VT Apple IPM – ‘Cover’ spray time

Category [tree fruit; IPM]

June 8, 2021

Sorry- I’m late on getting anything out, so I’ll cover the high points that are important for managing Vermont orchards in the next few days / week:

  1. It’s time to get a codling moth spray on for many orchards. CM is best managed by using the NEWA degree-day model. For your site, enter the first pheromone trap capture (Biofix) or, with less certainty, let the model predict emergence (that’s the default). Most materials should be applied between 100 and 200 degree days (base 50°F) from that date. For most orchards, that is now. A lepidopteran-specific material like Intrepid, Altacor, Belt, or Rimon (latter two should have been on a few days ago) is best against this pest.
  2. Plum curculio still has some activity left in it for this season in most orchards. If you covered the orchard with a relatively broad-spectrum insecticide at petal fall, border sprays will suffice to keep late-season damage down.
  3. Apple scab primary season is done pretty much everywhere. Scout the orchard meticulously for signs of scab, if you have it, keep up a Captan program until things are burned out. Otherwise, fungal diseases are probably good for a little bit.
  4. Fire blight- Streptomycin works!! We have tow partial rows at the UVM orchard with many dead trees that I plan to rip out (that’s another story), so I haven’t bothered spraying them this year. They are right in our Fire Blight-riddled cider block, which is 95-98% clean right now, but those Spitzenburgs are toast. Scout your orchard carefully for signs of the disease and plan to prune out ASAP, on a dry day. Except in the case of hail, do not apply streptomycin to an orchard that shows symptoms of the disease.
  5. Fertility- If you’re applying nitrogen, start making plans to back off and shut it down soon. This is a great time to apply magnesium, potassium, and other cations if our soil or foliar analyses calls for them.
  6. Every spray this time of year should include some calcium. On Honeycrisp, calcium should go on even if another spray material isn’t needed.
  7. Keep an eye on thinning. This has been one of the most inconsistent years I have seen in my time with this crop (25 years) and I’m seeing and hearing of fruit densities all over the place. It’s getting late to apply thinners, so while scouting for Fire Blight, keep an eye out for trees that need a little hand thinning.
  8. Water, if you can. Many areas of the sate are running dry, and we’re still in the window of maximum cell division that determines fruit size and quality.

All for now,