Issue #3, May 15, 2004

• Concur (tm) Seed Treatment Receives Section 18 Exemption

• Spring Frost Damage to Crops

• Cold Temperatures May Cause Crop Injury or Reduced Weed Control

Concur (tm) Seed Treatment Receives Section 18 Exemption
The following is a news release from the ND Agriculture Department

BISMARCK - Agriculture Commissioner Roger Johnson has declared a crisis Section 18 exemption for Concur(tm) Seed Treatment as an on-farm, seed treatment to control wireworm in sunflowers.  The exemption takes effect Monday, May 17, and expires June 1, 2004.  Johnson said he declared the exemption because lindane, the insecticide of choice for treatment of late-planted sunflower seed, is no longer available for this use.  "The unexpected loss of lindane means producers who plant their sunflowers later in the season will have no protection from wireworm, one of the most serious sunflower pests," Johnson said.  "Since wireworms can cause up to 15 percent yield loss in late planted sunflowers, I am confident that this situation meets emergency criteria."  The exemption allows treatment of sunflower seed at a rate of 8 ounces of  Concur(tm) per 100 pounds of seed.  Treated seed must also be labeled in accordance with the U.S. Seed Act.  Producers must follow all instructions, precautions and warning on the product label, as well as all use directions on the exemption label.  They must also have a copy of the exemption label in their possession during application.  Concur(tm) is manufactured by Gustafson, LLC, and marketed by Agriliance, LLC. Both companies have given full support for the crisis exemption.  North Dakota is the nation's leading sunflower-producing state, growing 59 percent of the U.S. total of oil sunflowers and 48 percent of confectionary sunflowers.  

