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ISSUE 4  May 28, 1998


BUCKWHEAT PLANTING TIME IS NOW

    Buckwheat is planted later than small grain, corn, beans and sunflower. It is very sensitive to spring and fall frosts and any seeding should be delayed until all danger of frost is past. Best planting dates are from May 25 to June 10 in most years. Research date of planting studies at Langdon during 3 years indicated significant buckwheat yield reductions when seeding was delayed to June 22 or later.

    It requires about 10-12 weeks after emergence to reach maturity. Buckwheat also is very sensitive to high temperatures and drying winds during blooming time in July and early August. Seedbed preparation is similar to flax. Delayed sowing permits killing several weed crops prior to seeding. Presently, no herbicides are labeled for use in buckwheat for weed control.

    Under good moisture and temperature conditions, buckwheat shades the ground rapidly. A seeding rate of 40 to 50 lb A is recommended. Seeding depth of 1 to 2 inches is desirable in moist soil. Shallow seeding is desirable for rapid emergence. A conventional grain drill can be used and seed treatment is not necessary. Buckwheat has limited response to fertilizers. It’s a heavy user of phosphate with needs similar to wheat. Nitrogen application should remain low because of problems with lodging and delayed maturity. Buckwheat should be swathed when most of the seeds are ripe. In the event of frost, swath promptly to reduce shattering losses.

    For more information on buckwheat production request NDSU Extension Circular A-687 (Revised 1997) available from your local county extension office or the NDSU Extension Distribution Center.


ANALYZING AND EVALUATING CROP PROBLEMS

    Persons working in crop production are often called upon to trouble-shoot in situations involving suspected crop injury from herbicides. These situations require careful analysis and scouting before judgements are formulated. For purposes of this discussion, I would like to define "injury" as stunting, delayed development or malformation of plant tissues which may or may not affect yields. Herbicide injury may result from applications to the crop, from residues in the soil or from drift.

    When evaluating crops involved in suspected herbicide injury, keep in mind that some other factors may have caused the observed effects or the herbicide may be only one of a combination of several casual factors. Look for other possible causes. Are there holes in the leaves or stems or pruned roots from insect damage? Has there been severe weather - wind, drought, hail, flooding, frost, high temperatures, etc. - that could have caused damage, Flooding damage in crops which recently occurred, greatly compounds the diagnosis. Could a disease be involved? Could it be excessive or misplaced row fertilizer or a nutrient deficiency? Or is the effect resulting from a combination of causes?

    Look for patterns of injury in the field. Herbicide injury is often in a pattern associated with soil types or movement of application or incorporation equipment. Observe other susceptible crops or weeds in the area for herbicide effects. For comparison, try to find a check area where no herbicide was applied in the same field.

    If you conclude that herbicides are the probable cause of crop injury, try to determine why the injury occurred. Limited crop tolerance to certain herbicides is sometimes a problem especially under heavy rainfall or sandy soils or on dry, loose soil. Misuse - high rates, wrong chemical, improper method of application, non-uniform application, overlaps, improper applicator adjustments and tillage operations that concentrate the chemical - are some reasons for herbicide injury. Some varieties/hybrids are more susceptible than others. Weather and soil conditions that cause plant stress may make the crop more susceptible to herbicide injury.

    Don’t be too hasty to evaluate the effects of herbicide injury. Give the plants a chance to recover. Check growing points to see if the plants have potential for recovery. Compare injury effects and weed control benefits. Stand counts and injured plant counts are important considerations. Unbiased yield checks in affected and unaffected similar areas of the same field are the best estimates.


EARLY CORN SEEDLING GROWTH STAGES

    As the 1998 corn crop grows and develops, one must understand the growth aspects of corn. This allows more timely management for nitrogen side dressing, rotary hoeing or cultivating or post-emergence herbicide applications. Once the corn seed absorbs water, it begins growth. The radicle (seed root) and plumule (seed shoot) both become visible. Emergence from the soil of the coleoptile is called the VE stage. Next stage is the V1 stage in which the first true leaf with a rounded tip appears. All subsequent corn leaves have pointed tips. When the first rounded tip leaf has a fully formed collar, stage V1 has been reached. The collar is a yellowish band that extends across the leaf at its base. V2 corn would exhibit two visible collars. Successive leaves appear on opposite sides of the stalk. The V3 stage occurs when the third leaf from the base of the plant has a fully formed collar. At this time, the growing point is still below ground. Very little stem elongation has occurred at the V3 stage. The corn seedling is approximately 6-7 inches tall. From V2 to V5 stage, early side dress applications of nitrogen can be safely applied..

    Destructive hail, wind or frost which damages the exposed leaves at V3 will have little or no effect on the below-ground growing point or final yield. Flooding however, at any time when the growing point is below the water level can kill the corn seedling in a few days if temperatures are high. After V5 and at V6 the growing point has moved above the soil surface. The stalk is beginning a period of greatly increased elongation. As the growing point comes to the soil surface, ear initiation has begun. Also, keep in mind that at the V6 stage, lateral roots can extend 12 to 14 inches each direction from the row. Therefore root pruning can be a problem if the corn is cultivated with the shovels set too deep. With 22 inch row spacings this problem could be even more severe. See table below:

Vegetative and reproductive stages of a corn plant

Vegetative Stages Reproductive Stages
VE emergence R1 silking
V1 first leaf R2 blister
V2 second leaf R3 milk
V3 third leaf R4 dough
* R5 dent
* R6 physiological
*       Maturity
V(n) nth leaf  
VT tasseling  

Duane R. Berglund
NDSU Extension Agronomist


POTENTIAL FOR HEAT CANKER AND WIND INJURY

    With the potential for warm sunny weather in many portions of North Dakota this week heat canker maybe observed on small grains. Heat canker is most common on plants less than 4 inches and is favored by dark soils and hot sunny days before plants a large enough to provide shade. Once jointing occurs and stem elongation begins the potential for heat canker is minimal. Heat canker is caused when plant tissues at the soil surface are injured by the hot soil. Typical symptoms are white bands on one or more leaves. These bands appear first at the soil surface but as plant growth occurs they will extend above the soil surface. In more severe cases stems may be constricted at the soil line and the seedlings may fall over.

