The yellow leaf disease, also known as chlorosis, is a common and frequent disease in the Begonia, which often occurs in the Begonia planted in the alkaline soil in the north.
In the early stage of the disease, the top shoots and leaves of the plant will turn yellow first, and the leaf surface tissue will turn yellow or light yellow, but the veins of the leaves will remain green.
With the aggravation of the disease, the whole leaf became yellow or yellow white, the edge of the leaf became gray brown, and the leaf gradually died.
First of all, when planting, it is necessary to select the appropriate soil, preferably light acid or neutral loam.
The initial stage can be perfused with 200 times of ferrous sulfate solution and sprayed with 0.5% ferrous sulfate solution. Once every 10 days, continuous irrigation and spray 3 to 4 times can obviously change symptoms.
When applying fertilizer, we often use rotten leaf fertilizer, cow manure and other organic fertilizer to improve the permeability of soil.
The pathogen is a kind of fungus, which overwinters on the diseased body of the host plant and spreads by wind, rain and water. The disease starts from late April to early May, and the peak period is in July, August and September.
In the early stage of the disease, the edge of the leaves will grow gray brown spots, which show irregular shape expansion, inside is gray brown, the edge is red brown.
In the late stage of the disease, the disease spots gradually expanded, which may become one strip, forming strip spots, and dried up, turning brown, with black granular matter growing in the spots.
At ordinary times, the maintenance and pruning should be strengthened to make the plant in the position of ventilation and light transmission.
In case of occurrence, 75% hundred chlorothalonil wettable granule 800 times liquid or 70% mancozeb wetting particle 400 times liquid or 50% 50% times of the wetting particle 500 times liquid spray, once every 11 days, continuous spraying 3 to 4 times can effectively control the disease.
During the period of disease onset, sprinkler irrigation is forbidden to reduce the development rate of disease.
