ISSUE 4    May 25, 2006


Algae in stock and nurse tanks can be a nuisance for both animals and for chemical application especially with hard water. Adding copper sulfate to the water will take care of the problem until the tank is refilled with fresh water. The process must then be repeated.

Dissolve 1 ounce of copper sulfate in 1 pint of water in a glass jar. Add 0.25 pt/1000 gallons of water. The copper sulfate will not affect herbicide and weed control. An alternative for nurse tanks is to paint the entire tank black. This eliminates the sunlight requirement which prevents algae growth.



Glyphosate passes through plant cuticles slowly as compared to other herbicides (see Glyphosate or Roundup brands in table titled, "Minimum Interval between application and rain for maximum POST weed control" - page 68 in the weed guide). Absorption of glyphosate is low compared to other weed species. Studies with radio-labeled glyphosate show only 20% absorption in some weed species. The labels of some glyphosate formulations give a rainfree period of only 0.5 to 1 hour but at least three weed scientists in the U.S. have shown decreased weed control with simulated rainfall within 4 to 6 hours after application with these formulations. Ammonium sulfate fertilizer applied with glyphosate allows inactivation of antagonizing salts in spray water and forms ammonium-glyphosate which enhances absorption and penetration through plant membranes.

Glyphosate is strongly absorbed to soil constituents and organic matter as evidenced by no soil residual after application. Dust and organic matter on leaf surfaces inactivates glyphosate. If glyphosate absorption is slowed during cold weather by hardening of the cuticle (which may or may not be true) then glyphosate on the plant surface may be susceptible to inactivation from dust especially if the wind blows. This applies also using slough water for spraying. Mud and soil in slough water will inactivate glyphosate. Addition of NIS or AMS will not overcome inactivation from dirt. Glyphosate is strongly and irreversibly absorbed to clay particles and organic matter.

Drs. Jingkai Zhou and Cal Messersmith at NDSU recently completed research on overcoming dust inactivation of glyphosate on eastern black and hairy nightshade. The paper is in review for publication so specific information cannot be given until accepted for publication but adding AMS or NIS only partially overcame antagonism and petroleum or methylated seed oil adjuvants did not reduced antagonism at all.

Do not add more water to increase spray volume and make spray droplets more dilute. Greater glyphosate efficacy results (with or without dust) in lower spray volume when spray droplets are more concentrated with glyphosate herbicide.



I get many calls and emails like the one below each day. As I answer these questions I realize that I use two main publications each time which may be useful to you.

Resource #1 - Remember the old Green Bibles? Even if you have an old one the good stuff is still in there. There is a certain section that, to me, is the most valuable parts of the book. The section is called the Pest Use Index and is located in the Section F (the section before the individual pesticide labels). The Weeds section comes after the Insect section and in my 2006 edition, the weeds part start on page F104. This section shows all herbicide labels that lists the weed. The herbicides may only suppress the weed or may describe more specific information for control so do not assume it will give complete control and always read each label before use.

If you have correctly identified a weed and want to know what controls it - this is a good place to start!

Lets use the Green Bible to answer the email below.

A producer brought in a plant from his field that we think is Cinquefoil (probably rough or sulfur). He applied 1 qt glyphosate (1 lb/A) + 2 fl oz dicamba per acre in an attempt to control the weed. The mixture shortens the plant and caused some disfiguration of this perennial plant but has not killed it. He has tried for a couple of years to control it but the weed keeps reproducing and spreading to other parts of the field. The operator is a no-tiller so tillage is considered a last resort. Any ideas as to what he might use for the control of this weed would be appreciated.

Answer: On page F111 of the Green Bible under cinquefoil it shows many products including Crossbow, Escort, Milestone, Remedy, Telar, Tordon, and 2,4-D.

I tried to access the information from the web site but required registration and password to get in. Maybe there is a way but this is one time when hardcopy is the easiest way to get the information needed.

Resource #2 - The other warehouse resource where one could find control of obscure weeds is a publication that started out as a USDA publication (the first edition I could find anyway) Farmers Bulletin No. 2183. "Using Phenoxy Herbicides Effectively" (1962) which is a compilation of the response of about every known plant to 2,4-D, MCPA, dicamba, picloram, and glyphosate. An expert committee revised it since then to fill in the blanks and it now called "Systemic Herbicide for Weed Control". I have made

several attempts and inquires to find a web site location but have failed. To remedy this, I will have (by the time this Pest Report is written) added this option on my NDSU Weed Science Web Page - address on the cover of the weed guide (



Because the ND Weed Guide is printed in December before the new herbicide prices are released for the coming season, the prices in the 2006 weed guide still contain the prices for the 2005 year and do not reflect 2006 prices. The herbicide price list has been updated for 2006 and can be found on the web version of the weed guide found at the NDSU Weed Science web site:

This web address is listed on the cover of the weed guide.

Herbicide prices do not include cost of such additives as surfactants, oils, fertilizer or application costs. Prices may vary depending on area of the state, wholesaler, bulk discounts, seasonal changes, quantities purchased and particular programs the manufacturing company offers. Prices are averages based on statewide dealer survey for small quantities. Producers should consult local agricultural product suppliers for exact price of each product in their area.

For 2006 summary, herbicide prices changed little. It seemed that the herbicides that are less used had a slight price decrease and those that are more popular had a slight price increase. One herbicide, in particular, that a higher than normal price increase was Spartan. But we knew this was going to happen with the phasing out of the DF formulation and replacing it with the 4L formulation.

Richard Zollinger
NDSU Extension Weed Specialist

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