l seed dressings help control seedling infection. Destruction of lentil stubble by burning, cultivation or grazing helps to minimise disease carry-over between seasons. Delay sowing until early June because early sowing increases the length of time the crop is exposed to disease. Ascochyta blights of field pea, chickpea and faba bean are specific to those crops and will not cause ascochyta blight on lentil.
See also 'Lentil: Integrated disease management'
Botrytis grey mould (Botrytis spp)
Botrytis grey mould (BGM) infects lentil seed and stubble but is generally only a problem in wet years, when it can cause crop devastation. A dense crop, lodging and rain in late spring provide ideal conditions for the disease to develop in the crop canopy. Wider row spacing, later sowing and reduced seeding rates will reduce crop canopy density and the likelihood of infection.
Symptoms of stem and pod rot
Botrytis grey mould (Botrytis fabae and B. cinerea) can infect any above-ground plant parts. Lesions on leaves and pods are initially dark green but turn greyish-brown as they mature. Grey mould also develops on flowers. If the canopy is wet for long periods the pathogen grows on the stems, which quickly become covered with a fuzzy layer of grey mould. This all occurs within the crop canopy, often unseen from above the canopy. When the weather turns dry, clouds of spores are released into the air when plants are disturbed. Severely infected leaves, flowers and pods wilt and fall to the ground. If wet conditions continue the stems become girdled, resulting in spreading patches of brown and dying plants within the crop.
Symptoms of seedling blight
Seed from severely infected crops is often discoloured and shrivelled. If infected seed is used for sowing, plant establishment is usually poor, due to low germination and seedling blight. Blighted seedlings emerge but are yellow and stunted, and usually die after one or two weeks. If germination takes place under wet conditions, mycelium from infected seedlings can grow through the soil to neighbouring plants, creating patches of blighted and dying plants in the field. When seedlings infected with BGM are pulled up, grey mycelium can often be found on the stems just under the soil.
The fungus that causes botrytis grey mould is always present to some extent on pulse crop residues, especially from chickpea, faba bean and vetch. Airborne spores released from old infected crop residues early in the season can infect new crops. Grey mould can infect lentil at any time during the growing season, but epidemics generally develop late, after the plant canopy has closed. Periods of high humidity in spring favour rapid development of the disease. The fungus may establish a foothold on senesced plant parts, or on tissues damaged by hail, wind or machinery. It can also attack healthy plants and has a broad host range that includes faba bean, vetch, chickpea, field pea and lucerne. Flowers and pods are particularly sensitive to botrytis grey mould infection, which reduces pod set and seed quality. After harvest, the fungus survives as mycelium on plant residues and as sclerotia in the soil to enable its long-term survival.
Prevention of BGM seedling blight begins with sowing disease-free seed. Seed treatment with thiram plus thiabendazole, or thiram alone will control most, but not all, botrytis infections.
Timing and management of crop canopy closure is important in botrytis grey mould control. Follow recommended sowing times and sowing rates for the district. Crops with excessive vegetative growth and lodging are more prone to infection and losses due to botrytis infection. Airflow through the crop canopy reduces the in-crop humidity and this reduces the severity of infection.
Apply foliar fungicides just prior to canopy closure to prevent botrytis grey mould establishing in a crop. Fungicides should be considered in crops or varieties that are more susceptible to botrytis grey mould infection.
Taller, erect varieties or slower growing varieties are at less risk of infection, irrespective of their disea