MSU Extension

Weather

Freezing temperatures were widespread across the region on the morning of Monday, May 13. Low temperatures were generally in the range of 27 to 30 degrees Fahrenheit, however there were many reports from fruit growers of temperatures being as low as 22 F in low areas or frost pockets. Low temperatures were generally at their coldest for three hours from 4 to 7 a.m. Most of our tree fruits were in bloom at the time. Strawberries are also in bloom; many growers started irrigation systems at 10 to 11 p.m. the evening before to protect from frost. Reports of 1 inch of ice formation were common in strawberries.

In grower visits that I made on Monday, I was able to begin to see damage to flower buds by mid-morning. As a preliminary assessment of damage, I would say that it appears more prevalent on a line from the Flint, Mich., area due south to the Ohio border. Damage was most notable in order of most damage to least damage in the following fruit crops: plums, pears, sweet cherries, tart cherries, apples, peaches, blueberries, fall raspberries and grapes. Look for more details on each of these crops in the individual crop reports that follow. Further crop damage will be assessed later in the week as the damage reveals itself a bit more.

Warmer temperatures are predicted over the next week, with the likelihood of no more frost predicted. I am concerned with these warmer temperatures that the threat of fire blight will be very high in apples and pears later this week.

Our season has caught up on itself to a point that we are almost back to normal in terms of growing degree day (GDD) totals and typical bloom times for our fruit crops. There was a point in early to mid-April that our season was running close to three weeks behind normal. Furthermore, there was a time a few short weeks ago that the fruit development and GDD totals in the southern tier of counties was distinctly ahead of fruit just to the north.

Our soils have dried to a point that there has been a great deal of field work completed in the last week. Most growers have completed their tree and small fruit planting for the season.

East Michigan growing degree day totals for March 1 to May 13

 Tree fruits

Apples were in bloom late last week with several good pollinating days. Some blocks saw a king bloom crop, but most had a snowball bloom. I expect to see petal fall to begin mid-week when warmer temperatures arrive.

Flower bud damage was severe in blocks at lower elevations at some farms with as much as 50 to 60 percent bud kill. There is a chance that these blocks can still have a decent crop of apples this season if we don’t get more cold weather. Freeze damage is extremely variable across east Michigan. Thinning in these blocks will be a major challenge this season. As a reminder, blocks that have had frost damage tend to thin much easier.

Insect activity has picked up a great deal in the heat of the past week. Oriental fruit moth trap catch, first reported early last week, was much higher later in the week with many growers biofixing on May 9. With the cold weather of yesterday morning, I would suggest that growers disregard the earlier trap catch numbers and biofix date and start the trap catch clock over again.

A new pest this week is a very few nymphs of white apple leafhopper. I continue to see just a bit of European red mite egg hatch; however, predators are doing a great job controlling them. I continue to see a few single rosy apple aphids feeding inside the flower buds; here again predators are doing a great job keeping their numbers in check. There is the typical number of redbanded leafrollers being caught in traps, with just a few larvae seen. Obliquebanded leafroller larvae are being found at a few orchards. Spotted tentiform leafminer trap catch is declining for the first generation adult flight, with a few eggs just starting to be found. Apple grain aphids and green apple aphids continue to be found with hungry predators feeding readily on them.

There is a record-setting number of predators being seen this season. This is a reflection of most apple blocks not receiving many insecticides last season due to the lack of a crop. Growers are looking to make their petal fall insecticide applications later this week or this weekend.

I saw my first apple scab lesions late last week. Most growers had an apple scab wetting event in the past week with the typical number of spores being caught in traps for this time of the season. I am concerned apple growers may be forgetting about controlling powdery mildew this season. I saw some new terminals late last week that appeared to be infected with powdery mildew. With recent, warmer than normal temperatures, some dew in the mornings and abundance of powdery mildew last season, growers need to apply mildewcides to control it.

Concern for fire blight blossom infection is high on my list for later in the week. Keep an eye on the two models on the Enviro-weather website to monitor possible blossom blight situations. Remember that the predictive model allows you to put in your own data or to create mock scenarios to help you decide how to manage fire blight during bloom. According to Michigan State University Extension, it takes about 24 hours once a blossom opens for it to be colonized by fire blight bacteria in the most ideal conditions (high temperatures). Then rainfall or heavy dew is needed to move that bacteria into the natural openings in the flowers to cause an infection. The first of the season’s Apogee applications will need to be made in the king bloom to petal fall window.

Pears are at petal fall. Damage to flower blossoms was extensive in many blocks I cheeked yesterday. It was rare to find a good blossom in some blocks. Pear psylla adults continue to fly; yesterday I saw my first egg hatch of the season.

Peaches are in the shuck. Growers have done a great deal of blossom thinning with the rope thinners in the last week. Damage in peaches is hard to access. About a third of the buds were damaged in the blocks I checked yesterday, another third seems to be OK or normal and the remaining third are questionable. Many growers are now wishing they had waited to begin thinning peaches due to crop loss from yesterday’s freeze event. Oddly, I am seeing very low to no oriental fruit moth trap catch in peaches this season, only in apples.

Sweet cherries are in the shuck. In the four sweet blocks I looked at yesterday for freeze damage, I saw a wide range of damage to buds. Most had some crop loss, with one having extensive damage.

Tart cherries are at petal fall to being in the shuck. Freeze damage to tarts was also variable, with less damage than sweets.

Plums are mostly in the shuck, with extensive damage to all the blocks I looked at yesterday. Growers need to be on top of black knot sprays at this time.

Small fruits

Strawberry bloom is just starting to open. Most growers frost protected two times in the last week – Sunday morning (May 12) for a light frost and again on Sunday night into Monday morning. As was mentioned earlier in today’s report, heavy ice formation was the case at most farms on Monday morning. Leaf growth and flower bud development are a bit out of sync this year with a noted lack of leaf development. I saw one strawberry planting with very light amounts of angular leaf spot on a few leaves late last week. Growers need to do a thorough job of scouting for this disease over the next few days.

Raspberries have 3 to 4 inches of new growth for summer-bearing types. They appear to have no freeze damage. Canes of fall-bearing types are about 8 to 10 inches in length, finally emerging in good numbers. At some farms, the color of the leaves was already dark green by mid-morning yesterday as a result of freeze damage, and by late afternoon canes were already turning over looking like they will collapse in the next day. So, this is the second or third time this season that canes have been killed back to ground level. Now they will be starting all over again, pushing back the start of harvest even more.

Blueberries are at late pink bud. Some of the flower buds that were more advanced when the freeze event of yesterday morning hit seemed to drop very easily when gently touched yesterday afternoon. Other buds seem to be in good shape. So, it is much too early to accurately assess damage at this date.

Grapes were at 1 to 2 inches of new shoot growth for many varieties when the freeze hit yesterday morning. All of these new shoots were burning back. Buds that were just in the process of opening seem to be in much better shape.