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The effect of plant resistance inducing products on fire blight (Erwinia amylovora) infection and severity on apple

Brian Lehman: Penn State Fruit Research and Extension Center

<div>Fire blight is a well-known destructive bacterial disease of pome fruit that can cause significant annual production losses and tree death. Management regimes consist of streptomycin applications at bloom to control blossom blight. In some years, even when blossom blight is controlled, outbreaks of shoot blight can occur and cause major fire blight epidemics, especially in newly planted high density plantings. Experiments were conducted at the Penn State Fruit Research and Extension Center in a greenhouse on one year-old ‘Gala’ trees grafted onto M.26 rootstocks and a field trial on ten year-old ‘Gala’ trees grafted onto B.9 rootstocks to test the ability of several products to activate a plant’s systemic acquired resistance (SAR) and reduce shoot blight severity. Products tested included <em>Bacillus</em> strains, copper products, plant-based products, and glycerol, as well as Actigard (a registered SAR product), which was used as a SAR standard for comparison. While none of the products provided the level of control demonstrated by Actigard, treatments using Cueva, Vacciplant, and Regalia showed a significant reduction in severity over the control in either the greenhouse or field trials. In addition, the application of glycerol and some <em>Bacillus</em> products also resulted in a slight reduction in severity. This study identifies some products that may be incorporated into a shoot blight management regime for young and newly planted orchards during bloom and post-bloom.</div>