Monday a week ago, I was a guest on These Days, the morning talk show on San Diego Public Radio, KPBS. I appear on These Days about once a quarter, where the delightful host Maureen Cavanaugh and I always start off on a topic or two. Soon, however, the many calls take us in all different directions – which is part of the fun.
This time, there was alot of talk about water and saving water in the garden. There were also several callers asking what might be wrong with their tomatoes. They seem fine, they said, but then, suddenly, they wither up and die.
I’d heard this once or twice in recent weeks but hearing again, and all from people in north county coastal San Diego made my ears perk up.
Since the weather up until this past weekend was incredibly cool and humid, even rainy, I wasn’t surprised to hear about powdery mildew or mold. Under these conditions, vegetable plants are especially susceptible to leaf pests and diseases.
It didn’t sound like verticillium wilt which is a common problem, especially with tomatoes. Leaves start to yellow along the veins, then brown and dry up altogether. Its one reason I recommend that gardeners don’t grow tomatoes in the same soil two years in a row.
No, this sounded different. I put my detective hat on and did some research.
My contacts at UC Cooperative Extension didn’t know the answer but reminded me that anyone can have plants and soil analyzed by the County Plant Pathologist. There is an office in Kearny Mesa and one in San Marcos. Visit their website for directions, and information on preparing samples before you bring them to their offices.
I checked out the list of tomato pests and diseases on the University of California Integrated Pest Management (IPM) Online database. This is one of my favorite resources. Check out UC-IPM information on tomatoes here.
Several of my most trusted colleagues suggested that in light of the damp, cool weather, perhaps we were seeing a disease called “late blight.” This is caused by a micro organism known as Phytophthora infestans. Actually, it is the same microbe that caused the Irish potato famine!
UC IPM didn’t have much on late blight, but I did come across some really interesting information on the website for Science Friday, one of my favorite public radio shows. Host Ira Flatow explores all kinds of interesting topics from space exploration to artificial hearts to butterfly migrations.
Last year, Flatow did a show on late blight threatening the tomato crop on the east coast. Listen to it here. Look for “Listen here” on the upper left hand corner of the window. The beginning of the show is all about the organism’s genome but towards the end, they talk about how to deal with it in the garden.
There’s also a Science Friday video of tomato farmers dealing with late blight last summer on the east coast. It is really interesting! Its on the same page as the radio program, just click the big photo of ugly tomatoes in the center of the window.
Is this the problem folks are having? The only way to be sure is to compare the symptoms and have infected plants analyzed at the county. But if your plants look like the ones in the video, please email me to let me know!