ISSUE 8 June 22, 2006
GLYPHOSATE PRICE QUIZ
With all of the different glyphosate formulations with their different concentrations and prices on the market, how do you compare them? For example, take these three hypothetical glyphosate products.
Price per gallon
Which glyphosate is the best buy (without considering the potential value of supporting services or guarantees)? Is it too confusing? There is an easy way to compare products by calculating the cost per pound of glyphosate. It’s easier than you think. Just follow this formula.
$/gal lb glyphosate acid/gal = $/lb of glyphosate
The missing piece of information is the concentration of the glyphosate in the jug. Check the ingredient statement on the label for the concentration of the glyphosate acid or acid equivalent (the glyphosate acid is the part that kills the weeds). Here are the label statements for these glyphosate products. The wording will differ among products, but look for the concentration of glyphosate acid per gallon.
Contains 4 lbs per gallon glyphosate, isopropylamine salt
Acid Equivalent: glyphosate acid = 30.4% (3 lb/gal)
Contains 5.5 pounds per U.S. gallon of the active ingredient glyphosate, in the form of its potassium salt. Equivalent to 4.5 pounds per U.S. gallon of the acid, glyphosate.
Contains 5 pounds per U.S. gallon of glyphosate acid equivalents.
Again, which glyphosate is the best buy? Just punch the numbers through the formula to get the answer. In this hypothetical example, Glyphosate #2 is the best buy at $4.89/lb of glyphosate. Glyphosate #1 is $5.33/lb glyphosate and Glyphosate #3 is $5.20/lb glyphosate.
Disclaimer: These prices were randomly picked to show how prices can be compared. They do not reflect any real product prices.
WHAT IS THIS WEED - WILD STRAWBERRY
I am receiving many calls and people sending pictures what they describe as wild strawberry. This plant is rough cinquefoil (Potentilla norvegica). Some people out west call it Norwegian cinquefoil (see common name).
Rough cinquefoil is in the Rose family, is an annual, winter annual, or biennial. Stems are 1 to 3 feet tall, rough, semierect and spreading. Leaves has three leaflets like strawberry, are hairy, and are coarsely toothed. It is can be missed by glyphosate even at full use rates.
ND PETITIONS BEING SUBMITTED TO EPA
The following are registration petitions that the ND Dept of Ag has funded to be put on the fast track in IR-4 to get EPA registration as soon as possible. These petitions may still take a few years before registration occur. This is an FYI only. Do not assume growers can use these products because they are in the registration process.
Pesticide common names are given instead of trade names because they may be several trade names for each common name. The active ingredients are herbicides, insecticides, and fungicides.
CROP ROTATION RESTRICTIONS
Each year I receive calls asking "Is it safe to plant crop X if I sprayed herbicide Y last year?" or "Can I recommend herbicide Y if a grower is planting crop X next year?" The answers to these questions are usually easy, but sometimes not popular. The reason the answers are easy is because most herbicide labels are quite specific in listing the rotational crops or intervals allowed AND the label is a legal document. So, if the label states "Do not plant the following crops", it means that it is not legal to plant that crop.
The obvious reason that a rotational crop may not be allowed to be planted is because the herbicide may carryover and injure the crop. Neither the grower nor the manufacturer wants this to happen. The manufacturer conducts field studies to determine the risk of carryover to rotational crops in setting rotational intervals.
The second reason some crops may not be allowed as a follow crop is not visible like injury. The EPA protects our food supply by only allowing acceptable levels of pesticide residues in food or feed. This residue level is called a "tolerance" and as long as the concentration of that pesticide is below the EPA-approved tolerance, it is legal. For example, sweet corn has a tolerance of 0.25 ppm for atrazine. In a high percentage of sweet corn, atrazine is not even detected, but the tolerance allowing a trace amount of atrazine is the safe guard provided by EPA.
If herbicide residues persist in the soil and are taken up by a rotational crop, that crop may contain illegal residues unless a tolerance exists or unless the manufacturer determined through field tests that no residues are detected in the rotational crop. Certain rotational crops are not allowed because the manufacturer has not conducted the field tests to determine that the crop is free of herbicides residues, even though the crop is not injured. This the case with acetochlor. Currently, the only crops that can be planted after acetochlor is corn, wheat, soybean, and sorghum. Basic manufacturers have conducted the necessary residue trials and EPA is completing the re-registration of acetochlor. The end result is many rotational crops will be added to the new label when issued.
Whether the crop rotation is not allowed because of the risk of crop injury or potential herbicide residues, or lack of registration, the answer to the question is the same. Read and follow the label. "Do not" or "Shall not" means do not. In some causes, the labels offer the user recommendations or advice such as "Injury may occur if soybeans are planted the following year." In this case, it is the grower’s choice if they want to accept the risk of injury, but they are warned. On labels, "should" is another word that is advisory.
Basically, if we want to have these tools available for our use and maintain the confidence of the public, we need to follow the label instructions.
On another note, there is evidence of application of unregistered products on crops. For example, the 2004 ND Pesticide Use Survey shows Assure II applied on 85, 000 acres of sunflower, dry bean, and flax. Assure II is not labeled on these crops. Residue studies have been completed but EPA has not yet set a tolerance or registered these crops.
This may happen in a year or two but this use is not yet approved. Other good alternative products, like Poast and clethodim (Select, others) are available so there should be no reason why Assure II should be applied until it is registered on these crops.
NDSU Extension Weed Specialist