Look for spots on the leaves with concentric rings, brown, drying out with black fruiting bodies later. It is probably similar to Capsicum Phoma blight and Phoma rot on tomato where it is usually only a problem in very wet seasons. The fungus is considered to be a weak parasite, or a wound pathogen, causing only a minor disease of bean infection needs plants to be damaged by weather or by insects. High humidity and temperatures less than 28☌ favour the disease. The fungus survives on dead plant material in the soil. There is a possibility that the spores of the fungus can be carried on seed. As the spores ooze out of the pycnidia through a hole at the top (Photo 3), they are splashed in rain (or irrigation water). Spread of the fungus occurs in wet weather which helps the discharge of spores. Large, dark spots occur on the pods, usually starting from wounds (Photo 5). Tiny black fruiting bodies (pycnidia) occur in the leaf spots, and these can be seen with the naked eye (Photo 4). Inside the pycnidia there are masses of spores. Sometimes, the centres of the spots dry and fall out ('shot-holes'). On the leaves, round, grey to brown spots, 6-12 mm wide, sometimes larger, with concentric rings (Photos 1-3). 217). It is also found growing on dead plant material. Sometimes infections start from rust pustules ( see Fact Sheet no. Symptoms & Life CycleĪ common fungus found in soils, causing a minor leaf spot disease on leaves and pods. Usually, either a wound pathogen following damage by insects and weather events, or a secondary invader of weakened or diseased plants. 239), citrus, and on weeds. In Solomon Islands, the fungus (as Phoma exigua) is reported as a large leaf spot on kauri (Agathis macrophylla). On a wide range of plants in numerous plant families it is particulary common on beans and other food legumes, e.g., cowpea and soybean, but is also recorded on capsicum ( see Fact Sheet no. Under different names e.g., Boeremia exigua or Phoma exigua (Ascochyta phaseolorum), it is recorded from Australia, Cook Islands, Fiji, New Zealand, Papua New Guinea, and Tonga. exigua is uncertain, and so far has only been recorded from Asia (China) and Oceania (Australia). However, the distribution of Boeremia exigua var. The name now given to the fungus is Boeremia exigua var. Common Nameīoeremia exigua previously known as Ascochyta phaseolorum, and Phoma exigua, and many other names.
Ascochyta spot, Boeremia exigua, on bean pods. Fungicides are available, but won't have much affect without the cultural practices previously mentioned.Photo 5. Mow when the grass is dry to avoid spreading spores. Never remove more that 1/3 of the blade at one cutting. Core aerate in the spring or fall to reduce or prevent thatch build up. Maintaining a vigorous lawn is the best prevention against Ascochyta leaf spot.
Can often see small, black pycnidia on the dead tissue just adjacent to the living tissue (use a good hand lens).
Infection occurs through the cut end of the leaf blade. The grass blade is usually killed from the tip down towards the base of the plant. The Ascochyta fungi seldom cause extensive damage. The Ascochyta fungi attack grasses during much of the growing season when humidity and atmospheric moisture are high or when irrigations and mowing are frequent. Ascochyta leaf blight or spot of turfgrasses is caused by more than 80 different fungi which can cause damage to Kentucky bluegrass, bentgrasses, Italian and perennial ryegrasses, fescues (red, meadow, sheep, and tall), redtop, and many other forage, weed, and wild grasses.
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