The key to using gardening products successfully is selecting the right product for the job. With the staggering number of products on the market, it's not always easy to pick the right one. In many cases, two products may appear to be similar when in fact they aren't. How do you tell the difference? Paul James provides the answers.
Horticultural Oils
Dormant oil and superior oil may sound interchangeable, but they are not. They are both oils, and they are both used to treat various pest and disease problems, but one cannot be substituted for the other.
Dormant oils are thick, viscous oils that are used primarily on fruit trees to control overwintering mites, scales and other insects. They are best applied when plants are fully dormant and temperatures are between 40 and 50 degrees Fahrenheit. In fact, if dormant oil is applied when temperatures are above 60 or so, it can seriously damage and even kill whatever it's sprayed on. It should never be applied to certain trees, including hickory, maple, beech and blue spruce.
Superior or highly refined oils are less viscous, and they can be applied virtually year round, as long as the temperature is not above 85 degrees. These oils not only kill a number of insects but also may have fungicidal properties.
Both oils have the potential to burn plant foliage under certain conditions. It is a good idea to spray a small area and wait a few days for signs of damage. If there isn't any, the product is safe to use. Plain old vegetable oil also works to smother insects and their eggs; however, getting it to mix with water requires the addition of soap. James advises that in some cases, it may be better to buy ready-mixed solutions.
Insecticidal Soap and Dishwashing Soap
Insecticidal soap is a specially formulated solution that kills soft-bodied insects such as aphids, mites and whiteflies. It's a contact poison that works by paralyzing bugs, which then die of starvation. Nondetergent dishwashing soap is often used as a substitute for insecticidal soap, but if the dishwashing soap is not diluted properly, it may burn plants. Regardless of which soap you're using, you can spray every two or three days for up to two weeks to control pest problems.
Selective and Nonselective Herbicides
Selective herbicides include a number of products that are designed to kill certain plants--weeds primarily--without harming others such as turf grass. Popular examples include pre- and post-emergent weed killers, various crabgrass controls and so-called weed-and-feed preparations. Nonselective herbicides, on the other hand, are designed to kill anything green they come in contact with, whether it's weeds or a prized rose bush. With few exceptions, all of these products are potentially dangerous. If you use them, do so carefully and in strict accordance with label directions.
Pyrethrin, Pyrethrum and Pyrethroids
Pyrethrins are a class of organic insecticides derived from the flowers of pyrethrum daisies, and pyrethroids are synthetic equivalents. Pyrethrins are available in both spray and dust form, and they work by quickly attacking an insect's central nervous system. Pyrethrins are highly toxic to fish, so never use them near any body of water. They are also moderately toxic to many mammals and should be used only as a last resort on hard-to-control insects such as squash bugs.
