West Michigan tree fruit update – May 9, 2017

Cold weather brings slow tree development.

Weather and crop development

Tree development continues to be in a stasis due to cooler than normal weather. Only slight leaf or flower development in tree fruits has taken place over the last week on the Ridge. Most apple varieties are in the full bloom stage with some petals beginning to fall. On the same trees, there will also be flower buds still in the pink stage. While this happens every year, it is very apparent this season due to the much cooler temperatures and slow forward movement in apple development.

There were two very cold mornings this week on May 8 and 9 leading to some injury to flower buds for apples. There is freeze injury in low-lying areas where expected, but also on the tops of hills from the freeze Monday morning, May 8. Temperatures dipped to the 28-degrees Fahrenheit mark or lower for several hours on the Ridge with colder temperatures in low areas. Frost fans helped a bit, but there was not a significant inversion due to cold daytime temperature prior to the cold nights.

Orchard blocks with micro sprinklers seemed to have had the least amount of bud injury from first observations. While injured flower buds can be seen, there are many that are still green. It is much too early to adequately assess the impact to our potential crop.

Sweet cherry is in the full bloom to petal fall stage with some damage from the cold, but again, it’s too early to determine the potential crop.

Peaches are past bloom and still in the shuck. There appears to be very little cold injury to peaches.

Pest report

A week of dry weather has eliminated the risk for apple scab infections for a short time. There are still primary scab spores to be matured and released, and the next significant rain event could release a big number that has been waiting for rain to release them. There have been 690 degree-days base 32 accumulated since first primary scab spores were caught March 30. This indicates roughly 90 percent of primary scab spores are mature, so we have several weeks to protect for primary scab—don’t skimp on your primary fungicide program now.

The recent cooler weather will be less of a risk for powdery mildew.

There has been no risk to apples and pears for fire blight blossom blight infections with the very cold weather. Warm weather is in the seven-day forecast and there will likely be ragtag bloom still present and vulnerable.

Bacterial canker in sweet cherry could get a significant foothold with the frosty conditions lately. The frost damages the green tissue and allows the bacteria to enter the tree.

It looks like the cool weather will move out later in the week and hopefully bee activity leading to pollination and fertilization of apples will help set fruit.

Insects have been holed up waiting for fairer weather. There is no significant activity to report.

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