I feel that because of this persistence, aminotriazole (in the hands of the amateur) should be confined to use around ornamentals where such hard-to-kill weeds as nut-grass, poison ivy and Canada thistle must be destroyed.
Additional Materials: New weed control chemicals are emerging from the laboratory; it is impossible to keep up with them. In addition, there are hundreds of materials already in commerce. There is, however, one fundamental and universal principle which must be followed in handling such materials, namely, read and adhere to the package directions.
If you only knew how many hours of work and testing went into the preparation of directions to protect you from personal injury and to protect your plants, you might appreciate how important it is to put on your bifocals and read all the print on the package. Above all, if a manufacturer thinks it is important to tell you his product has a residual period of 10 weeks, believe him. He isn't anxious to limit his sales; hence any restriction of this kind is put on the package for your protection.
WASHING OUT SOLUBLE WEED KILLERS
Many of the less-persistent weed killers are fairly soluble and will move downward in soil if subjected to heavy watering. Most of the 2,4-D products, for example, can be removed from surface soil by applying two inches of water. To know when you have applied two inches of water, set coffee cans at intervals under the sprinkler and when the can with the least water in it contains two inches, turn off the hose. Reseeding can be done immediately.
This washing (as well as rainfall), by the way, does not spoil the effect of the chemical on weeds you want to kill, provided the water does not go on for at least eight hours after application of a tri-ethanolamine salt, a sodium salt or an amine form of 2,4-D or 2,4,5-T. If ester forms of the chemicals are used, only one hour need elapse before it is safe to wash the soil, since ester types penetrate the plant tissues within that time.
Weed control is closely connected to soil care. The finest Gardener's Loam is not worth much if blighted by weeds. With the help of a great and ever-increasing selection of chemicals, the home owner can bar many kinds of undesirable plants from his lawn and garden. It can be done in three "stages": sterilizing the soil, killing germinating seed, and destroying mature weed plants. But weed-killing chemicals, too, present potential hazards from the build-up of toxic residues in the soil. In any event, the faithful observance of instructions on the package will assure maximum protection as well as value to the user, to the plantings being treated, and to the soil itself.