ISHS Acta Horticulturae 810: IX International Vaccinium Symposium
ENVIRONMENTAL REQUIREMENTS FOR INFECTION OF BLUEBERRY FRUIT BY COLLETOTRICHUM ACUTATUM |
| Authors: | J.M. Gillett, A.C. Schilder |
| Keywords: | anthracnose fruit rot, Vaccinium corymbosum, wetness duration, temperature, green fruit, blue fruit |
| Abstract:
Anthracnose fruit rot, caused by the fungus Colletotrichum acutatum, is a serious problem throughout the blueberry-growing regions of North America. As a first step towards the development of a disease prediction model, environmental infection requirements of C. acutatum were investigated. Three sources of ‘Jersey’ fruit were used in different replicated experiments: potted plants with small green fruit; detached twigs with large green fruit; and detached blue fruit. Green and blue fruit were inoculated with a suspension of 1 x 106 conidia/ml and incubated at 10, 15, 20, 25, or 30°C with 6, 12, 18, 24, 36, or 48 hours of wetness. At the end of the incubation period, fruit on potted plants were dried with forced air and allowed to ripen naturally. Green fruit on detached twigs were removed, surface sterilized, cut in half and placed on potato dextrose agar in Petri dishes. Detached blue fruit was surface sterilized and incubated at room temperature and 100% relative humidity. Fruit were evaluated for the presence of C. acutatum after 7–12 days of incubation. While low levels of infection were observed at 6 hr of wetness duration in each case, the infection percentage increased considerably after 12–18 hr of wetness at 20-25°C, 18–24 hr at 30°C, 24 hr at 15°C, and 36–48 hr at 10°C. The optimal temperature for infection was 25°C. Different stages of fruit maturity may have slightly different optimal conditions for infection. | |
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