Chen Hongfu

There are about 29 diseases of educated youth, including 23 fungal diseases, bacteria, nematodes and element deficiency 1 species, and 3 viral diseases. Twenty-three species have been found in China, among which stem blight, anthracnose, brown spot, black spot, damping-off disease, downy mildew and root cancer are serious, resulting in seedling death, early defoliation or dead plants in adult stage, and China loses about 10% of fiber due to illness every year.

brief history

Green hemp (abutilon) originated in China and was cultivated as early as 2,500 years ago as a raw material for clothes and ropes. China 1755 Yi Ding mentioned the role of crop rotation in preventing bacterial wilt and reducing dead seedlings in his book "Guide to Farmland". 1928, Kogoro Nakata of Japan and others listed the diseases of kenaf in North Korea. In the same year, the former Soviet Union (E.S.Kvashnina) conducted a preliminary study on kenaf diseases in the North Caucasus. In 1942 and 1943, Hiroshi Takeo and Guiqiyi investigated and discussed cotton and flax diseases in North China and Northeast China of China. The main agricultural pests and diseases in China and their control, compiled by the Plant Protection Department of the Ministry of Agriculture of China in 1954, described the disease and its control in detail.

Types and hazards

The main diseases of green flax are seedling disease, root disease, stem disease and leaf disease.

Seedling diseases

There are 9 species in China. Serious damages include Rhizoctonia solani, which leads to lodging and death of seedlings, especially in China and Japan. Downy mildew (downy mildew), which damages young leaves and tops, causes diseased leaves to fall early or seedlings to die, is widespread in Northeast China and North China. Beijing anthrax. In some areas of China, Indian, Japanese and American, Phoma adzuki can also cause seed rot, bud rot, seedling rot and seedling collapse.

Root disease

There are four kinds in China. Root knot nematodes. , widely distributed and harmful, can cause many kinds of tumors in the root system of hemp plants, cause yellow leaves and short plants, and are easily infected by fungi to cause root rot, especially in China and Indian hemp areas. Carbon rot leads to root rot and death. Agrobacterium tumefaciens Conn is a bacterial disease, which causes the roots to be hypertrophy-like and then rot, and it occurs in China and the United States.

Stem disease

Six species have been found in China, mainly including: stem blight, also known as macrophoma abutilonis nakata et takim. Most of them are dark brown, spindle-shaped or strip-shaped lesions at the height of 0/5 ~ 30 cm from the ground/kloc-,and then spread around the whole stem, exposing fibers. In severe cases, hemp stems will break and die, which is widespread in China. Stem rot. ) mostly occurs in the leaf scar about l meters above the ground. The lesion is spindle-shaped, with large protrusions, first red, then black spores. After the lesion splits, fibers can be exposed, and the lesion is curved. In severe cases, cannabis plants will die. China and Japanese hemp areas are common. Anthracnose, the lesion is dark brown, cracking and drying along the longitudinal direction of the stem. Carbon rot will lead to stem base and stem rot, and hemp plants will wither.

Leaf disease

China has found 10 species, mainly including downy mildew and Cercospora hollyhock. , Pholiota abutilon and Pholiota abutilon. Causes the leaves to produce necrotic spots with different sizes, shapes and colors, and the diseased leaves fall early. China and the former Soviet Union also have black spot disease. ) He Fei], leading to a large cloud-like lesion in the leaves and the death of the diseased leaves. In addition, kenaf in China and the United States is also harmed by tobacco ringspot virus.

Verticillium dahliae And Fusarium species. It is a common vascular disease in China, the United States and the former Soviet Union. The symptoms of leaves vary greatly. The stem is cut off, the vascular bundle becomes discolored, and the hemp plant dies in severe cases.

The diseases that have been seriously harmed by some hemp-producing countries in the world but have not been discovered in China are: Dugger's disease is a serious disease in Tashkent, the former Soviet Union, and tobacco fungal disease (Cladosporium her-barum Link) is in the former Soviet Union and the United States. In addition, cotton in the former Soviet Union was also infected with tobacco reticular virus, and cotton in the United States was harmed by mallow virus.

The pathogens of most diseases of kenaf can overwinter in seeds, diseases and soil, and become the source of infection at the beginning of next year. During the growth process, green flax was reinfected by wind and rain, insect pests and agricultural operations. Seeds and soil with high bacteria content, low temperature and rainy weather, susceptible varieties, high density, partial application of nitrogen fertilizer, low-lying and humid areas and continuous cropping of hemp fields are all beneficial to the occurrence of diseases.

disease control

The following are common methods to control this disease. ① Strictly implement the quarantine system. Prevent quarantine diseases, especially root rot, from being introduced into China. ② Seed treatment. Soaking or dressing seeds with thiram, triamcinolone acetonide or carbendazim can significantly improve seed germination rate and reduce seedling diseases. ③ Cultivation measures. Remove the sick and disabled, rotate crops, plant disease-resistant varieties, reasonably close planting, fertilization and irrigation and drainage. ④ Drug control. Spraying thiram, tuijunte, metalaxyl or carbendazim at the initial stage of the disease.

Qiu (1922 ~)

Sun Shougong

Plant pathologist. Lianjiang county, Fujian province. 1948 graduated from the Department of Plant Diseases and Pests of Fujian Provincial Agricultural College, and once worked as a teaching assistant in the Department of Plant Diseases and Pests of Taiwan Province Provincial Agricultural College. 196 1 received a doctorate from Kansas state university. After returning to Taiwan Province, he was appointed as the "China-Canada Joint Committee for Rural Rehabilitation" and a professor at Zhongxing University. 1975 to 1987, employed as a researcher at the Institute of Botany.

