Hi,

I can't be sure that your plants have late blight; some things look like it might be, but other things don't look like it.

In the third picture, the rightmost droopy leaf appears to have a blotchy spot in the middle of the leaf, but it doesn't quite look like LB from what I can see.

In the very bottom picture, one of the leaves further back also appears to have a spot of discoloration on it, assuming I'm seeing it correctly.

Let's not jump to an immediate conclusion, however. If this spreads more in the next day or two, then you may have a problem. Also, watch the stems. Late blight will spread to the stems in a couple of days.

When I had every tomato plant devastated by LB last year, the first sign was kind of a black-grey, oily-looking spot near the center of a few leaves. It was just like someone had put a good-sized drop of motor oil on some of the leaves. Other than that the leaves looked healthy.

The next day, more leaves had those black-grey oily spots. The oily spots from the previous day had the "fuzzies" (the spores). Not a lot of fuzziness, but it was detectable upon close inspection, sometimes on the underside of the leaf and other times on top. And, not the entire leaf, just one spot at first. With every passing day more and more leaves went through that process. The same thing appeared on the stems.

One of your pictures shows black on the edge of the leaves, and that's not the way late blight worked on my plants. The first spots were always just off center of the middle of the leaf, between the leaf's main "vein" to the middle of one side of the leaf, originally about the size of a dime. The leaves didn't curl like that and, when they turned brown, they initially turned brown where the mold had been. In other words, the entire leaf didn't turn brown or yellow at first.

With late blight, you would also see the same blotches on the stems within another day or two...small blotches at first, but with the ugly black-grey oily color and, often, the fuzzy spores a day or two later. I don't see that in your photos.

You may very well have some botrytis, which is not generally fatal and can be cleared up by keeping the leaves dry and perhaps using a fungicide to help it along. Botrytis will cause the edges of the leaves to blacken and eventually get slimy looking. It, too, can cause fuzzies.

Botrytis is usually caused by leaves that are wet and don't get to dry out for a few days.

I would remove the affected leaves, bag them up in plastic, and put them in the garbage. If you're doing overhead watering, stop it and just water at the bottom of the plant. :-)

If you are having lots of rain, there's not much you can do. Botrytis will improve once the weather dries out.

For right now, I would assume it's something more mundane. If it is late blight by some off chance, you will know it in a couple of days.

Is there any fuzziness on the affected leaves at all? I'm not seeing any brown spots to speak of, but I'm curious whether there's some grey or white fuzz on the undersides of the leaves. Late blight causes dark dead spots rapidly, then almost immediately makes grey fuzzy masses on the underside of the spots.

I'd rule out early blight, as that causes distinct brown spots that multiply fairly rapidly on the lower leaves and work their way up. I'm leaning more toward Fusarium wilt, which can cause general yellowing on one branch or one side of the plant, then wilting and dying of the affected leaves without any real spots involved. The first three pictures really look like it.

--Alison

Hi Alastair,
I am also growing my tomatoes in Lancaster county, and I have leaves exhibiting precisely the same symptoms. I hold with Alison that it is most likely fusarium wilt, but as you know we have had very little rain lately so I am holding out hope it is possibly water related.

I removed the drooping and yellowing leaves, although if it is fusarium, this probably won't help. I am just trying to make sure they stay adequetly watered as there is no rain forcasted until Saturday and hot weather in the upper nineties for most of the week. Good luck! and I hope you post how they do.

Is Fusarium Wilt common in USDA zone 6? I know it's virtually unheard of in zones 5 and colder. Just asking, because I don't know if zone 6 is borderline for fusarium. Verticillium wilt, on the other hand, can happen anywhere.

I would bring a speciman to a Cooperative Extension to confirm a diagnosis; they are usually equipped to make a quick diagnosis.

Torquill is far more knowledgeable than I am, so I would defer to Torquill's judgment. Just curious about fusarium in zone 6, to fight my ignorance. :-)

lionheart,

Keep in mind that I'm a California gardener, so I'm kind of fuzzy on the range for Fusarium -- you may be right that it's too cold there for it. It didn't look like Verticillium in the pictures, though; V wilt has a characteristic V-shaped yellowing at the ends of the leaves (not on every leaf, but on most of them). I'm not seeing that here, so I suggested Fusarium.

Cooperative Extension might be able to figure it out if given a sample of stem near the base of the plant, showing discolored vascular tissue, but given just a few leaves they'd be guessing just like us. :) When you don't have some diagnostic symptom like the V-shaped yellowing, it takes a culture to figure out which is which. Our county Cooperative Extension people aren't really equipped to do culturing (there's a guy at U.C. Davis who does it, or the folks at CDFA in Sacramento). It takes that discolored stem tissue to do a culture, though.

Ultimately I'm not sure it matters a great deal which one it is, as the consequences are similar. F wilt will get worse with warm weather, V wilt will be worse in cool weather, but you can't get rid of either. Hybrids with resistance to one generally have resistance to the other. And gardening in containers will avoid both.

--Alison

Hey Alison,

Thank you for the info. It's a big help.

I agree it's hit-or-miss with Cooperative Extensions. Some are well-equipped and have knowledgeable staff; others not so much. I've seen both types.

And, of course, you're correct...for all practical purposes it really doesn't matter if it's F or V wilt; the result is the same.

It's a bummer, especially when you have a short growing season where you don't get second chances.

All the best,

-Deb