TOMATO PLANT LEAF EDEMA!

I've seen nearly a dozen GW posts with pictures of leaves with spots that don't seem to match any disease or insect damage that are usually listed on reputable sites. I've had the unidentifiable spots on my plant leaves, too, and worried for a long time about disease.

I finally concluded that the cool wet Spring weather must have something to do with physiologically triggering the spots.

So after I read your post, I did some internet hunting, and dang if you aren't right! Sure enough, one of the causes of leaf edema is too much water that "stimulates an abnormal increase in the size and number of a group of inner cells". See this site for more information.

Here's pertinent information related to tomatoes about the condition:

Edema may be a problem on the following vegetables: tomato foliage and fruit; bean foliage and pods; cabbage; broccoli; cauliflower; Brussels sprouts; potato foliage; most cucurbit fruit, foliage and stem. Probably all succulent tissues of vegetable crops are susceptible to edema.

Symptoms

Symptoms of edema are variable and depend on the plant species, the plant parts affected, and tenderness of the tissue. Typically, symptoms appear on the succulent leaves, stems, flowers, and fruit of susceptible plants as single, minute, watersoaked "blisters," "wart," or galls.

Causes

Edema may be caused by any agent that stimulates an abnormal increase in the size and number of a group of inner cells. Edema can be induced by (1) spraying with some chemicals such as ammoniacal copper carbonate in an oil emulsion, (2) injuries resulting from wind-blown sand particles and sucking insects, (3) high light intensity (over 2000 foot-candles) for ivy geraniums, and (4) accumulation of water in the intercellular spaces.

The most common cause of edema is the presence of abundant, warm soil water and a cool, moist atmosphere. Under these conditions the roots absorb water at a rate faster than is lost through transpiration. Excess water accumulates in the leaf, some parenchyma cells enlarge and block the stomatal openings through which water vapor is normally released from the plant; thereby contributing to further water retention in the leaf. If this condition persists, the enlarged cells divide, differentiate a cork cambium, and develop elongate cork cells externally to form a periderm. The rupture of the epidermis by the enlarged inner cells and the periderm account for the raised, crusty appearance of older edema spots.

So, again, enthusiastic thanks! I and many other people would have worried ourselves nutty trying to figure out what the spots are!

Mulio is my hero! Just what this place needs....correct information.

You can see why somebody would think the plant had a disease with leaves wilting, discoloration, brown blotches, etc. All from the plant's uptake of so much water that the leaf-cells expand rapidly and plug up the respiratory pores on the surface. Then blisters form which turn brown and cause that part of the leaf tissue to die.

And Bob especially, wonder what you've been doing. John posts here from time to time, but I don't see you posting all that much.

Ah, what histories have been created in terms of online doings. LOL

Carolyn, just finding out that her old sprayer is dead so Freda has to go to Agway and buy a new one to get everything sprayed with Daconil re the Late Blight situation here in the NE. Double Sigh. And she just brought in a branch of one plant for me to look at but thankfully it's just too much moisture, not edema, but just too much moisture, but have to get that Daconil on the tomatoes, potatoes, squash, cukes, etc. ASAP. No, LB doesn't hit the squash and cukes; that's for powdery mildew, and that's correct information. LOL

Bob, however, has probably been goofing off somewhere.

I suppose if one helped the excess soil moisture drain/dry out more (make holes in soil) or stay cooler (mulch the soil) that might help.