This disease is caused by a fungus called Botrytis cinerea. Botrytis grey mould is the second most important disease of chickpeas and can infect plants at any stage of development. Under favourable conditions, the disease can develop rapidly, spread widely and cause complete yield loss. Chickpea genotypes with vigorous seedling growth, early canopy closure and early flowering are more likely to develop disease than other varieties. Use of badly infected seed can result in total crop failure where seed is not dressed with a fungicide. Crop losses are greatest in wet seasons, particularly when crops develop very dense canopies.
Plants may be attacked at any growth stage. Grey mould is most likely to first appear as a soft rot at the base of the stem in the collar region. The affected tissues become covered with a fluffy grey mould initially, (Figures 5.15 – 5.16).
As the disease progresses affected plants wither and die. Small black sclerotia may form on the surface of affected tissue when the plant dies. In older plants sometimes only a few branches on a plant are affected and the rest of the plant appears quite normal. Seedling infection can cause damping-off and considerable thinning of a crop.
Figure 5.15 Stem infection caused by botrytis. Note fluffy, grey spore mass covering lesion
Figure 5.16 Pod infection caused by botrytis
The fungus survives on infected seed, as a saprophyte on decaying plant debris and as soil-borne sclerotia. The disease is often established in new areas by sowing infected seeds, (Figure 5.17). Masses of spores are produced on infected plants. These fungal spores can be carried from plant to plant by air currents and spread the disease rapidly, (Figure 5.18). Once a crop has become established, the warm, humid conditions under the crop canopy provide ideal conditions for infection and spread of the disease.
Figure 5.17 Seed discolouration caused by botrytis infection
Figure 5.18 Disease cycle of botrytis grey mould in chickpeas. Illustration by Kylie Fowler
The disease can be prevented by using disease-free seed and applying fungicide seed dressing. Some cultural management practices such as lower seeding rates and wider row spacings are suggested to develop field conditions that are less favourable for the fungus. The resulting crops are more open and dry out quicker following moist conditions.
PHYTOPHTHORA ROOT ROT OF CHICKPEAS
DAMPING-OFF OF CHICKPEAS AND OTHER ROOT DISEASES