QUESTION: Surflan is called a preemergent herbicide. What does that mean, how and why are they used?
ANSWER: Preemergent herbicides are a class of weed killers that are applied to the soil before weeds emerge from the ground. The activity of these compounds usually kill germinating seedlings before they emerge from the soil. The new roots and/or shoots absorb some of the material and the plants die. The herbicides are applied to the soil and are usually incorporated into the soil by tillage or irrigation after application. This is necessary because environmental factors such as sunlight cause these products to degrade over time. With pesticides there are several names of each compound that must be understood to avoid confusion. For a single pesticide compound there are three classes of naming. The first is the long chemical name from which a good chemist can re construct the molecular structure. The second is the common name, which is registered and approved by the EPA and is peculiar to that compound no matter who the manufacturer is. This common name is analogous to a specific or Latin name of a plant. The third name is the trade name. This name is copyrighted by the seller, but the same chemical can have many trade names - similar to common plant names. After patent rights expire on the compound anyone can manufacture the chemical and give it any name they choose. All of this information is found on the label by law. For example, a common preemergent herbicide has a chemical name of; 3,5-dintro-N4, N4-dipropyosulfanilamide. The common name is oryzalin. Some trade names are Surflan (this is the name that the manufacturer uses), Monterey Weed Stopper, or Weed Blocker. The manufacturer sells this compound to others who package Surflan in smaller home use size containers and give their packaged material another name like Monterey Weed Stopper.
Surflan and several other preemergent herbicides are yellow to orange in color. This is because they were synthesized and discovered they had herbicidal activity by the dye industry. Surflan is bright orange. When it is being applied by city employees, for example, on median islands or in park landscapes, people have become irritated thinking they were using "Agent Orange!" This is not the case. The two are not related.
The best time to apply Surflan herbicide in the landscape is in the spring and/or again in the fall. Surflan persists from four to six months depending on environmental conditions. It works well over crushed granite or gravel that does not have plastic under it. Surflan can also be applied to lawns, flower beds (where flower seed is not planted), or it can be transplanted through. Surflan must be watered in within 30 days or it is broken down by sunlight. Here in the high desert it is best to get it watered in within the first week. With proper and timely application a "weed barrier" is formed and many grasses and broad leaf weeds will be controlled. As with all pesticides read the label and follow all instructions.