Tuesday, May 25, 2010

Late Blight Again!

(picture from North Carolina State University website)

A recent email from Grow It Eat It (a service of the Maryland State Extension) carried the bad news that Late Blight has been identified in tomato plants in a nursery in St Mary's County, MD. Boooo!

Late blight is a very serious fungal plant pathogen and can wipe out entire crops of potatoes and tomatoes. The organism produces a lot of spores and they can travel for many miles by wind. It survives over the winter in dead plant tissue to infest the following year's crop. It is especially difficult, I think, to get rid of it in greenhouses and potato fields. Greenhouses because they are warm year-round and potato fields because getting every single tuber out of the ground is nearly impossible. (I grew potatoes last year in recycling bins and finally ended up dumping the soil from the bins through my compost screen to get the little tubers. My plants weren't infected, luckily, I just wanted every last spud.)

Apparently late blight used to be more common in the United States but was nearly wiped out by new fungicides in the 70s. Late blight epidemics are especially hard for organic growers because they don't use fungicides. As popular as CSAs have become here in the eastern United States there were a lot of sad blog posts last year. Of course, resistant strains are becoming more prevalent, and fungicide isn't free, so late blight is no fun for mainstream agriculture professionals either.

It's been a much drier spring than last year so far, at least here in Maryland. Keep your fingers crossed that the efforts of the state extension and the dry weather can keep this fungus in check.