Symptoms (1) The 2nd instar larvae invaded the tender root tips of peanuts and formed irregular nodules. Nematodes burrow into the stele of peanut root, causing root exudate and nutrient loss, which is easy to cause secondary diseases. Root-knot nematodes colonize and feed, which stimulates the proliferation of root cells, constantly harms the root tips of new roots, and makes secondary roots cluster, making it difficult to absorb nutrients. The diseased plants grow slowly or lose their green, and the plants are short. At the beginning of flowering, the leaves turn yellow and thin, the leaves wither and fall off early, the flowers are small and bloom late, and there are few or no fruits. Nematodes can also invade the fruit shell, fruit stalk and root, and the fruit shell is damaged to form milky white bumps. After the disease, the worm tumor looks like brown scab, but it is rare. Fruit stalks and rhizomes form grape-like insect nodules.
(2) Control method ① Chemical control: Before sowing the long-acting slow-release agent, 3000 times solution of Tiandamycin or 200g of 48% chlorpyrifos per mu can be sprayed into the ditch, mixed with 20kg of fine soil, and directly applied to the bottom of the ditch for sowing. At the beginning of the disease, the roots were watered with 3000 times solution of tianda avermectin.
② Biological control: Paecilomyces lilacinus and chlamydospore of Verticillium wilt can obviously reduce the nematode population and dissolve its eggs.
2. Identification and control of peanut tetranychus cinnabarinus (1) Morphological characteristics: female tetranychus cinnabarinus is oval in back view, with a body length of 0.42 ~ 0.56 mm and a width of 0.26 ~ 0.36 mm, and its body color is red or reddish, commonly known as "red spider". There are 1 black spots on both sides of her body, and there are 3 cracks on the outside, close to the inside. The posterior view of male mites is rhombic, which is less than that of female mites. Tetranychus urticae is very similar to Tetranychus cinnabarinus, the difference is that Tetranychus urticae is pale yellow or yellow-green, has no red individual, and is nearly white to the naked eye, commonly known as "white spider".
(2) Occurrence regularity and harmful symptoms: Peanut occurs in Zhaoyuan City, Shandong Province 1 year 10 ~ 20 generations. As adults, they spend the winter netting in soil cracks, the rhizosphere of weeds at the edge of peanut fields or under bark, and usually gather in groups and lurk. Activities began in late March of the following year, and they moved into peanut fields from late April to early May, and the peak period was June and July, which could cause local harm to spring peanuts. When the rainy season comes in mid-July, the occurrence of Tetranychus urticae decreases rapidly. If the weather is dry, it can occur again in August, causing harm in peanut pod-setting period. Peanut was harvested in the middle and late September and moved to the overwintering host, and began to overwinter in late June 10.
Peanut spider mites clustered on the back of peanut leaves to suck juice, and the front of the damaged leaves began to turn gray and gradually turned yellow, and the severely damaged leaves dried up and fell off. At the peak of Tetranychus urticae, due to adult mites spinning and netting, there are 1 layer white silk screens on the surface of peanut leaves in the plots with high population density, and large areas of peanut leaves are connected together, which seriously affects the photosynthesis of peanut leaves, hinders the normal growth of peanuts, and makes pods shrink and reduce production.
(3) Control methods ① Agricultural control: reasonable rotation to avoid the harm of mutual transfer of tetranychus mites between hosts; Digging peanuts in time after harvest can not only kill a large number of overwintering spider mites, but also reduce host plants such as weeds; Eliminate weeds and overwintering insect sources in the field.
(2) Chemical control: When the diseased heart or disease and pest rate of peanuts is above 20% in the field, it should be sprayed in time, and the spraying should be even and must be sprayed on the back of leaves; In addition, weeds and other host plants along the field should be sprayed to prevent their spread. The specific method is to control the single occurrence plot of tetranychus cinnabarinus by spraying 2% avermectin 3000 times.
3. Identification and control of peanut nettle spot disease (1) At the initial stage of onset symptoms, the spot first appeared on the leaves at the base of the plant, and gradually showed symptoms on the upper leaves. The initial stage of infection is white reticulation. After that, the infection point spread radially outward with the vein, showing a star shape. The focus continued to expand, from white to dark brown, forming a reticular spot with unclear edges. Large spots can appear at high temperature and humidity, with a diameter of 1 ~ 1.5 cm. In the late stage of the disease, brown spots appeared on the back of the disease spots, and small black protrusions were born under the epidermis. When the temperature and humidity decrease, white to brown hyphal spots appear on the leaves, which can sometimes cover the leaves or form dark brown spots.
(2) Characteristics of diseases The occurrence of diseases is obviously related to stubble, cultivation methods, temperature and humidity, and rainfall. The disease of continuous cropping field is more serious, the film mulching field is heavier than the open field, the ridge planting is lighter than the flat planting, and the wheat interplanting peanut is lighter than the summer direct sowing. High temperature, high humidity and rainy weather during pod-setting period are beneficial to the epidemic of diseases.
