VT Apple IPM: Buds are moving fast

At the UVM Horticulture Research and Education Center orchards in South Burlington, buds rapidly moved toward and past the half inch green bud stage yesterday, depending on cultivar. Two more days in the 70s will just keep things moving. This is heading toward one of the earliest seasons in my recent memory.

Good news: things look to cool down a bit next week, with no frost in sight. Buds at half inch green can withstand temperatures into the low 20s (°F). There is also a pretty heavy potential bloom this year, so even if a percentage of buds are damaged, we may do all right in the end.

Bad news: as buds open further, they lose hardiness, so by tight cluster, we start to see damage in the mid-upper 20s.

Be careful of snake oils out there that purport to boost hardiness, but do consider getting foliar nutrition on a bit earlier than normal. And speaking of oils, now is a perfect time to get your oil on to manage mites and San Jose scale, the latter of which is becoming an increasing problem in area orchards.

Good news: dry weather means no scab.

Bad news: no scab development doesn’t mean the disease is going away, just that its development is slowed. You’ll need to deal with it sometime. Also, I’m concerned about water for the trees already- if you irrigate, get ready asap. If you don’t, think about installing a system.
Regional note: there is an increasing chance for rain in central and especially southern VT Sunday night into Monday. The further south you are, the more important it is to be covered.

Good news: no insects to really think about yet, aside from pollinators that are just emerging from their ground burrows, especially in sandy soil.

Bad (?) news: get your tarnished plant bug and European apple sawfly traps up asap. Three white sticky cards per block, half knee height (TPB), half head height (EAS). Check against the threshold table and quick scouting guide you have printed off and put on the refrigerator.

Good news: weather is looking great for spray applications.

What to do:

  • Apply copper to any blocks you haven’t yet, but back off as bud stages hit half inch green (HIG). Cuprofix seems to be the main material used now but really, any of the high metallic ion formulations will work. Use full label rates, but back off if you’re interpretation of HIG is being conservative to justify putting copper on that should have gone on this past week.
  • If you’re already past five days or so from your copper spray, and you’re south of, say, route 2, it may not be a bad idea to put on some mancozeb to provide some protection from the potential wetting event. Warmer sites may have 5-10% of apple scab ascospore mature and significant tissue exposed on advancing buds. You could also consider a cool-weather early season fungicide like Syllit, Vangard, or Scala to give a bit more boost if the wetting event is looking greater.
  • This is a perfect week for applying oil. Mix by solution, not rate per acre, and drop your speed down to really soak the trees. 100 gallons per acre minimum should be the plan. Adjust your rates down as the buds open up: 3% (3 gallons spray oil / 100 gallons water) is fine through early green tip; 2% through tight cluster; 1% as you get into open cluster and pink. Copper and mancozeb can be sprayed with oil, sulfur and captan definitely not.
  • When you can, apply foliar nutrients. This is a great time to apply Dr. Warren Stiles’ ‘cold weather prebloom cocktail’ of nitrogen (urea (3 lb./100 gallons dilute, or one of the liquid formulations like N-Pact at label rate), zinc (use label rate of your favorite product) and boron (0.1 -0.3 lb. B/acre). I would do these separate from the oil, maybe later in the week when more leaves have emerged to catch them and we don’t have to worry about the oil causing burning with the nutrients.
  • Separate from spraying, this is great weather to plant trees and do general orchard maintenance. You’re all done pruning, right?

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