The recent warm weather has advanced apple bud stages significantly — we are at the half-inch green stage at UVM HREC and continued warm weather should keep things moving. I recorded a video at the orchard yesterday showing the bud development at the farm and discussing the need for disease management this week. Thankfully, there is no cold weather in the ten-day forecast, but there looks to be a pretty good rain / wetting event starting intermittently on Thursday but really getting going Friday afternoon and through Saturday. Wind conditions look decent to good in the next few days, so growers should consider getting a protectant fungicide on as soon as reasonably possible. For inland and upland sires that have slower bud development and may still be at green or even silver tip, this may be a good time to put on your copper, for orchards in warmer sites, a more typical protectant is in order. If you can’t get in until after a few showers have already started wetting things, an early-season application of a material with some postinfection activity may help prevent infection from developing. We are planning to treat the UVM orchard Friday morning with a combination of mancozeb and Vangard, the latter of which works better in relatively cooler weather and is not effective against fruit scab, and is therefore best used prebloom. Vangard has a FRAC code

of 9, which places it in the Anilino-Pyrimidine class of fungicides. These are not much used at other times in the season, and thus are easily rotated with other chemistries (i.e., materials with a different FRAC number) as we make our way through scab season. The New England Tree Fruit Management Guide includes a good list of recommendations for reducing the development of fungicide resistance in your orchard:

• Use a sanitation program to reduce inoculum.

• Use a multi-site fungicide in every spray – FRAC groups M3 and M4 – captan, mancozeb or metiram.

• Change site-specific fungicides – FRAC groups 3, 7, 9 and 11.

• Use at least three active ingredients from three different FRAC groups over primary scab season.

• If possible, do not use any one class of single-site fungicide more than twice in a season. For many fungicides, labels limit applications to no more than 4 per season.

• Whenever possible fungicides should be applied preventatively, before infection periods. Labels may suggest post-infection uses, but these should be used only as a last resort.

• Apply the maximum label rate of single-site fungicides.

• Pre-mix fungicides containing two single-site ingredients – Merivon, Luna Sensation and Luna Tranquility – should still be mixed with a multi-site fungicide.

• Each ingredient in a pre-mix fungicide counts as an application. For example, Luna Sensation with both fluopyram (FRAC group 7) and trifloxystrobin (FRAC group 11) would count as an application of a Group 7 and an application of a Group 11.

For growers who manage tarnished plant bug in their orchards, white sticky traps should be up in your orchard now. We posted a video last year showing trap setup and placement. The next traps to go up should be European apple sawfly, using those same white traps hung at head height just a bit before pink bud stage. A basic apple scouting guide can be found here. It’s a large format 11×17 pdf file, but also prints fine on 8.5×11 paper.

Now (half-inch green through pink bud stage) is a good time to think about applying a foliar nutrient tonic to help developing buds as bloom approaches. A combination of nitrogen, boron, and zinc is recommended and will help improve fruit set.

The UVM Tree Fruit and Viticulture Program is supported by the University of Vermont Agriculture Experiment Station, UVM Extension, USDA NIFA E-IPM Program, and USDA Risk Management Agency.

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