East Michigan fruit update – May 16, 2017

Many reports of frost damage to apples from across East Michigan; other tree fruit crops seemed to have escaped injury.

Weather

Reports of frost damage and crop loss in apples have been common across most of the region, with the exception of fruit growers south of the I-94 corridor who saw less damage. For most growers, the coldest morning was Tuesday, May 9, and for others it was the morning of May 8. Over the past week, I also had reports of several mornings with scattered frost events; while not cold enough to damage tree fruit, it was cold enough that strawberries needed to be frost protected for a few hours.

Warmer or seasonally normal temperatures over the last week have resulted in our fruit crops growing again after a week of much below-normal temperatures. Our season is still normal to a few days behind normal in terms of degree-day totals and growth stages.

Most of our region has received rain over the last week, especially last night when thunderstorms moved through. Precipitation totals for the last two weeks very widely over the region, ranging from only a few tenths of an inch to just over 2 inches.

East Michigan growing degree-day totals for March 1 to May 15, 2017

Location

GDD42

GDD45

GDD50

Commerce (Oakland County)

479

361

210

Deerfield (Monroe County)

614

474

289

Emmett (St Clair County)

429

316

179

Flint (Genesee County)

550

424

258

Freeland (Saginaw County)

463

352

214

Lapeer (Lapeer County)

505

388

239

Pigeon (Huron County)

376

274

158

Romeo (Macomb County)

482

361

208

Tree fruits

Apples are 10 to 12 millimeters in the southern parts of the region and 5 to 7 millimeters for most other apple growers. There is still a fair amount of bloom on 1-year-old wood and ragtag bloom in many varieties, causing a concern for possible fire blight infection if the right set of rain and warmth comes in the next week or so.

Thinning will need to begin in the next few days. Apples have had a very long bloom period, maybe one of the longest growers can remember. Pollinators have been more active this past week, however with the long bloom period of cold temperatures, pollination is still questionable. Combine these factors with the frost and freeze events over the last nine days, and thinning decisions this year are going to be very difficult. Thinning in some varieties is needed, but be conservative in your approach. Consult the new carbohydrate model on our Michigan State University Enviroweather website to use the inactive model to help make your thinning decisions. You will need to click on the fruit tab at the top of the website, then to the Apple Carbohydrate Thinning tab on the left side.

The new insect pests to report this week in apples are plum curculio, rosy apple aphids and codling moth. In the last two days I found my first plum curculio when using a beating tray to scout for them. I have not seen damaged fruit, but with apples sizing quickly and predicted warm temperatures, I would expect to begin seeing stinging soon. Good numbers of rosy apple aphids are being seen in some apple blocks. Codling moth trap catch is high in most non-mating disruption apple blocks. A few green apple aphids and tarnished plant bug adults were found.

Overall, insect pests have been slow to develop over the last two weeks due to cold weather. Oriental fruit moth and redbanded leafroller trap catch continues at a slow pace. Obliquebanded leafroller larvae are on terminal leaves, with leafrolling taking place. Spotted tentiform leafminer adult trap catch is on the decline for the first generation adult flight. Beneficials are being found, and this week I am starting to see brown lacewing.

Apple scab leaf lesions are in just a few apple blocks. Spore discharge continues with each rain event. As discussed earlier in this report, growers need to be concerned about fire blight infections with bloom continuing in apples, especially where fire blight was a problem last season. The Enviroweather website has a great MaryBlyt tool to determine fire blight infection events. Also, look out for oozing fire blight cankers where it was a problem last season.

Pears are mostly 5 to 7 millimeters in size, with a good crop developing. Pear psylla adults are flying.

Peaches are at late bloom to shuck split. I have not seen much frost or freeze damage in peaches. Most growers have a good crop of peaches this season. Oriental fruit moth trap catch continues.

Sweet cherries are at late shuck split to 10 millimeters, with a wider than normal range of fruit sizes in most varieties. Most growers have a nice crop of sweet cherries this season.

Tart cherries are mostly at late shuck split to 3 to 5 millimeters in size. Most growers report they have a good tart cherry crop this season.

Plums are at early shuck split for European types and Japanese types out of the shuck to 8 millimeters in size. Some Japanese varieties have little to no crop on them this season.

Small fruits

Grapes are at bud burst for Concord types and European varieties have about 2 inches of new growth with flower buds just starting to emerge.

Strawberry growth has been very poor this season, mostly due to cold temperatures. Leaves have poor growth and flowers are small in size and vigor. I expect that with warmer temperatures predicted over the next few days that by late this week strawberry fields will look much better. Most fields need a small amount of nitrogen to help bring them around. Early varieties are at 40 to 50 percent bloom, with later varieties at 25 percent bloom. Most growers have frost protected one to two times the past week, some frosts were not predicted and growers have missed the opportunity to frost protect, resulting in some black blossoms.

Raspberry leaves are emerging from the bud with flower bud emergence continuing for summer fruiting types and tip dieback on many varieties. New canes are emerging from the ground in fall raspberries, but many fields appear to have been frosted and are not growing. The longest canes are about 6 inches long.

Blueberries are at full bloom for most varieties. Overall, there are a lot of bloom in blueberries this season. I have not found any signs of mummy berry mummies on the ground.

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