What fungal infection causes peanut leaf spot?

Identification and control of peanut leaf spot.

Peanut leaf spot is a disease caused by two pathogens, peanut black spot and peanut brown spot.

Peanut brown spot disease occurs early, appearing at the early flowering stage; Melasma occurs later, at the end of the needle period. Therefore, brown spot was more common in the lower leaves, black spot was more common in the upper leaves, black spot was more prominent in autumn peanuts, and brown spot was more common in spring peanuts. Both diseases can harm leaves, petioles, stems, ovary, stalks and pods, causing defoliation and early withering of plants in severe cases, affecting nutrient accumulation and resulting in pods that are not full, reducing the kernel yield and oil content, and easy to drop fruits and germinate seeds during harvest.

The main causes of leaf spot disease in peanut are closely related to short rotation cycle, high temperature and high humidity environment, weak disease resistance of varieties, poor sandy soil fertility and insufficient fertilization.

The effective control methods of peanut leaf spot are as follows:

Crop rotation. Peanut is rotated with water, and it is better to rotate with rice. Rotation of peanut on dry slope and corn, sweet potato and cassava and other dryland crops in 2 years can significantly reduce the damage of peanut leaf spot.

Improve the soil. Improve cultivation conditions, increase the application of organic farm fertilizer, improve the soil, and enhance the disease resistance of peanuts.

Choose disease-resistant varieties. To plant peanuts, it is necessary to choose varieties with strong resistance to leaf spot.

Pharmaceutical prevention and control. Peanut leaf spot includes peanut brown spot and black spot. The occurrence period is in the pod expansion period, when the field disease leaf rate reaches 10%, it should be timely leaf medicine control, commonly used pesticides are 50% carbendazim 600 times liquid, or 96% Tianda dimethyl mycolin 3000 times liquid, or 70% methyl buzine 600 times liquid spray.

Peanut bulbous shell of the short fat spores.

The characteristic is that you will find that the leaves have yellowish conditions and wax, and most of the leaves have the same symptoms of old age, and they are relatively short, looking malnourished, and the fruiting rate is relatively low.

This condition is characterized by a lot of red spots on the leaves of peanuts, and there are also a lot of bugs.

The features are still very obvious. Generally, it can be clearly seen on the epidermis, and some black-brown lesions will appear quietly in the vertical and pure manner, and the area is also very large, 7 15mm and can penetrate the leaves. The edges become particularly unclear, and they will slowly turn into small black dots in the later stages.

Peanuts have reticulated stains on the surface, and peanuts are very bitter, with a lot of mold entwined in the roots.

It mainly affects leaf patting, but also petioles and stems. Often, the lower leaves of the plant are the first to be damaged. Round or irregular black-brown patches are produced along the main veins.

It is surrounded by a distinct faded green circle with reticulated edges. Lesions do not penetrate the foliage. If there is rainy weather in the orange, the lesions are larger.

Once the leaf is infected, it is easy to fall off, and if the stem veins of the leaf are damaged, it will initially be small brown spots, and gradually expand into water-stained, elongated or oval lesions.

Peanut reticulum is characterized by mold-like spots on the surface of peanut leaves, and these reticulated lines are generally white and radial, and finally the limbs will gradually expand, and Bu Min will become black-brown.

Peanut reticulum disease is characterized by a white color that turns to a grayish-white colony at first. In nature, it is black spherical or oblate spherical.

Peanut reticulosis is a fungal disease of peanut. This causes the surface bond ridge of the peanut to rupture. Then peanuts will cause the cavity to leak and ulcerate.

Symptoms of peanut leaf spot: the initial lesion of brown spot disease leaf is a yellow-brown or rust-colored spot the size of a needlepoint, and then gradually expands to become a nearly round light brown or dark brown lesion of 1 10 mm, with obvious light yellow halo on the edge, and sometimes several lesions are connected together to form large lesions, and gray mold is produced on the old lesions.

The lesions on the stems and petioles are oblong. The diameter of the black spot lesion is 1 6 mm, smaller than the brown spot lesion, black-brown, the yellow halo is less or indistinct, there are many small black spots on the back of the diseased leaf in a wheel-like arrangement, and gray-brown mold is born on it.

Peanut leaf spot is very harmful to peanuts, today I will share with you how to prevent and control peanut leaf spot?

The prevention and control of peanut leaf spot should pay attention to the following points:

Peanut leaf spot usually includes brown spot and black spot, also known as early spot and late spot respectively. Peanut leaf spot disease is common in various flower production areas in China, and it is one of the diseases widely distributed and harmful on peanut in China. The yield of damaged peanuts is generally reduced by l0%-20%, and the yield is seriously reduced by more than 40%.

Brown spot disease generally occurs early, and as the disease progresses, the site of the disease produces nearly round or irregularly shaped lesions, up to 1-10 mm in diameter. The front of the leaf is dark brown, and the back is lighter, light brown or brown, with a yellow halo around the lesion. Under humid conditions, gray mold is mostly produced on the lesions on the front of the leaf, i.e., the conidia and conidia.

When the disease is severe, a large number of diseased spots are produced on the leaves, the diseased spots are connected, the leaves die and fall off, and only a few young leaves at the top are left. The stems and petioles are oblong, dark brown, and slightly concave.

Melanoma and brown spot can occur in a mixture, and melanoma lesions are generally smaller than brown spots, 1-5 mm in diameter, and nearly round or round. The lesions are darker in color, black-brown, and the front and back of the leaves are similar in color. There are usually no yellow halos around the lesions, or there are narrow, inconspicuous yellowish halos.

