Grape cultivation in California

California is a very important place for growing grapes, especially for making wine and eating fresh. In 2021, farmers grew a lot of grapes from over 800,000 acres of land. They harvested almost 6 million short tons of grapes, which were sold for about $5 billion. Some of these grapes were used to make wine, and some were sold fresh in stores.

The grape farms are mostly found in five counties: Kern, Tulare, Fresno, Riverside, and Madera. People in California eat more grapes each year, and the state is one of the biggest grape growers in the country.

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. Scientists also study the tiny living things in the soil that help grapes grow.

Grape farming has been very important for workers too. Many years ago, grape workers went on strike to ask for better conditions, and this helped change rules for workers in many industries.

Diseases of grape

Disease information is provided by UC IPM.

The state of California deals with several important grape diseases. One of these is Pierce’s Disease, first found in Los Angeles in 1892. It now costs the state about $100 million each year. Another disease is Grapevine red blotch-associated virus, which has been found widely in California grapevines.

Powdery Mildew is also a costly disease, having cost the industry $239 million in 2015. Grapevine Trunk Diseases are common too, including Botryosphaeria Dieback and Eutypa dieback. The Dagger Nematode is another common problem. Esca causes economic loss, with losses reported between $2,000 to $3,000 per hectare. The Grapevine Pinot gris virus has caused an active epidemic in the Napa Valley, with occurrence varying widely by grape variety.

Pests of grape

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

The European Grapevine Moth arrived in Napa County in 2009. Local, state, and federal officials, scientists, and industries worked together to stop it by 2015, and it was declared successful in 2016. There is still worry that it might come back. Climate change may make it easier for the moth to return.

Some animals can also harm grape crops. The University of California gives advice on how to manage these pests, which include birds, squirrels, deer, rabbits, and voles. They also offer tips for dealing with pests during different growth stages of grapes, like after harvesting. There are many tiny insects and bugs that can be a problem too, and scientists continue to study the best ways to protect the grapes.

Breeding of grape

This state has the largest breeding program for table grape in the country. The next largest program is at the University of Arkansas, which began using varieties developed here. Many popular table grape types were created here, like 'Perlette' and 'Red Globe' by Harold Olmo at UCD, as well as 'Flame Seedless' in 1973 and 'Fantasy Seedless' in 1994 by the USDA program in Fresno.

Researchers at UC Davis have found ways to help grapes resist diseases. In December 2019, they released several new grape types that can fight off a serious problem. These new types were protected by law and made available for others to use.

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

UCD stopped creating wine grapes in the 1980s, but in 2019, they released five new types that can resist a costly disease. This program continues to develop more varieties.

Scientists have been working hard since the 1950s to create grapes without seeds for both raisin and table grapes. Many of the world's seedless grapes began here.

Researchers have also studied the family history of grapes to learn more about their traits and improve them. Some popular grape types in California were found to be related to grapes from Italy.

Genetic engineering of grape

Up until around 2004, scientists didn’t know much about which genes from other plants could help grapes fight diseases. By 2014, researchers had found several useful genes. Some of these genes were moved into grape plants, and a few even created substances that could help protect the plants when they were grafted onto rootstocks. Some of the successful genes studied include pPGIP, a protein from a type of pear, and others developed by scientists at universities and research labs.

Treatments in grape

In California, farmers use many treatments to keep grapes healthy. Some treatments are used to stop diseases and pests that can harm the grapevines. For example, special sprays help protect grapes from harmful fungus and insects.

Farmers also use natural methods, like planting cover crops, to help control pests. Some treatments, like crab shell chitosan, help stop mold that can grow on grapes after they are harvested. These methods help keep grapes safe and healthy for people to eat.

Research in grape

Table grape growers in California pay a special fee for research and treatment of plant diseases like PD and GWSS. 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 known worldwide for its excellent wine research, especially at UC Davis's oenology programs.