Southeast Michigan fruit regional report – June 17, 2014

Strawberry harvest is in full swing across the region and even with most fruit growers receiving 0.5 inches of rain last week, soils remain dry. Primary apple scab season continues in the region.

Posted on June 17, 2014 by Bob Tritten, Michigan State University Extension

Weather

With the exception of warmer temperatures yesterday, June 16, cooler weather has persisted over the last week. Our season remains close to normal for growing degree day (GDD) totals. It is interesting to note that most strawberry farms started harvest late this season and that sweet cherries appear to be ripening earlier than normal.

Most of the region received around 0.5 inches of rain last Tuesday and Wednesday, June 10-11. Despite this rain event, most of our soils remain on the dry side. Growers continue to irrigate newly planted tree and small fruit blocks on a regular basis as well as established plantings. Michigan State University Extension reminds strawberry growers to monitor soil moisture supplies closely and continue to irrigate through this critical harvest period as the smaller developing fruits can suffer and ripen before the cells enlarge, causing a significant loss of yield.

East Michigan GDD totals for March 1 to June 16, 2014

Tree fruits

Apples in the southern parts of the region are 1.25 to 1.5 inches and near Flint, Michigan, are mostly 25 to 28 millimeters or about 1 inch. Fruits are continuing to differentiate in size, however I have not seen any June drop. Growers are continuing to access crop load in apples, with many growers reporting a spotty apple crop with wide swings in crop load between varieties. We have had a good amount of new growth in apples in the last three weeks.

In the last month I have continued to see increasing amounts of winter damage in a wide variety of apples. The tree collapse started to be seen in young trees with older, well-established trees showing signs of stress, scaffold limb and tree collapse in the last two weeks. This tree collapse is not consistent from farm to farm or even block to block. For example, the same variety, rootstock and tree age combination may be severely effected on one part of a given farm and appears to be unaffected on other parts of the same farm. The common thread for these collapsing trees appears where some sort of stress occurred in 2013, and these trees are now collapsing this spring and early summer. The stress could be caused by several things, including heavy crop load in 2013, dry soils last season, poor weed control, low fertility in the tree, leaf drop last season due to apple scab, topography or trees in lower areas more severely affected, and many other possibilities. In most cases, growers reported that it was hard for them to see evidence of this stress last season. The winter injury is to the tree trunk, just above the graft union. The cambium in the trunk is dark brown.

Woolly apple aphids are just starting to become active on tree trunks and are the only new insect pest to report in apples this week. A few rosy apple aphids continue to be found in apples. A few green apple aphids are just starting to be seen. Potato leafhoppers continue to be found with a few blocks starting to see some hopper burn from this pest. Many apple growers are finding heavy plum or apple curculio egglaying scar damage on fruit, mainly on the outside edges of blocks. This is old damage, however.

Obliquebanded leafroller feeding on leaves has also caused a fair amount of damage in many apple blocks. Codling moth and oriental fruit moth trap catch have continued to drop back in the last week. San Jose scale male trap catch has dropped back with crawlers expected soon. Good predator numbers continue to be seen in most apple blocks with many lacewings seen in the last week.

Powdery mildew symptoms are now being found in a few apple blocks, and is the only new disease to repot in apples this week. Fire blight infected branches continue to be seen at a few farms. Apple scab spore release is quickly winding down, however there were enough spores caught on spore rods in last Tuesday and Wednesday’s rain that I am not ready to call an end to primary apple scab season yet. I continue to find apple scab lesions on leaf tops and bottoms at just a few farms. We are very near the end of primary apple scab season, but staying covered for the next rain event is still highly recommended.

Pears are 21 to 23 millimeters with a good crop coming along on most varieties. All stages of pear psylla continue to be seen with a good amount of hatch in the last week.

Peaches continue to have poor growth with growers beginning to do a light pruning in trees that have some leaf growth. It is vital that growers leave as much foliage as possible on the tree as leaves will help foster healing. Dead trees can be removed, however if growers are considering filing with the USDA Farm Service Agency for Tree Assistance Program (TAP) funds, the trees need to be counted first.

Sweet cherries are unchanged in size and are 18 to 20 millimeters with most growers having 20 percent of a crop at best. Some of the fruits are beginning to change to a straw color and others are even beginning to turn red. I believe that many of these red fruits are getting ready to drop prior to harvest. Birds are already feeing on these red fruits. Larger scaffold limbs on stressed sweet cherry trees are continuing to collapse from winter injury. Here again as is the case in peaches, the cambium is dark brown from winter injury.

Tart cherries are mostly 11 to 13 millimeters with some of the fruits turning bright red, as is the case in sweets. Here again I believe that most of this fruit will drop prior to harvest. Birds are already feeding on these red fruits. Most growers have 40 percent of a crop of tart cherries this season.

Plums are mostly 21 millimeters for European types with a good amount of fruit drop in the last two weeks. Japanese plums have mostly dropped in the last week; in fact, I could not even find one fruit to measure its size.

Small fruits

Grapes have grown a great deal in the last week, now with 18- to 22-inch shoots with a few flower clusters opened for Concord and Niagara varieties. Wine grapes continue to have extensive cane death in most varieties. As in the case for summer raspberries and blueberries, this is variety specific. It is too early to prune these back; I hope to see more buds break in the next few weeks.

Strawberry harvest is underway at almost all farms in the region. Yesterday, June 16, I was at one farm where I saw my first gray mold for the season. I have a continuing concern that many farms are not applying enough irrigation to help size the smaller green fruit. In these fruit, cells need to enlarge a great deal in order to be good size when ripe. My concern is that growers may get two good pickings and then berry size will quickly diminish. I have been at a handful of strawberry farms in the last week or so where strawberry plants have begun to collapse just as berries are ripening or have small, stunted leaves and fruit. I now believe the root cause of this problem is related to winter injury to the crown of the plant. Plants continue to be analyzed at MSU Diagnostic Services, so keep checking here for more details as results become available.

Raspberries are at the end of bloom to small green fruit for summer fruiting types and fall bearing varieties are 24 to 30 inches in length. Summer fruiting red and black raspberries and blackberries continue to show signs of winter injury. Some varieties look normal in terms of growth and others have been killed to either the ground or snow line. Many of these weak varieties have been mowed back to the ground. These varieties will not have a crop this season. This winter injury is variety specific. Raspberry sawfly damage to leaves has been seen at a few farms, but the pest has come and gone for the season.

Blueberries are mostly 6 to 9 millimeters. Winter damage is showing up at more farms in the last week, some with twig death and others with entire canes dying back to the ground. This damage is variety specific and is not uniform from farm to farm. Where canes are dead to the ground, I suggest removeing all of the canes and starting the bush all over again. It will take a few years for the bush to rebound and become productive again. This can be done with a chainsaw or mower and needs to take place as soon as possible. 

This article was published by Michigan State University Extension. For more information, visit http://www.cnchemicals.com/. To contact an expert in your area, visit http://www.cnchemicals.com/, or call 888-MSUE4MI (888-678-3464).