Field Sprouts in Potatoes from Heat Stress

Emmalea Ernest, Extension Fruit & Vegetable Specialist; emmalea@udel.edu

This week I heard about three separate instances of potato tubers with sprouts at harvest. Sprouted potatoes have reduced quality, marketability and storage life. Field sprouts, also called heat sprouts, occur under environmental conditions that shorten or overcome dormancy in developing tubers. Field sprouting is associated with high temperatures and drought conditions, both of which have been present this season. Researchers have determined that high temperatures alone can induce field sprouts, which means that even well irrigated potatoes are at risk when temperatures are high.

Soil temperatures above 82°F for a month have been observed to consistently stimulate premature sprouting while higher soil temperatures (above 90°F) for a week can induce sprout formation. Average soil temperatures from DEOS weather stations for the last month and week are in the table below. Some locations have experienced soil temperatures that are likely to induce heat sprouts.

Average Soil Temperatures from DEOS Weather Stations

Some varieties are more susceptible to developing heat sprouts than others. Varieties with shorter storage dormancy tend to also be more prone to developing heat sprouts. Heat stress can also cause misshapen tubers and tuber chaining. This factsheet from NDSU includes images of these disorders: Potato Tuber Second Growth.