Grand Rapids area tree fruit update – June 11, 2024
Print
EmailSettling into summer on the Ridge.
Weather update
This week is starting out cold and calm but will warm considerably later in the week.
For a detailed look at the upcoming weather forecast, Jeff Andresen, Michigan State University agricultural meteorologist, has weekly 15 - minute talks posted every Tuesday.
Crop update
We are in June drop this week and fruit is starting to color.
Frost damage is becoming quite apparent on fruitlets. Frost rings and misshapen fruitlets are fairly widespread this season across varieties. Once June drop has settled, we will be able to better evaluate the impact this will have on the crop.
Early sweet cherry varieties like Black Pearl are close to fully ripe.
|
Growing degree day (GDD) accumulation since Jan. 1 as of June 11, 2024 |
5-year average |
|||
|
Stations |
GDD42F |
GDD50F |
GDD42F |
GDD50F |
|
Aetna-Fremont |
1135 |
595 |
983 |
565 |
|
Alpine |
1256 |
691 |
1059 |
615 |
|
Belding |
1225 |
675 |
1000 |
571 |
|
Conklin |
1247 |
681 |
1055 |
612 |
|
Grant |
1204 |
656 |
974 |
552 |
|
Kent City |
1212 |
658 |
975 |
554 |
|
Sparta |
1235 |
676 |
987 |
558 |
|
Sparta-Tower |
1231 |
669 |
997 |
565 |
|
Sparta-North |
1223 |
662 |
1039 |
601 |
|
Standale |
1316 |
742 |
1059 |
610 |
|
McIntosh growth stages |
GDD42F |
GDD50F |
|
First cover |
749 |
401 |
|
Second cover |
1061 |
607 |
|
Third cover |
1405 |
842 |
|
Fourth cover |
1759 |
1094 |
We typically report GDD accumulation starting at March 1, but this is not a typical year. We reached the required chilling hours on Jan. 15 to move into ecodormancy and start accumulating GDD. This means the heat we received in February mattered for this year’s crop. As such, I will be reporting GDD from Jan. 1 rather than March 1 this season.
Pest and disease update
Apple scab
We are moving towards the end of the primary apple scab season now.
While I caught zero ascospores following the night rain on June 6, I did catch two ascospores per rod following the rain from 5 p.m. June 8 to 9 a.m. June 9. This was a moderate risk event with 184% progress towards infection.
I will continue to scout for spores until we get two consistent zero spore collections.
Please remain covered with fungicides until primary scab season is concluded and no secondary lesions can be detected with careful scouting.
However, all spores count! No matter how few spores we catch, they all matter for controlling secondary scab. While one ascospore can create one lesion, each lesion can produce up to 100,000 conidia! Spraying now can prevent many sprays later in the season.
|
Timing |
Spores/Rod |
Risk Level |
|
4/26 9PM - 4/27/2024 8AM |
486 |
None |
|
4/28 8AM - 4/29/2024 1PM |
1384 |
Heavy |
|
4/30 1PM - 4/30/2024 2PM |
12570 |
None |
|
5/1 6AM - 5/1/2024 9AM |
6 |
None |
|
5/2 8PM - 5/3/2024 2PM |
2548 |
Moderate |
|
5/4 11PM - 5/5/2024 8AM |
1 |
None |
|
5/7 1PM – 5/8 9AM |
476 |
Moderate |
|
5/11 1AM – 5/11 11AM |
278 |
None |
|
5/12 10PM – 5/13 6AM |
None |
|
|
5/20 11AM - 5/21 12PM |
1020 |
Heavy |
|
5/25 5AM - 5/25 8AM |
24 |
None |
|
5/26 5PM - 5/28 10AM |
21 |
Heavy |
|
6/1 4PM - 6/2 10AM |
13 |
Moderate |
|
6/5 6AM - 6/5/2024 11AM |
1 |
None |
|
6/6 2AM - 6/6/2024 8AM |
0 |
None |
|
6/8 5PM - 6/9/2024 9AM |
2 |
Moderate |
Fire blight
Shoot blight
Shoot tips are starting to harden off this week. We strongly recommend using the combination of 2 ounces Apogee plus 1 ounce Actigard applications starting at king bloom petal fall and continuing every 10 days until shoots harden off. While the shoots are actively growing, they are more susceptible to shoot blight.
I am starting to see both shoot blight and blossom blight crop up in the area. Keep in mind that if you see branches collapsing without classic shoot blight signs, it could be blossom blight further down the branch.
If you have any fire blight infections, please reach out to me at brow1111@msu.edu. The Sundin lab is looking to sample different bacterial isolates throughout the state this year.
Powdery mildew
Primary powdery mildew lesions from overwintering inoculum have ceased sporulation. However, secondary powdery mildew is continuing to spread. I am seeing powdery mildew take over whole shoots this week. Keeping control over powdery mildew now will prevent it from becoming a wider spread issue later in the season. This hot dry weather is excellent for powdery mildew.
Fruit rot
Start incorporating control measures for bitter rot and black rot now. Mummies and fallen fruit contain inoculum for this season. They are beginning to sporulate and infect at this point in the season. Frog eye leaf spot from black rot is now visible across different blocks in the area.
Sooty blotch and fly speck
While these two fungal diseases appear later in the growing season, their control window starts now. Summer diseases need springtime control.
Bacterial canker of stone fruits
Bacterial canker of cherry (caused by Pseudomonas sp.) and bacterial canker of peach and plum (caused by Xanthomonas sp.) is popping up across the state this season. Both diseases are associated with “shot hole” in the leaves, brown dry lesions on the fruit and cankers in the trees. This can also be associated with gummosis production, which is a general stress response by the trees.
If you are seeing infections now, consider summer pruning to remove developing cankers, copper sprays at leaf drop, and dormant copper next spring.
Cracking from rain or wounding in sweet cherries leads to higher likelihood of American brown rot infection. As fruit gets closer to harvest, susceptibility to brown rot increases. Consider if brown rot management is needed. Using Indar may not be effective, even at the highest labeled rate of 12 ounces per acre. Previous research and resistance screening of American brown rot isolates in west central and northwest regions found that most screened fungal isolates had functional resistance to Indar. Find more information about this study. Effective materials for managing American brown rot include Merivon, Miravis and Cevya. Full coverage of all rows will be important to manage this disease.
Insects
Codling moth adult populations look to be decreasing in the area, but first-generation egglaying and egg hatch is expected this week.
Obliquebanded leafroller adults are active this week. My date of sustained catch is June 10.
No green fruitworms were caught in my traps this week.
The next generation of oriental fruit moth is emerging this week.
The second generation of spotted tentiform leafminers is high this week.
Potato leafhoppers are currently in the area. Keep an eye out for them in sticky traps and on the undersides of leaves. Look out for stippled chlorosis, burnt leaf margins or cupping of young terminal leaves.
Woolly apple aphid colonies are still active in orchards. If you used a spirotetramat treatment during petal fall, the first cover timing window, be sure to wait 10 – 14 days after application to make sure the product has taken effect before planning another spray.
San Jose scale crawlers are active in south Michigan this week. I expect crawlers are active in the area, but I have been catching parasitoids only. Keep in mind that controlling this round of San Jose scale crawlers will be easier than controlling future generations this summer.
European red mites are active in the area with visible bronzing in some blocks.
The first spotted wing drosophila have been caught in the area this week. As cherries move towards ripening, ensure they are covered for spotted wing drosophila.
Tufted apple budmoth and rose chafer are also listed as insects of interest for second cover.
For more information about regional reports, please visit the Michigan State University Extension website.
