Crawlies: The Most Common Pests and Diseases in the Vineyard

May 13, 2014
danielcody9@hotmail.com

Needless to say, diseases in your vineyard limit the production of grapes. There must be effective disease management for the vineyard to survive. Besides being costly, controlling them may have a negative impact not only on the environment, but on the workers and eventual consumers of the produce. A balance must be struck between use of synthetic pesticides and the maintenance of production goals.

The most common diseases are listed here.

Black Rot.

This fungus attacks the leaves, stem and tendrils in the spring. Early symptoms include small brown or black spots, but cause no serious damage. The fungus then spreads to the fruit where it will not be noticed until berries are about half grown. Diseased parts should be removed and destroyed at pruning time.

Black-Rot-Grapes

Black rot on a bunch of grapes

Botrytis.

This fungus attacks during flowering and is only apparent later in the season. Symptoms manifested are single berries turning brown and rotting; affected areas bear gray spore masses, an effect which is commonly known as ‘noble rot’. It will not grow at temperatures above 94 degrees F. It is best controlled by an integrated program using pruning and fungicides. To help reduce noble rot infections, an open canopy is the best option as it allows air circulation to keep the fruit dry.

Botrytis-Grapes

Botrytis causing noble rot on Riesling grapes

Downy Mildew

This pest attacks all green parts of the vine. Lesions are yellowish and oily, which later on becomes angular, yellow to reddish brown spots. All infected parts except older fruit are covered with white fungal growth during moist weather. To control use pre-bloom sprays.

Downy-Mildew-Leaf

Downy mildew on a leaf

Powdery Mildew

This character infects all green parts of the vine. Manifestations of disease include a white powdery growth on infected parts. Infected immature berries split and either dry up or rot; can cause off flavors in wine. To control this disease, spray starting at petal fall.

All of these diseases can be controlled through proper pruning, cultivating and spraying. Diseases that overwinter in old canes can be controlled by pruning out and burning all excess growth. The remaining vine should only contain the permanent trunk. Because the fungus which causes Black Rot can also come from old berries, cultivating the soil just before new growth begins in the spring covers old berries and reduces black rot infection. Timely application of fungicide is the key to using sprays to control diseases. Success as a grape grower will depend on understanding of spray equipment and the application of spray material.

 

Methods of Pest Control

Bird Control

Common pests of grapes include several species of birds, such as the robin, starling and blackbird. They do much damage to the fruit by plucking entire berries from the cluster or by pecking holes in the berries. These birds usually begin to feed on grapes before the fruit matures and after they have developed color. As soon as this occurs, control efforts must commence. Bird control methods’ effectiveness and cost varies. The most effective one is to cover the vines with plastic or nylon netting. The cost for the initial outlay is quite high but with careful handling, the materials (such as the net) may be usable for three to six years.

Deer

These animals can cause significant damage to the vines and foliage. The most effective method of keeping deer out is the use of fences. There are several designs available, from low-cost electric spider fences to 6 wire electric ones, or 8 foot high or higher non-electric models.

Insects

There are several insect types that can damage grape vines or fruit. However, they only cause serious injury occasionally. Frequent examination of plants for signs of pest activity is one key for controlling insect pests. Control should be applied before the plant is seriously injured.

Grape Berry Moth

This is the most important grape pest. This insect overwinters on the ground in cocoons. The adult lays eggs on the flower clusters or small fruit in late May or early June. In July, the mature larva forms a small leaf flap that it folds around its body. They either remain on the leaves or fall to the ground. Each larva feeds by tunneling through three or more berries and cause them to shrivel or fall to the ground. If larvae are found, apply approved insecticide. You can use pheromone traps to help monitor flight and egg-laying periods.

Grape Leafhopper

There are several species of this insect that damage grapevines. Adults are active, wedge-shaped insects, about 1/8 inch long. They are white to yellow with yellow or orange markings. They feed by sucking juices from leaves. Leaf injury reduces vine growth and interferes with berry ripening. To monitor infestation, examine undersides of leaves for their white cast skins. Start control measures if insect populations are large enough to discolor leaves.

Grape Phylloxera

This is a small aphid-like insect. It survives on the roots of susceptible cultivars throughout the year. Heavy infestation of this insect results in premature defoliation and reduced shoot growth. After a couple of years of heavy infestation, vine vigor and yield can be seriously reduced. Insecticides for the foliar form are only effective if used when nymphs are crawling on the outside of the leaf. The best time to spray is during the bloom-vine stage.

Cutworms

These insects cause serious damage by cutting off the developing canes, especially very early in the season. Damage occurs commonly in weedy areas. Weed control can reduce injury to plants. Approved cutworm bait is the most effective way to control this pest.