Pepper blight is one of the main diseases on pepper, which occurs throughout the country, with a short incidence cycle and a rapid epidemic rate. The general incidence is 20% to 30%, and the serious disease of the field is more than 70%, which can lead to harvest failure when severe.
Primary symptoms
It is mainly harmful to leaves, fruits and stems, especially the base of the stem is the most susceptible. Stem infections are mostly near the ground or at forks, with dark green, moist, amorphous patches first appearing, and then becoming dark brown to black spots. The diseased part is often depressed or shrunken, resulting in the wilting of the upper branches. The leaves are infected with spots with inconspicuous brown edges, and the roots of the diseased leaves quickly decay and fall off. Fruit infection mostly starts from the pedicle, appears like hot water scalding, dark green to dirty brown, the edge is not obvious spots, can make the local or the whole fruit rot, gradually lose water after becoming a black brown zombie fruit can remain on the branches. When the humidity is high, a sparse layer of white mold can grow on the surface of the infected site, which is the sporangium and sporangia of the pathogen.
Symptoms at the base of the stem
Stem-onset symptoms
Pathogenic features
The pathogen is Phytophthora capsicum, which belongs to the subphylum flagella. The sporangia are simple, hyphal-like and pale. The sporangia are apical, oblong-oval, pale, with papillary protrusions at the apex, and are 27.6 to 55.8 × 15.5 to 31.6 microns. Germination produces multiple zoospores with biflage. The oospores are spherical, yellowish brown, and have a diameter of 15 to 28 microns. The bacteria can also produce spherical, thick-walled spores, yellowish and single-celled.
Branching symptoms
Regularity of occurrence
Pathogenic bacteria mainly overwinter in the soil and on the disease residue with oospores, and generally survive for more than 3 years. Under the right temperature and humidity conditions, the oospores begin to germinate, producing zoospores that invade the roots, stem bases, and leaves of peppers. During the growth of peppers, the diseased plants successively produce sporangia and zoospores, which spread with irrigation water and rainwater, and re-infect multiple times. Pathogenic bacteria can also be transmitted through wind and rain splashing and agricultural operations, causing leaf, branch and fruit disease.
Fruit onset symptoms
Symptoms of late fruit onset
Cause of onset
The growth temperature range of the pathogen is 10-37 ° C, and the most suitable temperature is 20-30 ° C. When the relative humidity of the air reaches more than 90%, the onset of the disease is rapid, especially after heavy rains, the weather turns clear, the temperature rises sharply, and the epidemic occurs more severely and spreads rapidly. Heavy stubble, low-lying land, poor drainage, excessive use of nitrogen fertilizer, excessive density, and weak plants are all conducive to the occurrence and spread of the disease. It is most vulnerable to hanging fruit with chili peppers.
Prevention and control of the French side
(1) Selection of disease-resistant varieties: According to different seasons and cultivation methods, selecting suitable high-yield disease-resistant varieties is the most effective way to prevent the spread of epidemic diseases.
(2) Clean the countryside: the diseased plants found in the field should be pulled out in time, and the stumps and leaves should be removed in time after harvesting, reducing the source of initial infection, and the areas with conditions can be rotated with non-nightshade fruits and melons for more than 2 to 3 years.
(3) Strengthen cultivation management: when planting, it is necessary to fully cover the mulch film, strengthen the ventilation and drainage of the field, and strictly prevent the accumulation of water in the field. Shed cultivation should adjust the temperature of the greenhouse and the relative humidity of the air, so that the temperature is maintained at 25-30 ° C during the day, maintained at night at 14-18 ° C, and the relative humidity of the air is controlled below 70%, so as to facilitate the normal growth and development of peppers, which is not conducive to the development of disease infection and disease, and achieves the purpose of preventing and controlling diseases.
(4) Pharmaceutical control: after pepper transplanting slow seedlings, the first flowering stage, before and after rainy days on the open ground and before and before protective watering, pay attention to spray protection, you can choose the following agents or formulas for prevention and control: 38% frost azoxystril 800 times liquid, or with 58% methanol ling manganese zinc wettable powder 600 times liquid, or 64% antivenomy vanadium m8 wettable powder 500 times liquid, or with 25% methanol wettable powder 700 times liquid, or 56% azoxysporin 600 times liquid, 4% pyrimidine nucleoside antibiotic 500 times liquid, Or 75% Bacillus Qing wettable powder 600 times liquid, or 72.2% Pulik water agent 600 times liquid ~ 700 times liquid, or 40% frost plague spirit wettable powder 200 times liquid and other agents. Depending on the condition, spray once every 7 to 10 days, and spray 2 to 3 times.
In addition, it is also possible to carry out liquid irrigation to block the incidence center, you can use 50% copper wettable powder 600 times liquid, or 30% methyl frost 600 times liquid, or 25% methyl cream wettable powder 700 times liquid, or 72% gram anti-cream wettable powder 600 times liquid to the disease hole and surrounding plants irrigation roots, each plant liquid amount of 250 grams, irrigation 1 to 2 times, interval 5 days to 7 days.
Cultivated in the shed, it can be used in the early stage of the disease, with 45% bacterium clearing aerosol agent 250 grams to 300 grams per acre. Divided into 4 to 5 piles of smoke prevention and control.