MSU Extension

So far, the conditions for a healthy, small fruit crop season remain in place with temperate weather conditions and a good amount of moisture in the fields. This is in contrast to the past year’s crop season characterized by severe spring frost events and drought during the rest of the growing season.

As of May 28, 2013, the growing conditions are as follows. For the last seven days there was scattered precipitation in the area with an accumulation of 1.6 and 2 inches of rain. Regarding temperatures, during the same period the daily maximum temperatures fluctuated between the upper 70s and mid-80s with a daily average of 70 degrees Fahrenheit. On the other hand, night temperatures ranged from the low 30s and low 60s with scattered, patchy frosts that occurred during May 24 with minimal impact on the major small fruit crops, blueberries and strawberries.

According to Enviro-weather, the only day when the temperatures dropped around 32 F was during the early hours of May 24 (Table 1). An inspection conducted after the freeze/frost event in Ottawa and Allegan county blueberry and strawberry fields indicated that no major problems occurred as a result of those freezing temperatures. Some blueberry and strawberry fields located in Ottawa County registered temperatures below freezing for a short period of time and irrigation systems were turned on to protect those fields that were in full bloom or in a later stage.

Table 1. Time periods when near freezing conditions occurred around west Michigan on May 24, 2013 (Source: MSU Enviro-weather)

 For blueberries, it is important to mention that most varieties are well into the late stage of the bloom period with Bluecrop, Duke and other early varieties in the “petal fall” and “fruit set” stages. Strawberries are still in full bloom with heavy fruit set with no visible frost damage after the two days of low temperatures. On May 24, growers used the sprinkle irrigation for several hours to prevent frost damage. On the other hand, raspberries are developing with little or no damage after the frost event.

So far, there are relatively few problems in blueberries. Basically, crop management problems are related to weed management. In some fields, Virginia creeper and poison ivy are creating management problems since those species require intense labor and hand applications of the recommended herbicides. Michigan State University Extension horticulturist Eric Hanson reports that blueberry bushes covered by Virginia creeper vine may yield just 20 percent of their potential. This easily equates to a $5 to $10 loss per bush. He indicates that investing 15 minutes to carefully pull vines out of that bush and safely treat them on the ground is money well spent (see the MSU Extension article “Take advantage of fall weed management in blueberries”).

Another problem at this time is the presence of cherry fruitworms and obliquebanded leafrollers. The past week we saw the beginning of the emergence of cherry fruitworms overwintering generation around west Michigan. Depending on the location, the growing degree day (GDD) accumulation varies from 340 to 440 GDD (base 50 F). This accumulation corresponds to the accumulation since March 1 until May 27. According to our research, the current GDD accumulation in the southern counties is approaching the number of GDD required for the beginning of cherry fruitworm oviposition. The egglaying period starts at 432 ± 15 GDD (Base 50 F) accumulated after March 1 (see “New cherry fruitworm tool for IPM in blueberries”).

In addition to cherry fruitworms, we have observed some obliquebanded leafroller larvae activity in Allegan County blueberry fields. This is not uncommon. However, since the same application against cherry fruitworms will take care of the obliquebanded leafroller problem, not every year will this pest require specific applications of insecticide.

Growers must remember to avoid using Intrepid 2 F in areas considered problematic (Allegan, Muskegon, Oceana, Newaygo and Montcalm among others) for some endangered species of butterflies. Growers interested in using this insecticide in the restricted areas should obtain a copy of the Endangered Species Protection Bulletin from the EPA website. Growers should request the bulletin valid for the month when the insecticide will be applied.

If you have problems accessing this information, please email or call your Michigan State University Extension local office for assistance. If your blueberry field is located in one of the restricted areas, confirm if another similar product is available for fruitworm control.

For more insecticide options, please check the MSU Extension bulletin 2013 Michigan Fruit Management Guide (E154).

Blueberry advanced IPM cancelled

We like to inform our blueberry growers that the IPM scout training programmed for May 31 at the Ottawa County Fillmore Complex in West Olive, Mich., has been cancelled. The reason for the cancellation is the low number of people currently registered for the event. Even though we had numerous requests for developing this training, so far only a handful have registered. Because of the importance of the topics that will be discussed during the training, we will try to reschedule this event for a later date during the season.