Spring Frost Damage to Crops

Temperatures are expected to drop below freezing in areas of North Dakota and NE Minnesota tonight and later this week.  What type of damage will be result with some of our crops now just emerging and in vulnerable stages and subject to frost damage? T emperatures below 32 degrees F will cause water in plant cells to freeze and resultant ice crystals will kill cells by damaging cell membrane systems.  How different crop species react to freezing temperatures depends on where growth is taking place, where growing points are, and if cells have built in systems to prevent ice crystal formation.  Seedlings hardened by continuous low night and day temperatures are more resistant than seedlings hardened by alternating high and low day and night temperatures.  The cool nights we have had recently may have helped in the hardening process.  There are considerable variety differences in all crops and no research has been done on the varieties we are currently  growing.  
CORN: Corn plants less than 6 inches tall (V-5) or less will recover from frost because the growing point is still below the soil surface and usually not damaged.  Lethal cold temperature is a concern since a corn plant’s growing point region is relatively protected from the effects of simple frost while it remains below the soil surface.   Lethal cold temperatures (28 F or less) can penetrate the upper inch or two of soil, especially dry surface soils, and kill plant tissue directly, including coleoptiles and growing points.  Hopefully the rains of last week have wet the soils adequately to provide a buffering effect to the cold penetration.  Non-lethal injury by cold temperatures may cause deformed elongation of the mesocotyl or physical damage to the coleoptile in non-emerged seedlings, resulting in the proverbial "cork-screw" symptom and subsequent leafing out underground.  Historically very few corn fields have been destroyed by spring freezes.  Very limited research has been done on this subject.  Damage to seedlings could be (1) complete killing (2) injury so severe theat the resulting seedling is weakened to the point where it will never develop normal reproductive systems, 
(3) injury evident but seedlings remain vigorous and complete recovery can be expected.  Environmental conditions before or immediately after a low temperature greatly influence the extent of freezing injury.  If the temperature drop is gradual, plants are in better condition to resist injury and can stand surprisingly low temperatures.  Similarly, slowing rising temperatures after a frost and satisfactory soil moisture conditions are desirable to aid recovery.  Drought, wind and high evaporation are likely to aggravate the frost injury and lessen the chances of recovery.  
SMALL GRAINS: Our cereal grains will lose leaf tissue that freezes.  New growth will follow at the growing point before jointing is protected below ground.  In some cases the eventual maturity date may be delayed.  In some areas this has already occurred and new leaves have emerged and the crop is growing.  However, several frosts and destroyed leaf tissue can and will greatly weaken the growing cereal grains and may result in yield reduction.  Broad leaf crops that have their growing point at the top of the plant are more susceptible to frost damage than our grass species.  Soybeans, for example, are quite sensitive to frost.  Dicotyledonous plants such as sugar beet, sunflower, soybean, dry bean, and flax are more easily killed by frost than are small grains.
SOYBEANS: Soybeans are easily damaged by frost in the 28 to 32 F range.  Temperatures of 28 F for any extended period of time can completely kill soybean plants (stems and leaves).  During the early seedling stage (VE to VC), soybeans have some tolerance to temperatures of 29-30 F for short periods of time.  If the seedlings have been somewhat hardened off by cool temperatures for several days, then temperatures as cool as 28 F can be tolerated. Once true leaves emerge (V1 and V2) soybeans become more susceptible to freezing temperatures below 32 F for any extended period of time.  Unifoliolate leaf stage is slightly more frost tolerant than first or second trifoliolate stages.  
SUNFLOWER: Sunflower in the cotyledon stages can withstand temperatures in the 25-26 F range for short periods if they are just emerging from the soil.  Sunflower in the 2, 4 and 6 leaf stages become more sensitive with each development stage and terminal bud damage can occur. It’s known that if sunflower is in the 2-leaf or V2 stage then 26-27 F would be the lower limit. For the 4 and 6 leaf stages the 28-29 F is the lower limit.  Also, the tolerance can be influenced by the hardening off process.  That is if it is cool or cold for several days such as 33-34 F at nights and the seedlings become somewhat accustomed to the lower temps, then perhaps  a little better tolerance to lower temperatures.  It’s  going from warm temps to extreme freezing temperatures all at once that are the most injurious.  Wet soils and some dew also help in reduction of freeze injury.  Cold and dry conditions help add more to seedling injury.  
ALFALFA: Alfalfa will be damaged by temperatures in the mid to low 20's.  Growth of alfalfa is from the tip of the stem.  With frost damage the top will bend over and growth of the tip will cease.  Plan to take the first harvest as soon as field dries up enough for good equipment performance.
OTHER CROPS: Temperatures on 32 degrees F and below will kill buckwheat or drybeans, while canola and crambe will tolerate temperatures in the low 20's.  Crops such as field peas or lentils have good frost tolerance since growing points remain below ground in the seedling stages.  (Article written by Duane Berglund, NDSU Extension Agronomist)

Cold Temperatures May Cause Crop Injury or Reduced Weed Control

    Temperatures following herbicide application determine crop safety or injury. Cold temperatures cause concern for crop safety and possible reduced weed control. Plants degrade herbicides by metabolism, but plant metabolism slows during cool or cold conditions, which extends the amount of time required to degrade herbicides in plants. Rapid degradation under warm conditions allows crop plants to escape herbicide injury. However, cold temperatures during and after herbicide application increases degradation time of the active ingredient and may result in crop injury. Continued cold night and day temperatures cause metabolism to shutdown in plants, preventing herbicide degradation. However, herbicides may be sprayed following cold night-time temperatures if day-time temperatures warm to at least 60 degrees.    
    ACCase inhibitors, such as Achieve and fenoxaprop (Dakota, Cheyenne, Puma), may cause crop injury and give greater weed control when cold temperature follow application. Fenoxaprop is more active on grass weeds during cold temperatures. Risk of crop injury is much greater from fenoxaprop in cool/cold conditions.
    Wild oat is a cool season grass and is more sensitive to products containing fenoxaprop (Dakota, Cheyenne, and Puma) during cool rather than warm or hot conditions. Green and yellow foxtail are warm season grasses and may shutdown under cold conditions resulting in reduced control. Many broadleaf weeds are warm season plants and are controlled better during warm/hot conditions under active plant growth with sufficient moisture.
    Check the label for any temperature warnings for the herbicides you are planning to use.