Apple management at pink and into bloom

By Terence Bradshaw

I traveled around the Champlain Valley a bit today and saw apples well into the pink bud stage (and one open blossom), with a few caveats. Damage from the cold snap in early April is becoming more evident, which coupled with generally weaker trees going into the weather after the heavy 2015 crop may result in uneven and reduced bloom in many orchards. I observed many blossom clusters with damaged or missing king blossoms, missing side blossoms, and quite a few generally weak and lagging clusters. Orchards in Addison County are at pink, and I saw one with hives already in the orchard. In the northern Champlain Valley, buds are a couple of days behind at advanced tight cluster, but a warm day or two will advance things rapidly. Here are my thoughts on some management items to keep in mind:

Apple scab does not look like a concern until at least the end of the week, and the rains over this past weekend did not trigger an infection period in most central and northern Vermont orchards based on NEWA data, but southern Vermont orchards appear to have had an infection event. Keep an eye on the weather and apply coverage before the next rain events during this peak period of ascospore maturity and release, but you can find other things to do until later in the week at least.

However, insect management at pink may be important in some orchards. I observed sporadic damage from tarnished plant bug and redbanded leafroller today, and have heard reports of some green fruit worm active in some orchards. The upcoming weather looks warm but not hot, and bloom may be extended so a pink insecticide targeted at those pests if observed in your orchard while scouting may be warranted. Growers in the southern Champlain Valley have likely missed the boat if an insecticide gas not yet been applied since bloom is right around the corner; in the northern Valley, tomorrow May 10 looks like a good day weather-wise to get a spray on if desired. Remember, if you have blooms and/or active bees in the orchard, insecticides must be kept on the shelf for the time being.

This is a good time to focus on in-row weed management, either via herbicides or cultivation. Similarly, nitrogen fertilizers should be going on now, both to the soil and foliar if the latter is desired especially to give cold-damaged buds a bit of a boost. Remember to follow Dr. Wes Autio’s recommendations for Prebloom Nutrient Applications for Apple Trees: 3 lbs/100 gallons (dilute equivalent) urea; 1 lb/100 gallon Solubor (or equivalent); and label rates of zinc chelate.

Many growers have asked about my thoughts on thinning in this complicated year. My advice now (and of course there isn’t anything to do until petal fall at least, I definitely don’t recommend a blossom thinner this year given the low bud count and/or damaged blossoms we’re seeing) is to sit tight and observe: look at your blooms as they open; at bee activity during bloom; and at the weather after pollination windows (you want temperatures >60°F and sun to get optimum fertilization of pollinated flowers). Besides the relatively weak and/or variable bloom in many orchards, most spur leaves have emerged under cool, cloudy weather, and therefore will have thin cuticles and will make trees more susceptible to thinning. Every orchard is different, given the block history, cultivar, tree age, and general health/stress level of trees, and growers should be thinking about thinning needs in their orchards over the next week or so and be prepared to thin cautiously this season.

As always, please refer to the 2015 New England Tree Fruit Management Guide (plus the 2016 updates) for specific spray material selection and always follow the label.

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