First, papaya major diseases Papaya disease is currently known in a variety of species, of which the most common and most dangerous is the virus caused by papaya ring spot mosaic disease. In addition, there are anthrax, leaf spot, and storage diseases. 1. Papaya ring spot mosaic disease Papaya ring spot mosaic disease, commonly known as mosaic disease, occurs in the main planting areas of papaya. (1) In the early onset of symptoms, water stains appear between stems, veins, and veins of young leaves. Subsequently, yellow-green and dark green and light green mosaic symptoms appear on the young leaves, on the epidermis of susceptible fruits. Water-stained round spots (ring spots) also appear, and several round spots can be combined into irregular shapes. During the cold period, most of the leaves of the diseased plants fell off and the young leaves became deformed. (2) Pathogens and transmission Pathogens of papaya virus include papaya mosaic virus, papaya ring spot virus, and papaya leaf-defying virus. The natural transmission media is peach aphid and cotton aphid, and the transmission rate is very high. Friction is very easy to spread, and the leaves of diseased plants in the field can be infected by contact with the leaves of healthy plants. (3) Incidence conditions 1 climatic conditions. In warm and dry years, serious problems occur. Therefore, under the climatic conditions in Guangzhou, there may be two peak periods of disease and one strain of disease returning to the green period in one year. From April to May and from October to early November, the monthly average temperature is 20-25°C, the most common strains are the symptoms, and the most obvious symptoms are; from July to August, the average temperature is 27-28°C. During the period, symptoms disappear or slow down. The high temperature has an inhibitory effect on the virus, and the diseased plants are heated to 40° C. per day for 4 consecutive days for 4 hours. The diseased plants return to green and the lesions disappear, but after a few days of high temperature, the symptoms reappear. 2 orchard location. Because this disease is mainly transmitted by locusts, any plant that is adjacent to the old orchard or neighboring orchard disease has a fast onset and a high incidence. The orchards planted year after year have an early onset and high incidence. 3 The growth period and growth status of the plants. Papaya can be infected with ring spot mosaic disease throughout its growth and development stages. (4) Prevention and control methods There is no radical method yet, but comprehensive prevention and treatment measures based on cultivation measures are adopted. 1 Select resistant varieties. 2 Strengthen cultivation and management, improve cultivation and management measures, and enhance plant resistance and disease resistance. 3 timely removal of diseased plants. 4 eliminate the source of disease and properly isolate it. 5 drug off. Spraying drugs regularly on a regular basis, in the peak period of aphid migration, especially in the dry season to check the spraying. The locusts around the orchard like to inhabit weeds and should pay attention to clearing. 2. Papaya anthracnose This disease is another important disease after papaya ring spot mosaic disease, and it commonly occurs in production areas such as Guangdong, Guangxi, Fujian and Taiwan. The disease can occur throughout the year, with the most serious fall. The incidence of young fruit and mature fruit is more, and the disease can continue to be harmed during the storage period of the fruit. (1) Symptoms The disease mainly damages the fruits, followed by damage to the leaves and petioles and stems. The victim's fruit surface first appeared yellow or dark brown spots of water-stained spots. As the lesions gradually expand, the lesions are sunken in the middle, concentric ring patterns appear, and the scarlet sclerotiophores grow on the surface, and then become dark spots. On the leaf blade, lesions mostly occurred on the tip and leaf margins, were brownish, irregularly shaped, and had small black spots on the spots. (2) Pathogens and pathogenicity The pathogen is anthrax pathogen, which is overwintering in the diseased body. Under conditions of high temperature and high humidity, it is conducive to the occurrence of diseases. Conidia are spread by wind and rain and insects, and are invaded by stomata, wounds or directly from the epidermis. (3) Control methods 1 Winter Garden. Thoroughly remove the body of the disease, concentrate burned or buried deeply, and spray Bordeaux multi-injection once. 2 chemical control. From August to September, the onset of the season sprayed every 10-15 days and sprayed 3-4 times. The medicament can be sprayed with 70% thiophanate-methyl wettable powder 800-1000 times, or 40% chlorfenone suspension 250-350 times, or 50% carbendazim wettable powder 800 times, and timely remove the disease. fruit. 3 Pick fruits timely to avoid over-harvesting. To avoid injuring the fruit when picking, spray 70% thiophanate-methyl wettable powder 1000 times two weeks before fruit picking, which can play a role in preservation and preservation. 3, papaya tumor disease (1) symptoms of smaller leaves, petiole shortened, young leaves tip dead and brown, leaves can be curled, shedding, male flowers variable male, flowers often withered. When the fruit is very small, it falls off. There is milk outflow on the fruit, young leaves, flowers, stems, and white dry matter on the outflow site. The fruit has symptoms of milk efflux during the young fruit stage and even early mature stage, and most of them are outflowing on the sunny side of the fruit. After the peel sheds the juice, it will slowly fester and soften. The ulcerated part will turn brown, and the no ulcerated fruit will have knobs. Uneven. Severe diseased fruits were degenerated and aborted, and young white seeds became brown and necrotic. (2) Pathogen This is a physiological disease caused mainly by the lack of boron in the soil. (3) Control methods to supplement boron in a timely manner. Boron may be applied to the soil or boron may be applied to the roots, and boric acid or borax may be used. Dig a small hole next to the plant, apply 2-5 grams of borax per hole, or boric acid 3 grams per hole, usually 1-2 times. The external application of boron can be sprayed with 0.2% boric acid water, spraying once every Other week for a total of 3-5 sprays. The application of borax or boric acid should be completed when the papaya plants are budding. Second, the main pests of Papaya harm Papaya common pests are Papaya round scale insects, spider mites, locusts, snails, etc., seedlings are often affected by ground tigers, giant salamanders and other underground pests. 1. Red spider (1) Hazardous characteristics: Chengyu and Ruoqiang are active on the back of leaves and absorb juice. The green leaves of the victims were yellowed and the yellow spots were seriously damaged. The symptoms were mosaic symptoms. The chlorosis of the damaged leaves affected photosynthesis, and the leaves were severely detached and the plant growth was affected. (2) Regularity of occurrence The papayas cultivated in the Guangdong region are endangered by spider mites throughout the year. They occur more than 20 generations per year and overlap from generation to generation. However, peaks occur from April to May and from August to November. (3) Control methods 1 Agricultural control. When the papayas are cut off, timely removal of field residues and weeds is required. 2 biological control. It was found that the spider mites could be sprayed 3-4 times to reduce the larvae and protect the natural predators. 3 In the peak period, chemical control was performed. Drugs should consider the type, method and frequency of pesticides and try to protect natural enemies. Colloidal sulphur suspension agent can be used 250 times, spraying once every 5-7 days in the larval incubation period, and spraying 2-3 times. Acaricides may also be used, such as 73% Creutine 1500-2000 times, 5% Nicoroxide 2000 times, 50% Torc 2000-2500 times. 2. Aphid locust is one of the main insect vectors of papaya ring spot mosaic disease, and it mainly has peach aphid and cotton aphid. Its control methods: 1 nursery should be away from peach host plants, clear field weeds. 2 Cut off diseased diseased locust strains. 3 surface covered with silver gray film drive. Seedling and pre-growing period with 32 mesh net room flood control. 4 Aphids were detected and applied at the peak of their application. Can be used 50% Bataan soluble powder 1000 times, 40% Dimethoate EC 1000 times, 50% Aowei Wei WP 2000-3000 times, 50% Malathion EC 1500-2000 times and other insecticides Use alternately.
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