By: John Ippolito, PAg, Regional Crops Specialists, Kindersley
Stemphylium blight is often found in lentil fields in Saskatchewan. Characteristic symptoms begin as small beige lesions on leaves. In many cases it is not identified until the tan-coloured leaves are evident across the top of the canopy, as show in the picture.
The disease is caused by a fungus called Stemphylium. The fungus commonly occurs as a saprophyte, meaning that it infects plant tissue that is already senescing and is not host-specific (can infect a range of crops when environmental conditions are favourable). One of the most common species causing stemphylium blight is Stemphylium botryosum, which prefers temperatures above 25 C and a minimum of eight hours of leaf wetness for infection to occur. High relative humidity is also favourable for disease development.
Until recently, it was not known whether this disease should be of concern to lentil producers. Recent research at the University of Saskatchewan has shown that the impact is more on quality than quantity. Quality impacts can be in the form of seed staining and smaller seeds – particularly when infections occur in the early stages of flowering.
Fungicide applications specifically for stemphylium blight control are not currently recommended. Applications of fungicides for the control of anthracnose and ascochyta would be expected to provide some suppression of stemphylium blight.