Osmanthus fragrans leaf blight and its control

Leaf blight symptoms

Early days

Leaf blight initially appears in the form of lesions starting from the tip or edge of the Osmanthus fragrans leaves. The initial lesions are yellow-green or light brown in color and are generally not easy to observe.

Mid-term

The lesions gradually expand to reddish brown or grayish brown and begin to take on clearly observable shapes, most of which are irregular circles. At this time, the color on the back of the leaves with diseased spots is very light, but the color on the edges of the leaves is darker.

Later

The later stages of leaf blight are also a period worthy of considerable attention. At this time, not only do the lesions merge with each other, but the small spots at the beginning turn into large plaques. Moreover, many small black particles will grow on the lesions, which are actually the conidia of the pathogen.

harm

Leaf blight can occur in Osmanthus fragrans at any time of the year, and the disease will cause a large area of ​​Osmanthus fragrans leaves to turn yellow and fall off. In severe cases, the bacteria spread in large quantities in the spring, rendering large tracts of osmanthus forests useless, thus causing us considerable economic losses.

How to prevent and treat

Eliminate the source of disease

In spring, the pathogen will spread in large quantities. Therefore, one way to prevent leaf blight is to completely remove the leaves that have been infected with the pathogen at the turn of autumn and winter before spring (either by burning or burying them).

Sterilization

Sterilization and disinfection are mainly aimed at transplanted Osmanthus fragrans. Not only should the diseased leaves be removed, but 50% carbendazim wettable powder should be diluted 500 times and sprayed on the transplanted Osmanthus fragrans seedlings for disinfection. 0.1% potassium permanganate solution can also be used for sterilization and disinfection.

Daily maintenance and prevention

If you weed and loosen the soil of Osmanthus fragrans frequently and keep the environment ventilated, bacteria will not easily breed or spread quickly. In addition, in order to improve the disease resistance of osmanthus, it is necessary to water it in time during high temperature and drought.

treat

If the osmanthus is seriously ill, it is necessary to spray it with drugs to treat leaf blight every half a month starting from June. It can be mancozeb wettable powder or thiophanate-methyl wettable powder. Lime-double-volume Bordeaux mixture is also effective against leaf blight. Spray three or four times and the leaf blight will improve.