In contrast to the rest of the population, those of us in the fruit growing community hate warm March weather, and this year looks like another which will potentially give s us early bud break and much stress over the sudden loss of time to get dormant-season work done and the increased risk of weather-related issues during bloom (I don’t like to say the f-word at this time of year). Reports out of the Hudson Valley suggest that they may see green tip this weekend, at least in the southern part of the region. I wouldn’t translate that to suggest that we will see green tip in the immediate future, but it’s coming. I did a very quick comparison of accumulated and projected degree days at the UVM Hort Farm in South Burlington, VT and Marlboro, NY in the lower Hudson Valley of New York. Weather models to predict early season phenology stages prior to bloom are not well-developed or published, but in general, models use a base of 4°C (which I have rounded to 40°F) above which tree phenological development occurs. Remember that this is quick and dirty: I used the simplest method to calculate degree days ((daily max temp + daily min temp) /2 – base temperature); I used a combination of NEWA and weather.com forecast data; my base temperature is somewhat arbitrary; and I’m only making comparisons based on a limited time scale and set of farms. Accumulated degree days in South Burlington as of yesterday were 24.8, contrasted to 57.4 for Marlboro, NY. If green tip were to come in the southern Hudson Valley this weekend, that would be at around 80-90 DDb40°F (accumulated degree days at base 40°F). Based on weather predictions, we would have acquired around 50 DDb40°F by March 20 (the end of the ten-day forecast). Compare that to the spring of 2012, when the odd warm March temperatures were in the 80s rather than the 60s, and green tip was observed at the Hort Farm on March 19 with 106 accumulated DDb40°F.
My point here is that we should expect an early spring based on past and predicted weather, but we likely won’t see green tip (and the beginning of the pest management season) until after April 1 in Vermont based on my very rough guess. This gives growers time to get caught up and ready for spray season, so don’t be complacent.
Given the generally heavy crop in Vermont orchards in 2015, fruit bud density is expected to be relatively low this year. That means that pruning can be a little lighter to compensate for fewer fruit buds. That doesn’t give license to ignore your end of season pruning, but suggests that trees may be breezed through a little quicker if you have wrap up pruning to do. The winter has been generally good for outdoor work, so most orchards should be easily caught-up. My take home: get finished up in the next two weeks, then get ready for spraying season. After the soil dries a bit (and hoping that this early mud season is truly early and not just extended), push your pruning brush or flail mow in-place for high density plantings with smaller pruning wood. Calibrate your sprayer. Get your early season spray materials ordered and on-hand for when the season starts. No really, calibrate your sprayer. Be ready to properly oil the orchard if you have had any issues with mite flareups or San Jose scale, the latter of which I have seen not only in orchards but also on fruit in grocery stores. Remember that oil should go on at full dilute or no more than 2x concentration to be most effective; I’ll discuss that further in a future message. So when you calibrate your sprayer, be sure to reserve a setting for high-volume applications, either by switching to higher-output nozzles, reducing travel speed, or both.