There are also several other difficulties with the use of herbicides by home gardeners. Many herbicides are nonselective and will kill the vegetables, as well as the alien labs carts. Others are selective and can be used only with certain vegetables or control only certain weeds. Home gardens generally contain many vegetable and weed species, which makes using selective herbicides difficult. Some herbicides may also damage nearby vegetables or remain in the soil and damage future plantings.
Even if available and effective, herbicides may not be legal for use on a specific vegetable or at the time when they are needed. The herbicide application rate may be very low and extreme accuracy in application may be absolutely essential. Overlapping applications may kill vegetable crops and, if areas are skipped, weeds will not be controlled. Required pre-harvest intervals (PHI’s) or waiting periods between application and harvest can be lengthy and must be observed. Herbicides may also be effective only for a short period of time or produce results slowly. Despite all these problems, there are occasions when herbicides may be successfully used in home gardens. The following suggestions will assist home gardeners in effectively using herbicides.
1. Understand the difference between preemergence and postemergence herbicides. Preemergence herbicides are effective only before weeds germinate. Postemergence herbicides work on weeds that are actively growing.
2. Understand the different formulations of herbicides available and how the formulation affects use. Some of the more common formulations are emulsifiable concentrates (EC), flowables (FL), wettable powders (WP) and dry flowables (DF). All are designed to be mixed with water and sprayed on the area to be treated. Wettable powders and dry flowables may settle out unless the sprayer is shaken periodically. Herbicides may also be formulated as granules (G). These are to be spread evenly over the soil surface.
3. Plan the garden in detail. Plan to locate all the crops for which a specifi c herbicide may be used near each other. This allows treatment of larger areas with less effort.
4. Follow all instructions on the label. This is extremely important. Failure to follow the label instructions precisely may result in harm to the applicator, the environment or the crop. Preemergence herbicides require weed-free soils without lumps or clods. Most are best applied to moist soil and shallowly incorporated by tilling, irrigating or natural rainfall. They must be applied uniformly and at the proper rate to be safe and effective. Postemergence herbicides may be applied over the top of the growing crop and weeds. Again, it is essential that all aspects of the label directions be understood and followed. If you have any questions, consult your county Agricultural Extension agent.
5. Rinse spray equipment. Residual herbicide in sprayers may damage crops. Many gardeners who use herbicides purchase spray equipment for herbicides only and keep it separate from equipment used for insecticides and fungicides.
6. Calibrate application equipment accurately. Inaccurately applied herbicides may be ineffective or dangerous. If there is a question on how to apply a specific herbicide, contact your local county Agricultural Extension office. The two most suitable herbicides for use on home gardens are Trifluralin (Treflan) and Sethoxydin (Poast). Trifluralin is sold in many formulations, each designed for specific uses. Trifluralin prevents the germination of most grasses and some broad-leaved weeds (for several weeks) and must be applied before these weeds germinate. Sethoxydin kills growing grasses. It requires only a short waiting period between application and harvest and may be applied to a wide range of vegetables.
Proper use of herbicides may involve grouping vegetables according to the herbicide that may be applied to them, as well as paying attention to rate, timing, uniformity and method of application. Remember, label directions must always be read and followed.
The stale seedbed technique is a system that controls weeds prior to the planting of the crop. The theory is that most weed seed that germinate are found in the top 2 to 3 inches of soil. With soil temperatures of 70 degrees F or higher and moist soil, most of the weed seed in the top 2 inches of the soil will germinate in 2 to 4 weeks after a tillage operation. Therefore, a generalized procedure follows.