Control of brown rot of papaya

Symptoms: Brown rot mainly harms fruits, but also flowers and tender shoots. Fruit disease, the initial brown nearly round small spots, and then with the development of disease, the spots continue to expand, when the conditions are appropriate, the spots quickly expand the whole fruit surface, and gradually extend to the flesh, serious, so that the whole fruit rot. After losing water, the diseased fruit becomes brown stiff fruit, hangs on the branches, does not fall for a long time, the pathogen on the flower stalk or fruit infects the branches, forms brown ulcer spots, affects the normal transportation of nutrients and water, inhibits the growth and development of the branches, and causes the branches to die. 2. Pathogenesis rule: The disease belongs to fungus disease, and its asexual generation belongs to botrytis of subphylum Hemiphyta. The pathogen overwinters on the dead fruit, and the pathogen can also infect the diseased branch after overwintering. In the spring of the following year, after the temperature rises, the pathogens on the diseased fruits and branches produce conidia, which are transmitted by wind and rain. Around early May, when the young fruit formed, most of the bacteria invaded from the wound of the fruit. Therefore, heavy insect pests, insect damage more brown rot is also serious. Early or more rainfall years, early and heavy disease, low-lying cultivation land, vulnerable to waterlogging, weak tree vigor is also suitable for disease. Fruit expansion period, in case of storm, hail and other natural disasters, to the fruit surface caused by more wounds, but also conducive to the invasion of bacteria and disease. 3. Prevention and control methods 1. Treatment of sick and disabled bodies. After harvest, papaya combined with winter pruning, pruning diseased branches, removing diseased fruits, concentrated burning, can effectively reduce overwintering bacteria source. 2. Chemical control. In early spring, before papaya sprouts, spray 1 time of 5 degrees of stone sulfur mixture;3-4 months after papaya blossoms to before fruit harvest, spray 50% carbendazim 500 times or 50% methyl thiophane 800 times every 10-15 days, spray 2-3 times continuously, and can also cure leaf diseases. 3, insect injury. The peach moth is an important pest that harms papaya fruit. In mid-to-late June, when papaya fruit expands, female moths lay eggs in the hollow of fruit stalk and the gap between the joints. After hatching, the larvae bite through the pericarp and bore into the fruit. It not only eats pulp vertically and horizontally, but also causes insect wounds, which is conducive to the invasion of germs. Control method: spray 90% crystal trichlorfon 1000 times solution or fenitrothion emulsion 1500 times solution every 7 days for 3 times in succession during larva incubation period.