Northern Michigan FruitNet 2002
Weekly Update
James E. Nugent      Gary E. Thornton       William M. Klein
NW Michigan Horticultural Research Station
Michigan State University

May 21, 2002

WEATHER

Weather this past week has been very cold. Inversion freeze events occurred on the mornings of 5/19, 5/20 and 5/21. The coldest morning in NW Michigan was Sunday, 5/19, with low temperatures throughout NW Michigan's fruit belt in the 20's Fahrenheit. Significant frost damage occurred to tarts, sweets and apples, particularly in the lower areas and areas where air flow is more limited. Unfortunately, the best tart crops left in NW MI after the wind freeze on 4/21 and 4/22 were in the lower, protected sites, and these sites tended to receive the most damage on 5/19. Pollination conditions were very poor last week, with high temperatures reaching the lower 60's only one day.

GROWTH STAGES

Apple: Red Delicious—pink
Pear: Bartlett – white bud
Sweet Cherry: Napoleon – petal fall
Tart Cherry: Montmorency –full bloom
Plum: European type – petal fall
Grapes: Chardonnay – late bud swell

COMMODITY REPORTS

Apples survived the wind freeze in April, but they were significantly damaged in colder sites on 5/19. The apple crop potential remains fair to good in sites with excellent air drainage. Scab spore release has been very low throughout the state these past two weeks. Between the pink and petal fall stages, apple scab spore release is typically at its peak. This peak has not occurred yet, but with warm temperatures in the future it still may materialize. Insect activity has been very slow to develop this spring. Spotted tentiform leaf miner averaged only 7 per trap this past week at the NWMHRS, and no American plum borers were caught. The first codling moth was caught this week. Growers who will be monitoring for this pest need to hang their traps this week. The warmer temperatures being forecasted will dramatically increase trap catches this next week. 

Tart cherries in NW Michigan were further damaged by frost on 5/19. Expect a very short crop in NW Michigan. At the NWMHRS, Montmorency has the lowest bud survival of any tart cherry under evaluation. This was due almost exclusively to the severe damage caused in Montmorency by the April wind freeze, compared to moderate to no damage at that time in the other 26 selections in Dr. Amy Iezzoni's planting. Frost on 5/19 did considerable damage to sweet cherries. We can still expect a better crop than tarts, but the sweet crop will be well below average. Some tart cherries and all sweet cherries have leaves that are expanded enough to allow them to be susceptible to cherry leaf spot infections. Protectant fungicides should be applied to guard against future infection periods. A protectant, like Bravo, is excellent against cherry leaf spot, and fair to good against brown rot. Some Montmorency trees in their early bearing years are exhibiting bud death symptoms caused by necrotic ringspot virus (NRSV). This "shock symptom", commonly called "red bud", can occur when the trees experience a period of exceptionally warm temperatures during bud development. While we've had nothing but cold weather, in mid April there was record warmth for a few days during early bud swell. Hence, the NRSV this year caused bud death at an early stage. Those buds were killed but still remain on trees without developing. 

All newly planted tree fruit are susceptible to climbing cutworms. Activity from this pest should increase with warmer weather. Both tar paper guards and trunk sprays work well to protect buds from cutworm activity. 

Slugs are active in strawberries. The populations are likely higher than in recent years, due to the cool wet weather.

Please send any comments or suggestions regarding this site to: 

Bill Klein, kleinw@pilot.msu.edu
Last Revised: 5-21-02