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Gray mold
The disease has a limited geographical distribution, occurring only in India, Syria, Morocco and the USA. It is a minor disease with few economic consequences.
The disease is caused by Botrytis cinerea Pers. ex Fr. The fungus has a wide host range and thus can manage to survive almost throughout the year. It is also reported to be seed borne to a limited extent. The disease development is favored by moist and cool temperatures (I 8-22°C) and a thick plant canopy that creates a favorable microenvironment. Thus, an early sown crop gets more disease than a late-sown one.
Symptoms: Symptoms first appear on flowers. Especially in the morning, they are covered with the dirty, white moldy growth of the fungus, which causes their death. With the continuation of a favorable microenvironment (weather conditions and thick plant canopy), infection develops on lower leaves on which the characteristic dirty white fungal growth is distinctly visible. This results in shedding of lower leaves. Later, the whole plant becomes infected and dries up (Fig. 21).
The affected plants may appear in patches that enlarge as the disease spreads.
Control: Treat seed with a fungicide such as benomyl or chlorothalonil (0.1-0.3%) to check seedborne inoculum.
Adjust sowing date to avoid maximum disease development. Normally, less disease develops in a mid- or late-sow crop.
Protect the crop with fungicide sprays of chlorothalonil (2-3 L/ha) or vinclozolin (Ronilan, 1-2 L/ha).
Alternaria blight
The disease occurs in certain lentil-growing countries such as Egypt, Ethiopia and India, but is not an important disease.
The disease is caused by Alternaria tenuis which has been lately renamed Alternaria alternata (Fr.) Keissler. The fungus has a wide host range and thus can survive throughout the year.
Symptoms: Symptoms first appear at the tips of leaflets as small pale spots on margins (Fig. 22). These progress into the leaflets and become necrotic and dark brown to blackish in appearance.
The infection spreads to other branches and the leaf infection gives the plant a blighted appearance.
Control: Prevent spread of the disease by a single foliar spray of dithane M-45 (3 L/ha).
Other minor leaf diseases
A number of fungi have been recorded on lentil leaves. However, they usually do not cause any appreciable damage or have economic consequences. They include:
Cercospora lensi and/or C. zonata have been reported to cause leaf spot in lentil. These spots are water-soaked and present in the center and on the margin of leaves, which finally dry and fall off.
Cladosporium herbarum (Pers.) Link causes general yellowing of infected plants on which the moldy growth of the fungus is conspicuous (Fig. 23).
Cylindrosporium sp. causes leaf spot as well as stem canker (Fig. 24). It has been reported exclusively from Syria.
Helminthosporium sp. has been isolated from lentil leaves in Turkey.
Phoma medicaginis (Malbr. & Roum.) causes leaf spots similar to those described for Ascochyta lentis.
Septoria sp. causes spots on lentil leaflets which become speckled when the fungus forms its pycnidia (Fig. 25).
Stemphylium hotryosum Walr. has been reported from Bangladesh, Syria and the USA. Leaflet tips are discolored in a way similar to that incited by certain mineral deficiencies.
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