Pepper disease and pest control

Pepper blast

Pepper blast, also known as pepper base rot, fast decay and Blackwater disease, is the most important pepper disease in pepper growing areas in the world. It was first discovered in Sandraman, India in 1926, and later occurred in Indonesia, Malaysia, Cambodia, South America and some countries in Africa. Many pandemics occurred in Sarawak in Malaysia, resulting in a massive reduction in pepper production and the abandonment of seriously ill pepper gardens. Pepper blast was first prevalent in Hainan Province in 1960, which destroyed a large area of pepper orchards. The pepper area was not restored until 1969, but it was damaged by pepper blast from 1970 to 1972, and 78% of the pepper gardens were destroyed by the disease, causing serious losses to pepper production in China. The disease also occurred in pepper growing areas of Guangdong, Yunnan and Guangxi.

Symptoms: the root system, base of the main vine, branches, leaves, flowers and fruits of the pepper plant are all affected. The damage caused by the base of the main vine (called pepper head) is the greatest, which often causes the wilting and death of the whole pepper. At the base of the main vine above and below the ground where 20cm had been corked, there were no obvious symptoms in the initial stage of the disease. when the outer skin was scraped off, the endodermis blackened and the xylem was light brown. Longitudinal section of the main vine saw that the xylem duct blackened, with brown stripes spreading up and down, and the junction between the disease and health was not obvious. In the later stage, the outer skin blackens, decays and falls off, the black liquid flows out of the decaying xylem (hence the name of Blackwater disease), and the stele splits into a loose bundle of ductal fibers. Digging and examining the diseased plants, it can be seen that the roots close to the infected underground main vines infected, blackened, rotted, and gradually extended to the root tip, while other roots in the lower layer have not been harmed, which is obviously different from pepper water damage and fertilizer damage starting from the root tip necrosis, and then the symptoms of big root rot. When the plant is infected and decayed at the base of the main vine, the whole leaf canopy becomes dull and dehydrated, and the leaves wither and fall off. If the weather is dry and hot, such diseased plants can suddenly wither within a few days, and finally turn black with the tender vines, and the dead vines can fall off one by one.

The leaves on the lower branches of the plant were first susceptible to the disease, and began to be light brown or gray-black water-stained spots, which rapidly expanded into black-brown and round spots, with radiating edges and inconspicuous contours, and white mildew grew on the back of the diseased leaves when the environment was humid, that is, the hyphae and sporangia of the pathogen. When the climate is dry, the mildew disappears, the disease spot turns grayish brown, and the diseased leaves finally fall off. The cortex of twig vine infection produces waterlogged, dark green disease marks, which fall off one by one when seriously ill. Inflorescence and ear infection usually starts at the top, producing water stains, and then blackens and dries up.

Pathogen: the pathogen is a fungus, the scientific name is Phytophthora capsici and parasitic Phytophthora. Belonging to the subphylum algal bacteria, downy mildew order. The occurrence rates of these two kinds of Phytophthora are about the same in pepper growing areas in China, and they are the main pathogens of pepper blast.

Infection cycle: both Phytophthora and Phytophthora pathogens can survive in the diseased tissue and soil of pepper plants. Bacteria-containing soil, diseased (dead) plant tissue and other host plants can provide the source of primary infection bacteria. The pathogen is mainly transmitted by running water (running water, irrigation water) and wind and rain. People, animals, farm tools, seedlings and large snails can also carry bacteria to spread the disease. The germ tube of sporangium or zoospore can invade from the natural orifice or wound of the host, or directly penetrate into the young tissue and inoculate the main vine of cork pepper. The incubation period is 15-20 days, and the incubation period is 2-5 days.

Epidemic rule: the epidemic of pepper blast is closely related to the soil type, topography, cultivation measures and rainfall in the pepper garden. In general, heavy soil viscosity, poor drainage or low-lying stagnant water occurs early and the disease is serious; on the contrary, the disease of sandy soil and good drainage is mild. Pepper gardens with concentrated pepper gardens, no shelterbelts, or sprained pepper heads when changing pillars, or weeding in sick gardens on rainy days, or pepper gardens where diseased plants are not removed and sprayed in time, are often prevalent in rainy years, especially in years with many typhoons. The epidemic of the disease in one year can be divided into the stage of central disease strain (area), the stage of universal spread, the stage of serious disease and the stage of mass death and the stage of decreasing epidemic rate. The disease began to occur on a small number of plants from March to April every year, and the epidemic period of blast was from August to November. Prevention and control methods: in order to control the epidemic of pepper plague, comprehensive disease control measures should be adopted with the combination of agricultural measures and chemical control.

1. Agricultural preventive measures

(1) to select a site to build a new pepper garden, it is necessary to do a good job in land planning and farmland infrastructure. That is, to choose good water permeability and easy drainage of the land to grow pepper; pepper garden should not be too concentrated, each pepper garden area of 3 to 5 mu is appropriate, all around a good shelterbelt; garden to repair terraces or contour up the border, dig a good ring garden drainage ditch and small drainage ditch between rows to prevent bacteria from spreading through running water; low and flat areas to build piers to plant pepper.

(2) the disease-free seedlings should not be cut in the disease garden as cutting material, and the seedlings should be raised in the disease-free land.

(3) strengthening tending management, weeding and fertilization should be carried out on sunny days, and pay attention to not injuring pepper head and root system; properly pruning the branches close to the ground to reduce the humidity of pepper head and reduce the disease of lower leaves; cultivate soil in time to make pepper head rise above the ground, prevent pepper head from stagnant water and germs from invading pepper head with running water; timely remove litter and diseased and dead pepper head in the garden; do not apply nitrogen fertilizer. Cover plants or cover with hay between rows of pepper orchards to reduce the spread of germs in running water and splash when it rains.

(4) to grasp the disease in time and do a good job in isolating the epidemic season of diseases in the disease areas, especially in the rainy season of typhoons, special personnel should be sent to inspect the disease in each garden. Once diseased plants are found, medicine should be applied in time to prevent and control the disease, and people and animals should not be allowed to enter the disease area. farm tools used in the disease area should not be brought to the disease-free garden. In field management, the disease-free garden should be first, and then the disease garden. Stop weeding, fertilizing and other agricultural activities in the disease garden when the soil is wet on rainy days, so as to reduce man-made transmission.

2. Chemical control

At the initial stage of the disease, 1% Bordeaux solution or 40% aluminum triethylphosphonate wettable powder 100 times solution should be sprayed on the central area (plant) and surrounding plants, and 1% copper sulfate solution or 1% Bordeaux solution should be used to spray the soil between rows in the disease area. Dig out the dead plants in time, transport them out of the garden and burn them, and the diseased soil should be dug and exposed to the sun or irrigated with 1% copper sulfate solution for disinfection.