http://www.durgan.org/URL/?LDTDV 6 September 2009 Is this Potato blight (Phytophthora Infestans)? I was absent when the potato stalks died off, but was told they died rather quickly, so didn't get a view of the leaves at that time. When digging the potatoes about 50 or so pounds from about 15 plants, I obtained about 10 potatoes that had this rot, and bad odor. I carefully discarded these, and assumed that it was rot exacerbated by wet weather. The pictures depicted were culled from the stored potatoes. I did not take pictures of the infected potatoes when digging, but the rot is similar, with one slight difference. The dug potatoes when the wound was probed had a stringy web like structure sort of like bubble gum being pulled. There is blight in my area this year, from Newspaper reports.
What is really being asked in the first post is: Can one be certain that this is late potato blight from appearance of the tuber alone? After studying the pictures on the various sites on the internet, I am of the opinion that is is late blight. Unfortunately, there are few pictures of the disease on tubers, and many sites simply plagarize pictures from one or two sites presenting pictures of the diseased tuber. I was looking for some variety for comparison with my photos.
If you think your potatoes have Late Blight, you should check your tomato plants. It would be very unusual to have potato plants dead from Late Blight without tomatoes in the same garden eventually showing signs of the disease. Tomatoes are as susceptible as potatoes to Late Blight, which is extremely contagious. Here is a link to Cornell's site with very good pics of Late Blight on tomatoes: http://www.hort.cornell.edu/department/Facilities/lihrec/vegpath/photos/lateblight_tomato.htm Perhaps you've already seen Cornell's pics of Late Blight on potatoes, including four pics of affected tubers, but here's the link in case you haven't seen it yet: http://www.hort.cornell.edu/department/Facilities/lihrec/vegpath/photos/lateblight_potato.htm
Thanks, Blight is present in my garden almost beyond a doubt. Tomatoes are far worse than these pictures depict. From 30 plants I picked 2 five gallon pails of blighted tomatoes yesterday. The vegetation is completely devastated. Plants will be pulled today and placed in the garbage. Unfortunately, the two five gallon pails of tomatoes were put through he chipper/shredder and placed on the compost heap. Stored potatoes will be culled often and any that are diseased discarded. I am pretty certain all the tubers were removed from the growing area. The area has been rototilled three times for various reasons, so I doubt any more tubers are left in the ground. All infected tubers were placed in the garbage.
It has been a horrible year for my tomatoes too. All of them are now dying from Fusarium wilt and late blight. To ensure your field free of those germs, you might want to considering using some of those outlawed "cosmetic" potato dusts in the field somehow (Thanks to McGuinty government for banning it). I heard lime may also work.
