VT Apple IPM: Managing freeze-damaged trees

I spent a bit of the day fielding calls and assessing trees from a few counties after last night’s freeze event. Growers in the Champlain Valley largely escaped extensive freeze damage; I doubt Grand Isle County even saw a light frost. This was a textbook lake effect phenomenon. Inland and upland orchards or orchards in lower sites appear to have extensive crop loss, some likely will see a complete loss of crop. Here are a few items to consider as we pick up the pieces:

  1. Unless you had multiple thermometers in multiple locations and heights in your orchard, you don’t really know the temperatures that any particular tree saw. There has been a lot of extrapolating from neighbor’s stations which can be helpful, but not to the degree of accuracy that would tell you the critical difference between 30° and 28° (or 25° and 22°).
  2. Buds don’t read critical temperature charts– there are a number of factors that can affect bud hardiness, including cultivar, age, water or nutrient stress, etc. But we can assume that temperatures at or below 28° will start to show some real damage.
  3. At this time, the most important thing to do is to assess your damage visually. This is really easy to do as damaged buds will show by now. I sent this link yesterday that will be helpful to review again. Basically, pinch the ovule at the base of the bud with your fingernail or a razor blade so you cut it at the equator. The interior should be completely green with no browning or worse, blackening. This can be seen without intense magnification but growers my age or older ought to have your readers with you. I also looked at buds today with someone who is color blind and realized that that condition makes it had to see the damage, so if you are, have someone else do the assessment.
  4. Think about your strategy based on your freeze condition. Inland, and assuming your orchard saw 25° or colder? Go to your best spots- at the top of the hill, healthiest trees, buds collected head height- if you see extensive damage there, you can assume that the lower spots of the orchard are as bad or worse. In the Champlain Valley, your weather station said 29, 30°? Go to the low spots and assess, if you don’t see extensive damage then your better-sited trees are probably okay. Do a thorough assessment and write it down, especially of you will be applying for a crop insurance payment. I would start with 50 buds collected methodically and randomly from the canopy for each block and variety. If you have more than 50% damage, look more.
  5. If you do have extensive damage and you have crop insurance, contact your agent ASAP. Even if you think you don’t have damage, keep an eye out in the coming weeks. Weakened buds can abscise later, or fruit may develop frost rings that make them unsaleable as fresh fruit.
  6. Thinning could be really easy (no crop, no thinning) or more difficult, especially in blocks with inconsistent fruit set and levels of damage. All things being equal, trees will respond more easily to thinning chemicals after experiencing a freeze. If you have more than 50% damage, consider at most a light thinning protocol this year. More than 80% damage? Leave the thinners out altogether.
  7. My suggestion this morning to consider applying Promalin may have been a bit premature or at least lacking in further nuance. My thought at 4 am as I was looking at the temperatures was to offer whatever I could to growers who would need to source a material few to none of us keeps on-hand and get it on the trees within 24 hours. I was not thinking that a) there only existed nine bottles in the entire state, b) many orchards were at petal fall and so were past the phenology labeled for use of the product for this purpose, and c) orchards that got really cold and had 100% crop loss or severe damage from temperature below 24-25° would not respond- a dead bud is a dead bud. I do plan to collect data at the handful of orchards who applied Promalin to see if we can add to the fairly sparse dataset on its efficacy in these situations.
  8. If you have no fruit, trees still need to be managed. The important things to stay on top of are apple scab, fire blight if you see any, foliar insects on young trees, and wood-damaging insects like borers. Keep your fungicide program up for the next month or so (is apple scab season ever going to end, despite us seeing next to no scab?). Keep weeds away from trunks, especially if you will be backing off insecticide sprays for fruit feeders like codling moth or apple maggot that would normally help manage borers. Back off or eliminate nitrogen fertilizers- fruit really slow the vegetative growth of fruit trees so when there are none, the trees can be excessively vigorous. Consider applying Apogee or Kudos to reduce vegetative growth and stiffen up cell walls in vegetative shoots to reduce canopy size and make shoots less susceptible to fire blight.
  9. Start thinking about your marketing for this season. Many of the most affected orchards are small pick-your-own or retail operations. They may be side gigs or a family’s main income. Most are diversified to some degree. Consider whether you’ll need to buy fruit in and provide customers some other reason to visit the orchard- foliage hay rides, corn maze, pumpkin patch. There are fruit in the region that can be brought in, so start making those connections and thinking about how you’ll keep cash flow this fall.

I have been a member of the Vermont orchard family for almost 30 years now, and I am always impressed with the camaraderie and collective sense of purpose that we share. These events can be major hardships, potentially even devastating. Let’s see how we can help one another and keep this incredibly important industry, and each and every farm within it, afloat and even thriving after a challenging, somewhat unexpected event that could have affected any of us.

Please reach out if you need anything,


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