Beware of soot disease when growing mango

In recent years, mango soot disease has caused more and more serious harm to mango fruit, which has greatly affected the fruit quality. The following briefly introduces the symptoms and hazards of soot disease, the occurrence of the disease and the methods of prevention and treatment, in order to provide reference for the majority of fruit farmers.

First, symptoms and hazards. Soot disease mainly harms the fruit of mango and also affects the branches and leaves to a certain extent. When the fruit grows to fist size, a few small black spots can be observed on its surface, as if stained with a small amount of coal ash, which is the initial manifestation of fruit disease. As the fruit grows, the black spots expand, forming a black stain, which usually develops from the pedicel to the waist. When the fruit body is dry, it is difficult to wipe off the black stain. If the contaminated fruit is immersed in water for a few minutes, the black stain can be washed off gently with wet gauze. In particular, it should be pointed out that the disease only affects the fruit epidermis and has no direct harm to the pulp. The appearance of the damaged fruit is poor, and in serious cases, the whole pericarp becomes black like black ink, and the commodity value is greatly reduced. The main effect of soot disease on leaves is to reduce the photosynthesis of leaves, but according to the author's observation on many fruit farms in this county in recent years, the effect of soot disease on leaves is not very great.

Second, the occurrence of the disease. 1. Natural environmental factors. The topography, ventilation and light of the orchard are closely related to the occurrence degree of soot disease. Generally speaking, the orchard has high topography, large distance between fruit trees, good ventilation and illumination, less ground weeds and small relative humidity of orchard microclimate, so the disease is mild, and vice versa. 2. Pest factors. The black stain on the surface of the fruit is actually a large number of coal bacteria. The honeydew secreted by Homoptera insects (shell insects, leafhoppers, aphids and red spiders, etc.) adheres to the branches, leaves and fruit surfaces of fruit trees. Honeydew is rich in a variety of organic compounds needed for the growth of coal bacteria, which provides an environment for the mass reproduction of coal bacteria. In the event of Rain Water, honeydew will flow down the water, coal bacteria will also develop downward, forming the so-called "mango tears" phenomenon.

Third, prevention and control methods. 1. Prune the fruit trees in time after the fruit is harvested every year, cut off the withered leaves and old leaves, collect the cut branches and leaves into piles, and burn them. Weeds in the garden should be cleared regularly, especially during flowering and fruiting, and withered grass should be burned or buried. In order to control Homoptera insects regularly, we should pay special attention to the shell insects (usually elliptical shield), because the adults have waxy shells on their bodies and have strong resistance to pesticides, so the effect of application is good only in the nymph period when the shell is not formed. The nymph stage of shell insects is in mid-May, mid-late July, mid-late September and early October. Seize these periods and spray with 1000 times 40% omethoate EC. Shell insects are mostly hidden on the bottom of the leaves, so attention should be paid when spraying pesticides. 2. Prevention and control of coal bacteria. 30% copper oxychloride gel suspension 800 times solution and 70% methyl topiramate wettable powder 800 times solution can be used to spray or spray copper master. Experiments show that the effect of the latter two is better. In theory, it is best to spray once a month or two, and those without conditions can be sprayed once in flowering and fruiting respectively, but the effect will be slightly worse.