Why are many of my tomatoes ripening on a table inside instead of on the vine?
These are Pruden’s Purple (foreground) and Cherokee Purple (background) on the left, and Milano Plum tomatoes on the right, in a scene I’m used to creating just before frost when all potentially viable tomatoes are brought inside to ripen. This is not a sight I want to see in August.
But … when tomato vines begin developing brown patches on leaves and stems, and continue to do so at an ever increasing rate, it’s time to take action.
Fearing dreaded tomato late blight, I took photos and collected samples of leaves and stems with brown patches. I then carefully removed the plants, cutting each stem into pieces that would fit into a trash bag. Four five-foot tall tomatoes that I nurtured from seed, and should have been in their prime, were reduced to common trash. Normally, I compost plant waste but it’s not good practice to compost diseased plant material.
I called the Connecticut Agricultural Experiment Station and reached Dr. Yonghao Li, plant pathologist in the Plant Disease Information Office. After reviewing my emailed photos Dr. Li asked to see the actual samples. He suspected some sort of blight.
I packed each tomato leaflet between dry paper towels and sealed two stacks of samples in zip-lock bags, then mailed them, express delivery, so they would get to Dr. Li before completely drying out.
Dr. Li called after inspecting the samples under microscope to report no blight; no bacterial disease of any type. We ruled out pesticide/herbicide drift from a neighboring property, sunscald as this would not cause browning patches on stems, and soil (I used new commercial composted potting soil for each potted tomato). Dr. Li suggested some sort of virus might be the cause.
Unfortunately, he said testing for a virus is not as simple as microscopic inspection for bacterial infection. Each virus test requires an individual test kit and still may not provide definitive results. In other words, virus testing is not cost effective. I’ve compared my diseased tomatoes with photos of virus-infected tomatoes and found no match.
Dr. Li suggested my tomato problem may be seed-borne. I started this year’s plants from the same seed (from two separate seed suppliers) as last year and had the same problem at about the same time with my 2011 tomatoes. In both seasons, this and last, small brown spots began showing up on leaves at all levels of the plant, some expanded to larger size with yellowing at the outer edges while brown patches developed on some stems and at some leaf nodes. The heirloom Pruden’s Purple and Cherokee Purple tomatoes were the first to show these signs, followed by Milano Plum tomatoes. Last year the Manyel tomatoes were the last heirloom to show signs and, this year, my one Manyel plant still looks healthy.
I’m very appreciative of the assistance of Dr. Li and highly recommend other gardeners seek the advice of the Plant Disease Information Office.
I’m relieved that my tomatoes don’t have blight but I’m still at a loss to explain the disease cause. I can guarantee that next year I’ll start with fresh tomato seed, likely from different companies.