VT Apple IPM: Likely scab infection period this week

It’s looking like we have a likely apple scab infection period coming midweek in most parts of the state. Anyone who went into the rain / snow with copper or a fungicide, that’s likely gone. We’re also getting into the window where more spores are maturing (aside from cooler upland / inland sites, you probably still have <5% mature spores). Warmer sites should pay attention to this one, and apply a protectant (mancozeb, captan if you haven’t used oil in the past 10 days, sulfur if organic) and consider adding an early-season systemic like Vangard / Scala / Syllit if you aren’t sure about coverage going into the last event. That last suggestion is only for orchards in the warmest regions (warmer / lower elevation parts of Windham / Bennington / Addison counties), As I mentioned before, in most orchards, the overwintering inoculum was relatively low and the ascospore maturity was just starting to get underway before the rain.

With the cool down, we’re back at near-normal bud stage timing, so I’m becoming less concerned about frost to apples. Any time you have to material and sufficient spur leaves to intercept it, plan on applying foliar nutrients (nitrogen, boron, zinc) to strengthen buds prior to bloom.

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