Weekly Fruit Update - June 15, 2022

Annie Klodd, Extension Educator - Fruit Production, kloddann@umn.edu

Apples

Apple fruitlets on SweeTango in White Bear Lake, 6/15/2022

 

Apples are between 10-20 mm this week. Aborted fruit (fruitlets that will not grow to maturity) is now apparent or is being dropped by the tree. This makes it easier to estimate crop load and whether or not to do more chemical thinning. Identify them by smaller size and yellow pedicels (see below). They also fall off easily when brushed or shaken.

An aborted apple fruitlet with a yellow pedicel, 6/15/2022

 

Apple pests: Codling moth flights started last week. We sprayed for codling moth last week in Minnetonka, and this week traps contained 0-3 moths each (average 0.83 per trap). This is below the economic threshold. In Preston, most traps contained 0. In White Bear Lake, most traps contained 0, with three traps containing 5 or more. No apple maggots have been caught at any of the trapping sites. Read the Midwest Fruit Pest Management Guide for information on economic thresholds, and when to spray each insecticide.

Apple diseases: Disease risk is low at this time. Apple scab ascospores have been 100% released. If apple scab was effectively controlled before this point, it should not be a problem. If it was not effectively controlled, monitor for lesions on leaves and fruit in order to determine whether further sprays throughout the season will be needed. Sooty blotch, fly speck, and Cedar apple rust are not concerns at this time; experts recommend controlling for CAR until two weeks past petal fall.

Grapes

Grapevines are currently in bloom. 

Itasca grape clusters in bloom, 6/14/2022.

Pests: Feel free to take a break from spraying! It is best to avoid applying pesticides during bloom if possible, particularly insecticides. Insecticides during bloom are rarely necessary, because most insects that feed during this time are not economically significant. Keep an eye out for grape berry moth, however, populations do not often get large enough in Minnesota to warrant an application.

Herbicide drift: Lawn care services and row crop applications apply significant amounts of dicamba and other growth-regulator herbicides like 2,4-D in May and June to control broadleaf weeds. Unfortunately, this sometimes drifts (volatilizes) and injures grapevines and other sensitive crops. Look for misshapen, stunted, and cupped leaves. Suspected drift can be reported to the Minnesota Department of Agriculture within 45 days in order for an investigation to be conducted. The impact of herbicide drift is highly variable.

Grapevine leaves impacted by 2,4-D and dicamba drift from a neighbor's yard, 6/12/2022.

 

Strawberries

Strawberry season is coming up in the next week or two, with berries between bloom and ripening.  

Pests and diseases: The main insect pests to watch for are tarnished plant bug and thrips. For diseases, blooms are suspectible to infection by botrytis and anthracnose, especially around warm, wet weather. Information on management options are in the Midwest Fruit Pest Management Guide and last week's fruit update.

Strawberries in bloom and fruit set in White Bear Lake, 6/15/2022.

Raspberries

Summer-bearing raspberries are mostly in pre-bloom right now. Summer-bearing raspberries growing in high tunnels have likely started producing fruit, a well as low-growing laterals from the stumps of fall-bearing varieties.

Pests and diseases: Raspberry cane borer is now active. The photo below was taken today, June 15 in Chanhassen. They girdle the tips of canes to lay eggs. Their damage is not usually extensive enough to warrant insecticides, but if it is, then spray before bloom. Find infested canes by the two perforated lines. Snip them off below the lines, and throw them away to dispose of the eggs inside.

Raspberry cane borer damage identified by two distinctive lines, 6/15/2022

For further questions not discussed here, commercial growers may contact Annie Klodd at kloddann@umn.edu or Marissa Schuh (IPM) at mschuh@umn.edu. Home gardeners should contact Ask a Master Gardener.