Southwest Michigan fruit update – May 21, 2024
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EmailWarm weather is increasing insect activity in area fruit plantings.
Weather
The week started with warm temperatures and intermittent thunderstorms. Tuesday was our warmest day with a high of 87 degrees Fahrenheit. There were scattered showers and gusty winds throughout the week. The weekend remained relatively warm and partly sunny, with highs in the upper 70s and scattered showers, especially in the afternoons and evenings.
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Southwest Michigan GDD summary from March 1 – May 20, 2024 |
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|---|---|---|---|
|
Station |
GDD 42 F |
GDD 45 F |
GDD 50 F |
|
Benton Harbor (SWMREC) |
855 |
694 |
468 |
|
Lawton (Lawton) |
856 |
697 |
469 |
|
Fennville (TNRC) |
747 |
593 |
382 |
|
Grand Junction |
839 |
679 |
457 |
|
Average for the SW region |
830 |
672 |
450 |
A weather report by Michigan State University meteorologist Jeff Andresen is available online.
Tree fruit
Spongy moth, formally gypsy moth, larvae are abundant in areas in southwest Michigan, and have the potential of causing problems on young fruit plantings. Based on biofix of May 6 for catch of San Jose scale adult males (Fennville trapline), crawlers from this generation are expected 400 to 450 degree-days base 51 F later. Current GDD51 sum at the Southwest Michigan Research and Extension Center as of May 21 is 204 and is projected to be 308 by Monday, May 27. Crawlers are expected by the first week of June—earlier if the weather turns hot. Plum curculio continues to be actively attacking fruit.
Apricot fruit (Haroblush variety) are 32 millimeters (mm) in diameter at the Southwest Michigan Research and Extension Center.
In peaches and nectarines, protection against plum curculio and tarnished plant bug is still needed if there is a crop. Flagging of branch tips by oriental fruit moth larvae damage is expected to show up soon in unprotected trees. If peach scab has been a recent problem, one or two sprays, typically Captan or sulfur, can help suppress the buildup on twigs. Rusty spot spray coverage from shuck split to pit hardening is needed for susceptible varieties.
In cherries, Montmorency tart cherries are 12 mm in diameter. Rough estimate is that we have 60 to 65% of a full tart cherry crop in Berrien County. Management of cherry leaf spot and plum curculio are the major concerns now. Progibb (gibberellic acid) treatment for prevention of blind wood is generally started the year after planting, beginning about three weeks after full bloom. The Michigan State University Extension Fruit Management Guide E-154 has more details on treatment.
In plums, Shiro Japanese plum fruit are 22 mm and Stanley European plum are 18 mm in Berrien County. Fruit set is somewhat scattered, with clumps of fruit in some areas of the trees and not in others. Egglaying scars by plum curculio have been visible starting about two weeks ago in central Berrien County. Protection against this pest and plant bug should be ongoing, if the crop load is sufficient to justify the expense. Critical time for fungicide control for black knot is petal fall to approximately late June when new growth slows.
Apple fruit range from 18 to 30 mm diameter, a big jump from last week. Ethrel and Accede are the last ditch chemical thinning options at this point. A good summary of thinning tactics from MSU is available online. Symptoms presumably from the fire blight infection periods on April 28 and 29 in central Berrien County were detected Friday of last week on Romes. Orchards should be scouted carefully for this disease and strikes cut out. The storm on Monday, May 20, may have spread infections that are showing now.
Apple scab ascospores catches are decreasing but still significant—expect to continue control until at least the first week in June. Continued management of powdery mildew and juniper rust is needed for susceptible apple varieties. Biofix of May 6 for codling moth (first catch of moth at the Fennville research station) can be used to predict larvae hatch, 200 to 250 degree-days base 50 later. Approximately 218 GDD50 was reached Tuesday, May 21, at the Southwest Michigan Research and Extension Center in Berrien County. Insecticides with action against larvae are needed now, if pheromone disruption or early treatment during egglaying has not been done.
Pear (Bartlett) fruit are up to 22 mm in diameter at the Southwest Michigan Research and Extension Center. Continued scab sprays are needed to protect green tissue against infection. Pear psylla immature and adult insects are abundant on fruit in some blocks and are beginning to cause gumming and sooty deposits.
Small fruit
In grapes, wild grape bloom is underway. Wild grape bloom is used as a biofix for grape berry moth. Biofix is when 50% of clusters are at 50% bloom. See this article for more information: Using the MSU Enviroweather grape berry moth model in 2018.
Juice grapes and advanced hybrid wine grapes are very close to bloom. Expect bloom in these varieties soon. With the warm weather in southwest Michigan this week, bloom may be seen in the next day or two in some locations.
For varieties still a week or more from bloom the warm, wet weather we have been experiencing recently and the weather coming up, the focus should be on protecting the developing foliage from phomopsis and early infections of downy and powdery mildew. Phomopsis infections from a couple weeks ago are showing up on foliage.
For varieties that are immediate pre-bloom or blooming, the focus should expand to include the spring concerns and the bunch rots: phomopsis, black rot, anthracnose, downy mildew, botrytis bunch rot and powdery mildew.
Blueberry bloom is complete, and bees are being taken out of fields. Small green fruit are developing. With bloom finished and green fruit on the bush, disease control refocuses on anthracnose infections to young green fruit. Cranberry and cherry fruitworm have been caught. Second applications of fertilizer are being applied and weed control sprays are continuing.
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Strawberries have set fruit with early varieties already being harvested in southern Berrien County. All the leaves are out by now: maintain fungicide coverage to protect the leaves and help prevent botrytis as fruit begin to show. Slugs have been reported in some fields.
Bramble bloom is in swing in raspberries and blackberries. Raspberry sawfly scouting should begin. This insect eats leaf tissue between the veins giving them a skeleton-like appearance.
Upcoming meetings
Our weekly Monday Night South Michigan Fruit IPM Meetings will once again be a hybrid format. The meetings will be held in-person at the Southwest Michigan Research and Extension Center, 1791 Hillandale Rd, Benton Harbor, MI 49022, with virtual attendance available online. Our next meeting is Monday, June 3, at 5:30 p.m. No advanced signup is needed for attending in-person. The meetings are free, and one pesticide applicator credit is available for each meeting.
The Unconventional Fruit Working Group 01: Orchard and Vineyard Floor Management will be May 29 from 12:30 - 1:30 p.m. via Zoom. This is a virtual meetup group for fruit farmers who grow fruit using non-conventional practices, including organic farmers. Each 1-hour meeting has a theme, with the first meeting theme being "orchard and vineyard floor management." After a short educational presentation, farmers can share their experiences and listen to the experiences of other farmers. Sign up here. For more information, contact Derek Plotkowski at plotkow5@msu.edu.
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. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.
