Here is one sharpshooter you want nowhere near your grassy knoll, your backyard or your vineyard.
To your left: the glassy-winged sharpshooter, Homalodisca coagulata, an insect fast making itself the bane of California's wine industry. Much as mosquitos spread malaria as they feed, so the sharpshooter serves as the principal transport and delivery system for Pierce's disease (Xylella fastidiosa), a bacterial infection that turns the water-bearing tissues in a plant into black sludge, ultimately starving the plant to death. While the bacterium is harmful to an array of plants, its chief victim is the grape vine.
Pierce's disease is widely blamed for the near-destruction of wine grapes as a viable crop in much of southern California. A thriving wine industry existed in this part of the state through the 19th century, but the disease destroyed tens of thousands of acres of vineyard by 1895. After an extended absence, the current resurgence of Pierce's disease made itself known in the industry's last major southern bastion, Temecula, in 1997. It has now begun to make its presence felt in northern California wine-growing counties, such as Napa, Sonoma and Mendocino.
If this discussion of glassy wings hasn't yet left you glassy-eyed, more details are available at places such as the Glassy-Winged Sharpshooter News and Information Service of the California Farm Bureau Federation, and the University of California, Riverside. And if you don't already have reason to dislike these creatures, consider this ahead of your next al fresco social affair:
The threat to the urban environment is real. Heavy infestations of the sharpshooter produce copious amounts of "leafhopper rain," rendering backyard barbecues and other outdoor activities downright unenjoyable. A shady spot in the backyard is a nice retreat on a hot summer day but it could be a nuisance because of the sharpshooter. Sharpshooters excrete water droplets when they feed on plants. These droplets eventually wet people, cars, backyard play equipment, pools, cars and sidewalks. Sharpshooters filter out minerals and amino acids from the liquid sucked from plants. They filter so much water to get adequate nutrition that it excretes a sizeable droplet of water about every three seconds.
What to do, what to do? Given the problematic relationship between Californians and pesticides -- featuring prominently in this Harper's Magazine article by William Hamilton (yes, the cartoonist and chronicler of wine-bibbing preppy sorts) from May, 2001 -- the state is currently letting its anti-sharpshooter hopes ride on the backs of small parasitic wasps, which lay their own eggs among sharpshooter eggs, the latter serving as a ready smorgasboard for the wasp's emerging young. In tribute to these winged warriors, a new somewhat gothic double dactyl:
Spread vile bacteria,
Sicken our grapes.
Fly, waspish rescuers!
Fly! Let your young drive their
Stakes through the hearts of these
Vampires sans capes!
Of course, annoying as the sharpshooters are in themselves, the problem here is not so much the insects as it is that the disease they spread remains incurable. The Pierce's pathogen might be among those for which a genetic solution could be found, but any research to develop resistant stock must overcome a different sort of force of nature: the Environmental Protection Agency. Dr. Henry Miller of the Hoover Institution writes:
There are several ways to introduce or enhance the resistance to Pierce's disease in new variants, or varieties, of grapevines. One logical approach is to transfer genes that confer resistance into California's grapes from distantly related, non-commercial grapes that possess natural immunity. But conventional grape breeding is a notoriously slow and uncertain process, and attempts to use the more sophisticated and efficient gene-splicing techniques have run afoul of EPA and local regulatory policies. So does the approach of University of Florida researchers who have patented a group of resistance genes that are a synthetic version of those found in a variety of organisms. (And so also does another gene-splicing trick that could permit new vines to bear fruit years earlier than usual.)
The EPA discriminates against gene-spliced varieties, by regulating even more stringently than chemical pesticides any plant that has been modified with gene-splicing techniques to enhance its pest- or disease-resistance. This policy, which has been attacked repeatedly by the scientific community as unscientific and irrational, has badly damaged agricultural research and development. It flouts the widespread scientific consensus that gene-splicing is more precise, circumscribed and predictable than other techniques. New gene-spliced varieties can not only increase yields, make better use of existing farmland and conserve water, but -- especially for grains and nuts -- are a potential boon to public health, because the harvest will have lower levels of contamination with toxic fungi and insect parts than conventional varieties. Moreover, by reducing the need for spraying crops with chemical pesticides, they are environmentally and occupationally friendly.
The link to Dr. Miller's article comes via Iain Murray writing at The Commons Blog, where he adds:
If we want to save the California wine industry, rescinding those EPA regulations would be a good start. It'd be easier than trying to change the weather.
At least the weather gives us something to talk about as we shelter indoors with our guests, fast-disappearing Chardonnay in hand, to evade the leafhopper rain.
The Murray post also notes wine-related comments in the latest global warming study/simulation from the Union of Concerned Scientists. In addition to alarming predictions such as the disappearance of most of the snow pack from the high Sierra (and with it much of California's water supply), the report has this to say about our beloved grapes;
For wine grapes, excessively high temperatures during ripening can adversely affect quality, a major determinant of market value. Assuming ripening occurs at between 1,150 and 1,300 biologically active growing degree days, ripening month was determined by summing modeled growing degree days above 10°C from April to October, for both baseline and projected scenarios. Monthly average temperature at the time of ripening was used to estimate potential temperature impacts on quality. For all simulations, average ripening occurs 1–2 months earlier and at higher temperatures, leading to degraded quality and marginal/impaired conditions for all but the cool coastal region under all scenarios by the end of the century (see Table 3, which is published as supporting information on the PNAS web site). As with other perennial crops, adaptation options to shift varieties or locations of production would require significant time and capital investment.