Leaf Spots, is a common disease on many Plant Can be caused by a range of fungi, Glomerella cingulata , Ramularia rebi and Spectoria apiicola also have their own entries. Leafy plants grown soft (as with nitrogen-high fertilizers) are vulnerable in wet season, especially if overcrowded. Leaf spot typically occur in spring and autumn.
Symptoms and damage
Brassicas; Older leaves show brown spots, with concentric rings of tiny fungal bodies, which carry spores. Sometimes these leave holes in leaves. On spinach, the spot are light brown or grey, with brown or purple edges. Ornamental bulbs, corms and rhizome; Dry, dark, sunken spots are appear on leaves; sometimes the whole leaf turn brown (especially in winter). If spots merge (for instance o irises), leaves can be killed. Hellebores; Black blotches appear on buds and petals. Rhododendrons; circular purple patches, which turn brown, appear on leaves. Weak specimens are at risk.
Prevention and control
Vegetables; cut off and dispose of affected leaves from Leaf Spot. Thin plants to minimize the risk of further infection. Practice crop rotation. Spraying affected plants with a foliar feed can boost recovery. Adding potash to the soil before sowing spinach can reduce the plants ‘susceptibility to disease.
Ornamentals; cut off affected leaves and spray the plant with mancozeb. Rhododendrons; Boost recovery (especially if the plant has been severely affected) with a foliar feed and check that the soil type is appropriate (i.e,of a low enough pH and with and adequate humus content).Source;Leaf Spot Disease
