Brown and grey blight (<i>Colletotrichum coccodes </i>and <i>Pestalotiopsis theae</i>)
These fungi are considered weak pathogens and usually only affect plants that have been weakened by improper care or adverse environmental conditions. Often they occur together.
The diseases are favoured by poor air circulation, high temperature, and high humidity or prolonged periods of leaf wetness. When young twigs of susceptible cultivars are cut and used to root new plants, latent mycelium (fungal growth) in the leaf tissue may start to invade nearby cells to form brown spots, and this may lead to death of leaves and twigs.
Symptoms consist of small, oval, pale yellow-green spots first appearing on young leaves. Often the spots are surrounded by a narrow, yellow zone. As the spots grow they turn brown or grey, concentric rings with scattered, tiny black dots become visible and eventually the dried tissue falls, leading to defoliation. Leaves of any age can be affected. The tiny, black spots on the lesions contain the fungal spores. Rain splash transports the spores from one plant or site of infection to another. If the spores land on a leaf, they germinate to start a new leaf spot or a latent infection.
- Avoid plant stress.
- Grow tea with adequate spacing to permit air to circulate and reduce humidity and the duration of leaf wetness.