26 June, 2010

Downy Mildew a Permanent on Basil?

It looks like something in nature has a thing about pesto and salad. Last year tomatoes were ruined in the east by late blight. Late blight turned up already this year in Louisiana and parts of Maryland. Growers had 1,000s of acres wiped out by the disease. Now the main component in  pesto, basil, is under attack by a grayish fungus called downy mildew. Downy mildew often attacks squash and cucumbers along with many ornamentals. Now it has begun an assault on basil the mainstay of summer gardens around the U.S.

First signs of affliction include a band of yellow haze on the upper surface followed by small grayish black spores on the under side of the leaves. While not toxic to humans the mold is quite unsightly. Removing leaves infected in the home garden is the only well suited control. However on commercial farms this labor heavy activity is not practical.

The disease is currently spreading through New Jersey. Unfortunately sweet large leaf basil, the most popular variety, is most susceptible. Lesser known varieties like lime and lemon are not easily affected by the disease.

More information in the Washington Post