West central Michigan small fruit update - May 24, 2022

Blueberries are in full bloom and without a late spring, frost damage or drought stress, the fruit load looks excellent.

West central Michigan continued under weather conditions characterized by unseasonal low temperatures and rainy conditions. However, these prevailing conditions are not having a negative impact on small fruit crops, blueberries, raspberries, strawberries, etc.

Up until now, May 24, average daily minimum and maximum temperatures have remained around 48 and 70 degrees Fahrenheit, respectively. Rainy conditions during the last seven days left a rain accumulation that fluctuated between 0.5 and 1.25 inches depending on the location, The heavy precipitation occurred in the vicinity of Grand Junction, Michigan, and the smallest amount around West Olive, Michigan. Current growing degree day (GDD) accumulation varied from 328 GDD (base 50 F since March 1.) to 428 GDD. The largest accumulation occurred at Grand Junction and the minor accumulation at Fennville.

As of May 24, blueberry crop conditions look great. Without late spring frost problems or drought stress, plant growth and development has proceeded without problems. However, over the past two weeks, growers reported low pollination activities by honey bees. However, short periods of sunshine that occurred between rains or overcast sky, bees were very active at blueberry fields.

One potential problem that may need growers’ attention is the presence of mummy berry in fields with a history of mummy berry infections. Therefore, we need to put attention to shoot strikes on tender growths and twig blight. So, keep up with the fungicide applications against mummy berry if you had problems in the past.

The same is valid for Anthracnose fruit rot. This fruit rot disease is becoming the number one problem for many growers. Our 2021 evaluation of the blueberry IPM program indicated that 38% of the growers responding to our survey considered Anthracnose as their #1 disease problem. Therefore, if you are having Anthracnose problems at harvest, you need to initiate its control since the beginning of the bloom period. Do not wait until you see the problem at harvest—by then it is already late to have an efficient fruit rot control.

For more information on Anthracnose fruit rot management, review Michigan Blueberry Facts: Anthracnose Fruit Rot (Ripe Rot) (E3039). Also, please check the 2022 Michigan Fruit Management Guide (MSU Extension Bulletin E-154) for recommended fungicides and doses for managing this fruit rot.

In addition to diseases, growers need to focus their attention on managing the cherry fruitworm and cranberry fruitworm complex. According to our pest phenology model, the forecasted activity for these insects at this time is presented in Table 1.

Table 1. Fruitworm phenology model forecast for the next seven days at west central Michigan.

Insect

First adults

Second eggs

Current Degree Day accumulation (5/24/2022)

Grand Junction, MI

Fennville, MI

West Olive, MI

Cherry fruitworm

238±30

432 ± 15

428*

328

339

Cranberry fruitworm

375±20

460±20

428

328

339

Once again, insecticide applications for fruitworm management at this time should be carried out according with the label to prevent pollinator exposure to pesticides during bloom.

Current recommended insecticides include Grandevo, Venerate, and Intrepid. Please check the 2022 Michigan Fruit Management Guide (MSU Extension Bulletin E-154) for other recommended products and doses.

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