Tomato Gray Wall

Are your tomatoes ripening unevenly? When you cut into them, do the walls look gray? It’s probably tomato gray wall. Also known as graywall and blotchy ripening, this disorder occurs when environmental conditions are less than ideal.

Tomato with gray wall (Edward Sikora, Auburn University, Bugwood.org) CC BY 3.0 US

Tomato gray wall symptoms

While the rest of your tomato plant looks fantastic, with sturdy stems and lush leaf growth, tomatoes affected with graywall ripen unevenly with both red and yellow areas. This yellow mottling starts appearing when the fruit is green. As the fruit matures, these areas can turn gray and become sunken. These symptoms are not the same as yellow shoulder. 

When tomatoes develop yellow or green shoulders, it is from too much heat and sunlight, and symptoms are limited to the upper portions of the fruit. Tomato gray wall can be seen all around the fruit.

If you cut open an affected tomato, you will see that the walls of the fruit are gray, yellow, brown, or green. Anything but red. Look closely, and see the vascular tissue has turned dark brown. If the rest of the plant looks affected, it is probably tomato mosaic virus.

Tomato gray wall causes

Several conditions can cause gray wall in tomatoes. Some you can change, and some you can’t. Extreme heat, fluctuating temperatures, and high humidity can stress plants into responding with gray wall. Overcast skies during hot weather, fog, and excess shade can cause blotchy ripening. Overly wet or compacted soil can also cause tomato graywall. Too much nitrogen, or insufficient potassium or boron, can also cause tomato gray wall. [Have you tested your soil lately?] Scientists also believe some bacteria, fungi, and the tomato mosaic virus may be part of the problem, but they’re still exploring those possibilities.

Tomato gray wall prevention                                       

You can prevent tomato gray wall by providing good drainage, improving soil structure, planting tomato mosaic-resistant varieties, and feeding your plants appropriately.