Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
I know this seems very obvious to most growers, as we have sunscald every year in our vegetable plantings. This year just seems to be especially bad as I have gotten several calls from growers about a strange problem in their peppers that looks like sunscald, but couldn’t be. The reason given that it could not be sunscald is because the plants have thick foliage and the fruit seem well covered. Sunscald occurs when peppers or other vegetables are exposed to the direct rays of the sun during hot weather; the damaged areas may become papery and bleached or tan colored, and these areas often are covered with a black fungal growth (Photo 1). It is more apparent on plants that have sparse foliage or that have lost a large proportion of leaves to a leaf-defoliating disease. But almost all the farms I visited had plants that looked very good (Photo 2). The problem is that pepper plants often lean to one side or the other because of winds blowing them in certain directions. When this occurs sunscald can be especially prevalent on previously shaded pepper fruit that are suddenly exposed to the sun, even for a short period time. Photo 3 shows one of these leaning pepper plants and several fruit that were damaged by this sudden exposure resulting in sunscald. The damaged areas are vulnerable to infection by fungi (Black mold), and bacteria, so that at times a pepper fruit will be found that is a soupy, smelly watery mess. Sunscald is most prevalent on green fruit. Staking and tying pepper plants will greatly decrease the leaning plants and greatly decrease sunscald. The pepper plants do not have to be tied often, usually once is all it takes and stakes do not need to be any taller than the pepper plants (so broken tomato stakes work well) (Photo 4). Peppers in a tied vs. non tied section of field had vastly different sunscald problems. The stake and tied section had less than 2% of fruit sunscald damaged; the non-tied section had 17% sunscald damaged fruit for the same variety planted the same day.
Photo 1. Pepper fruit with small and large areas of sunscald
Photo 2. Pepper plant that appears to have good foliage and fruit cover but still has sunscald fruit
Photo 3. Leaned-over plant exposing covered peppers, resulting in several sunscald fruit
Photo 4. Staked and tied pepper plants, 4-5 plants between stakes, one string