Alternaria mali is a plant pathogen.
Alternaria mali makes a huge damage to leaves of plants. As an on-line article said: Alternaria blotch has been a serious problem in North Carolina since the late 1980s. By 1993, growers in nine counties in southern and central Virginia reported seeing this problem, some with as much as 50 to 60 percent defoliation on 'Delicious'. Although leaf blotch severity may vary from year to year, there are strong indications that it has spread to new areas in North Carolina and Virginia, and could become a problem in more northern areas of the mid-Atlantic region. Disease severity is aggravated by severe mite infestation. Maintaining good mite management is an important factor in preventing severe disease development. (K.S. Yoder & A.R. Biggs, n.d.)
As reported by (K.S. Yoder & A.R. Biggs, n.d.) the Alternaria mali disease cycle is “The fungus can overwinter as mycelium on dead leaves on the orchard floor, in mechanical injuries in twigs, or in dormant buds”. And after that, in the next year “Primary infection takes place about one month after petal fall” (K.S. & A.R., n.d.). The optimum temperature for disease is in a “range of 77 to 86 F (25-30 C)” (K.S. Yoder & A.R. Biggs, n.d.) and in a wet condition. Infection occurs at optimum temperatures “with 5.5 hours of wetting” (K.S. & A.R., n.d.), and two days after infection, a serious outbreak occur in the garden. The disease will efficiently attack susceptible cultivars by a special chemical toxin which produced by fungus (K.S. Yoder & A.R. Biggs, n.d.). Leaves will be infected by the fungus and apples just fine. According to Sawamura (1990), normally the fungus will not attack fruits, except the one which is a very susceptible cultivar, in this condition; fruit-spotting will be on the tree or in storage. Effected plants will show spots on leaves which enlarged in circular. Normally, hypha has a lacking ability adhere on hosts’ surface, but under moist conditions light-grey mycelium might be presented on the surface (CABI &EPPO, n.d.). Sometimes fungus can also causes soft rots on fruit which already has damages on the skin (CABI &EPPO, n.d.).
Campbell, N.A.,&Reece, J.B. (n.d.).International edition biology: Plant defense (6th ed.).San Francisco: Benjamin Cummings.
Lee, C.V.; Kim, K.H. (1986) Cross tolerance of Alternaria mali to various fungicides. Korean Journal of Mycology 14, 71-78.
Osanai, M.; Suzuki, N.; Fukushima, C.; Tanaka, Y. (1987) Reduced sensitivity to captan of Alternaria mali Roberts. Annual Report of the Society of Plant Protection of North Japan 38, 72-73.
Sawamura, K. (1990) Alternaria blotch. In: Compendium of apple and pear diseases (Ed. byJones, A.L.; Aldwinckle, H.S.), pp. 24-25 American Phytopathological Society, St. Paul, USA.
Yoder, K.S., & Biggs, A.R. (n.d.). Alternaria Blotch, Alternaria mali. Retrieved November 10, 2007, from http://www.caf.wvu.edu/kearneysville/disease_descriptions/omaltblo.html