Previously, this research better defined the role of fruit mummies in the development of apple rot diseases. A recent outcome of this research was the identification of factors that helped explain the potential sources of inoculum and the observed prevalence of summer diseases. Research from 2008-2011 suggests that reducing the number of chemical thinning applications would reduce potential inoculum for apple rot pathogens. The identification of additional production practices in 2010 and 2011 that reduced disease inoculum in season and prevented post-harvest disease development stands to further and promote pesticide stewardship.
impact statement issue
Summer apple diseases—black rot (Botryosphaeria obtusa), white rot (B. dothidea), and bitter rot (Glomerella cingulata), fly speck (Zygophiala jamaicensis) and sooty blotch (Species complex)—can severely impact apple orchard profitability in warmer production regions of New York. In addition to fruit rot, Botryosphaeria species may also cause severe limb and trunk cankers on apple trees. Fly speck and sooty blotch disease often emerge in storage and greatly limit organic apple production in New York. A slight shift toward a warmer climate could result in an increased prevalence of these diseases in many apple production regions in New York. It is known that apple rot pathogens survive in mummified fruitlets resulting from chemical thinning. However, no studies have investigated which pathogens or complex of pathogens reside in mummies, the extent to which pathogens overwinter in mummies, or the impact of production practices have on pathogen presence in mummies. Specifically, there is little information regarding the impact of thinning and standard fungicide programs on pathogen presence or quantity of mummified fruitlets. Also, the impact that dead shoots and mummified fruitlets have on the development of fly speck and sooty blotch is also unknown.
impact statement response
Five years of research in experimental orchards in Geneva and at the Hudson Valley Laboratory suggest that apple rot pathogens and several other apple pathogens colonize mummified fruitlets. Apple scab chemical management programs appear to have slight but repeatable impacts on the number and colonization of mummified fruitlets by pathogens. Varieties that retain fewer mummies by comparison do not appear to be affected by fungicide programs. Fungicide resistance surveys of black and white rot populations from research orchards indicate no shifts toward fungicide resistance in benzimidazole or strobilurin chemistries. Field experiments in the 2008 and 2009 growing season to investigate the impacts of apple bloom thinners and growth regulators indicate that timing of chemical thinning applications can lead to increased retention and colonization of mummified fruitlets. However, specific chemical thinners do not have differential effects on mummified fruitlet retention or colonization. In 2010 and 2011, it appears that both pruning and removing mummified fruitlets may also affect the severity of fly speck and sooty blotch infections. Addition experiments investigating the impacts of pre-harvest fungicide applications suggest that choice of fungicide used before harvest can impact the level of post-harvest summer disease incidence and fruit quality.
impact statement summary
Summer diseases of apple can result in considerable production losses in warmer New York apple production regions. This project endeavors to understand the persistence and survival of apple summer rot pathogens in addition to summer fruit blemish diseases as a means of refining management recommendations and practices.
Other federal research funding
Competitive Hatch Federal Formula Funds Initiative
Other private funding
2010 New York State Agricultural Integrated Pest Management grants
