MSU Extension

Weather

Heavy rain storms this past Saturday, June 27, brought between 3 and 5 inches of precipitation in the southern tier of counties to many fruit growers, resulting in an abrupt end to strawberry harvest, flooded fields and the need to recover fruit crops from pests. Areas to the north received around 0.5 to 0.7 inches of precipitation in the past week through the Flint, Michigan, area and no rain to the north.

Several Michigan State University Enviro-weather stations reported record rainfall totals for the month of June in the southern few tiers of Michigan counties. Over the last four weeks, our spring and early summer have gone from droughty to now far too much rain for most fruit growers, resulting in waterlogged soils. While rainfall totals for the last month have varied greatly over short distances, generally most growers have received between 5.5 and 7 inches of rain in June, with some receiving 8 to 11.5 inches of rain in June. This being said, there are a few farms that have consistently “missed” these major rain events, and soils on these farms remain on the droughty side.

Our season is running four to seven days ahead of normal for growing degree day (GDD) totals for most of east Michigan. Two of our MSU Enviro-weather stations have broken the 1,000 figure for GDD base 50 in the last week. In terms of the beginning of harvest for sweet cherries and summer red raspberries, our season is about five days ahead of normal.

Tree fruits

Apples continue to size very well this season, with great leaf growth and a good amount of new terminal growth in the past three weeks. Most apples are at 1.875 inches to the largest fruit at 2.25 inches. June drop has ended for most growers, with hand-thinning now in full swing for many apple growers. Overall, our apple crop is shaping up to be better than most growers expected a few weeks ago.

Our insect pressure is generally light these past few weeks, with good numbers of beneficial insects. The exception here is San Jose scale crawlers in a few blocks and the start of obliquebanded leafroller and oriental fruit moth larvae in terminals in just a few blocks. No apple maggots or brown marmorated stink bugs have been caught in traps this season. My first sighting of Japanese beetle adults as of yesterday, June 29, is the only new pest to report this week. San Jose scale crawlers are very active at this time and are starting to crawl to fruit. Now is a critical control period for San Jose scale in blocks where they have been found as they will begin to wax over in the next week or so and this control window will close. While obliquebanded leafroller adult trap catch is done for first generation, I am just starting to see very small larvae in terminals in just a few apple blocks.

Oriental fruit moth trap catches continue to decline for first generation flight as well, but as with obliquebanded leafrollers, few very small larvae are seen in just a few apple blocks. Growers need to do a good job of scouting for obliquebanded leafroller and oriental fruit moth larvae at this time. A few masses of woolly apple aphids are just starting to be found this week moving from pruning wounds to suckers in the interior of the tree. A few colonies of rosy apple aphids continue to be found on interior twigs. A few green apple aphids and apple grain aphids continue to be found, but predators or beneficials seem to be doing a good job of controlling all three aphid pests at this time. A few potato leafhopper adults and curled leaves as a result of their feeding injury continue to be seen. European red mite adults and eggs continue to be seen in very low numbers. Good numbers of beneficial insects are actively feeding in most apple blocks. This week, good numbers of lacewing adults and tachinid flies are found.

Apple scab lesions continue to show up on leaves and fruit, as do widely scattered fire blight strikes, with a few growers continuing to see new strikes on a regular basis. Powdery mildew-infected twigs continue to be seen in a few apple blocks. The leaf stage of black rot, known as frogeye leaf spot, is found in more apple blocks these past few weeks, even in young apple blocks.

Pears are mostly 1.375 inches in size. All stages of pear psylla continue to be seen.

Peaches are 2 inches for those few growers with a crop this season; pit hardening has not begun. Growers continue to hand-thin peaches and prune winter-damaged trees, removing dead and dying trees. Green peach aphids are found in a few blocks. Bacterial leaf spot-infected leaves continue to be seen in many peach blocks, especially in blocks with no crop this season where pest control has been reduced.

Sweet cherry harvest started late last week for most cherry growers, the earliest ever at some farms. The fruit took on a small swell in size this past week, with minor amounts of fruit cracking as well. Bird feeding is a problem in most blocks. I have two reports of brown rot found in just a few blocks. No spotted wing Drosophila (SWD) have been caught in traps.

Tart cherries have colored well in the last week with most fruit taking on a swell to 16 to 18 millimeters in size. Cherry leaf spot-infected leaves are yellowing badly at some farms with a fair amount of leaf drop on trees with a big crop on them. Cherry leaf spot needs to be controlled at this time as new leaves continue to emerge. Birds are also starting to be seen in tart cherries. No SWD have been caught in traps.

Plums are about the same size as last week, 19 to 23 millimeters for European plums and 1 inch for Japanese plums. There is a fair amount of fruit drop this week. Black knot is starting to be seen on wild and unsprayed plum trees.

Small fruits

Grapes are at buckshot-sized fruit for concord types. European varieties are at petal fall for the few varieties with a crop this season. Last week, I saw a big crop of fruit at the few farms that grow seedless varieties. This fruit will need thinning over the next few weeks. I saw my first Japanese beetle adult yesterday, June 29. Downy mildew has been seen at a few farms this week. Many European varieties have extensive winter kill and growers have either pruned them back to just above the bud or pulled them out entirely.

Strawberry harvest has wrapped up in the southern parts of our region as a result of heavy rain, and harvest continues in areas to the north. Growers still harvesting hope to have enough high quality berries to be able to pick into the weekend. Many growers are continuing to struggle with heavy rainfall over the last three weeks. Berry quality from heavy rainfall is an issue for many growers as well. Berries have a pinkish cast or a water-soaked part of the berry, mostly on the shoulder of the largest berries. Some growers also report berries having a fermented smell to them this season. Demand for wholesale, ready-picked and pick-your-own strawberries is very strong this season. Wholesale and ready-picked berry growers are having a hard time finding labor with a few reports of ripe berries going unharvested.

Gray mold has been seen at more farms in the last few days, mainly due to extensive moisture. Strawberry leaf spot is just starting at a few farms. Slugs are found at most strawberry farms.

Raspberry harvest of early maturing varieties started over the weekend. Other summer varieties are at large green fruit to fruit coloring. Black raspberry harvest is just getting started. Fall red raspberry canes continue to put on good new growth, with the longest canes 48 to 54 inches long. This season, I am finding lots of flower buds or “bud berries” formed at this time on the shorter lateral canes of fall raspberries. These early berries are not part of the main crop. No SWD have been caught in traps.

Blueberry fruit is continuing to color on early varieties, especially the largest berries in the cluster. While most of the largest fruit remain at 17 millimeters, the smaller fruit took on good amount of size this past week. No SWD or blueberry maggots have been caught in traps.