In this Issue:

VEGETABLE NEWS

Vegetable Insect Pest Update

BERRY NEWS

Flower Initiation

APPLE NEWS

Weekly Trap Counts

MDA PUBLICATION

“Greenbook 2007” Highlights Innovative Demonstration Farm Projects

To Our Readers

Order: 2007 Minnesota Vegetable Guide

Insect, Pest Fact Sheets

Flower Initiation

Thaddeus McCamant, Specialty Crops Management Specialist, Northland Community & Technical College

By late summer, most berry plants have stopped growing.  Raspberries are reaching their maximum height.  Strawberries stop producing new runners.  Blueberries stop making new leaves.  In actuality, the plants are still growing, but in ways less visible to the casual observer.  Late summer is a critical time for berry plants, because the roots are still growing.  The plants start storing starch as food reserves and the plants start making flower buds for next year’s crop.

All berry plants make floral buds at the base of their leaves.  You can already see the floral buds on blueberries which are at the tips of the branches and are larger than the leaf buds.  You can estimate the number of blooms blueberry plants will produce next spring by counting the number of floral buds on each branch.  Raspberries have mixed buds with flowers and leaves and healthy canes will produce more flowers per bud.

Buds on a blueberry branch in late summer. The larger upper bud is a floral bud; the lower small bud is a leaf bud.

Strawberry crowns are like blueberry branches that have been compressed to 1-2” in length.  The buds at the base of each leaf can turn into either a runner or a flowering stalk.  During the long days of early summer, the buds turn into runners. The short days of August signal the plant to start making floral buds instead of runners. 

In Minnesota, strawberry plants start making flower buds about August 15.  In cool weather, the plant will start making floral buds in early August, while hot weather can delay floral bud initiation.  With the rain and clouds of the past week, the plants have definitely started making floral buds across the state.  The plants will continue to make floral buds as long as daytime temperatures climb above 50ºF. 

Strawberry growers should try to keep their plants green and healthy as long as possible in the fall.  One reason why people mow their plants after picking is that new leaves can make floral buds without being shaded by old, diseased leaves.  Leaf diseases (on new leaves) in late summer can also lower yields the following year, but thresholds have not been established for most leaf diseases.  Most new strawberry varieties show some resistance to leaf spot and leaf scorch, so the worst leaf disease in Minnesota is powdery mildew.  Powdery mildew typically disappears by mid-September, but can harm plants in August.  If you are interested in controlling powdery mildew, fungicides should be applied before Labor Day.

Make sure your plants have sufficient nitrogen in at this time of year.  Leaves low in nitrogen will die earlier and give you a smaller crop.  Don’t let your plants dry out if hot weather returns.  Never spray 2,4-D between August 1 and November 1.  2,4-D interferes with floral initiation by fusing several flower buds into one large, “doughnut” shaped flower and reduces yield.

As you look at your strawberry fields, remember, they are not just waiting for winter to come.  Instead, they are already busy preparing for next spring.  Your job is to help your plants stay healthy during this busy time.

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Co-Editors: Bill Hutchison (hutch002@umn.edu), Department of Entomology, University of Minnesota, Jeanne Ciborowski, Minnesota Department of Agriculture, Ag. Resources Management and Development Division, and Suzanne Wold-Burkness (woldx018@umn.edu), Department of Entomology, University of Minnesota

The Newsletter is published weekly from May through August, cooperatively, by the Minnesota Department of Agriculture (MDA) and the University of Minnesota (U of MN).  Reports are posted on the U of MN and MDA web sites on Fridays.  If you have suggestions and/or comments, please send your contributions by 4 p.m., Wednesday to Jeanne Ciborowski, 651-201-6217, jeanne.ciborowski@state.mn.us , MDA, 625 Robert St. North, St. Paul, MN  55155.  You can access the Newsletter at the U of MN web site in htm format at: www.vegedge.umn.edu/MNFruit&VegNews/mnindex.htm and at the MDA web site in pdf format at: www.mda.state.mn.us/plants/pestmanagement/ipm/ipmnews.htm

Partial funding for this publication is provided through partnership agreements with the Minnesota Fruit and Vegetable Growers Association (MFVGA) and the United States Department of Agriculture – Risk Management Agency (RMA).  These institutions are equal opportunity providers.

DISCLAIMER

Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current manufacturer directions.

Last Revised July, 2007 by woldx018@umn.edu
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