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Apple maturity and integrated pest management information.
The Grand Rapids, Michigan, region is expecting cooler temperatures this week with nighttime lows in the 50s and 60s. This will help fruit reddening. While rainy conditions and potential thunderstorms are apparent on Tuesday morning (Aug. 6), the rest of the week will have minimal rain and moderate temperatures.
Peach harvest continues in the area and early pear and apple harvest is underway.
Please keep in mind that stop-drop materials can be very useful to manage harvest windows during this early season, especially if color is a concern, and the windows to effectively use them may be coming up sooner rather than later.
Premier Honeycrisp and Wildfire Galas will be maturing in the next couple of weeks in this area.
The first varieties, like Lodi and Pristine, are already harvested.
Gingergold apples were sampled at two locations in Kent County this week. These apples are nearing maturity and developing a nice blush color. They still taste a bit starchy.
Collection Date
Firmness (lbs)
Soluble Solids (°Brix)
Starch (1-8)
Paulared apples were sampled at two locations in Kent County this week. These apples are mature and are being harvested this week. They taste excellent. I am seeing a bit of watercore in these apples, which is not too surprising.
Collection Date
Firmness (lbs)
Soluble Solids (°Brix)
Starch (1-8)
Zestar! apples were sampled at one location in Kent County this week. These apples will be harvested this week as well.
Collection Date
Firmness (lbs)
Soluble Solids (°Brix)
Starch (1-8)
Growing degree day (GDD) accumulation since Jan. 1 as of Aug. 6, 2024
5-year average
Stations
GDD42F
GDD50F
GDD42F
GDD50F
McIntosh growth stages
GDD42F
GDD50F
6th cover
7th cover
8th cover
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.
Keep up control measures for bitter rot and black rot. Be sure to save a shot of Merivon for directly before harvest.
If you have sooty blotch and flyspeck developing, their symptoms should now be visible. Please keep control for these fungal diseases in mind. The Enviroweather model can take your recent fungicide applications into account for making management decisions.
Cherry leaf spot is much more widespread than typical years, even in orchards with consistent programs. We are now seeing some early defoliation associated with cherry leaf spot, which can both harm this year’s crop and the overall tree health. Keep in mind that cherry leaf spot lesions look like small, reddish-purple dots (2-3 millimeters across). A key symptom is white, fluffy fungal growth on the underside of the lesions. These lesions can overtake leaves and lead to defoliation. We are especially seeing these symptoms in leaves that also have bacterial canker symptoms. While this disease is primarily thought of in tart cherry production, it can certainly impact sweet cherries too.
With cherry harvest now concluded, I am seeing orchard defoliation in the area more commonly. Keep in mind that stopping control at this point in the year will limit the amount of carbohydrates being stored by the tree and can increase the risk of winter injury. This can also impact next year’s fruit set.
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 of these 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.
While cherry harvest is over now, peaches are also susceptible to 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 in cherries. 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.
The second generation of adults are now flying and populations will be declining this week. Egg deposition will be finishing out this week. Eggs are continuing to hatch, but in lower numbers. Consider this article on codling moth management .
Obliquebanded Leaf Roller populations are present in low numbers across the area.
The third generation of oriental fruit moth has concluded their peak adult emergence. Keep an eye out for fruit damage at this time in addition to shoot tip damage.
For more information about regional reports, please visit the Michigan State University Extension webiste.
