- Worldwide distribution. On wide range of plants, especially beans and other food legumes; also on citrus and capsicum. Minor fungal disease,
- Weak pathogen, requiring wounds from insects or weather to enter leaves and pods.
- Grey to brown spots on leaves, 6-12 mm diameter, with concentric circles; sometimes falling out. Darker spots on pods. Tiny, black, spore-containing sacs on spots, seen with naked eye.
- Spread occurs in wet weather; spores ooze from sacs and blown in wind and rain. Possibly, seed-borne.
- Cultural control: certified seed or treat seed in hot water (50°C for 25-30 minutes); remove volunteers; select well-drained soils; avoid damage by strong winds, and during cultural operations; weed; after harvest, handle beans carefully; collect and burn crop debris; crop rotation.
- Chemical control: probably not needed as wound pathogen; if required, use pyrethrum, or synthetic pyrethoids.
Pacific Pests, Pathogens, Weeds & Pesticides
Bean (Ascochyta) leaf spot (319)
Photo 2. Ascochyta spots on bean leaves, Boeremia exigua. The spot on the left shows concentric rings and a dark margin.
Boeremia exigua; previously known as Ascochyta phaseolorum, and Phoma exigua, and many other names. The name now given to the fungus is Boeremia exigua var. exigua.
AUTHORS Grahame Jackson & Eric McKenzie
Information from (including Photos 2&5) Diseases of vegetable crops in Australia (2010). Editors, Denis Persley, et al. CSIRO Publishing; and CABI (2016) Boeremia exigua var. exigua (leaf spot). Crop Protection Compendium. (https://www.cabi.org/cpc/datasheet/40426); and from (including Photo 4) McKenzie E (2013) Boeremia exigua: PaDIL - (http://www.padil.gov.au). Photo 1 R.J. Reynolds Tobacco Company Slide Set R.J. Reynolds Tobacco Company, Bugwood.org. Photo 3 Howard F. Schwartz Colorado State University, Bugwood.org.
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.