MSU Extension

After a fairly mild winter and warmer than normal January and February temperatures, March brought winter back to the forefront with colder than normal temperatures, windy conditions and a little snow. What a welcome sight for tree fruit growers and Michigan State University Extension educators! 

According to MSU Enviro-weather, degrees-days were accumulating in February at an alarming rate, but have been at a standstill for nearly all of March. Early guestimates indicated we were ahead of normal degree-day accumulations by 25 days in late February, which is unheard of. Mother Nature is tricky and has a great sense of humor and the cooldown in March was just what we needed to slow the train down.

Degree-day totals for the general west Michigan area continue to be ahead of the normal average by about seven days. There is some speculation that degree-days accumulated before the chilling requirements are met for tree fruits might not be added to the totals from Jan. 1. If we use 1,000 hours for chilling for apples, the Sparta Enviro-weather station met this on Feb. 20. This could mean you should subtract 38 degree-days from the base 42 total, and that would put us only two or three days ahead of normal averages.

This is all speculation and there are many variables to consider. Chilling hour requirements for apples range from 800 to 1,200, and each variety has a different requirement. We don’t know the requirements for all the new varieties, so using 1,000 is an educated guess. Soil temperature and moisture, sunlight and site all play a part as well.

It just feels like we aren’t 10 days ahead in plant development. Feelings aren’t scientific, but I am basing this on observances of other plant species development. Every year I take note of development in other plants to help direct when I think apples will begin. As of March 27, 2017, I don’t see development in other plants that usually happens ahead of green tip in apple. For example, maples usually drop flowers about a week to 10 days ahead of apple green tip and this is just beginning. The grass greens up about a week or more first. Forsythia needs to look like they are ready to bloom, and I haven’t seen that yet. Ornamental crabs usually break bud at least a week before most apples, and I just started to notice this in the last day or two.

Again, just speculation based on experience and my gut telling me we have a week or so to go yet for first green on McIntosh, our indicator variety. There is a little green showing on warmer, sandier sites known to be early. Also, there is a huge difference in varieties and sights across west Michigan.

In 2016, official green tip in McIntosh was March 28 and we will be later than that. The average first green date is April 10 and we will likely be a week or so ahead of this date with the forecasted temperatures I see for the next week or so. The forecast is for near or slightly above normal temperatures with no big swings to colder or warmer than usual. It is likely that a gradual addition of degree-days will bring a nice slow ease into early growth. There are no clear weather systems driving the forecast models, so this can all change quickly. You know this.

Diseases

There is not much chance for precipitation in the forecast, but be ready to put cover sprays on for apple scab about a week from now. Copper sprays can be started at any time, but are best placed as close to green tip as possible to get the most longevity from this early scab and fire blight management tool.

I am expecting primary apple scab spores to be ready to go with the first warm rain. I’ve done squash mounts to get an early look at spores, but did not see any that were mature. It could be my poor technique, as it is likely, with the ups and downs of the winter weather, they should be ahead in their development similar to 2016.

Sweet cherries have not moved forward very much in their bud development, so there is plenty of time to apply dormant copper sprays for bacterial canker management, although some research suggests copper does no good due to widespread resistance of Pseudomonas bacteria to copper. If you have pruning to do in sweets, find a string of warm, dry days for this task. Warm temperatures (over 65 degrees Fahrenheit) and no rain are not favorable for canker. As green tissue develops, it becomes susceptible to canker infections if something happens to allow bacteria entry into tissue—this includes frost or freezes and pruning. Avoid pruning sweet cherries in cool, wet conditions.

Peach leaf curl sprays should definitely be considered this spring if you did not get applications on last fall. The recent pattern of cool and wet weather are perfect environmental conditions for the peach leaf curl fungus to get a foothold in early developing buds. This is not the year to skip peach leaf curl sprays.

Insects

No activity to report for tree fruit insects at this time unless the hundreds of lady bugs and the occasional brown marmorated stink bug in my house count. Green fruitworm could start to fly soon. If you have the time, scout for European red mite overwintering eggs in blocks with high populations in 2016 especially. Dormant oil sprays are your first defense against San Jose scale, which continues to be higher in some blocks in recent years.

Spring Spray Meeting announcement

The annual Spring Spray Meeting will be Thursday, April 20, from 4 to 6 p.m. at the Goodfellow Farm, 2267 12 Mile Rd, Sparta, MI 49345. Please use the orchard entrance near Laubach Road, west of the house drive. We will meet in the large white building located behind the houses.

This meeting is sponsored by the Michigan State Horticultural Society and MSU Extension. Michigan Department of Agriculture and Rural Development pesticide recertification credits and CCA credits have been requested.