Grape cultivation in California

California is a very important place for growing grapes, especially for making wine and eating fresh.

The grape farms are mostly found in five counties: Kern, Tulare, Fresno, Riverside, and Madera.

Growing grapes needs careful work. During the time when the grapevines are resting, farmers cut the old branches to help new growth. This is important for healthy vines and good grapes.

Diseases of grape

California has several important grape diseases.

One of these is Pierce’s Disease. It was first found in Los Angeles in 1892. Another disease is Grapevine red blotch-associated virus, found widely in California grapevines.

Powdery Mildew is also a costly disease. Grapevine Trunk Diseases are common too, including Botryosphaeria Dieback and Eutypa dieback. The Dagger Nematode is another common problem. Esca causes economic loss. The Grapevine Pinot gris virus has caused an active epidemic in the Napa Valley.

Pests of grape

For insect pests see Glassy-winged sharpshooter and Blue-Green Sharpshooter.

The European Grapevine Moth came to Napa County in 2009. Officials and scientists worked together to stop it, and by 2016, they were successful. People still worry it might return. Climate change could make it easier for the moth to come back.

Some animals can also harm grape crops. The University of California offers advice on how to manage pests like birds, squirrels, deer, rabbits, and voles. They also give tips for dealing with pests at different times when grapes are growing, such as after harvesting. There are many tiny insects that can cause problems, and scientists are still learning the best ways to protect the grapes.

Breeding of grape

California has the biggest program for growing table grapes in the country. The next biggest program is at the University of Arkansas. Many popular table grapes were created here, like 'Perlette' and 'Red Globe'. Harold Olmo at UCD made these grapes. The USDA program in Fresno made 'Flame Seedless' in 1973 and 'Fantasy Seedless' in 1994.

Researchers at UC Davis found ways to help grapes stay healthy. In December 2019, they shared new grape types that can fight off a big problem. These new grapes were protected by law and others could use them.

The San Joaquin Valley Agricultural Sciences Center in Parlier makes new types of table and raisin grapes, like the Thomcord. Since the 1980s, scientists there have created many new grapes, sometimes using wild grapes from North America.

UCD stopped making wine grapes in the 1980s, but in 2019, they shared five new types that can resist a costly disease. This program keeps making more grape types.

Scientists have worked since the 1950s to make grapes without seeds for both raisins and table grapes. Many seedless grapes in the world started here.

Researchers also studied the family history of grapes to learn more about them and make them better. Some popular grapes in California are related to grapes from Italy.

Genetic engineering of grape

Until about 2004, scientists didn’t know many genes from other plants that could help grapes fight diseases. By 2014, they found some useful genes. Some of these genes were put into grape plants. A few made things that helped protect the plants when they grew on special roots. Some of the genes studied were pPGIP, a protein from a pear, and others made by scientists at universities and labs.

Treatments in grape

In California, farmers use many ways to keep grapes healthy. Some treatments help stop sickness and bugs that can hurt grapevines. For example, special sprays protect grapes from bad fungus and insects.

Farmers also use natural ways, like planting cover crops, to help control bugs. Some treatments, like crab shell chitosan, help stop mold on grapes after they are picked. These ways help keep grapes safe and healthy to eat.

Research in grape

Table grape growers in California pay a special fee for research and treatment of plant diseases. In the fiscal year 2009–2010, this fee raised $735,000, mostly from the southern San Joaquin Valley. You can learn more about these topics in the sections on Pierce's Disease, Glassy-Winged Sharpshooter, and Treatments in grape.

California is famous for its wine research, especially at UC Davis's oenology programs.