Southeast Michigan fruit regional report – May 27, 2014

There have been a lot of codling moth and plum curculio at apple farms in the past few days.

Posted on May 27, 2014 by Bob Tritten, Michigan State University Extension

Weather

Some areas of the region had another 1.5 inches of rain in the last week, with most growers getting just a few tenths. Soil moisture supplies vary greatly over the region, with some growers reporting extremely dry soils and others having so much moisture that field work has stopped entirely. With the warmth of the last week, our season has moved back towards normal. Our season is still behind normal, but only three to four days.

East Michigan growing degree day (GDD) totals for March 1 to May 26, 2014

Tree fruits

Apples in the southern parts of the region are 7 to 9 millimeters and near Flint, Michigan, are at petal fall for most varieties while a few, including Northern Spy and Ida Red, still have some bloom. Growers are assessing crop load in apples. It appears that crop load is extremely variable this season. Most growers are not seeing as many fruit as they anticipated a few weeks ago when they were looking at buds. Some varieties were light on bloom, including Fuji, Red Delicious and Honeycrisp at many farms, although this varies greatly from block to block.

Apple growers are considering their options concerning thinning. I would suggest a moderate approach at this time for most varieties. Goldens appear to be heavy as of May 27 and growers may consider a more aggressive approach with this variety. Recall that Phil Schwallier with Michigan State University Extension has been suggesting that growers consider the 6-millimeter stage as another opportunity to thin. Many growers are going to be starting at this early thinning window on varieties that appear to have a good fruit set. Lastly, according to the carbohydrate thinning model, trees will only be under a mild stress for the next five days, so normal rates should work well.

In last week’s regional report, I shared news of apple trees starting to collapse or having very small leaves and being much further behind other apple trees. Most of these trees are growing on M.9 rootstocks, but not all. Jonathan and related strains are mostly affected, but other varieties are also starting to show the same symptoms. Further investigation of these symptoms points to potential winter injury to the tree trunk just above the graft union. The cambium in the trunk is dark brown with the majority of the damage on the east and north sides of the trunk. More time is needed to determine the entire impact of this problem, but in the meantime keep an eye out for this at your farm.

Insect pest pressure has continued to pick up over the last two weeks. Insects that I have seen in high numbers for the last week include codling moth, plum curculio and many leafroller species. New insect pests to report this week include lots of mullein bugs, a few apple curculio, a few apple grain aphids, a few rosy apple aphids, a few white apple leafhoppers, San Jose scale males in traps and oystershell scale crawlers as of today, May 27, and some apple rust mites. Codling moth adult trap catch has jumped in the last few days with many growers biofixing in the last day or so. Plum curculio pressure has also been high, as well as lots of leafrollers.

Oriental fruit moth trap catch has leveled off or stayed just below the biofix levels for most growers. Oddly, I am not finding as many tarnished plant bugs this past week. We are seeing European red mites in increasing numbers at several farms and growers need to scout for them this week. Two-spotted spider mites are continuing to be found in low numbers at many farms. Spotted tentiform leafminer adults continue to be caught in traps, but numbers remain low for the second week as the first generation flight has ended. With apples at petal fall, spraying operations are back in full swing as growers have quickly moved ahead as each variety reached this stage.

With bloom last week, most growers sprayed for fire blight infections. I am seeing some streptomycin burn on apple leaves. We continue to have apple scab spore release with each rain event; spore numbers continue to decline. I am finding a few more apple scab lesions on leaves in the last week.

Pears are 9 to 11 millimeters with a good crop coming along. Pear psylla adults continue to be very active with our warm days, with all stages present.

Peaches continue to look rough with trees that were under stress last season not leafing out at all. I have not seen one peach flower this season, but I did find one grower who had five blossoms on one variety last week. In the last two weeks or so, I am seeing a few leaves emerging from the most vigorous shoots in the tops of trees. It appears that there is extensive winter damage in peaches this season comparable to or now even worse than cold damage that occurred in winter 1994.

Sweet cherries are 10 to 12 millimeters with most growers reporting 20 percent of a crop at best.

Tart cherries have a wide range of fruit sizes this week from late bloom still open to fruit that is 6 to 8 millimeters in size. Most growers have 40 to 60 percent of a crop of tart cherries this season.

Plums are mostly at shuck split to 6 millimeter fruit for European types and some of the Japanese plums are 7 to 8 millimeters in size.

Small fruits

Grapes are at 4- to 8-inch shoots with flower clusters exposed for Concord and Niagara varieties. Wine grapes have extensive cane death in most varieties; I am just starting to see 10 percent of the winter-damaged vines begin to form a new leaf bud. It is too early to prune these back.

Strawberries are at full bloom with no green fruit present yet. Most strawberry growers are applying fungicides to control gray mold. Strawberry clippers continue be found commonly at many farms. I am also finding more tarnished plant bugs this week as well as a few two-spotted spider mites. Angular leaf spot disease continues to be found at more farms this past week. Growers need to do a thorough job of scouting at this time to check for the angular, water-soaked translucent lesions on leaf surfaces. A copper application may be needed at this time to control angular leaf spot.

Raspberries are continuing to show signs of winter injury, especially summer red and black raspberries and blackberries. Some varieties look normal in terms of growth, now these have flower clusters visible. Some growers have mowed off summer raspberry varieties because of lack of growth due to winter injury. These varieties will not have a crop this season. This winter injury is variety specific. Canes of summer fruiting types have a significant amount of cambium browning, indicating potential winter injury.

Fall raspberries continue to emerge from the ground and are now 8 to 12 inches in length. New canes of blackberries continue to emerge from the soil, with the tallest 12 to 16 inches in length. All of the canes from last season are dead to the ground.

Blueberries are mostly at full bloom to petal fall. Small twigs continue to die in many blueberry varieties due to winter injury.

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).