Petal fall

By Terence Bradshaw

Today’s alert will be brief. Fire blight remains a serious concern in any orchard that has open blossoms, apply streptomycin at 24 oz/acre plus 1 pint/100 gallons finished spray within 24 hours of a wetting event to any trees with open blossoms. Organic growers, Serenade and possibly Double Nickel are your best options. That said, some sites have never seen fire blight, so this may be less important in cooler regions like the northeast kingdom or inland Vermont, but this is as big a potential infection event as I’ve ever seen. But remember, no blossoms, no need to treat. Symptoms should be showing next week if infection occurred earlier this week.

That said, and given the heat, spray nothing else until it cools down Sunday or Monday. Many sprays that are applied at this time of year (Captan, sulfur, thinners, many emulsifiable liquids) can cause leaf and/or fruit burn if high temperatures come soon after application.

When you do get in for a petal fall spray after cooler (<85°F) weather resumes, cover up for scab, and include a kick-back material if appropriate and you weren’t covered for these latest infections. NEWA indicates that all ascospores that could cause primary infections are mature and will be released in the next significant rain event but I wouldn’t put 100% faith in that. The European RIMpro model which takes many more factors than NEWA’s scab model into account still estimated 14% immature ascospores, and many orchards had a good bit of inoculum going into 2016, so prepare to stay covered for at least another week or two.

Insects are flying, and as soon as you can get into your orchard with no bee activity get a broad-spectrum material on the whole orchard. Codling moth are flying in virtually every orchard assessed, but their larvae are not yet a concern until moths mate and eggs hatch in a few weeks. European apple sawfly and plum curculio, however, are in most orchards now.

Thinning. I really can’t make a blanket recommendation, nor are any of the other specialists in the region. If you had good bloom, even with some king blossoms missing, and you likely had good pollination, then apply a mild to moderate thinner as soon as it cools off. Only on light-blooming blocks should you avoid thinning altogether. Reassess in a week. For what it’s worth, I intend to cover the UVM orchard with carbaryl only on Monday, then reassess at the end of the week. I know I’ll need to work a bit harder on the Empire and Honeycrisp, less on the Macs. But that’s my orchard. Yours is likely different.

Have a good weekend and feel free to shoot questions my way if you have them.

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