Control Methods and Technical Key Points for Papaya Brown Rot
Generally planted in rows in the ground, but can also be grown as potted specimen plants. The best planting time is before bud break in early spring or after leaf fall in early winter. When lifting seedlings from the nursery, keeping the root system intact is one of the keys to successful planting. Generally, large seedlings for planting should be kept with a soil ball, while small seedlings should retain some native soil depending on the situation. After planting, the seedlings should be...
I. Symptoms: Brown rot mainly damages the fruit, but can also harm flowers and young shoots. When the fruit is affected, small brownish nearly round spots appear first, then as the disease progresses, the spots continuously expand. When conditions are suitable, the spots quickly spread over the entire fruit surface and gradually extend into the flesh, and in severe cases, cause the entire fruit to rot. After the diseased fruit loses water, it becomes a brown mummified fruit, hanging on the branch and not falling for a long time. The pathogen on the pedicel or fruit infects the branches, forming brown canker spots, affecting the normal transport of nutrients and water, inhibiting the growth and development of the branches, and causing the branches to die.II. Disease occurrence pattern: This disease is a fungal disease, and its asexual generation is Monilia of the Deuteromycotina. The pathogen overwinters on mummified fruits, and the pathogen on diseased branches can also cause infection after overwintering. In the spring of the following year, after the temperature rises, the pathogen on diseased fruits and branches produces conidia, which spread by wind and rain. Around early May, after young fruits form, the pathogen mostly invades through wounds on the fruit. Therefore, when pest damage is severe, there are more insect wounds and brown rot is also more serious. In years with early or abundant rainfall, the disease occurs early and severely. Low-lying cultivation sites prone to waterlogging and weak tree vigor are also suitable for disease occurrence. During the fruit expansion period, if there are natural disasters such as violent storms and hail, many wounds are caused on the fruit surface, which also favors pathogen invasion and disease occurrence.
III. Control Methods
1. Dispose of diseased plant residues. After harvesting papaya, in combination with winter pruning, cut off diseased branches, remove diseased fruits, and burn them in a centralized manner, which can effectively reduce the overwintering inoculum source.
2. Chemical control. In early spring before papaya sprouting, spray 1 time with 5 degrees Baume lime sulfur mixture; from after papaya flower drop to before fruit harvest in March-April, spray 1 time every 10-15 days with 50% carbendazim 500 times or 50% thiophanate-methyl 800 times solution, spraying 2-3 times consecutively, and it can also control leaf diseases.
3. Prevent insect wounds. The peach fruit borer is an important pest damaging papaya fruit. In mid-to-late June, just when papaya fruits are expanding, female moths lay eggs in the stem cavity of the fruit and in gaps along the suture. After the larvae hatch, they bite through the fruit skin and bore into the fruit. They not only feed across the flesh in all directions, but also cause insect wounds, which favor pathogen invasion. Control method: during the larval hatching period, spray 90% crystal trichlorfon 1000 times solution or fenitrothion emulsion 1500 times solution, once every 7 days, spraying 3 times consecutively.