Moisture Stress Symptoms in Vegetables and Grains

A cardboard box filled with freshly dug red potatoes sits in a field of dirt.

By Sharah Truett

Howdy farmers! Last year, we had a doozy of a drought. It got so bad that the Department of Ecology issued a Drought Emergency for the Sequim-Dungeness River Watershed. By the end of April 2025, the snowpack of the Dungeness-Elwha watershed was only 55% of normal. Farmers experienced a very dry and warm spring and early summer, as well as an extremely dry June with only 18% of precipitation recorded at the Elwha Ranger Station. If you are a farmer with questions about how to get through future droughts, give the WSU Extension Office a call. We are happy to help.

Here’s a little information about how to prepare for dry times and how to recognize drought stress in your crops. Here goes:

In the spring, carefully monitor soil moisture and make sure to irrigate enough to bring the soil to capacity. Once the dry season begins, be looking for signs of moisture stress. If you see moisture stress in part of your field, make sure to apply irrigation to the whole field, otherwise it may be too late by the time you see widespread symptoms. Here is a chart showing how different crops show moisture stress as well as the most critical moisture times for each crop.

CropMoisture Stress SymptomsCritical Growth Period
BeansWiltingBloom and fruit set
Sweet CornDull green color, curling, rolling of leavesTasseling, silking, ear-filling stage to harvest
Tree FruitsDull leaf color, leaf rolling without recovery by eveningFull bloom to 4 weeks after bloom, fruit set, last 2 weeks to 30 days prior to harvest
TomatoesGrayish green color, droopy, wilting, leaf rollingAfter fruit set
OnionsDull color, wiltingBulb formation
Small GrainsDull green, curled leaves, firing of lower leavesBoot through soft dough
PotatoesDark green colored leaves, wilting during the heat of the dayTuber formation and growth
Grass Hay and PastureDull grayish, green colorEarly spring through first harvest
This table describes moisture stress symptoms on various crops as well as the most critical moisture times for each crop.

To get more detailed information from WSU, check out the WSU publication “Visual Crop Moisture Stress Symptoms.