(3) Control methods ① Selection of disease-resistant varieties: The varieties (lines) with good resistance are Hua 37, 10 and1,8, Fenghua 8 and Huayu 26, which have good disease resistance and high yield and can be adopted according to local conditions.
② Improved cultivation techniques: crop rotation, which can rotate with sweet potato, corn, soybean and other crops. Remove the disease and reduce the source of bacteria. Deep tillage and deep tillage can reduce the source of bacteria on the soil surface. Reasonably increase fertilizer and improve disease resistance.
③ Chemical control: Within 3 days after peanut sowing, use 25% Diphenyl Triazole wettable powder or 60% Carbendazim, both of which are sprayed on the ground with 500 times solution, so as to block the source of bacteria in the soil and reduce the initial infection. The above chemicals can be mixed with acetochlor herbicide for spraying and weeding.
You can also spray 500 times of 70% mancozeb wettable powder, 50% carbendazim wettable powder or 15% triadimefon wettable powder on the leaves at the early stage of the disease, and add 600 times of "Tianda 2 1 16" every 10 ~ 65438.
4. Identification and prevention of symptoms of peanut bacterial wilt (1) Peanuts are generally the most susceptible to this disease at the early flowering stage. At the beginning of the diseased plant, 1 and 2 leaves at the top of the main stem wilted first, delayed opening in the morning and closed early in the afternoon. 1 ~ 2 days later, the whole plant or one leaf of the diseased plant withered sharply from top to bottom, the color was dim and green, and the diseased leaves turned brown and brown in the later stage. The diseased plant is easy to pull up, the main root tip, fruit stalk and fruit pod are dark brown and wet rot, and the root nodules are dark green. The diseased stems are cut longitudinally and the vascular bundles are dark brown. White mucus can be seen by slightly squeezing the cross section under moisturizing.
(2) Periodically occurring germs spread in contaminated soil, diseased plant residues, contaminated weeds, miscellaneous manure and contaminated manure, and spread through rainwater, irrigation water, farm tools and insect vectors. Bacteria can survive in soil 14 months to 8 years. Pathogens invade from root wounds and natural wounds of plants, multiply in vascular bundles, secrete toxins, cause catheter blockage, and plants lose water and wither. Then, the pathogen enters the intercellular space between cortex and medullary parenchyma, causing it to disintegrate and rot, spread again and infect repeatedly. According to the investigation, high temperature and high humidity are the most favorable conditions for this disease. When the temperature is above 25℃, the amount and degree of rainfall will determine the occurrence of the disease. Generally, it is more serious when it rains on sunny days, long-term drought showers or long-term rain suddenly clears up; The sudden change of soil temperature and humidity or the increase of nematodes in the community cause serious damage or decay of the root system; Low-lying land with poor drainage is more serious than high slope land; Sandy soil, thin soil layer and poor water and fertilizer conservation are more serious than loam and fertile soil; Continuous cropping field is more serious than rotation field; Acid soil is more serious than weak alkaline soil; Grass damage is more serious than community grass damage. In addition, there are significant differences in resistance among varieties.
(3) Control methods ① Agricultural control: select high-yield and disease-resistant varieties and rotate them reasonably. Where there is water source, paddy-upland rotation is implemented, and the control effect is better. Dry land can be rotated with melons and Gramineae crops for 3 ~ 5 years, avoiding continuous cropping with solanaceae, Leguminosae and sesame. Short-term irrigation before sowing peanuts in dry land will lead to a large number of pathogen deaths. Adopt high ridge cultivation, timely sowing and reasonable close planting to prevent shading and flooding in the field. Pay attention to drainage and waterlogging prevention to prevent water accumulation in the field and water-borne diseases.
Formulated fertilization technology, sufficient base fertilizer, increased application of phosphorus and potassium fertilizer, appropriate application of nitrogen fertilizer and foliar spraying of "Tianda 2 1 16" were adopted to promote the stable growth and early development of peanuts. Lime can be applied to acidic soil to reduce soil acidity and alleviate diseases. If a diseased plant is found in the field, it should be pulled out immediately, taken out of the field and buried deeply, and disinfected with lime. Remove diseased plants and residues in time when harvesting peanuts to reduce the source of soil diseases.
② Chemical control:
Seed dressing: Before sowing, soak 50g of special seed dressing agent with "Tianda 2 1 16", and mix 750g of peanut seeds with 20kg of water. Don't bury seeds.
Spraying: After peanut seedlings are in full bloom, spraying 72% agricultural streptomycin 4000 times and 10% world high 2500 times per mu. In order to increase the efficacy, it can be mixed with "Tianda 2 1 16" Zhuangmiaoling 600 times.
5. Identification and control of peanut leaf spot. Peanut leaf spot is caused by two kinds of bacteria, namely peanut black spot and peanut brown spot.
