Southwest Michigan fruit update – May 3, 2022

Michael Reinke<reinkem3@msu.edu>, William Shane and Cheyenne Sloan<sloanche@msu.edu>, Michigan State University Extension - May 03, 2022

Blooming of fruit crops is becoming more widespread. Bees are visiting open flowers.

Bee hives near a woodline. — Many crops are blooming or near bloom. Bees are active. At this time of year, growers should be careful about what and how they spray their crops. If possible, avoid spraying. If sprays are necessary, do so when bees and other pollinators are not flying. Photo by Mike Reinke, MSU Extension.

Weather

Last week was cool. It started with high temperatures near 40 and lows near freezing. A mild warm up at the end of the week brought highs up near 60. Average high temperatures this time of year are in the mid-60s.

The only major rain event occurred late on Saturday. A line of storms followed Lake Michigan. Areas near the lake saw rain amounts near 1 inch. Locations inland had much less. Soils are still wet throughout the region.

The coming week will be slightly warmer than last week. Most days should see highs near 60 with a slight warmup to near 70 over the weekend. An inch or more of rain is expected today (Tuesday) with more rain possible on Thursday and Friday.

With the cool week, we picked up significantly fewer growing degree days (GDD) than last week, 42 GDD base 42, 13 GDD base 50. Three weeks ago, we were near normal for degree day accumulation. We are now 12 days behind the long-term average. We have lost over a week in accumulation in the last couple weeks.

Southwest Michigan GDD summary from March 1 - May 2, 2022
Station	GDD 42 F	GDD 45 F	GDD 50 F
Benton Harbor (SWMREC)	294	216	121
Lawton (Lawton)	292	219	126
Fennville (TNRC)	258	189	105
Average for the SW region	290	216	124
Average last week	248	187	111

GDD table — This graph shows the degree day (GDD42) accumulation over the last 10 years and the long-term average (black dashed line). We are currently 12 days behind the long-term average.

Tree fruit

Development has continued despite the cold week. Most stone fruits are blooming. Apples and pears are not far away either. During bloom, be cautious with sprays, avoiding when possible, and spraying at night when necessary to avoid harming pollinators.

The recent wet weather has slowed down progress on pruning. Biofix for black stem borer and oriental fruit moth was near April 24 for much of the region. Oriental fruit moth egglaying will begin soon. Mating disruption treatments for oriental fruit moth should be up this week for full season efficacy. Ovicide spray timing for this pest should be next week.

Apricots bloom is ending and most varieties are in the shuck.

Peach and nectarine are blooming. Low levels of copper generally help suppress bacterial spot populations. Brown rot control is needed for warm wet conditions during bloom. Thorough removal of mummies from trees is important for managing this disease.

In cherries, sweet cherries are at full bloom, tarts are at early bloom. Expansion of first bract leaves (beginning of risk period for cherry leaf spot infection) for central Berrien County was estimated as April 24 (250 GDD base 42 after Jan. 1).

In plums, Japanese plums are at full bloom. European plums are at early bloom. Prune out black knot and dispose of the knots by burning or removing them from the orchard. Sanitation is an important step in managing this disease. Fungicide control generally starts at green cluster. European plum (most varieties) is more susceptible than Japanese to this disease. Brown rot management is needed when wet weather and temperatures in the range of 60 to 80 degrees occur during bloom.

Apple varieties in central Berrien County range from tight cluster to king bloom. Remedies for blind wood include notching above dormant buds plus plant growth regulator (PGR) treatment and is best from green tip to tight cluster but can be done two weeks before bud break to after full bloom. Best time is half-inch green.

Scab sprays are needed during the primary scab season from March to early June to protect against ascospores released in rains. Protectants are preferred over systemic fungicides at this time of year for scab control to reduce the number of systemic fungicide applications and thereby slow the development of resistance. Powdery mildew and rust control generally start at pink. Tarnished plant bug damage has been seen in the area. This insect becomes active when we see temperatures above 70. A pyrethroid spray before bloom is warranted if you expect you have tarnished plant bug pressure.

Apples blossoming. — Most apple varieties are at pink. Some king bloom has been seen in southern Berrien County. Photo by Mike Reinke, MSU Extension.

Pear buds are at full white to bloom and require protection against scab. Be prepared for fire blight management at bloom. Pear psylla egglaying has been detected.

Small fruit

There has been no damage from cold weather in small fruit yet this spring. They still need temperatures below 25 degrees to see significant damage.

Grape buds are still at early swell in vinifera cultivars and bud break in juice varieties, with Berrien County a few days ahead of other counties. Some color can also be seen in early hybrid wine grapes such as De Chaunac.

Blueberry flower buds are at early pink bud in Van Buren County to early bloom in southern Berrien County. Green leaf tissue is out. This is still a good time to be scouting for mummy berry. Spores are being released now. The window to apply copper, Sulforix or lime sulfur products to suppress early season diseases is quickly closing.

Strawberry flower trusses are emerging from the crowns. Growers are applying straw between the rows. Maintain early season fungicide coverage to protect the leaves.

Strawberries coming up from the ground. — Flower trusses are emerging from the crown. Growers are covering rows with straw. Photo by Mike Reinke, MSU Extension.

Bramble leaves are unfurled. Shoot elongation has begun and new canes are emerging in fall bearing raspberry fields. Dormant pruning should be completed. In summer bearing raspberries, last year’s primocanes should be headed (cut back) to the desired height and all floricanes from last year should be removed. Lime sulfur treatments for anthracnose can still be applied at reduced rates.

Cranberries are still dormant, fields are red.

Currant and gooseberry are blooming.

Hops bines are being burned back. This is to promote better and more consistent flowering late in the season. Stringing of hopyards continues.

Hops growing. — Hops are continuing to grow. Most will be burned back for better timed growth later in the year. Stringing is continuing. Photo by Mike Reinke, MSU Extension.

Upcoming meetings

Our regular Southwest Michigan Monday Fruit IPM Updates will be moving to a hybrid format. The meetings will be held in person with virtual attending also available online. You do need to register to receive the Zoom link and password for these meetings. The webinars are free of charge and two pesticide applicator credits are available for each meeting.

This work is supported by the Crop Protection and Pest Management Program [grant no 2021-70006-35450] from the USDA National Institute of Food and Agriculture.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).