Botrytis Grey Mould of Lentil
Note Number: AG1275
Published: June 2008
Updated: August 2012
Reviewed: November 2016
Botrytis grey mould is a serious, but sporadic disease of lentil in Australia. The disease is capable of causing serious yield losses, particularly in dense, early-sown crops, when spring rainfall is high and there are prolonged wet periods. An integrated approach to managing Botrytis will minimise yield losses.
What to look for
All aboveground plant parts of lentil can be affected by botrytis grey mould. Symptoms initially appear either on the crop canopy or on flowers and pods, depending on the location of the crop. The most damaging symptoms become apparent after the crop has reached canopy closure, and a humid microclimate is produced under the crop canopy. The disease first appears as small, discrete, cream coloured lesions on lower leaves. These lesions can enlarge and coalesce to infect whole leaflets which later senesce, and fall to the ground. Unlike ascochyta blight, no small black fruiting bodies (pycnidia) can be seen within the lesions.
If conditions remain conductive for disease,i.e. warm and wet under the crop canopy for at least 4 days, infection can spread to the lower stems. When that happens, lesions will girdle the stem and the stem will become covered with a furry layer of grey mould. This eventually causes stem death, and the whole plant dies. Often occurring before the onset of flowering and pod fill, infection will continue to spread, resulting in patches of dead plants within crops (Figure 1).
Fig 1. A lentil crop with advanced botrytis grey mould. Note the dead patches of plants.
Pods which become infected will be covered in a grey mouldy growth . Some pods will rot and turn brown when dried out (Figure 2). Seeds within these pods fail to fill properly and are often discoloured and shrivelled. When infected seeds are sown pre-emergence root of seeds and damping off of young seedlings can occur. The stems of infected seedlings are often covered by masses of grey spores at the soil line.
Fig 2. A lentil pod infected by Botrytis cinerea. The grey mouldy growth is typical of this disease.
Pods which become infected will be covered in a grey mouldy growth, will rot and turn brown when dried out (Figure 2). Seeds within these pods fail to fill properly and are often discoloured and shrivelled. When infected seeds are sown seedling blight can occur. Seedling blight is characterised by the appearance of grey mycelium growth on the stem at the soil line.
The fungal pathogens Botrytis cinerea and Botrytis fabae that cause botrytis grey mould, can survive on infected seed, on infected trash (Figure 3), and as sclerotia in the soil or on alternate hosts. Botrytis cinerea and B. fabae have a broad host range including faba bean, chickpea, field pea, lupin and pasture legumes such as lucerne and clover. Other host species include a wide range of ornamental and horticultural crops.
Sowing botrytis infected seed can give rise to infected seedlings reducing seedling survival and crop establishment. Old infected trash is an important source of fungal inoculum. Spores are produced on old trash and are carried by the wind into new crops where infection can occur. Under favourable conditions of high humidity and moderate temperatures, the disease can spread rapidly; producing spores on newly infected tissue, and further spreading the disease within crops. The development of botrytis grey mould epidemics is largely determined by the prevailing environmental conditions, especially the presence of moisture.
Environmental conditions and canopy density are primary factors that influence the development of botrytis grey mould epidemics in lentil crops. The formation of a favourable microclimate under the crop canopy, especially following canopy closure and humid conditions after rain, favour the development and further dispersal of the botrytis grey mould pathogens.
Fig 3. Lentil stems with advanced infection by Botrytis cinerea. Note the formation of sclerotia by the fungus for survival.
Botrytis grey mould can occur in all areas where lentils are grown, but is most common in districts with rainfall greater than 400mm. Losses due to the disease can range from minor to very serious, depending on the lentil variety grown, location of the crop, time of infection and amount of spring rainfall. Unprotected crops can lose up to 30 per cent of yield. In addition, seed can be discoloured due to pod infection by the pathogens, which reduces its market value.
Management requires a combination of farm hygiene, resistant varieties, crop monitoring and the use of fungicides. When growing a new variety, obtain a copy of the variety management package for information on specific disease management.
Use varieties with the greatest resistance to botrytis grey mould. Warning – all varieties are susceptible to grey mould when disease pressure is high.
Only use seed with less than 5 per cent botrytis infection or preferably use seed with nil infection. Using old or damaged seed can reduce seedling vigour and increase susceptibility to infection. See the DEPI Information Note: Seed Health Testing in Pulse Crops (AG1250) for more information.
Use a registered seed treatment for the control of seed-borne diseases in lentil. Fungicides can have a deleterious effect on rhizobia. Therefore, seed should be treated with fungicide and then inoculated with rhizobia in two separate operations. Rhizobia should be applied to seed immediately before sowing, especially on acid soils.
Avoid planting this season's crop near old lentil, faba bean, chickpea, vetch or lathyrus stubble. These crop residues can harbour Botrytis. The grazing or burying of stubble will reduce the carryover of disease into the following season. Allow a break of at least 3 years between lentil crops.
Time of Sowing
Avoid early sowing. Early sowing and high sowing rates can cause rank crop growth, lodging and increased risk of grey mould. Follow the recommended sowing rates and sowing dates for your district.
Use Foliar Fungicides
In areas of high risk, it may be necessary to apply foliar fungicides to protect the crop, especially if a susceptible variety is being grown. Fungicides should be applied before canopy closure for best results. If conditions remain conducive for disease (warm and wet) follow up sprays may be necessary 12 - 14 days later.
Fungicides containing mancozeb, chlorothalonil, carbendazim, or procymidone have activity against Botrytis. See the Australian Pulse Bulletin Pulse Seed Treatments and Foliar Fungicides for more information on foliar sprays.
Plan to harvest as early as possible to minimise disease on seed.
Detailed information on each of the pulse diseases can be obtained from:
- Agriculture Victoria Information Notes.
- Pulse Australia
- National Variety Trials
- Grain Legume Handbook.
- Victorian Winter Crop Summary
- Victorian Pulse Disease Guide
- Seed Health Testing in Pulse Crops (AG1250)
- Pulse Seed Treatments and Foliar Fungicides
Contact/Services available from DEDJTR
Field Crops Pathology, Grains Innovation Park, 110 Natimuk Rd, Horsham 3400. Tel (03) 5362 2111, or the DEDJTR Customer Service Centre 136 186
Acknowledgments: This Information Note (AG 1275) was prepared with assistance from Trevor Bretag, Horsham and Luise Sigel, Agriculture Victoria, Horsham. Support by Agriculture Victoria (DEDJTR) and the Grain Development Corporation is gratefully acknowledged.
Last Updated: November 2016
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Published by the Victorian Government Department of Economic Development, Jobs, Transport and Resources Melbourne 2016
© The State of Victoria Department of Economic Development, Jobs, Transport and Resources Melbourne 2016
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