Petal fall and spraying this week

By Terence Bradshaw

What an amazing weekend it’s been, weather-wise. I still need to check bud stages, my cider varieties here at 1500’ elevation in central Vermont are still at around half-inch green, and so are not an indicator of what things look like around the state in more typical orchards. However, I imagine many varieties are approaching petal fall, and growers may be itching to put on an insecticide of thinning spray.

The weather for the next three days (Tuesday-Thursday I mean) calls for pretty extreme heat, by May standards, anyway. Given that likely spray materials now include potentially phytotoxic fungicides (captan, sulfur) and insecticides (carbaryl), and that thinners will be very active if applied in this heat, I urge caution. I also don’t like to apply anything in temps of 85° or hotter.

I’ll look over bud stages in the next day or so and check the weather for later this week. Chances look decent for our first apple scab infection period in a while on Friday, and it could be a doozie. Combine that with need to thin and manage post-bloom insects, and we could be in for a complicated spray week.

If you spray anything now, I’d only consider streptomycin on highly susceptible varieties in orchards with recent fire blight infection. In that case, a coat of fungicide (not captan or sulfur because of phytotoxicity issues) may not be a bad idea. But in most cases, I’d lean towards no treatments and plan on an evening / night / crack-of-dawn-when-it’s-cooler treatment window later in the week.

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