MSU Extension

Crop stages

In Van Buren County, Bluecrop and Rubel in Paw Paw, Grand Junction, Gobles and Covert, Mich., are starting petal fall, Jersey are at 10 to 25 percent bloom, and Elliot are nearing 10 percent bloom. In West Olive, Mich., in Ottawa County, Bluecrop, Rubel and Blueray are at 10 to 25 percent bloom, Jersey are at 10 percent bloom, and Elliot are at trace bloom.

Weekly insect pest report

We are still catching cherry fruitworm moths in traps at all the farms we visit in Van Buren and Ottawa counties, however the numbers we caught last week were low due to cool weather. Cherry fruitworm flight should increase with the warm up that will occur this week. Also, with this warmer weather, we will reach the growing degree day (GDD) accumulation for the start of cherry fruitworm egglaying in Van Buren County by the middle of the week.

Cherry fruitworm egglaying begins approximately 100 GDD (base 50°F) after cherry fruitworm moths are caught consistently, and fields with a history of cherry fruitworms should be protected at this time using a bee-safe insecticide. Growers and scouts can check growing degree accumulations either on-site if weather monitors are in place, or online from the nearest Enviro-weather station. (See this example of current and predicted growing degree days from Enviro-weather stations in southwest Michigan.) The start date at the top of the Enviro-weather page can be changed to the date when moths were first caught on your farm to get growing degree days accumulated since moths were caught at your sites. We do not expect cherry fruitworm egglaying to begin at our Ottawa County sites until the weekend (May 5).

We are still catching the same contaminant moth in cherry fruitworm traps, although it appears the flight of this insect is declining. This moth is larger than a cherry fruitworm moth and has mottled dark patterns on the wings, while cherry fruitworms are dark with a series of thin, shiny bands across the wings. See this previous article for pictures to help distinguish these two moths and for more information on fruitworms.

Growers and scouts should continue checking cherry fruitworm traps, and cranberry fruitworm traps should be in fields already to ensure detection of the start of the flight of this pest. We may see the first cranberry fruitworm moths at some warmer sites in Van Buren and Berrien counties by the end of this week. Traps should be baited with a pheromone lure and hung in the top half of a bush on the perimeter of a field. Place traps in known "hot spots" where the pest has been seen in the past. These areas are generally adjacent to woodlots, so if you are not sure if you have cranberry fruitworms, these are the best areas to begin trapping. Traps should be checked twice weekly until moths are caught consistently. This will identify fields with pressure from cranberry fruitworms, and will also enable the identification of the start (biofix) of cranberry fruitworm flight, when moths start to be trapped consistently.

At 100 degree days (base 50) after biofix, sites with a history of cranberry fruitworm infestation should be protected with a bee-safe insecticide such as Intrepid at 8 oz/acre. The immediate post-bloom timing is the most important timing for fruitworm control, with many more options available for control, once honey bees are removed from the field. A detailed article about fruitworm management has been posted at the MSU Extension News website.

At the farms we scouted, we did not see leafroller larvae or feeding damage, but growers and scouts should be on the lookout for these early season pests. To scout for leafrollers, examine five flower clusters and five leaf clusters on 10 bushes on the field border, and five flower clusters and five leaf clusters on 10 bushes in the interior of the field. Look for leaf or flower clusters that have feeding holes or webbing in the cluster. These pests are generally not economically important in Michigan, but if 3 to 5 percent of buds have feeding damage, growers may want to consider a specific control targeting these insects. View more information and pictures of leafrollers from our scouting pages posted at blueberries.msu.edu. It has been our experience that sprays targeting cherry and cranberry fruitworm are also well timed to effectively control other moth pests such as leafrollers, spanworms and tussock moths.

Gall wasp emergence at infested sites in Ottawa County slowed over the last week because of cold weather, but we should see increased emergence over the next week as the weather warms up. Growers should not use bee-toxic insecticides for gall wasp control at this time in fields where bees are foraging.

Newsletter update

The MSU Blueberry Team has moved to a new format for information delivery in which timely articles and scouting reports will be prepared for online delivery at the at the Michigan Blueberry Facts website, or www.blueberries.msu.edu, and MSU Extension News. If you want to get an email alert when new articles are posted, just go to the bottom of the Michigan Blueberry Facts website, and sign up for the RSS feed. Or just check back regularly for new information, such as these scouting reports. Please let us know what you think of this new format.