Photo 1. Yellow patches on the upper surface of the leaves of tomato leaves infected by leaf mould, Passalora fulva.
Photo 2. Underside of a tomato leaf showing spots of leaf mould, Passalora fulva, where spores are produced.
Tomato leaf mould
Passalora fulva (previously known as Fulvia fulva, Mycovellosiella fulva and Cladosporium fulvum).
Worldwide. In warm temperate and tropical countries. Asai, Africa, North, South and Central America, the Caribbean, Europe, Oceania. It is recorded from American Samoa, Australia, Fiji, French Polynesia, New Caledonia, New Zealand, Papua New Guinea, Samoa, Solomon Islands, and Tonga.
Yellow spots and patches occur on the top surface of the leaves (Photo 1), with brown to green spore masses on the lower surface (Photos 2&3). The diseased areas join together and the leaves dry up and die.
Survival between crops occurs in a number of ways. The fungus survives as spores or as "mycelium" (the cotton-like growth of the fungus) in dead tomato plants of the previous crop. It is spread as spores in air currents, by water splash, or on tools and clothing. There is a possibility that spread also occurs by insects and on seed.
The fungus causes a serious disease in cooler, wetter areas. The loss of leaves, from the bottom of the plant upwards, is rapid. Yield reduction is related to the time of infection. If plants are infected before fruits are formed, considerable crop loss occurs. In severe cases, the flowers and, occasionally, the fruit are attacked. Infected flowers may fail to set fruit. Occasionally, the fungus causes an internal blackening of the fruit.
Note, in Samoa, fruit yields of susceptible varieties were tripled when fungicides were used to control the disease.
In Solomon Islands, it is an important disease in the highlands. It is less common in coastal areas where another leaf mould disease occurs on tomatoes called black leaf mould, Pseudocercospora fuligena (see Fact Sheet no. 45).
Look for the yellow spots and rapidly developing irregular patches on the upper surfaces of the lower leaves, with brown to green areas on the under surface. Look for plants where leaves dry up and die rapidly.
Note, there is another disease that has similar symptoms. It is called tomato black leaf mould, caused by the fungus, Pseudocercospora fuligena (see Fact Sheet no. 45). This fungus and Passalora fulva can only be distinguished by looking at their spores under a microscope.
Leaf-mould resistant varieties are available. However, the fungus mutates readily (there are at least 12 races), and varieties may not be resistant to them all.
The cool, wet, conditions in Pacific island countries favour the disease such that fungicides are needed to give adequate control. The products to use are chlorothalonil, copper oxychloride or mancozeb. Treatment should start when the yellow spots are first seen, and continue at 10-14-day intervals until 3-4 weeks before last harvest. It is important to spray both sides of the leaves.
AUTHORS Helen Tsatsia & Grahame Jackson
Photo 3 Kohler F, Pellegrin F, Jackson G, McKenzie E (1997) Diseases of cultivated crops in Pacific Island countries. South Pacific Commission. Pirie Printers Pty Limited, Canberra, Australia.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.
This fact sheet is a part of the app Pacific Pests and Pathogens
The mobile application is available from the Google Play Store and Apple iTunes.