Friday, June 18, 2010

Hot off the Press: Late Blight in 2010?

Welcome John, thanks for following!

Please don't let it be true! I came across a report in Organic Gardening e-newsletter that made my heart sink:Tomato Blight Strikes Again in 2010!

I would
say that I was fortunate last year not to be devastated by this disease. I managed to get most of my harvest in before my plants' presumably affected branches were almost all stripped away.

However, in growing more tomatoes than last year and potatoes for the first time, I am hoping my garden does not get affected! To date, I have not seen any evidence of blight. Have you?

Original Article:

RODALE NEWS, EMMAUS, PA—Anything but the tomatoes! Unfortunately for home gardeners and farmers alike—including some of us here at and our Organic Gardening tomato blight, is starting to appear in parts of the country. And, as before, it's threatening gardeners' most prized possessions—their juicy, homegrown tomatoes. "Unfortunately, I think it's a matter of time before it's widespread," says Meg McGrath, PhD, associate professor of plant pathology at Cornell University in Ithaca, New York. "Hopefully, people will be more knowledgeable of the disease this year, realizing it's a community disease. If you end up with it, you have to take care of the problem, you can't let it fester in your garden." colleagues—the funguslike pathogen known as late blight, commonly called

THE DETAILS: Maryland reported the first outbreak this growing season, with Pennsylvania, Kentucky, and Canada following suit. The disease is cropping up in all types of settings, from backyard gardens to fields and high tunnels on farms. McGrath says plant pathologists have not been able to pinpoint the source of each outbreak this spring, but notes that the disease needs a living host and can overwinter in potatoes left in the soil or in storage. (Late blight affects potatoes too, and caused the Irish potato famine in the mid-19th century.)

Photos courtesy of Meg McGrath/Cornell University

If a stem is OK, but you start to see nickel-size or bigger olive-green or brown patches on a plant's leaves, with some white fungal growth underneath, your plant has most likely been struck by the disease. The brown areas are likely to first appear in the early morning or after rain. Sometimes the spot is surrounded by yellow, or looks water-soaked, explains McGrath.

A nursery supplying tomato seedlings to big-box stores was blamed as the source of last year's tomato blight outbreak. However, once infected plants are in the environment, things can get ugly quickly, affecting plants far and wide. Tomato blight spores on infected plants are easily swept up in wind currents and carried high into the atmosphere, where they can potentially travel for long distances, even between states. The spores survive up there in ideal weather conditions (rainy, or even just humid and overcast days), and then fall into gardens and onto farm fields with the next rain.

WHAT IT MEANS: This is bad news for this year's tomato crop. What's worse, McGrath says if tomato blight sticks around for a few more years, it could very well become endemic in this area. That's bad news especially for organic growers, who nix the use of toxic fungicides. And while some copper products are approved for organic use, they aren't benign to soil or human health, either. "For organic, copper is the best choice," she says. "But people should make sure they understand that just because it's an organic product, it isn't as safe as water."

While truly blight-resistant tomatoes aren't currently available, some tomato varieties tend to fare better against tomato blight. These include, according to Cornell University's Vegetable MD Online, Golden Sweet, Juliet, and Legend. McGrath says Matt's Wild Cherry has also shown some resistant properties against late blight.

Here's how to deal with the tomato blight threat:
Evict these garden volunteers. McGrath says volunteer tomato plants—ones that spring up from last year's seeds that took root from dropped fruit—are a major concern for spreading this often lethal and very contagious disease. They may be hidden within your dense pea plants, harboring tomato blight without your noticing they're there, so check carefully.

Seek and destroy. Cornell instructs gardeners who find a hotspot, that is, a group of infected plants located around relatively healthy ones, to destroy the unhealthy ones immediately. Also take out the ones directly beside ones infected with late blight of tomatoes and potatoes. Proper destruction practice for plants infected with tomato blight: Pull them, double-bag them, and send them to the landfill. McGrath stresses that it's really important for gardeners and farmers to monitor their potato and tomato crops—ideally, several times a day—to quickly spot and remove an infected plant before disease spreads. It's possible this may save some of your plants, but there's no guarantee.

Spread the word. Give your tomato- and potato-growing neighbors a heads-up on this disease, and forward this article to as many people as you can. McGrath says education is key, so gardeners know to act quickly and remove any plant infected with tomato blight before spores form and spread to other plants.

Additionally, here are two resources with great photos from the University of New Hampshire (my Alma mater):

Best of luck to us all!

No comments: