|Hoagland, Lori - WSU, WENATCHEE, WA|
|Abi Ghanem, Rita - WSU, WENATCHEE, WA|
Submitted to: Phytopathologia Polonica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 2005
Publication Date: July 1, 2006
Citation: Mazzola, M., Brown, J., Abi Ghanem, R., Izzo, A., Cohen, M.F. 2006. Progress towards development of biologically-based strategies for the management of apple replant disease. Phytopathologia Polonica. v 39. p. 11-18. Interpretive Summary: Control of soil borne pathogens and parasites is crucial to the successful establishment of new orchards on old orchard sites. Although soil fumigation can effectively achieve this goal, there is a desire to develop environmentally sustainable measures that are compatible with current orchard management systems and achieve effective disease control. A wheat cover crop and rape (Brassica napus) green manure crops each provided a degree of disease control and increased growth and yield of apple. However, the response observed was inferior to that attained through soil fumigation and was not likely to provide growers the returns necessary to sustain economic vitality. The use of rape seed meal, a bio-product of oil extraction from seed, when used in conjunction with the fungicide mefenoxam was as effective as soil fumigation for the control of replant disease at certain sites. The alternate treatment was less effective on sites where the lesion nematode contributed to disease development. This plant parasitic nematode rapidly recolonized orchard soils and within one year had attained populations equivalent to or greater than that present before soils were treated. Additional Brassica seed meals have been identified with enhanced capacity for nematode control, weed control, and that do not require the fungicide co-application for effective disease control. This opens the possibility for use of this disease control strategy in organic production systems.
Technical Abstract: Alternative measures to the use of pre-plant soil fumigation for the control of apple replant disease, were evaluated in the orchard. A one-year wheat cover crop consisting of three short-term cropping periods with removal of plant material after each sequence and a three-year B napus green manure significantly enhanced growth and yield of Gala/M26. However, in each instance the resulting disease control and growth response were inferior to that achieved through pre-plant soil fumigation. A three-year bare fallow and one- or two-year B. napus green manure neither supressed disease development nor enhanced tree growth. Pre-plant RSM amendment in conjunction with post-plant mefenoxam soil drench provided effective disease control and the resulting tree growth and yield were comparable to that attained in fumigated soil at Columbia View orchard. At the WVC orchard, the growth response attained with the alternative treatment was inferior to pre-plant soil fumigation, which was associated with an apparent re-infestation of RSM-treated soils and tree roots by Pratylenchus spp. As alternative brassicaceious seed meals have been identified that possess enhanced nematicial activity and do not induce Pythium spp. proliferation, this control strategy has significant potential for application in organic production systems. Ancillary benefits of initial weed control and improved soil fertility will further stimulate grower adoption of this alternative replant disease control strategy.