Archive for the 'Grape threats' Category

20
Mar
10

buggy info on “one of the most valued cultural and economic crops in the world”!

I’m copying in the following article from Oregon.gov. I thought it was very concise in explaining the pest issues grape farmers/wine producers have to deal with. Many of you may have heard of phylloxera, the granddaddy of all grape attacking pests. This article explains this, but what they fail to articulate clearly is that because this little aphid-like organism can’t hurt the lowly American rootstock grapes (labrusca), all European grape vines (vinifera) have to be grafted on it to survive, hence all the famed wines of France, Italy, Spain, etc can’t survive without the lowly Welch’s grape juice variety grapevine root stock. I surmise that this is the main reason the French hate us so… anyway, it’s an interesting read on many of the perils wine grapes must endure.

Grapes (Vitis spp.) are one of the most valued cultural and economic crops in the world. Unfortunately, grape plants are plagued by many natural enemies. Regulations governing the trade of grape plants are some of the most strict and complicated in the business. This grape regulation page will cover the common pests and pathogens and the various quarantines that apply.

Historically, one of the most important pest outbreaks on grapes began in 1860 in Europe. A tiny aphid-like organism called grape phylloxera, Daktulosphaira vitifoliae, was accidentally introduced from North America and spread throughout Europe. Grape phylloxera feed on leaves and roots of grape plants. The resulting damage causes root girdles that lead to severe decline or death of plants. North American grapes (Vitis labrusca) are fairly resistant to phylloxera but European wine grapes (Vitis vinifera) are highly susceptible. France in particular lost nearly 90% of all of its vines by the late 1800s. As a solution, grape plants throughout Europe were replaced with vines grown on North American rootstock.

More recently, Xylella fastidiosa, the bacterium that causes Pierce’s disease, gained a lot of attention in California. The disease was documented in California in the late 1800’s, but became a major problem with the introduction of the leafhopper insect, Homalodisca vitripennis, in the 1990’s. H. vitripennis, commonly known as the glassy-winged sharpshooter, was accidentally introduced into California from the southeastern United States. Pierce’s disease was able to spread rapidly with the aid of this vector insect. The disease destroys the water-conducting xylem of grape plants, leading to plant death in 1 to 5 years. California mounted an extensive control effort against the sharpshooter that appears to be paying off. There are currently hotspots of Pierce’s disease in Napa and Sonoma counties, and in other countries such as Mexico and Venezuela.

Another major concern for grape plant sanitation is viruses. Some resources claim that there are over 50 viruses known to infect grapes throughout the world. Viruses are especially worrisome because they can be difficult to detect, easy to spread, and difficult to control. Some grape viruses such as grapevine fanleaf virus (GFLV) and tobacco ringspot virus are vectored by nematodes (nepoviruses). Others such as grapevine leafroll-associated viruses (GLRaV) and corky bark disease are vectored by insects like leafhoppers and mealybugs. GLRaV is of special concern to Oregon at this time. The virus stunts plants and can reduce crop yield by as much as 40%. While GLRaV has already spread to all grape-growing regions of the world, it has a limited distribution in the Pacific Northwest.

The vine mealybug (Planococcus ficus) was recently introduced into California from Europe or Mexico in the mid-1990’s. P. ficus, like aphid, suck sap from host plants and result in reduced plant vigor. The mealybug is also more effective in spreading GLRaV than other vectors, and also excretes much more honeydew than other mealybug species. The honeydew alone can ruin a grape harvest. Vine mealybug has rapidly spread through California since it was first detected in 1994, but it has never been found in Oregon. The ODA recently adopted an emergency quarantine order for vine mealybug on grapes being transported into Oregon for crushing or as table stock.

13
Mar
10

Mailbag Saturday – starved for water…

Question:

With the recent news of a moth in Napa that likes to snack on Cabernet grapes, I saw a brief mention that Temecula was hit hard by the glassy winged sharpshooter a few years back.  Do you have any insights on the history of that event? Brian, Sacramento

Answer:

“Hit hard” is an understatement. Ravaged is more like it! Pierce’s disease (the name of the virus carried by the Glassy Winged Sharp Shooter) was (and still is) such a scare for the California wine industry that all Temecula grapes were quarantined for many years. The history if this blight is complicated, so I did what any lazy blogger would do, I searched out a very interesting article on the subject. I’m attaching the recent article published in the Riverside Press Enterprise. This article talks about what’s currently happening, the history of Pierce’s disease and what’s currently being done to control/stop it. And people think wine is easy to make… HA!!!

Click here for news link on Glassy Winged Sharp Shooter




Patrick Bartlett


A conversation about food, wine, and the art of living well!

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