Plant Pathology

Infection biology of key cranberry fruit rot pathogens
Funding: USDA-CSREES Northeast-IPM Program, Cranberry Institute
Cooperators: Peter Oudemans, Patricia McManus, Peter Bristow, Andre Levesque
Cranberry fruit rot (CFR) continues to be a destructive disease in MA, causing significant losses in the field and in storage. This was the second year of a 2-year project investigating the overwintering inoculum sources for four key pathogenic fungi. Leaves and stems (1-, 2-, and 3- years old), berries from the previous season, and the duff layer were sampled five times during the growing season and plated on acidified cornmeal agar. Colletotrichum was only occasionally found in leaves and stems; Phyllosticta was found in all aged leaves and stems; Physalospora was found solely in older leaves; Colephoma was not detected and remains a mystery. A field trial employed eight schedules of two chlorothalonil (Bravo) applications with the first application at early bloom to subsequent fruit development. Flowers and fruits were sampled weekly and half were cultured, while the other half was frozen for eventual analysis by reverse dot blot DNA hybridization (RDBH). In addition spores trapped in airborne and waterborne traps will be analyzed by RDBH. Field and storage rot were evaluated in field trials to determine which timing schemes afforded the best fruit rot control. Only the treatments where the first application occurred after fruit set had significant levels of fruit rot.

Epidemiology and etiology of upright dieback
Funding: USDA-CSREES Special Grant; Cooperators: Nora Catlin, Ph.D. candidate; Card Cranberry Co., A.D. Makepeace Co.
Upright dieback regularly occurs in MA beds, and often increases in severity following periods of drought stress that occur during the previous growing season. Although Phomopsis vaccinii is routinely isolated from affected upright, proof of pathogenicity had been lacking for the fungus. Typical symptoms of the disease were obtained by inoculating tissue culture-grown ‘Early Black’ and ‘Stevens’ plants under aseptic conditions. Successful disease was also obtained by inoculating rooted cuttings of these cultivars in the greenhouse. In both instances, the fungus could be re-isolated from the tissues. The fungus was able to advance no further than the second year tissue, Symptoms of the disease could also be produced (less severe) by inoculating plants with the fungus Fusicoccum putrefaciens.

Validation of a reduced fungicide strategy for management of cranberry fruit rot
Funding: USDA-CSREES Pest Management Alternatives Program, CCCGA
Cooperators: Peter Oudemans, Patricia McManus, Peter Bristow, Cranberry Growers’ Service
Field trials that will be utilized for 4-5 years were established on State Bog and Parker Mills Bog to examine different fungicide schedules wherein fungicide applications will be reduced and its impact on fruit rot development assessed. The keeping quality forecast will also be critically evaluated and compared to a model devised by Skybit, Inc.

See Also: Dr. Frank Caruso Bio