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Disease management

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  • Leaf chopping (flail mowing) is done in fall or early spring to reduce scab inoculum.
  • Urea treatment is applied in fall or early spring to reduce scab inoculum.
  • Trees are pruned annually to remove diseased wood (primarily fire blight and black rot) and apple mummies (rot disease inoculum).
  • A dormant to green tip copper compound application is made to suppress fire blight.
  • First fungicide spray is delayed an appropriate time according to previous year's scab incidence using potential ascospore dose evaluation, and ascospore maturity level in the current season.
  • Unless visible infections develop, fungicides for scab management are applied only until the end of primary scab season, using 100% ascospore maturity and release and sufficient time to allow symptoms from the last infection to be visible.
  • Apple scab infection periods are measured using leaf wetness and temperature.
  • Fungicide treatments for primary apple scab are made according to infection periods, tree growth and estimates of the remaining effectiveness of the previous fungicide application.
  • Resistance management is considered when making fungicide applications, by either tank-mixing two or more modes of action in a single spray, or rotating modes of action such that materials in the same FRAC group are not applied consecutively.
  • Treatments for fire blight follow a fire blight forecast model (e.g. Maryblyt or CougarBlight), or specific Extension or consultant recommendations based on such a model.
  • Fungicide applications exclusively targeting powdery mildew or rusts are not made unless there is a history either disease in the block.
  • Where rust diseases are a problem, alternate hosts (primarily red cedar and juniper) within 300 feet surrounding orchard are removed.
  • Fungicides for sooty blotch/flyspeck are applied based on an accumulated wetting hours and estimated fungicide depletion.
  • Plantings are located so that trees are least 75 feet away from wooded or shrubby borders to reduce pressure from sooty blotch and flyspeck fungi.
  • Orchards are replanted with a minimum three-year gap between tree removal and new tree planting. During the gap, cover-crops selected to suppress nematodes, reduce soil compaction, improve weed suppression, and benefit soil health in general are planted.
  • On sites prone to flooding or with heavy soils, trees are planted on raised berms and/or drainage is installed.
  • Experimental block of disease-resistant trees is planted.