Submitted to: Annual Review of Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/2011
Publication Date: 5/7/2012
Citation: Mazzola, M., Manici, L.M. 2012. Apple Replant Disease: Role of microbial ecology in cause and control. Annual Review of Phytopathology. 50:45-65. Interpretive Summary: Replant disease of apple is a major limiting factor to the development of an economically viable orchard on sites previously planted to this crop. Replant disease of tree fruits, and apple in particular, continues to yield consternation within the research community attempting to define and control the problem and amongst growers struggling to utilize non-fumigant measures to manage the disease. Biological resources indigenous to the orchard soil system can be utilized to assist in mitigation of the functional pathogen complex, but will require active management to attain the quantitative and qualitative changes within the complex community of soil microorganisms that is necessary to obtain effective disease suppression. Progress toward achieving this goal continues to be hindered by an inadequate appreciation of the myriad of biotic and abiotic factors, and their interaction, that may limit tree growth when planting new orchards on an old orchard site. Likewise, a clear assessment as to the specific disease and the causal biology responsible for limiting growth of new trees when established on old orchard sites is a pre-requisite when attempting to manage apple replant disease without subjecting the site to pre-plant soil fumigation.
Technical Abstract: 1. Apple replant disease (ARD) has been reported from all major fruit-growing regions of the world, and is often caused by a consortium of biological agents. Development of non-fumigant alternatives for the control of this disease has been hindered by the absence of consensus concerning the etiology of the disease. Significant work conducted in a diversity of apple growing regions around the world have yielded unanimity regarding the involvement of certain fungi, oomycetes and plant parasitic nematodes in the etiology of replant disease. As such, by focusing on these diagnostic pathogens, control measures may be developed that provide economically and ecologically sustainable methods for control of this disease. Approaches to manipulate microbial resources endemic to the orchard soil system have been proposed to induce a state of general soil suppressiveness to replant disease. Such a long-term strategy may benefit the existing orchard through extending the period of economic viability, and reduce overall disease pressure to which young trees are exposed during establishment of successive plantings on the site. Alternatively, more near-term methods have been devised to achieve specific quantitative and qualitative changes in soil biology during the period of orchard renovation that may lead to effective disease suppression.