How to Manage Pests
UC Pest Management Guidelines
A tan center and a dark border around an irregularly shaped lesion distinguish Stemphyllium leaf spot from other leafspot diseases. Once the border is formed, the spot ceases to get larger in size. New spores will form in the center of the leaf spot.
Stemphyllium leaf spot is a cool season foliar disease. Cool temperatures (60-70°F) and moist weather favor infection and spread. The disease is usually found in first and second cuttings. Because defoliation occurs only under heavy disease pressure, Stemphyllium leaf spot is not considered as serious as some other leaf spot diseases.
No known control measures are used. Early harvest is an option with severe infestations. Some varieties may have more levels of resistance than others, but companies do not commonly report resistance to this disease.
UC IPM Pest Management Guidelines: Alfalfa