Control of postharvest storage rots of apples and pears in The Netherlands

Postharvest diseases are a major problem in long storage of apples and pears in The Netherlands. Despite intensive preharvest spraying programs significant losses occur. Over 150 heavily affected many apples (mainly 'Elstar') and pears (mainly 'Conference') from packinghouses in different regions of The Netherlands were evaluated for decay symptoms and causal organisms. Assessments showed that the most important pathogens are Neofabraea spp. (apples and pears) and Cadophora spp. (pears). Infection by these two pathogens occurs in the orchard but remains latent until storage. Other pathogens such as Botrytis spp., Pencillium spp., Fusarium spp., Alternaria spp., and Cladosporium spp. were isolated at low frequencies and are considered of minor importance. However, new problems with sooty blotch and lenticel rot of apple were noticed, most likely caused by other, not yet identified pathogens. Pathogenicity testing and characterization of isolates are on-going. For major pathogens, qPCR assays are developed. Samples of substrates (e.g., leaves, cankers, soil) were monthly taken from 10 apple and 10 pear orchards in 2012. Samples were assessed using the qPCR assays for presence and dynamics of pathogen populations. This information on the pathogen life cycles is needed for the development of innovative strategies to prevent postharvest losses. Storage conditions may significantly influence disease development. Recently, the project “KWALIFRUIT” was launched to identify the optimum harvest stage of pome fruit and optimal storage conditions for maximum fruit quality and storage life and minimal postharvest losses.