He was engaged in plant virology research in 1960s, and found and named rice yellowing disease, which proved to be a virus disease carried by the black-tailed leafhopper, belonging to Rhabdoviridae. He established the direction of field control and successfully purified the virus. 1965- 1968 studied the cell culture of cicada in Illinois state university, established several cell culture lines, developed the fluorescent antibody quantitative technique of WondTumour virus and potato flavivirus, and applied it to the study of rice yellow leaf virus. He has published more than 60 academic papers.

Begonia disease

Legonia's disease

Xing Yong

More than 30 species are known in the world, and there are about 199 15 species in China. Powdery mildew, gray mold and so on harm leaves, stems and flowers. The leaves are mainly damaged by Legionella, anthrax and bacterial leaf spot. Rhizomes or roots are mainly harmed by Rhizoctonia solani, stem rot and Rhizoctonia solani, and roots are mainly harmed by Agrobacterium tumefaciens and meloidogyne incognita. There is mosaic disease (CMV) in virus diseases. Bacterial leaf spot, powdery mildew and gray mold are common and serious. Local damping-off and basal rot occur more frequently.

Bacterial leaf spot

Mainly harmful to leaves, there are small and round waterlogging spots with yellow halo around them, which expand into dark brown withered spots and spread to the whole leaf surface. Finally, the leaves die early and fall early, and there is tremella pus in the affected area when wet. The pathogen is Xanthomonas campestris var. campestris. A plant bacterium. Harm begonia, such as begonia argentea, begonia rubra (B.coccinea), begonia (B.coan-siana), begonia toads (B.rex.) and begonia perefrons. The pathogen mainly overwinters in diseased leaves and residues and invades from wounds or stomata. When it is exposed to wind, rain or water, water droplets splash and spread. The incubation period is usually 7 ~ 10 days. Disease control: we should pay attention to cleaning the countryside and improving cultivation measures, such as clearing diseased plants, keeping the distance between plants or potted plants, keeping the relative humidity in the greenhouse at about 40%, and not leaving water droplets on the leaves when watering or irrigating; Spraying agricultural streptomycin, copper hydroxide and other fungicides when the disease occurs.

powdery mildew

The harm is second only to bacterial leaf spot. White powdery spots are produced on the surfaces of leaves, stems and flowers, which are connected together in severe cases. Pathogens: Begonia sinensis in Beijing, Yunnan and Henan, Begonia yunnanensis in Yunnan, erysipelas, ascomycetes and powdery mildew on Begonia; Begonia yuanshanensis (B.laciniata var.lormosana) reported in Taiwan Province Province is elliptic, Hemiptera and filamentous. South China is not easy to form sexual behavior. There are at least two different types of pollen spores. The host is all kinds of begonia. Pathogens have physiological differentiation. There are obvious differences in disease resistance among host species or varieties. Begonia argentea is highly susceptible to disease, and begonia four seasons is moderately susceptible to disease. It can occur at 10 ~ 26℃, and high temperature (32℃) is not conducive to bacterial infection. Bacterial control: clear the field and spray triamcinolone acetonide and colloidal sulfur when the disease occurs. In addition, there are reports on the prevention and treatment of chlorpyrifos, actinomycin and buprofezin.

gray mold

(See blue disease).

damping off

Causes the seedlings to collapse or the cuttings to rot. When it is hot and humid, white flocculent mycelium can be seen on the surface of dead seedlings and nearby soil. The pathogen is pythium. It belongs to the class Oomycetes downy mildew. Before sowing, the pot soil is not disinfected, accumulated water, watered too much, and covered with too thick soil is easy to get sick and die. Soil-borne diseases. Disease control can disinfect the basin soil with Dixintong before sowing.

Basal rot

It leads to brown rot of the stem or stem base, and in severe cases, the leaves are also killed, forming a large circular spot of waterlogging. When wet, there are a small amount of brown mycelium and brown granular sclerotia in the affected area. The pathogen is cucurbitaceae, which belongs to basidiomycetes and myxomycetes. The asexual state is Rhizoctonia solani, which belongs to semi-unknown bacteria and asexual order. Disease control: In order to keep the plants ventilated and transparent, potted soil was treated with pentachloronitrobenzene before sowing, and validamycin was poured at the onset.

Yuan Qiu (1909 ~ 198 1)

Aurora Li

Plant pathologist. People from Nanjing, Jiangsu. 1932 graduated from the Agricultural College of Jinling University, and successively served as technical assistant, technician and technical director in Nanjing Central Agricultural Laboratory and Chongqing Municipal Government Agricultural Extension Committee. 1947 went to the university of Nebraska for further study, and 1950 received a doctorate in natural science. After returning to China in the same year, he successively served as a professor at Jinling University, Hubei Agricultural College and Northwest Agricultural College. He was the first director of China Botanical Pathology Society, the director of China Botanical Protection Society and the chairman of Shaanxi Botanical Pathology Society.

In scientific research, he mainly engaged in the study of wheat and cotton diseases, and made contributions to the prevention and control of wheat scab and rust. Since 1953, he has been responsible for the research of cotton verticillium wilt for a long time, bred the first cotton disease-resistant variety "Xinong Zhongsan" in Shaanxi Province, studied and clarified the transmission route of cotton verticillium wilt seeds, and put forward the inspection technology of cotton verticillium wilt seeds and the disinfection method of drugs; Participated in the identification and division of physiological types of cotton Fusarium wilt, promoted the identification of cotton variety resources and breeding of disease-resistant varieties, and 1978 won the National Science Conference and Shaanxi Science Conference Award. His main works include cotton wilt, wheat scab, cereal crop diseases, pasture and green manure crop diseases, tree diseases in protected areas, etc., and he has published more than 50 academic papers.