Pierce's Disease

The History of PDPierce’s Disease, also referred to as PD, is a disease in specific plant life that reduces their ability to use the soil for its nutrients and water. It is a bacterium that clogs the vessels in the vine that draws these two necessary items from the soil underneath it. Essentially, what happens is that the vine starves, unable to get the necessary elements; it occurs very slowly and ultimately dies. PD (Pierce’s Disease) effect grape vines, as well as stone fruits, citrus, and almonds.Back in the late 19th century, a pathologist of plants investigated the first Californian outbreak of the disease and thus the disease was subsequently named after Newton Pierce. However, the disease has been in existence since the 1880’s, when it was then known as Anaheim disease, because it was within the Anaheim area that it was first discovered.Throughout the years, vineyards have had to fight PD over and over. Severe outbreaks have occurred and after much research and testing, it was discovered that Pierce’s disease is spread by an insect.The Physiology of PD and what parts of the vine it attacksPierce’s Disease is a slow killing plan disease. It can take up to one year before the vine will begin to show symptoms and signs of the bacteria. It can then take up to three years before the plan will eventually succumb to death by the disease. How can you tell that the grape vine was withered by PD? Well, once killed it is black and very withered. However, there are signs of other symptoms before it reaches that stage. For example, when infected, the vines may promote shriveled or dried grapes, leaves that are underdeveloped, discolored vines, and even growth troubles, it will not be as large as it should.The insects that spread this disease through grape vines is called the blue-green sharpshooter and the glassy-winged sharpshooter. These are tiny, flying insects that are essentially known as leafhoppers. They feed on the juice from the plants. Upon feeding, the disease transfers from the mouth of insect to an otherwise healthy plant, infecting it with the disease.Pierce’s Disease, affects the vascular system of the plant. It multiplies and houses in the xylem of the plant, which is a water system that is similar to piping. As stated it is a slow process and difficult to discover until the plant has been infected for one year.One good thing about PD, is that is does not affect humans in any way, nor does it affect the quality of the wine produced by these grape vines. It is however, responsible for the death of many grape vines throughout California and other wine producing areas. The susceptible varieties and what to do to prevent PD infectionsThe only real combative measure against Pierce’s Disease to date is to be attentive to your grape vines and plant varieties that are resistant to the disease. At this time, even with all the research, plant pathologists and scientists have not been able to produce a rootstock, spray, or solid practice that will prevent or reduce a PD infection.The only real suggestion is to plan grape vine varieties that are resistant to the disease. Here are the resistant varieties:Orlando Seedless – This is a table grape with great flavor and fairly easy to grow. It will need some pruning and thinning of clusters to maintain, but produces a great tasting wine. Not only is this variety resistant to PD, but also Powdery and Downy Mildew. It is susceptible to Anthracnose and Black Rot however.Blanc duBois – This a variety of grape for white wines. There is no need for rootstock in most cases, and produces nice sized berries and clusters. As with Orlando Seedless, it is resistant to Downy Mildew and PD, but susceptible to instances of Anthracnose and Black Rot. This variety is not good for soils that are high in pH and poorly drained.Other great resistant varieties include Black Spanish, a variety for jellies, juices, and red win, Champanel, a variety for red jelly, Favorite, a child of Black Spanish, and Roucaneuf, a table or white wine grape. As well as Herbemont, Norris, Stover, Lake Emeral, Conquistador, Suwannee, Daytona, Miss Blanc, Miss Blue, and Mid South, are all PD resistant varieties.Overview The best defense against Pierce’s Disease at this time is to eliminate susceptible varieties and stick with those that have a known resistance, at least until someone develops a solid defense for other varieties.Danie WiumAuthor of the Complete Grape Growers Guide

Comments? Questions? Email Here

© HowtoAdvice.com

How to Advice .com