Pesticides enable farmers to grow enough high quality food, in an ever shrinking area of farm land, to feed the many people who live in the cities. Growers face tremendous competition for their crops from insects, fungi, weeds, spider mites, blights, rodents, etc. Without the use of pesticides, the food on the grocery store shelves would soon disappear because organically-grown foods cannot yet be produced in large enough quantities to feed the world’s population. Much effort and cost is expended to assure the safe usage of pesticides, and indeed our foods are safer than many people believe. One of the safeguards involves the testing of foods prior to harvest and/or processing for residual pesticides (called “residues”). Ironically, organic foods may require testing, also. For example, since fungicides are not used, they may contain dangerous mycotoxins (toxins produced by molds) such as patulin and aflatoxins.
Columbia Food Laboratories offers individual tests for over 550 different pesticides in food, vegetation, soil and water. We also have many multi-residue screens available. Our most comprehensive Multi Residue Screen is the P2220. It screens for over 420 pesticides and is applicable to food commodities and plant materials. We have other screens specifically for soil or water.
Profiles (Multi-Residue Screens)
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- P2200 Columbia Pesticide Profile (for food/vegetation)
- P2220 Multi Residue Pesticide Profile (for food/vegetation)
- P2700 Herbicides, Non-Ionic (for food/vegetation, soil or water)
- P2800 Herbicides, Ionic (for food/vegetation, soil or water)
- P2950 Carbamate Pesticide Profile (for food/vegetation, soil or water)
- P7000 National Organic Program Pesticide Profile
- Commodity-specific profiles:
potato, mint, apple/pear, strawberry, sweet potato/yam, onion, honey, hay, etc.
- Organophosphate/organochlorine pesticide profiles (for soil or water also)
- Customized profiles are frequently designed upon request
Specialized Individual Analysis
- Glyphosate (Roundup)
- Imidazolinone herbicides (the “Imi’s”: Arsenal, Pursuit, Raptor, Cadre, Scepter)
- Sulfonylurea herbicides (the “SU’s”)
- Dithiocarbamates (EBDC, Mancozeb, Thiram, Zineb, etc.)
- Fumigants in soil, grains, nuts (methyl bromide, Telone, propylene oxide, etc.)
- Chloramphenicol, streptomycin & oxytetracycline antibiotics in honey
- Many others (please call us for information about specific pesticides or see list)
Residue levels in food
Foods are routinely analyzed to determine if there are any detectable levels of pesticides. If any are found, they must be below the Maximum Residue Limit (MRL) set by the consuming country. The MRL’s for several countries can be found by following the links on the External Links page of this web site. MRL’s have a large safety factor built in for human consumption.
Soil herbicide carry-over
A herbicide could be used against weeds in one type of crop, without harming that crop, whereas other types of crops might suffer damage. Carry-over problems can occur during crop rotation if residues of a herbicide remain in the soil from the previous growing season. To estimate the total amount of a pesticide in a field from the ppm in a soil sample: Parts per million signifies how many parts of a given compound is found in one million parts of the soil being analyzed. Soil is generally considered to weigh about 2 million pounds per acre in the 6 inch surface layer. Therefore, 1 ppm of a pesticide in soil is equivalent to approximately 2 pounds of active ingredient per acre, assuming uniform distribution. ppm (w/w basis) = mg/kg 10,000 ppm = 1%
Detection of spray drift
Spray drift is the spreading of a pesticide beyond the intended borders of the area being treated. Common causes are wind, too hot conditions resulting in volatilization, and, accidental over-spray. Spray drift can be detected and measured by fairly simple means if steps can be taken at the time of application. One easy method is to place a paper towel or coffee filter on the ground before or during spraying. Afterwards, place the paper (using gloves) in a Ziplock bag and send to the lab to be analyzed. If unable to take a sample at time of application, vegetation samples can usually be analyzed later. However, delay works against this method because all pesticides begin decomposing in the environment due to sunlight, moisture, temperature, absorption and dilution by plant tissues, etc. Many pesticides are detectable within two weeks of application, while others may be detectable several months later. In either case, a call to the lab to discuss details would likely be helpful.
Cross-contamination of spray mixes
Failure to adequately clean the mixing or spraying equipment tank when changing from one pesticide to another can result in cross-contamination of a subsequent spray mix. This may have no apparent effect, or, may result in crop damage. Obviously the best way to detect this would be to save a small portion (e.g., one ounce) of every tank mix (especially when herbicides were previously used) until it is determined that there are no problems from the application. Determining the cause of damage at a later time is subject to the same environmental factors mentioned above. If it becomes apparent that vegetation or soil samples may need to be tested, take the samples as soon as possible and store them in the freezer. This prevents further breakdown of any residues which may still be present.
Anti-sprout compound levels on potatoes
Even under optimum storage conditions potatoes can only be kept so long before sprouting begins. Sprout inhibitors are used to extend the storage time through the Winter and Spring until a new crop is harvested. The level of inhibitor is monitored so that just enough is used to prevent sprouting without causing excessive residues. If this were not done, fresh whole potatoes would be unavailable for some portions of the year.
Herbicide Damage Issues
The following websites may be helpful when diagnosing herbicide injury to plants:
- Diagnosing Herbicide Injury on Garden and Landscape Plants – Purdue University ID-184
- Documenting Suspected Herbicide Damage – North Dakota State U./ U. of Minnesota WC-751
- Herbicide Injury Diagnostic Key – U. Wisconsin HIDK
- Herbicide Injury – Forestry Images pictures
- Herbicide Injury Information and Photographs -Texas A&M U. TWIG
- Weed Killer Damage to Plants – Kemper Center for Home Gardening (Missouri Botanical Garden)
Please call us to discuss special applications or to receive free quotes for pesticide analysis.