See:
Ash (Fraxinus spp.) - Anthracnose
Cause Mycosphaerella effigurata and M. fraxinicola (formerly Phyllosticta viridis) are fungi that have been reported from Oregon and Washington. Other fungi that cause leaf spots on Oregon ash include Pseudocercosporella fraxini (formerly Cylindrosporium fraxini), Septoria fraxinicola (formerly Marssonina fraxini), and Phyllosticta innumera. The fungi overwinter in fallen leaves. They produce spores in spring during early shoot elongation in rainy weather, which also favors infection. More spores produced in the first lesions can produce new infections on healthy leaves.
Symptoms Mycosphaerella causes brown spots with yellow borders. M. fraxinicola spots are 5 to 15 mm; those caused by M. effigurata are 3 mm. Numerous spots may coalesce into large necrotic areas. May also get the profuse development of black-fruiting bodies, which usually run together to form black crusts on the under surface of the leaves. The result is premature defoliation.
Pseudocercosporella fraxini - leaf spots cause indefinite brown blotches. Minute black dots (fruiting bodies) form in the brown areas on the lower surface of lesions.
Cultural control
- Rake and destroy fallen leaves.
Chemical control Begin sprays at budbreak and continue at regular intervals during wet weather.
- Armada 50 WDG at 3 to 9 oz/100 gal water. Do not use a silicone-based surfactant. Not for nursery or greenhouse use. Group 3 + 11 fungicide. 12-hr reentry.
- Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. Group M5 fungicide. H
- Cleary's 3336 EG at 12 to 16 oz/100 gal water. Group 1 fungicide. 12-hr reentry.
- Daconil Weather Stik at 1.38 pints/100 gal water. Group M5 fungicide. 12-hr reentry.
- Mancozeb-based products. Group M3 fungicides. 24-hr reentry.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
- OHP 6672 4.5 F at 10 to 14.5 fl oz/100 gal water. Group 1 fungicide. 12-hr reentry.
- Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 1 fl oz/gal water. Labeled for use against rust and may be effective on this disease. Group 3 fungicide. H
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
- Tourney EZ at 1 to 4 oz/100 gal water. Group 3 fungicide. 12-hr reentry.
References Owston, P.W. 1990. Fraxinus latifolia Benth. Oregon Ash. Silvics of North American Hardwoods, 12:339-342.
Shaw, C. G., and Harris, M.R. 1960. Important diseases and decays of trees native to Washington. Ag Extension Service, WSU. Extension Bulletin 540.