Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
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. Switching to white plastic mulch for later spring plantings can reduce losses significantly (white plastic will be 10-20 degrees F cooler that black plastic mulch) and white particle films sprayed at the base of plants over the mulch can also reduce plant losses to heat necrosis.
Heat necrosis on pepper stem next from excessive temperatures from black plastic mulch
Damaged stem tissue where pepper stem is touching black plastic mulch during high temperature periods before the plant has produced a canopy to shade the plastic.