Control Methods for Mango Sooty Mold and Algal Leaf Spot

(1) Mango sooty mold:

1. Symptoms: This disease mainly occurs on leaves and fruit. A layer of black fuzzy material covers the surface of leaves and fruit, resembling soot, hence the name sooty mold. In severe cases, the entire leaf and fruit are covered by mycelium (soot). This type of fungus mainly grows on the outer surface of leaves and does not easily penetrate the leaf tissue, so it is easily wiped off.

2. Pathogen and occurrence pattern: The scientific name of the pathogen is Capnodium mangiferae P. Henn. This fungus mainly relies on the honeydew secreted by aphids and leafhoppers; when aphids and leafhoppers occur in large numbers, sooty mold is also more severe. The pathogen favors humidity, so mango orchards planted too densely and with excessive shade are prone to the disease.

3. Control methods: Controlling aphids and leafhoppers is an effective way to prevent this disease. After the disease occurs, spraying 0.3 degree Baumé lime sulfur mixture or dithiocarbamate has a certain effect.

(2) Mango algal leaf spot:

1. Symptoms: This disease mainly occurs on leaves, on both the upper and lower surfaces. Initially, small round spots the size of a needle head appear, white to pale yellow-brown, and gradually expand radially in all directions, forming round or irregular slightly raised felt-like spots with uneven edges, gray-green or orange-yellow. Later the surface becomes relatively smooth and the color deeper.

2. Pathogen and occurrence pattern: The pathogen is Cephaleuros virescens Kunze. It occurs in orchards with poor, thin soil, overgrown weeds, low-lying terrain, damp and shady conditions and poor light penetration, as well as on old trees with weak growth and on old leaves and branches in the lower part of the canopy. It absorbs water and mineral nutrients from the mango tree, but has little direct impact on the mango tree.

3. Control methods: Rational fertilization with increased phosphorus and potassium fertilizer; moderate pruning; attention to ditching and drainage, etc., can reduce the disease. Remove and burn fallen leaves to reduce the pathogen. In severely affected orchards, before the spots are still gray-green in early spring and have not yet formed swimming spores, spraying 0.5:0.5:100 Bordeaux mixture 1 to 2 times has a good effect.

(3) Mango purple root disease:

1. Symptoms: This disease mainly damages the base and roots of seedlings. The affected parts turn purple-black, the cortex rots, and the xylem becomes dry and decayed. The aboveground part of the plant grows weakly, the leaves fade to yellow, and finally the whole plant dies. The underground diseased parts are covered with purple-red root-like rhizomorphs on the surface, and when moist a layer of purple-red velvety film forms, and later flattened spherical sclerotia may form.

2. Pathogen and occurrence pattern: This disease is caused by infection by a fungus (Helicobasidium sp.). The pathogen overwinters in the soil and, when conditions are suitable, infects from the roots or root crown of the plant. Nurseries with heavy clay soil, poor aeration, easy compaction and poor drainage are more severely affected.

3. Control methods: Promptly pull out diseased plants and burn them in a centralized manner, and scatter some lime in the diseased planting holes for disinfection; drench the roots with 25% carbendazim 500-fold solution or copper-ammonia mixture 400-fold solution, with the soil thoroughly wet as appropriate; use 70% dexon 0.5 kg, add 20 to 25 kg fine soil and mix well, then scatter it near the plant roots, or add 350 to 400 kg water and pour it over the soil surface; for every 667 sq m use 40% quintozene 3 kg, add 10 to 25 kg fine soil to make poisoned soil, and broadcast it on the soil surface at the plant roots.