The Farm Town Potato FaminePosted: August 8, 2011
We had an unusually cold and wet spring in our real-life farm town. Farmer D & I were happy that we managed to get a garden in at all. And now that it’s hot and humid, the garden is doing great…except for our potatoes.
We planted a mix of Red Pontiac and Kennebec seed potatoes in early June. A couple of weeks ago Farmer D noticed that the plants were starting to wilt. He called our local Ohio State University Extension office and spoke to a Master Gardener. Nick , the garden expert, told D that we had a case of late potato blight.
Late blight was the cause of the Irish potato famine in the 1840s…and is still alive and kicking. Left untreated, blight can destroy entire potato crops.
According to the OSU Fact Sheet:
Late blight appears on potato or tomato leaves as pale green, water-soaked spots, often beginning at leaf tips or edges. The circular or irregular leaf lesions are often surrounded by a pale yellowish-green border that merges with healthy tissue. Lesions enlarge rapidly and turn dark brown to purplish-black. During periods of high humidity and leaf wetness, a cottony, white mold growth is usually visible on lower leaf surfaces at the edges of lesions. In dry weather, infected leaf tissues quickly dry up and the white mold growth disappears. Infected areas on stems appear brown to black and entire vines may be killed in a short time when moist weather persists.
You don’t need a close-up to see that our plants look bad.
On potato tubers, late blight appears as a shallow, coppery-brown, dry rot that spreads irregularly from the surface through the outer 1/8-1/2 inch or more of tissue. On tuber surfaces, lesions appear brown, dry, and sunken, while infected tissues immediately beneath the skin appear granular and tan to copper-brown.
Late blight is caused by the fungus Phytophthora infestans. Unlike most pathogenic fungi, the late blight fungus cannot survive in soil or dead plant debris. For an epidemic to begin in any one area, the fungus must survive the winter in potato tubers (culls, volunteers), be reintroduced on seed potatoes, or live spores must blow in with rainstorms.
We had some spotty potatoes last year—we should have bought fresh seed potatoes instead of using culls from last year…that, and early planting right before a long, wet, cold spell, created the perfect recipe for potato disaster.
The Master Gardener recommended we apply a protective fungicide to the plants, not dig up the potatoes until the vines are dead, and get new certified seed potatoes to plant next year.
So much for me sneaking out for some fresh baby reds.