AgAlerts 2002 From Griggs County
By John Swenson, Griggs County Extension Agent

Issue # 6, June 4, 2002

Canola Toxicity to HRSW

    This field of HRSW followed canola that was hailed out.  The large amount of straw and seedlings most likely caused some toxicity problems this spring.  The following pictures illustrate the swaths that average 18 feet apart.

Canola Toxicity in HRSW    Canola Toxicity in HRSW    (click on picture to enlarge)

Mosquito Controls

    Environmental conditions have not been very favorable to mosquito hatching or development.  In preparation for the possible invasion of this insect, there are a few treatments that will help control the hatch and thus reduce the possible problem.  Where standing water is a problem around the home or farmstead, one of the recommended treatment programs is the use of Bacillus thuringiensis var. israeliensis (B.t.i.).  Products include:   

    A bacterial larvacide that is non-toxic and will not harm non- target, beneficial organisms. Higher rates are recommended in water with high organic content (e.g., sewage disposal systems, waste lagoons). Pretreatment is recommended when larval populations are high, aquatic vegetation is dense, or the water is highly polluted with organic material.  For more information on mosquito life cycles, larval and adult control, link to the this publication.  NDSU Bulletin E-72, "Mosquitoe Management".

Giant Mosquito has been located near Luverne ND.

mosquito1.jpg (197465 bytes)     (click on picture to enlarge)


 Effect of High Temperatures on Wheat Yields

    With the majority of the HRSW crop being planted late, high temperatures during the early vegetative stage can have an effect on yields.  HRSW is a cool season cereal crop and prefers growing temperatures under 80 degrees.  The crop will grow faster under warmer conditions but this reduces the number of days the plant can intercept sunlight, and could expect less yield since sunlight is the driving force of growth.
    Yield factors for HRSW include 1.) Plant population, 2.) Number of spikes and spikelets and 3.) number of spikelets that produce a seed.  Most of the crop is emerging with good plant populations so we are getting past the first yield factor.  As the crop reaches the 4-5 1/2 leaf stage, tillers and spikelets develop.  This is when high temperatures can have an effect on yield.  Experimentation has shown that high temperatures during the 4-5 1/2 leaf stage, results in reduced number of spikes (tillers), spikelets or shorter spikes.  We experienced a major reduction of spikelets in the 1988 growing season due to very high temperatures (90 -100+ degrees) during this stage.  It wasn't uncommon to see spikelet  counts of 9 to 11 per spike.  

Tillering in Spring Wheat

    There are two types of stems in wheat.  A wheat plant has a main stem and a variable number of tillers. Wheat tillers in an orderly way.  At the seed piece there are three nodes.  One node can form a tiller, termed the coleoptile or T 0 tiller.  The other two nodes can form adventitious roots.  The plant decides whether or not to initiate this tiller when the main stem has about 2 to 2.5 leaves.  Most varieties grown in ND don't initiate a high percentage of T 0 tillers.  At the base of the first leaf there are five nodes.  One of these nodes can form a tiller, called the T 1 tiller.  The other four nodes can produce adventitious roots.  This is a vigorous, productive, and important tiller.  The plant decides whether or not to produce this tiller when the main stem has about 2.5 leaves.  There are also five nodes at the base of the second leaf.  Again, one node can produce a tiller, the T 2 tiller.  The other four nodes can produce adventitious roots.  The plant decides whether or not to initiate this tiller position at about the 3.5 leaf stage.  This is the most important tiller of spring wheat.  
    The initiation of important positions like the T 1 or T 2 tillers is not automatic.  If wheat is under stress between the 2 to 3.5 leaf stage of the main stem (only 2-3 weeks after emergence), these critical tillers and the adventitious roots associated with them, may not be formed.  There is no mechanism to initiate these tillers and roots later in the growing season.  Stresses that reduce tiller initiation include seeding too deeply, inadequate fertility, soil compaction, heat or drought.  Many other tillers can be produced late in the growing season.  However, these and other late forming tillers are often too immature to form a head when the main stem gives the order to do so (about the late 4 to early 5 leaf stage).  These late tillers either abort during hot weather in July or linger to form green, immature, nuisance heads at harvest.  Late-forming tillers are no substitute for the critical T 1 or T 2 tillers.
    The degree of tillering determines the number of heads per acre.  An average spring wheat yield of 35 bushels/acre can be produced with about eight main stems/ft of row (6" spacing) and the average of one vigorous tiller per plant.  However, for a high yield potential, a good stand of main stems and high (>90%) initiation of the T 1 and T 2 tiller positions are needed.  With a 6" row spacing, there should be about 12 plants/ft of row.  A 90% initiation of T 1 and T 2 tillers is a practical goal.

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