Peanut brown spot occurred earlier and appeared at the early flowering stage; Black spot occurred late, only in the next needle stage. Therefore, brown spot disease is mostly in the lower leaves, and black spot disease is mostly in the upper leaves. Black spot disease is more prominent in autumn peanuts, while brown spot disease is more common in spring peanuts. Both diseases will damage leaves, petioles, stems, ovaries, stems and pods. In severe cases, it will cause defoliation and premature death of plants, affect nutrient accumulation, lead to insufficient pods, reduce grain yield and oil content, and easily drop fruit and germinate seeds at harvest. The main causes of peanut leaf spot disease are closely related to short rotation cycle, high temperature and high humidity environment, weak disease resistance of varieties, poor sand strength and insufficient fertilization.
The effective control methods of peanut leaf spot disease are as follows:
① rotate. Peanut paddy-upland rotation is better than rice rotation. Rotation of peanut with corn, sweet potato, cassava and other dryland crops once every two years can obviously reduce the harm of peanut leaf spot.
② Improve the soil. Improve the cultivation conditions, increase the application of organic farmyard manure, improve the soil and enhance the disease resistance of peanuts.
③ Selection of disease-resistant varieties. When planting peanuts, we should choose varieties with strong resistance to leaf spot.
④ Chemical control. Peanut leaf spot includes peanut brown spot and black spot. When the rate of diseased leaves in the field reaches 10%, it should be sprayed in time. Commonly used pesticides are 50% carbendazim 600 times solution, 96% acetamiprid 3000 times solution, or 70% thiophanate-methyl 600 times solution spray.
6. Identification and Prevention of Peanut Root Rot (1) Symptoms Peanut root rot can occur at all growth stages of peanuts. Peanut infection before emergence after sowing can cause rotten seeds and buds; Root rot and seedling blight caused by seedling injury; The damage of adult stage leads to root rot, stem base rot and pod rot. The overground part of the diseased plant shows short growth, yellow leaves and finally the whole plant withers. Because the disease mainly occurs in the roots and vascular bundles, the roots turn brown and rotten, the vascular bundles turn brown, the main roots shrink and dry, and look like rat tails. There is a yellowish-white to reddish mold layer (conidiophore and conidia of the pathogen) on the surface of the affected area.
(2) Peanut root rot is caused by Fusarium Hemiptera. Include Fusarium oxysporum, Fusarium solani, Fusarium pink, Fusarium putrefaction and Fusarium moniliforme. They can all produce asexual microspores, megaspores and chlamydospores. Microspores are oval to oval, colorless, mostly unicellular, 2 ~ 3.5 μ m× 5 ~ 12 μ m in size, and megaspores are sickle-shaped or crescent-shaped, with 3 ~ 5 septa. Chlamydospores are nearly spherical, solitary or strung, with a diameter of 7 ~ 1 1 micron. Bacteria live in the soil for several years, belonging to vascular parasites, which can block the catheter and secrete toxins, causing plants to wither.
(3) Pathogens mainly overwinter in the soil with diseased residues, and become the main primary infection source of diseases. Seeds, pods and soil mixed with diseased bodies can also become the primary source of infection of the disease. Pathogens are mainly spread through running water, fertilization or agricultural operations. The primary inoculum is mainly chlamydospore, and the secondary inoculum is conidia, which can directly invade from the wound or epidermis of the host and propagate and spread in the vascular bundle. Usually continuous cropping, low terrain, shallow soil layer, continuous low temperature, rainy weather or sudden sunny weather, or less rain and drought are more serious.
(4) The comprehensive control measures should be mainly cultivation and disease prevention, supplemented by chemical control.
① Close the seeds: collect, select, dry and store the seeds; Turn the seeds over before sowing, remove discolored, moldy and damaged seeds, dress the seeds with 40% triadimefon carbendazim wettable powder accounting for 0.3% of the seed weight, seal them for 24 hours and sow them.
② Reasonable rotation: determine the rotation mode, crop collocation and rotation years according to local conditions.
③ Do a good job in the cultivation management centered on fertilizer and water: improve the irrigation and drainage system, improve the waterlogging and drought resistance of the planted land, and clear the ditch in time to drain waterlogging and reduce humidity after rain; Increasing fertilizer and improving soil, carefully preparing soil and improving sowing quality; Sow in time according to the weather conditions; Pay attention to the application of net fertilizer and do a good job in field hygiene.
④ Timely application of pesticides to prevent and control diseases: After the full seedling stage, strengthen inspection, and immediately spray or irrigate the diseased plants to block the central diseased plants. You can choose 96% Tianda hymexazol 3000 times solution or 40% triadimefon carbendazim wettable powder 1000 times solution. Use daily 2 1 16 mixture 1 time, spray twice continuously every 7 ~ 15 days, alternately smear and spray thoroughly.