An Epidemiological Study of Mummy Berry Disease of Highbush Blueberry

Timing of susceptibility of highbush blueberry cultivars in northwestern Washington to Monilinia vaccinii‐corymbosi, the cause of mummy berry

“…The start of ascospore release coincided with bud swelling to tight cluster stages of floral buds and closed bud to 2–5 mm green tissue stages of vegetative buds and ended at early/late pink floral bud stages and the unfolding and separation of leaves. These observations were similar to those for the mummy berry life cycle on highbush blueberry in Michigan (Ramsdell et al ., , ), and suggest that the earlier development of floral buds compared to vegetative buds may be a general characteristic in highbush blueberry. Recommendations for mummy berry control have traditionally focused on fungicide applications that are timed based on vegetative shoot development (Ramsdell et al ., , ).…”

“…These observations were similar to those for the mummy berry life cycle on highbush blueberry in Michigan (Ramsdell et al ., , ), and suggest that the earlier development of floral buds compared to vegetative buds may be a general characteristic in highbush blueberry. Recommendations for mummy berry control have traditionally focused on fungicide applications that are timed based on vegetative shoot development (Ramsdell et al ., , ). However, the results here show that floral buds break earlier than vegetative buds in northwestern WA, potentially leaving susceptible tissue unprotected if fungicide timing is based on vegetative tissues.…”

“…Variation in susceptibility of blueberry cultivars was shown to be related to the timing of their phenological development and the overlap with the timing of the release of ascospores (Pepin & Toms, ; Ehlenfeldt et al ., ). Based on previous research, floral buds were most susceptible at bud burst and tight cluster stages and vegetative buds were most susceptible when 6–13 mm of green tissue was presented (Ramsdell et al ., , ; Hildebrand & Braun, ). Reports from various blueberry‐growing regions in the US have provided contradictory information on the resistance/susceptibility of cultivars (Pepin & Toms, ; Stretch et al ., ; Pscheidt & Ocamb, ).…”

“…Blueberry plants are susceptible to primary infections when young tissues are emerging from floral and vegetative buds (Milholland, 1974). Recommendations for the timing of fungicide applications have been based on the developmental stage of vegetative tissue, not floral tissue (Ramsdell et al, 1973(Ramsdell et al, , 1974. This is presumably because shoot strikes have been reported to be more common than floral strikes in other blueberry growing regions (Hildebrand & Braun, 1991;Penman & Annis, 2005).…”

“…Efforts to improve the timing of fungicide applications have therefore focused on vegetative shoot development (Ramsdell et al, 1974;Ehlenfeldt et al, 1996;Lehman & Oudemans, 1997b). Timing of bud break generally occurred earlier for floral buds compared to vegetative buds on highbush blueberry plants (Ramsdell et al, 1973;Batra, 1983) and at the same time on lowbush blueberry plants (Hildebrand & Braun, 1991). Disease incidence did not differ between floral and vegetative bud tissues on lowbush blueberry when inoculated with ascospores at susceptible stages (Hildebrand & Braun, 1991).…”