Control of Main Grape Diseases (3)

Powdery mildew

It mainly harms the leaves, fruits and tendrils of grapes.

Sysptoms

White or faded green spots appear on the leaf surface or back of grapes during leaf development and gradually expand, and powdery white mildew spots appear on the surface, which spread all over the leaves in severe cases, causing the leaves to curl or dry up.

The infected fruit has a black awn-like pattern, covered with a layer of white powder, and the skin of the diseased part becomes purple-brown to gray-black, causing the fruit to harden, crack, and fall off.

Chemical control

Cyproconazole,  oxazol, thiophanate methyl, myclobutanil, azoxystrobin, triflumizole, prochloraz, difenoconazole.

Brown spot

It mainly harms the middle and lower blades.

Symptoms

It can be divided into two types: large brown spot and small brown spot.

Large brown spot

The color of the front spot is deep in the middle and light in the edge, and the back spot is covered with gray-brown mildew.

Small brown spot

The color of the front spot is dark and light in the middle. When the humidity is high, the back of the spot is covered with gray-black mold layer.

At the beginning of the disease, the spot on the front of the leaf is brown spot at first, and then expanded into round or oval brown spot.

The center of the lesion is brown, with sparse concentric rings, and the boundary of the lesion is obvious.

Chemical control

Tebuconazole, myclobutanil, diniconazole, pyraclostrobin, azoxystrobin, chlorobromoisoc-yanaria Acid, propiconazole, difenoconazole, thiophanate methyl.

Gummy stem blight

It mainly occurs at the stem base of more than 2-year-old branches and tendrils, and can also damage new shoots and fruits.

Symptoms

The tendril base near the ground is easy to be infected. At the initial stage, the disease spot is reddish brown, slightly sunken, and then expands into a large dark brown spot.

The epidermis of infected tendrils is filamentous and easily broken, and many small black spots appear on the surface of the diseased part .

Leaves turn yellow, edges curl, new shoots wither, and veins,petioles and tendrils grow black streaks.

Fruit symptom is similar to caucasus grape black rot, except that small black grains will be denser.

Chemical control

Chlorothalonil, difenoconazole, copper hydroxide, copper succinate, cuaminosulfate.

Grape alternaria spot

It mainly occurs on the rachis of young ears, and the incidence of fruits is less.

Symptoms

At the initial stage, brown water-soaked spots appeared on the rachis of young panicle branches, which quickly expanded and then caused the rachis to turn brown and die.

Fruit withers and falls off due to dehydration, and sometimes black mildew appears in diseased parts.

Small round dark brown spots appear when young fruits are infected, and the surface of the disease spots is scab-like with the continuous expansion of fruits.

When the fruit grows to medium size, the scab falls off and the ear shrinks and dries up.

Chemical control

Boscalid, copper quinolate, carbendazim, thiophanate-methyl, iprodione, kresoxim-methyl.