snake oil n. A worthless preparation fraudulently peddled as a cure for many ills.

The never-ending search for truly-amazing chemicals to protect corn roots from rootworms continues. I have had many questions from curious farmers about the insecticidal powers of kerosene, molasses, sulfur, or turpentine. They have

heard testimonials from neighbors who got excellent control when one of these products was used to control corn rootworms. When it comes planting time and using these unconventional products, many have thought about it, some have tried it, and a few have survived to tell about it (their corn didn't fall down!). But what do we really know about the true performance of these products?

Fortunately, entomologists at the University of Wisconsin have evaluated the root-protecting abilities of kerosene, molasses, sulfur, and turpentine. During 1995 they conducted two tests. In both tests, molasses and sulfur were applied as dry formulations during planting. The kerosene and turpentine were blended into the bag of seedcorn one day prior to planting. Three standard corn rootworm soil insecticides and an untreated check were included. Test 1 was planted on May 5; test 2 on May 12.

Roots were dug in July and the root injury was rated on the Iowa 1 - 6 scale. Briefly, here is the scale:

1. no injury;
2. a few feeding scars;
3. at least one root pruned back to 1 1/2 inch of the stalk;
4. one complete node (circle of roots) pruned back;
5. two complete nodes of roots gone; and
6. three complete nodes eaten off.

We should see a root rating of 3.0 or less if the product provided excellent root protection. Root ratings of 4, 5 or 6 are bad news and tell us that a product did not protect roots.

The results should be convincing (see table). Kerosene, molasses, sulfur, and turpentine did not protect corn roots from insect damage. In test 1, the Lorsban, Force, and Counter gave excellent root protection, while the unconventional treatments had approximately 1 1/2 to 2 nodes of roots eaten away. In test 2, the soil insecticides gave good protection again whereas the unconventional treatments had approximately one node destroyed. In both tests, root ratings from the unconventional treatments were similar to those in the untreated check, which means doing not at all was just as good as using kerosene, molasses, sulfur, or turpentine.

Comparison of kerosene, molasses, sulfur and turpentine to 
conventional insecticides for corn rootworm control, University of 
Wisconsin, 1995

                                    lb. AI/         Root
                Product             acre *          rating

Test #1        Lorsban 15G          1.00            2.45
               Force 3G             0.10            2.65
               Counter 20CR         1.00            2.95
               Molasses             6.7             4.60
               Kerosene             0.5 cup         4.65
               Turpentine           0.5 cup         4.85
               Untreated check      ----            5.10
               Sulfur               9.0             5.25

Test #2        Counter 20CR         1.00            2.15
               Force 3G             0.10            2.20
               Lorsban 15G          1.00            2.55
               Untreated check      ----            3.30
               Kerosene             0.5 cup         3.90
               Molasses             6.7             3.95
               Sulfur               9.0             3.95
               Turpentine           0.5 cup         4.25


* Rates are based on 40-inch row spacing. Material applied in a 
per-cup formulation was blended in the bag of seedcorn one day 
prior to planting.

These four products will not protect corn roots. They are nothing more than snake oil. They should be avoided. But what about the testimonials that claimed rootworm control? There probably werent enough rootworms to cause significant injury in those fields. Another word of caution is that a person who sells or promotes one of these products for corn rootworm control would be distributing a nonregistered pesticide which is in violation of FIFRA. That person would be subject to civil and criminal penalties.