On the lesions on the dorsal surface of the leaves, there are usually many small black spots (concentric rings) in the shape of concentric rings and a layer of gray-brown mold, i.e., conidia and conidia. After the pathogen infects the leaves, it forms lesions, from small to large, the leaf tissues and cells are damaged, affecting photosynthesis, and it is easy to cause defoliation. The fungus infects the stalks, producing black-brown lesions, which turn the stalks black and die.

Prevention and control methods of peanut leaf spot disease:

1) Reasonable crop rotation to avoid continuous stubble. Peanuts are rotated with sweet potato, corn, rice and other crops for 1-2 years; After the peanut is harvested, the diseased leaves of the residual plants in the field should be removed in time, and the peanut fertilizer should be deeply buried or used as feed.

2) Pharmaceutical prevention and control. The fungicides used for the prevention and control of leaf spot are 800-1500 times of 50% carbendazim wettable powder, 500-800 times of 75% chlorothalonil wettable powder, and 300-400 times of 70% mancozeb wettable powder, 1:2:

200 (copper sulphate: lime; water) Bordeaux liquid, "agricultural resistance 120" 200 times liquid, etc. The disease control index starts to spray at 10%-15% of the diseased leaf rate, and the disease index is 3 5 o'clock, and then sprays once every 10-15 days depending on the development of the disease.

Spray 2-3 times for heavy disease.

3) Choose disease-resistant varieties. Peanut varieties with mild susceptibility are used in various places according to local conditions, such as Jihua No. 2, Jihua No. 3, Luhua LL, Luhua No. 14, etc.

Characteristics of peanut leaf spot: black spot and brown spot are overwintered on the diseased residues in the soil with hyphae or hyphae, and the mycelium directly produces conidia under suitable conditions in the following year, and spreads with wind and rain. Conidia are produced on the lesions and become the source of reinfection in the field.

Brown spot disease generally begins before flowering. The pathogen develops at an appropriate temperature of 25 to 28 degrees Celsius, adapts to temperature greatly, and is more resistant to low temperature than the black spot pathogen, so it occurs earlier than the black spot disease. Melanoma occurs slightly later than brown spot.

The growth and development temperature of the fungus is 10 37 degrees Celsius, and the optimal temperature is 25 30 degrees Celsius.

When the relative humidity is more than 80%, the rainy days are more than 3 days, the rainfall is more than 10 mm, and the dew days are 3 to 4 days conducive to the disease pandemic. In the field, the onset of disease is usually mild in the early growth period and severe in the later stage. The disease of young leaves is mild, and the disease of old leaves is more severe. There are some differences in disease resistance among varieties.

The occurrence of the disease is also closely related to the continuous cropping and growth of peanuts. The disease is mild in crop rotation land; The disease is severe in continuous cropping land, and the longer the continuous cropping period, the more severe the disease. Good soil quality, high fertility level, good flower growth potential, and mild disease; However, sandy land, sloping land, thin soil layer, low soil fertility, and poor flower growth potential are seriously affected.

Peanut leaf spot is a general term for leaf black spot, brown spot and net spot, which can occur in the same plant or even on the same leaf. Brown spot disease occurs early, starting to appear in the field at the early flowering stage. Black spot and net spot disease occur late, and most of them start to appear in the field during the full flowering period. The incidence of black spot and net spot disease is more severe, causing severe defoliation.

The three types of lesions mainly occur on the leaves, and the petioles, leaflets, and stems are also affected. It begins to develop on the lower older leaves, and gradually spreads to the upper leaves, and when the disease is severe, it can form lesions on the stems, petioles, fruit needles and other parts. The leaf spots on the front of the leaf have a clear yellow glow wheel around it; The leaves are yellowish-brown to dark brown.

1.Brown spot disease. It mostly occurs on the front of the leaf, the lesion is yellowish brown or dark brown, round or irregularly shaped, about 4 10 mm in diameter.

There is a clear yellow halo around the lesion, like a frog's eye, and the dorsal color of the leaf becomes lighter, and there is no yellow halo. Sometimes a grayish-white mold is formed on the lesions. Oval lesions are formed on stems, petioles, and fruit needles, dark brown, slightly depressed.

2.Melanoma. Occurs later than brown spot disease, the lesions are small, round, dark brown or black-brown, 1 6 mm in diameter.

The edges of the lesions are neater than those of brown spots, and there are no yellow halos or are not obvious. The leaves are dorsal with many black granular dots, arranged in concentric rings, on which are clusters of spore peduncles and conidia. Please refer to it.

The Cercosporidium State of Mycosphaerlla Berkeleyi is called the short fat spore stage of the peanut bulbous shell. Synonyms Cladosporium personatatum, Cercospora personata, etc. The fruiting body is born on both sides of the leaf, mostly on the back of the leaf.

The peduncle is born under the epidermis, nearly spherical or elongated, brown to black, 75-197 m wide. The conidia are very tightly clustered, blue-brown to smoky-black, uniform in color, regular in width, erect or slightly curved, with 1-3 knee-shaped vertices, unbranched, smooth, sporal scars distinct, thick and prominent, wide, located at the vertices, with 0-1 diaphragm, size. Conidia dark blue-yellow, cylindrical, inverted club-shaped, erect or slightly curved, obtuse at the top, inverted conical truncated at the base, basal umbilicus distinct, wide, with 1-8 diaphragms, mostly 5, not constricted, size.

In addition to harming peanuts, it is also harmful to leguminous plants.