Grand Rapids, Mich., tree fruit regional report – September 18, 2012

A recap of the 2012 tree fruit season, including a weather summary and this year’s disease and insect problems.

Weather and crop summary

2012 was one for the record books in many aspects of tree fruit production - mostly not positive. Due to mild winter weather that began in November 2011, a week of 80 degree weather in mid-March broke dormancy of all tree fruits. We had the earliest apple green tip date ever recorded on March 17, which started the season off three weeks ahead of the normal average date of April 10. Adding to the problem was that there were about 20 frost or freeze events between green tip and the end of May, which were three times as many as average. The freezes on April 27 and 29 were the most damaging and apples were in bloom at that time (three weeks ahead of average bloom dates).

Growing degree day accumulations have remained two to three weeks ahead of normal for much of the season. As of mid-September, degree days are now extremely ahead of normal averages. In fact, for base 42 and 50, the totals accumulated are now more than what is normally an average for a whole year, so another data point for the record books this year. A lengthy period of no rain has led to drought conditions for much of the state. Even with a light to no crop, fruit trees look very stressed from the dryness and lack of spray inputs.

The early spring spurred tree growth and several cold snaps reduced most tree fruit crops to about 10 to 15 percent of a crop for an estimated apple crop of 2.5 million bushels for Michigan. There was variability in crop set that mostly depended on the site. There are some orchard sites with no fruit at all and other blocks with 30 to 40 percent of a crop.

Disease problems

Depending on the site, there were 14 to 17 wetting periods during primary scab season, nine to 11 of these were apple scab infections. There were between 4 and 7 inches of rainfall recorded at the six different Enviro-weather stations in the west central area (Grand Rapids to Ludington, Mich.). There is a level of scab in orchards this year, but this is most likely due to those blocks ending their spray programs early due to the freeze events and no crop.

Fire blight was less of an issue this year than usual, but there were a few days during bloom when the blossom blight risk was high and preventative sprays were needed. The use of Apogee for shoot growth control has significantly reduced the amount of fire blight we’ve had in the last two years and growers still applied it this year even though they knew there was little crop.

Powdery mildew levels were much more prevalent in susceptible apple varieties in 2012. The weather was hot and humid very early in the season (0.25 inches green through bloom), which got mildew established early and made it difficult to stop, especially in blocks with no crop and no spraying.

Insect pests

After the record-breaking early biofix dates, the tree fruit insects in general were pretty normal in their development, and even lower and later to arrive than expected. There were some higher than expected codling moth numbers in 2012. In blocks with little management, fruit damage from codling moth was very high. There was some concern about a possible third generation of codling moth this year, but the trap numbers did not reflect this occurring at any significant level.

Obliquebanded leafroller numbers were significantly lower than expected. In some cases, they just could not be found. This is somewhat surprising given the low management of many blocks. Perhaps the very hot weather had a negative effect on this pest. European red mites were overall lower than expected in a hot, dry season. There are a few blocks with high numbers and bronzing, but overall, this pest was off this year. Perhaps European red mites are much lower due to the much higher number of beneficials present.

Apple maturity

Like many other tree fruit crops, apple harvest is two to three weeks ahead of normal dates and moving along very quickly. Our apple maturity testing is showing a broad range of maturity even on the same tree. Physiological disorders are more pronounced in 2012 due to the lighter crop load. Frost rings and check marks are the norm rather than the exception this year. Fruit size is much lower than expected, given the short crop. This might be due to the droughty conditions somewhat, or from the fact that many of the fruits that are present were set on one-year-old wood or have very low seed counts and even no seeds. Growers are reporting picking out shorter than expected, yet they feel the estimated crop numbers are, unfortunately, about right.

For more information on apple maturity reports in Michigan, see 2012 MSU apple maturity program and reports.

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