Stem Heat Necrosis

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Temperatures have topped 90 °F this past week. With the high temperatures, there is potential for transplant loss due to stem heat necrosis.

Late spring planted peppers are very susceptible to stem heat necrosis on black plastic mulch. This is where the high temperatures at the mulch surface causes damage to the stem, often causing plants to collapse. When daytime temperatures are in the high 90s, the surface of black plastic mulch can be as high as 140°F, which will kill plant cells.

Controlling stem heat necrosis starts with using larger transplants with thicker stem diameters. Make a larger hole when transplanting. Switching to white plastic mulch for later spring plantings can reduce losses significantly (white plastic will be 10-20 °F cooler than black plastic mulch) and white particle films (clay or lime based) sprayed at the base of plants over the mulch can also reduce plant losses to heat necrosis. Putting a small mound of clean sand around the plant stem will also eliminate this problem.


Heat necrosis on pepper stem next from excessive temperatures from black plastic mulch.