    In most cases of heat canker on small grains the growing point of the seedling is not injured. Most plants will recover with minimal affect on crop productivity.

    Severe leaf damage can occur in small grains as a result of wind blown soil particles which sand blasts the young seedlings. This type of injury only becomes serious when the growing point or the flag leaf is severely injured. Grain in the three to five leaf stage should recover. Plants in the one to two leaf stage may be more vulnerable because they lack carbohydrate stores to grow new leaves. In most instances with good soil moisture and cool temperatures these plants will recover.

    Any stress during small grain development will result in reduced productivity. While yield of small grains is determined at harvest, yield potential is determined early in the developmental phases of growth. Yield is determined by the number of heads, number of kernels on a head or head size, and the weight of the kernels. Tillering in small grains typically begins at around the three leaf stage and continues through the five to six leaf stage; varying with environment and variety. Head development is initiated during the four leaf stage. Consequently stress during these early stages, including the two previously discussed, has a negative effect on the final yield of a crop.

    The amount and kind of stress will determine how much potential yield is lost. The most dramatic reductions in yield due to stress during early development are typically from drought, high temperature, and fertility. Further more, high temperatures and limiting moisture tend to compound each other. The relative effect of heat canker when the growing point is not damaged is relatively minor compared to that of limited moisture and high temperatures. Stress during early development, while it does impact productivity, is rarely cause for destruction of an established crop.

Michael D. Peel
Extension Agronomist, Small Grains


LATE SPRING PRUNING TIPS

    With the warm spring weather through the entire month of May and with many areas getting ample rainfall, plant growth is proceeding faster than expected. Many question if additional pruning is acceptable at this time. The answer is a qualified "yes" - because of two important considerations:

    1. The plants that are subject to fireblight bacterium should not be pruned unless necessary. These would include the apples, crabapples, cotoneaster, pears, mt. ash, and Juneberries. If any have had a history of past problems with fireblight, it would be a good idea to begin a preventative spray program with streptomycin either alone or in combination with benomyl or captan. Do not apply within 30 days of harvest with pears or 50 days of harvest with apples. Spray after a hail storm. Streptomycin is not registered for use on cotoneaster, crabapple, or mt. ash.

    Pruning the "bleeders" now is recommended. These would be the maples, birches, elms, and black walnuts that were not pruned during the dormant season. None should require heavy pruning, just "touch up" aesthetic cuts to help them fit into your landscape better and withstand the vicissitudes of nature.

    2. Flowering shrubs such as the forsythias, lilacs, and spirea can be pruned now if needed, but get the job done before July 1. This is because the flowers for next spring season form in mid-summer on the current season’s growth. Pruning in summer or fall would remove most, if not all, of the potential flower buds for 1999. Try not to "lollipop" these shrubs with an electric hedge trimmer, as that eventually destroys the natural shape of the plant. Prune selectively instead, removing those canes that are old and unproductive or unsightly. Make the cut right to the base of the plant.


A DISEASE OF GROWING INFAMY

    This disease is becoming as common an occurrence as dandelions in the lawn in early spring - Black Knot of chokecherries. The fungus (Plowrightia morbosum) causes conspicuous coal-black knotty swellings on twigs and branches of chokecherries, the landscape tree commonly planted across our region. It also occurs on cultivated plum trees.

    Environmental conditions of recent years - wet, humid weather; high winds; and damaging hail - have all contributed to the spread of this disease. If these knots only looked ugly, there would be no problem, and I could make light of them, much like I do with nipple gall of hackberry trees. But this fungus kills the tree a branch at a time, until it has lost any landscape value, and the tree must be removed.

    The best immediate action is to prune out and destroy all infected branches, making the cuts at least 2 to 3 inches below the swollen knots. Remove any wild plums or cherries in the vicinity if possible. If caught and carried out early, an annual pruning in conjunction with a spraying program, may save the infected tree. Lime sulfur, sprayed during the spring dormant season, and followed with Bordeaux mixture before flowering and again after petal fall.

    I find many people are loathe to prune their trees and attempt control using a spray schedule alone. Keep in mind the sprays will not "cure" the already infected branches. They must be removed by pruning first. Other management approaches would include checking cultivar selections of plum to see if resistance to this disease is listed, attempting to plant plum or chokecherry selections as far away as possible from any native plantings that may be infected with black knot. Finally, consider planting other species of Prunus which are not susceptible to black knot. Neither black cherry (Prunus serotina) nor pin cherry (Prunus persica) are hosts of this disease.

    Like most diseases, the infection is often not noticed until it has gone too far. Inspect any plum, chokecherry, or Mayday trees (Prunus padus) for the onset of this disease, and prune out the affected branches immediately. Caught early enough, the specimen or fruit tree may be saved and continue to add value to your landscape and provide some good fruit to enjoy!


Ron Smith
NDSU Extension Horticulturist and Turfgrass Specialist


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