AgAlerts 2001 From Griggs County
By John Swenson, Griggs County Extension Agent

Issue # 4, May 29, 2001

• Harvesting Prime Alfalfa Hay

• Soybeans, How Late Can I Plant?

• Ash Anthracnose

• Forest Tent Caterpillar

Harvesting Prime Alfalfa Hay

    Dr. Ken Albrecht of the USDA Dairy Lab in Madison, Wisconsin developed the PEAQ (Predication Equations for Alfalfa Quality) system in the early 1990's.  The PEAQ system is based on observing and/or measuring two alfalfa growth characteristics within a target area of the field, the most mature stem and the tallest stem.  The recommended maturity stage to begin harvesting changes with the height of the alfalfa.  The taller the stem, the earlier harvest must start in order to harvest prime hay.  For example, an alfalfa plant that is 20 inches tall can be harvested at late flower for the most mature stem and still make prime hay; whereas, a 30 inch tall alfalfa plant must be harvested by late vegetative stage in order to make prime hay. The following table show what growth stages are used in the PEAQ system.

To obtain greater than 151 Relative Feed Value (RFV) in the bale, harvest must begin when the PEAQ system estimates the forage quality at 175 to 180, since harvesting losses will reduce the quality of the final product.

Soybeans, How Late Can I Plant?

    Several questions have arisen as to when to stop planting soybeans.  Griggs County is in maturity Zone 4.  Soybeans with maturity group 00 or earlier are recommended.  As we approach June 1 soybeans that have a maturity rating higher than 00 are not recommended.  Some factors that can affect maturity include planting depth.  The longer it takes to germinate and emerge will increase maturity.  So if soil conditions are favorable for shallow planting (1"- 1 1/2" depth) can help.  Also, what type of summer will we have.  In the past few years we have had good growing degree days along with a late fall that helped maturity.  This is the big question, will it happen again in 2001?  Try avoid putting soybeans under any stress due to herbicide injury or alkaline soil conditions.  This will increase maturity.  
    Late planting can result in yield reductions.  NDSU estimates that soybeans planted last week (May 21-27) could have a 5 to 10% yield advantage over soybeans planted this week (May 28-June 1).  So plant early maturing varieties in favorable soils to give soybeans a better chance of maturing and avoiding frost injury. 

Ash Anthracnose

    The cool wet conditions  of the last week could have affected green ash trees that were just beginning to leaf out.  These conditions favor the infection of ash anthracnose which is caused by a fungus called Gnomoniella fraxini.  Besides premature leaf drop, symptoms include deformed and discolored leaves.  Leaves may show brown to black lesions, often associated with leaf veins; and the leaves may curl along the main vein.  While premature leaf drop is dramatic, it is not usually detrimental to the tree since a flush of new growth will follow.  If defoliation occurs over a number of years, this could have an affect and cause early decline.  
    The best management for this disease is to rake up and destroy all the fallen leaves.  This will reduce the amount of pathogen available to cause new infection.  Fertilizing with high ratios of nitrogen to promote growth will provide for optimal refoliation.  The treatment with a fungicide is not practical and expensive for large well established trees.  However, smaller, newer trees will benefit from these applications.  Treatments with a chlorothalonil product (Daconil Ultrex, Ortho Multipurpose Fungicide Daconil) after the first infection can reduce subsequent infection.

        (click on picture to enlarge)

Forest Tent Caterpillar

    Reports of forest tent caterpillar (FTC's) in eastern North Dakota are increasing.  This insect has been consistently causing problems in North Dakota since 1997.  Since defoliation is early in the year and healthy trees will usually develop a second flush of leaves, tree health is usually not affected.  However, the insects can become a nuisance during early to mid June.
    Forest tent caterpillars overwinter as fully developed larvae in egg cases which are laid in masses encircling small twigs.  The tiny caterpillars emerge in spring and can often be found first near the egg masses.  Unlike other tent caterpillars, FTCs do not produce large, unattractive webs.  The caterpillars do congregate on stems and branches during the day.  FTCs feed on ash, aspen, basswood, birch, cottonwood, elm, maple, oak, poplar, and other hardwoods.  As the larvae enlarge, keyhole-shaped spots along their backs and brad bluish lateral bands become evident.  These markings make identification relative simple.
    Controls:  Bt products works well to control young caterpillars, while permethrin, pyrethrins or other insecticides are needed for older larvae.  These controls work well for younger trees but become harder to apply to older mature trees.  Always follow pesticide labels for rates and application directions.
    Ensuring that trees have adequate water can help trees recover from early season defoliation; however do not fertilize trees during FTC outbreaks. 

Please Contact Our Office For Additional Information
E-mail: griggs@ndsuext.nodak.edu
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