Grand Rapids area tree fruit update
The holding pattern continues…
Tree fruit growth stages
In the general Grand Rapids area, there is some green showing on the earliest apple varieties on the earliest sites, and you can see slight movement in buds each day. It was a bit surprising that with the 80-plus temperatures on April 10 that there wasn’t more tree movement. The rains from the cold front that moved through early April 11 bypassed this area.
In general, the degree day totals in the Grand Rapids area are 5 to 7 days later than normal averages for this date. Updated degree day information can be found at www.enviroweather.msu.edu for the weather stations in the Grand Rapids area. As a reference, in 2010, first green for Macs was on March 23, 2010. The average first green for MacIntosh (or other mid-season varieties) in the Grand Rapids area is around April 11. We will be only a couple of days later than this average for 2011 and it’s shaping up to be more like 2009 when first green on Macs was on April 12.
Growers are wrapping up winter pruning of apples and removing brush from blocks. Ground applied fertilizer applications could be started at any time. Keep in mind the light crop in 2010 and balance your nitrogen accordingly. I would expect tree planting to start at any time as field conditions allow.
Tree fruit pests
Copper applications to sweet cherries for bacterial canker should be started at the latest bud swell stage before any significant green tissue shows up to avoid any issues with phytotoxicity. Keep in mind that bacterial canker is a cool, wet weather disease. If you have some light pruning to get done in sweet cherry, today would be an excellent day to finish that up and then cover with copper ahead of the cool, wet weather predicted for later this week. If you have to make any big cuts, leaving a stub can be helpful to manage canker in sweets. It is best to avoid pruning sweets in cool, wet conditions.
Copper use in apples for the earliest apple scab spray is highly recommended this season. Copper is an excellent scab material. It is thought that apple scab spores mature early with heavy snow cover, so we should be ready for any early scab infections and be ready to cover for them. This is likely to be true for this year as I’ve been checking for spores for the last couple of weeks and there were 3 spores in total for an average of 1.5 spores per rod from the rain April 8. Since there was no green out in 99% of the apples around Grand Rapids, and there were only two hours of wetting, there was no risk for apple scab infection from this rain event. However, this presence of a few ascospores tells me that the early rains of 2011, when there is only a little of green tissue out, should be taken seriously as possible scab infections. Preventative scab sprays will be crucial this year mostly because we have control materials that work best ahead of an infection rather than as eradicants.
European red mite eggs can be found, but numbers appear to be normal or even lower than normal so far. Blocks that had high numbers of mites late in 2010, should be checked carefully for red mites. Some apple and peach blocks had unusually high numbers of San Jose Scale in 2010. Delayed dormant oil sprays are still the best management tool for scale pests, but they do come with risks, not to mention difficulty in application.
It’s not too early to start putting pheromone ties up for Oriental fruitmoth in stone fruits or for codling moth in apples. Since there have been no pesticide applications made yet, it’s a very safe time to have workers doing this task. We rarely get this much extra time in the spring to do pheromone tie applications. Be aware in putting up pheromone ties in peaches that haven’t been pruned yet - you don’t want to prune them off accidentally later.