Pierce's disease is caused by a bacterium, Xylella fastidiosa, that shuts down a plant's xylem, or water transport system. There are three known strains of Xylella. One causes citrus variegated chlorosis, and phony peach disease. This strain has not been found in California. Another strain causes alfalfa dwarf disease and this one has been found in southern California. The third causes almond leaf scorch, oleander leaf scorch, and Pierce's disease in wine, table, and raisin grapes. In the 1800s, this strain decimated 35,000 vineyard acres in southern California. More recently, it has wiped out a huge number of vineyards in Temecula, in Riverside County. Some say the disease is cyclical and once it hits an area, grapes should never be planted there again.
Xylella is transmitted from plant to plant by a native insect vector called a leafhopper. Both the native bacterium and the leafhopper also live in roses, ornamentals, oaks, redwoods, ivy, blackberries, orchards, and riparian vegetation with no adverse affect. Once the leafhopper feeds on an infected plant, it carries the bacterium for life. Even if it feeds on a plant that is not susceptible to infection, the plant will act a reservoir for the disease. In the past the blue-green sharpshooter was the leafhopper responsible for spreading the disease in a limited way in northern California. More recently, another leafhopper, the glassy-winged sharpshooter, has arrived in California from somewhere in the southeast U.S. It has a much larger territory than its smaller cousin, and is responsible for wiping out acres of vineyards in Temecula, in Riverside County.
As of now, there is no cure for Pierce's disease, so efforts have been concentrated on stopping the leafhopper vectors. In February of 1999, California state Senator Chesbro, representing the second district which includes wine country, introduced bill number SB 671 having to do with advertising restrictions for alcoholic beverages. By March 27, 2000, SB 671 had been completely transformed and now calls for $14 million dollars, to fight Pierce's disease. As the bill stands now, there are no restrictions on how this money is to be spent, and it does not require matching funds from the industry, as is the norm.
An ongoing, federally funded ($360,000), pilot project to control the spread of the glassy-winged sharpshooter, is being conducted in Riverside. There have been aerial applications of Lorsban on 233 acres of citrus in Riverside. Lorsban, or chlorpyfifos, is an organophosphate that inhibits cholinesterase, an enzyme required for proper nerve functioning. It is moderately toxic to humans (it damages the central nervous system, respiratory system, and is a skin and eye irritant), is highly toxic to freshwater fish, aquatic invertebrates, estuarine and marine organisms, and birds, and kills honeybees. Lorsban is up for review by the EPA under the new stricter standards the Food Quality and Protection Act of 1996. It will probably be banned. Is the Riverside pilot project a last ditch effort by DowElanco Chemical Corporation to unload huge amounts of it before it is banned?
The project also includes the systemic use of imidacloprid, or Admire, (also found in Advantage flea control for pets) for the last two years. They are injecting plants with Admire to make the plants poisonous to all insects for a long period of time. It is also toxic to birds, bees, and, to a lesser extent, fish.
Now when you purchase a plant from a local nursery, it may already contain a systemic insecticide that will kill the insects in your garden. What happens if leaves from these plants fall in the water and get nibbled by fish? California State Fish and Game has recently allowed for the removal and re-planting of riparian plants that might harbor leafhoppers. Will the re-plants kill insects and fish? (See EXTOXNET ace.ace.orst.edu/info/extoxnet/ghindex.html for more information on these insecticides.)
Many experts believe, that Pierce's is a cyclical disease which shows up in mainly riparian areas, and that nothing can be done about it except for not planting in these areas. Due to the high profit in winegrapes, many vineyard developers have insisted on planting in these at-risk areas, and have refused to leave buffer zones between their vines and riparian areas and residential areas with ornamental landscapes. Some growers have also begun removing native, riparian vegetation to slow a native insect from spreading a native bacterium to their non-native cash crops. And now they want $14 million tax dollars to go towards quarantining of ornamentals, spraying of nursery plants, and possibly aerial spraying of pesticides!
Do we really want $14 million of unrestricted tax money going to bail out agri-business - and a luxury crop at that? Does poor planning on their part constitute a "state of emergency" on our part? Is Pierce's disease the first of many more "emergencies" caused by the larger problem of monoculture? How many more will we have to bail out?
Although Pierce's has been found in the Hopland and Potter Valley areas, as of yet, no glassy-winged sharpshooters have been found in our county, or north of the Central Coast, for that matter. If SB 671 passes, the money will be distributed at the county level. A task force, which has been set up at the state level, is studying areas like bio-control, identification of the pathway of transmission, plant resistance and anti-bacterials. Dave Bengston, our county Agricultural Commissioner, recently called for a quarantine of all nursery plants coming in from infected areas down south. He wants them to be inspected thoroughly, or treated with pesticides. Although he is attempting to slow the spread of the leafhopper, he knows it will eventually reach this county. Fortunately, Bengston has stated that "Spraying doesn't work; sharpshooters have a highly developed sense of taste, and as soon as they taste a pesticide, they jump to another plant," so it looks like Mendocino County, at least, is safe from being treated indiscriminately with organophosphates.
Our Concern: Statewide growers have known about this disease for a long time. They have not used preventative measures such as leaving buffer zones between vines and riparian habitat, homes with ornamentals, and orchards, or not planting in historical Pierce's disease sites. Now, one of their first areas of research involves aerial spraying of toxic chemicals that will affect far more that their target insect. Poor planning on their part does not constitute an emergency on our part! Why not enforce emergency buffer zones of 400 –500 feet to prevent leafhoppers from jumping into their vineyards? Why not quarantine the movement of grapes from infested areas, to unaffected areas like Mendocino County? Thousands of tons of grapes are imported into our area each year during the harvest season. Although the fruit of the plant is not the most likely hideout for a leafhopper, shouldn't they start by policing their own industry first? Instead, grape barons and politicians want us to pay for them to toxify our nursery plants, our environment, and ourselves so they can attempt to maintain their bottom line in a lethal experiment that probably won't work.
Contact the following people and tell them you do not want your tax dollars going to bail out a luxury crop industry that refused to take appropriate precautions to protect itself! Tell them not to pass a bill with unrestricted, unmatched funding.
Senator Chesbro: (the author of the SB 671 bill) 468-8914 [Ukiah office]
50 D St., Suite 120-A Santa Rosa, CA 95404
State Senator Carol Migden: (the chair of the appropriations committee) 916-319-2013
Governor Davis: (he's the one pushing the bill and has told the committee that there is no opposition! (415-703-2218) State Capitol, Sacramento, CA 95814
Dave Bensgton, Mendocino County Ag commissioner.
Tell him you do not want nursery plants that have been treated with insecticides imported into the county, and if they are here, you want them labeled!
Call your local nursery and tell them the same thing.
(Wendy Blankenheim is the founder and coordinator of the Community Action Network, a community organization working towards the regulation of vineyard expansion and the reduction of the use of agricultural pesticides in Mendocino County. For more information, or to volunteer your time or make a donation, call us at 895-3616, To get on our e-mail action list, e-mail us at wecan@prodigy.net. CAN is continuing our research the area of Pierce's disease, and will keep you updated and informed.)
Copyright Mendocino Environmental Center 2000
Permission granted to excerpt or use this article if source is cited