Northwest Michigan fruit update – August 2, 2022

Tart cherry harvest is ongoing in northwest Michigan; fruit quality is still holding but fruit is starting to soften as it ripens. Brix levels are high in tart cherries this season.

Gala apple.
Photo 1. Gala at the Northwest Michigan Horticulture Research Center, Aug. 2, 2022.

Weather report

The month of July was full of beautiful summertime weather. We had some hot days as well as some cooler ones but almost all filled with sunshine. We did have rainfall on Aug. 1, and again, rainfall varied across the region (Table 1). Even with the rain, conditions remain dry for much of the region, which has helped maintain fruit quality. The forecast is calling for continued warm daytime temperatures, and tomorrow the temperatures will rise quickly with potential rain/thunderstorms. By the weekend, daytime highs are predicted to be back up in the low 90s.

Table 1. Rainfall totals (inches) for Aug. 1, 2022.

Enviroweather station

Rain (inches)



East Leland




Elk Rapids






Old Mission


Bear Lake








Crop report

Most sweet cherry harvest is wrapping up. There are still open farm stands and U-pick sweet operations open. Tart cherry harvest is ongoing, and fruit quality has held up surprisingly well. However, fruit is quite ripe, and we are hearing more reports of wind whip and declining quality as we move through the region. We did some brix testing late last week, and the sugar content in Montmorency tart cherry was as high as 17 brix! Fruit is delicious.

Apples are sizing and color is much more visible this week in many varieties (Gala, Photo 1).

Disease report

We had another low cherry leaf spot infection period yesterday, Aug. 1. Overall, leaf spot in commercial blocks is quite low. We have lots of leaves defoliating in our leaf spot efficacy trial at the Northwest Michigan Horticulture Research Center (NWMHRC). Growers are putting on post-harvest leaf spot applications at this time.

With this hot and dry weather, it seems we have dodged the American brown rot bullet in cherries for 2022. As mentioned above, we have observed little brown rot infection in sweet or tart blocks.

Pest report

We have identified small obliquebanded leaf roller larvae floating in cherry tanks in recent days. These larvae have been identified to be small larvae. This insect is not an internal feeder of cherry but rather considered an infestation pest as the larvae are dislodged from the tree with the mechanical shaking process and fall into the tanks as growers harvest. Most larvae are very small, likely first to second instar. These larvae will float to the top in tanks with water. Obliquebanded leafroller larvae can be difficult to identify when they are small as they are not the characteristic green color of older larvae. Growers should look at the brown (brownish black) head capsule: it will appear wider than it is high compared to head capsules of other moth species. The larvae turn more of a green color as they age.

Spotted wing drosophila (SWD) numbers continue to increase, but more slowly than we anticipated. The warm and dry conditions have resulted in a slowed increase in population size. Growers need to keep fruit protected from SWD through harvest.

Today, we released an SWD natural enemy in the northwest part of the state—the first release in Michigan! Ganaspis brasiliensis is a tiny biocontrol wasp that lays eggs inside SWD larvae, and the wasp larvae eat the SWD from the inside out. This biocontrol agent has been in quarantine for over two years, but has been granted approval by APHIS, and releases of this wasp have been made in multiple states. We released G. brasiliensis near cherry orchards in northwest Michigan, and MSU will release more wasps in blueberry later in August. This natural enemy has the potential to reduce SWD populations if it survives in our region. We were so excited about today’s release (Photo 2).

A Ganaspis brasiliensis vial.
Photo 2. Ganaspis brasiliensis vial to be released next to a tart cherry orchard in northwest Michigan.

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