In fact, when the disease occurs very late in the season, it may actually provide a little bit of a benefit in defoliating the plants in time for red chile harvest. Growers can take several steps to prevent crop damage, starting with thinning their chile. Powdery mildew attacks the lower leaves of chile plants first. The disease causes a small lesion on the upper sides of leaves and a grayish powdery growth on the undersides. It gradually works its way up the plant as the disease develops.
Sulfur is the only fungicide registered for powdery mildew in chile.
Growers who can get the sulfur on early on the undersides of leaves and lower part of the plant canopy can see some reduction in disease severity. The smaller plants are, the easier it is to get ground rigs into the fields to apply sulfur, she said. The material must be reapplied if rain washes it off. Growers have another treatment option until the end of July, Goldberg said. Rare only five years ago, powdery mildew appears to be entrenched in southern New Mexico.