lines. Common ground tigers, grubs, grubs and crickets all occur at seedling stage. Ground tigers, commonly known as soil silkworms, are harmful to larvae; Gryllotalps, commonly known as local dogs, can be hurt by adult larvae; Grubs are the larvae of scarabs; Crickets are called cricket, cricket and adult larvae. Root irrigation and poison bait are the main methods of control, and the suitable time for medication is morning and evening (after 6 pm). Only Qingyuan Bao, Sanbao Qihua, green crystal biological agents, Bt agents, Bacillus thuringiensis, Cordyceps sinensis, Bacillus, Beauveria bassiana, Derris, Melia azedarach, tobacco lime water, etc. can be used.
armyworm
Also known as millet night thieves and pruning insects, commonly known as multicolored insects, wheat silkworms, marching insects and so on. Lepidoptera leaf-eating pests, which harm larvae, mainly occur in the seedling stage of sorghum from May to June, and can eat all leaves and stems of sorghum when they occur, causing serious losses. Because of its social, migratory, omnivorous and gluttonous characteristics, it has become the main agricultural pest in China.
The mature larvae are 38 mm long. The head is reddish-brown, with eight-shaped brown thick longitudinal stripes on both sides. Because of the different food and environment, the body color varies greatly, from light green to dark black; When it happens, the back is often black, and the abdomen is light and dirty. The newly hatched larvae are clustered, and the first-instar larvae can only eat mesophyll, which makes the leaves appear white spots. The second instar larvae mostly harm the back of the leaves at the base of the plant. After the third instar, the food intake increases greatly, and the leaves can be nicked and suspended animation begins. When disturbed, they will quickly curl up and fall to the ground. Larvae are photophobic. They lurk in the soil cracks in the rhizosphere on sunny days and climb on plants in the evening or cloudy days to do harm. When larvae occur in large numbers and lack food, they often migrate to nearby plots in groups to continue to do harm. The 5th-6th instar larvae enter the gluttony stage, and their food intake accounts for about 90% of the whole larval stage. After the 6th instar, it was buried and pupated. Larvae feed on Gramineae and develop rapidly, and eclosion adults lay more eggs.
Adults lie in the daytime and go out at night, start to move in the evening, feed at dusk, mate and lay eggs at midnight, and look for hidden places at dawn. It has strong chemotaxis to sweet and sour liquid and lays eggs and withers. Adults need to feed on nectar to supplement nutrition, and when the nectar source is rich, the egg production is high; Adults like to lay eggs in dense fields, and wheat, millet, rice field, dense planting field and fertile irrigation field are beneficial to the occurrence of this insect.
Control method: (1) trapping and killing adults. Taking advantage of the habit that adults mostly lay eggs on the leaves of cereal crops, 20- 100 straws were inserted in the field, and new straws were replaced every five days, and the replaced straws were burned centrally. (2) Use sweet and sour pans, black lights, etc. Trap and kill adults and reduce the number of insects. (2) According to the forecast, control the larvae before 3rd instar.
Mansfli
Insect-boring pests of Diptera Muscidae, commonly known as sorghum stem flies and stem borers, mainly overwinter in plants as larvae, and also overwinter in sorghum tillering seedlings and soil as larvae or pupae in the late growth stage, with 7 generations a year. Sorghum damaged by larvae invades the heart leaves from the trumpet mouth or leaf gap before the first hatching, and then burrows into the heart leaves gap near the growth point to feed, resulting in dead seedlings or abnormal ears, commonly known as "cutting the heart." After the larvae invaded, they gave up 1 day, and in severe cases, the dead heart rate was as high as 60%-70%, or even no harvest. Adults have the habit of eating aphid honeymoon dew and rancid animals. Eggs are mostly scattered on both sides of the main vein on the back of the innermost three heart-shaped leaves or at the tip edge, with 24-34 eggs per insect per plant/kloc-0. . Most of them occurred in the sorghum seedling stage in the middle and late May and early June.
Control method: (1) Sow in time; (2) Remove dead seedlings in time; (3) trapping and killing adults with poison bait; (4) Dotting toxic soil or perfusion of liquid medicine.
aphid
Commonly known as "insect-weariness", insect-weariness, honey stinkbug and oil sweat, they are the main pests of sorghum. Sorghum seedling stage and heading and filling stage generally occur. After overwintering with eggs, winged viviparous female aphids migrated to sorghum from late May to early June of the following year, causing harm. At first, some aphids appeared, and most of them gathered on the back of the lower leaves of sorghum to suck juice, which made the injured leaves turn red and withered in severe cases. Then it gradually spread to the upper leaves until the ear, and the winged aphid spread throughout the field. When the insect body is damaged, it secretes a lot of honey dew, which drips on the stems and leaves, and the oil shine, leading to mold parasitism. The severely damaged leaves withered, the stems were soft and bent, and even heading was impossible. If the temperature is high from heading to filling stage, and there is high temperature, drought and little rain for several days, aphids will occur in large numbers.
Control methods: (1) interplanting with soybean at the ratio of 6: 2 to improve the ecological conditions in the field; (2) yellow board; (3) Initial spray control.
Sorghum borer
Commonly known as sorghum borer, Lepidoptera borer, mostly occurs in the middle and late growth period of sorghum. The insect overwinters in corn and sorghum stalks as mature larvae, with 2-4 generations a year. Adults lie down during the day and come out at night, which is phototactic, but not strong. The newly hatched larvae often congregate in the heart leaves to feed on mesophyll, and reticular spots and many irregular holes can be seen in the injured leaves. Eating stems after the third age can bite off the growing points early and cause dead seedlings, and the stems are easily damaged by the wind in the later stage.
Sorghum should be used twice before and after flowering and at the initial stage of filling.
Preventive drugs: 1. Preventive drugs can be selected: CuSO4, Cu(OH)2, sulfur mixture, turpentine mixture, Weibao, Sanbao Qihua, quicklime, etc. 2. Insecticides can be selected: biological pesticides such as Qingyuanbao, Sanbao Qihua, green crystal biological agents, Bt agents, Bacillus thuringiensis, Bacillus, Beauveria bassiana, Penicillium, and plant pesticides such as Azadirachta azedarach, Derris, walnut and tobacco.