WSU POTATO ALERT ASSISTS TO HELP RECOGNIZE POTATO CROP SYMPTOMS OF SUN STRESS

Washington State University (WSU) Potato Alert dated July 15, 2024, reviews the signs of sun stress on potatoes, the plant’s ability to acclimate, and discusses how to utilize irrigation to cool potato crops. The severity of heat stress on potatoes is dependent on how high the temperature is, how quickly the temperature rises, the length of exposure to high temperatures, and how irrigated the crop and soil are. Prolonged periods of drought conditions, temperatures that spike quickly, and sustained temperatures of at least 10 degrees above the norm create prime conditions for potato heat stress.

Foliar symptoms of potato heat stress include leaf rolling, deterioration, or dropping. Potato plants may develop smaller leaves, tip or windburn, or have wilting leaves in response to heat stress. In extreme heat, leaves can experience heat crinkle. Pathologists haven’t been able to specify a causal relationship, but potato crops in the Columbia Basin have exhibited Toxic Seed Piece Syndrome (TSPS) during heat spikes. Tuber symptoms of heat stress include heat sprouts, misshaped tubers, and pink eye.

Potatoes acclimate to high temperatures through biochemical changes and structural and physiological modifications that help them tolerate, avoid, or dissipate heat. Heat shock proteins help stabilize other proteins during high temperatures to allow proteins to return to normal when heat stress subsides. This is one biochemical response to heat stress. Antioxidants and osmoprotectants are other biochemical responses to heat stress. Potato plants utilize morpohological responses too, such as leaf rolling and leaf positioning for less sun exposure. Potato plants will also modify their leaf cuticle wax in response to sun exposure to protect against dehydration and they strategically cool themselves utilizing transpirational cooling. Transpirational cooling is a physiological process that moves water through the plant and provides an effective evaporative cooling environment when the soil is adequately moist.

Irrigation is an important tool in potato crops and essential for cooling and mitigating heat stress during high temperatures. Estimation of the amount of water that is transferred to the atmosphere through combined evaporation and transpiration is called evapotranspiration (ET) and is useful in determining water use and irrigation schedules. WSU’s AgWeatherNet (AWN) provides ET rate estimates for over 40 crops, including potatoes, and offers several tools to assist growers with irrigation.

Before and After Heat Wave Irrigation Guidelines

• Maximize your irrigation systems’ water application capacity.
• Limit runoff by enhancing water infiltration.
• Anticipate water needs by looking at weather forecasts and crop ET charts.
• Frequently check soil moisture.

For more detailed information, go to WSU Potato Alerts here.

Have questions?

Contact:

Carrie H. Wohleb, Ph.D.
Professor / Vegetable & Seed Extension Specialist
WSU Extension - Grant County - Columbia Basin
Tel: (509) 707-3510 or Email This email address is being protected from spambots. You need JavaScript enabled to view it.