Control of brown rot of planted papaya

First, symptoms: Brown rot mainly harms fruits, but also flowers and tender shoots. Fruit disease, the initial brown nearly round small disease spot, and then with the development of the disease, the disease spot continues to expand, when the conditions are suitable, the disease spot quickly expand the whole fruit surface, and gradually extend to the pulp, serious, make the whole fruit rot. After losing water, the diseased fruit turns into a brown stiff fruit, hangs on the branch and does not fall for a long time. The bacteria on the pedicel or fruit invade the branch, form brown ulcer spot, affect the normal transport of nutrients and water, inhibit the growth and development of the branch, and cause the branch to die.

Second, the regularity of the disease: the disease is a fungal disease, and its asexual generation is a cladosporium of the subphylum semichi. The pathogen overwintered on the stiff fruit, and the pathogen on the diseased branch could also be infected after overwintering. In the following spring, after the temperature rose, the bacteria on diseased fruits and branches produced conidia, which were spread by wind and rain. Around the first ten days of May, when the young fruit was formed, the bacteria mostly invaded from the fruit wound. Therefore, if the insect pests are serious, the brown rot will be serious. In the years with early or more rainfall, the disease is early and serious, the cultivated land is low-lying, vulnerable to waterlogging, and weak trees are also suitable for the disease. During the fruit expansion period, in case of natural disasters such as strong wind, torrential rain and hail, there are many wounds on the fruit surface, which is also conducive to the invasion of germs.

III. Prevention and control methods

1. Deal with the sick and disabled body. After the harvest of papaya, combined with winter pruning, cutting off diseased branches, removing diseased fruit, concentrated burning, can effectively reduce the source of overwintering bacteria.

2. Chemical control. In early spring, before papaya germination, spray Baume 5 degrees stone sulfur mixture; from March to April after blossom to fruit harvest, you can spray 50% carbendazim 500 times or 50% methyl topiramate 800 times every 10-15 days, 2-3 times, and can also treat leaf diseases.

3. Prevent insect damage. The peach borer is an important pest that harms the papaya fruit. In mid-late June, when the papaya fruit was expanding, the female moth laid its eggs in the pedicel and cavities of the fruit. After the larvae hatched, they bit through the pericarp and ate into the fruit. It not only eats flesh vertically and horizontally, but also causes insect wounds, which is conducive to the invasion of bacteria. Control methods: during the larval incubation period, spray 1000 times of crystal trichlorfon or 1500 times of fenitrothion emulsion, once every 7 days, for 3 times.