Home Remedies,Repellents, &25(b) Products:
Dr. Bastiaan M. Drees, Professor & Extension Specialist
Department of Entomology
Texas A&M University System
College Station, TX
There are a whole host of "actions" a nursery crop producer can use to try to manage insects in the greenhouse/nursery operation. However, many "novel" methods can be costly and sometimes, ineffective. Producers of nursery crops should make every effort to study the available management options and select the least toxic, most target-specific and cost-effective methods available. Seeking scientific data regarding the effectiveness (efficacy) of available alternatives can help in the decision-making process.
The systems approach called Integrated Pest Management (IPM) is promoted widely for management of insect, disease and weed pests. This approach stresses the practice of good horticultural (cultural) practices, such as optimum fertilization, with the recognitions that under- or over-fertilized plants can be more susceptible to insect and mite outbreaks. However, fertilizers are not marketed as pesticides requiring registration by the Environmental Protection Agency (EPA). Furthermore, I know of no companies marketing fertilizers with written claims to control or prevent insect/mite pests on their fertilizer product's label.
Home remedies. A never-ending list of "home remedies" have been proposed and tried to control pests. Books, such as The Healthy Garden Handbook (Simon & Schuster, Inc., New York, 192 pp.) by the editors of Mother Earth News, list tantalizing approaches, including use of companion planting, use of traps and barriers and homemade plant sprays. With regard to the latter, they write:
"Most insects and animals naturally shy away from food that tastes or smells bad or that makes them ill. This behavior has set untold generations of gardeners to work concocting countless homemade repellents. Recipes vary widely, but the vast majority use as ingredients members of the allium family (onion, garlic, chives), hot peppers (jalapeno, cayenne), pungent herbs (basil, nettle, coriander, anise, eucalyptus, wormwood, cedar, peppermint) - or some combination thereof. What works in one garden won't necessarily work in another, however, so individual experimentation may be necessary."
Still other home remedies are passed by word-of-mouth. For instance, there has recently been a lot of discussion about the use of dilute solutions of hydrogen peroxide for control of certain pests. Most of these "remedies" are not available as EPA registered pesticide products and lack scientific studies that document their effectiveness.
Repellents. Recently, two products have come onto the market that are EPA registered pesticides being marketed as insect/mite repellent foliar sprays: Garlic Barrier Insect Repellent (99.3% garlic juice, CAUTION), is labeled for use on ornamentals (flowers, shrubs, and trees) for repelling aphids, bagworms, beetles, borers, chafers, curculios, cutworm, leafhoppers, leafminers, leafrollers, maggots, mealybugs, mites, plant bugs, sawflies, scale, spittlebugs, webworms and whiteflies. However, there is no mention of use in greenhouses other than in the "Agricultural Use Requirements" section on the label discussing protective clothing and the 4 hour restricted entry interval (REI). Hot Pepper Waxô Insect Repellent (3% capsaicin and related compounds, CAUTION), can be used on ornamentals outdoors and indoors to repel aphids, spider mites, thrips, leaf miners, whiteflies, lace bugs, and scale. Data supporting the effectiveness of these products can be requested from the manufacturers.
In the context of IPM, the use of pest repellent foliar sprays can be debated. Since these products are properly used to "keep insects from getting on plants and trees", they must be applied to pest-free, non- infested plants. Once pests arrive, their use is to be either terminated or augmented with a pesticide which can actually reduces pest numbers. These repellents do not claim to actually kill insects/mites.
Spending time and money to treat pest-free plants contradicts the IPM concept that pesticides are to be used only when pests reach or exceed the Economic Threshold (ET). On nursery crops, the ET is somewhat subjective (although the Texas Floral and Nursery Law mandates sale of "pest-free" plants), but usually occurs when pests or pest damage is first detected. The exception to this practice is when use of a preventive application, e.g., use of media-applied systemic insecticide, is justified where there is a history of (or high probability of) a crop becoming infested. On the other hand, the ingredients in these repellents are considered "organic" and some of the least-toxic methods when applied, even though the signal word, CAUTION, occurs on the product labels. Yet another question comes to mind: with such a wide range of "pests" the Garlic Barrier product label claims to repel, do applications also repel beneficial insects or natural enemies? Olkowski, et al., in Common Sense Pest Control (The Taunton Press, Newton CT, 1991, p.125), state: "We do not recommend garlic for aphid control since it kills the natural enemies of the aphid as well as the pests". The bottom line, of course, is whether the use of these products has been shown to be cost-effective, regardless of the pest management philosophy to which one prescribes.
25(b) Products. On March 6, 1996, the Environmental Protection Agency published "Exemption of certain pesticide substances from Federal Insecticide, Fungicide, and Rodenticide Act requirements" (40 CFR Part 152, Federal Register Vol. 61, No. 45). With this action, pesticide products containing exempted ingredients no longer require EPA approval to be marketed as insecticides (although they will need to be approved for sale in Texas by the Texas Department of Agriculture). Exempted ingredients include: castor oil, cedar oil, cinnamon or cinnamon oil, citric acid, citronella and citronella oil, cloves and clove oil, corn gluten meal, corn oil, cottonseed oil, garlic and garlic oil, geranium oil, lemon grass oil, linseed oil, malic acid, mint or mint oil, peppermint or peppermint oil, rosemary or rosemary oil, sesame or sesame oil, soybean oil, thyme or thyme oil, white pepper, and some others. Already, several pesticides, including Garden-Ville Organic Weed Control (2% sodium lauryl sulfate) and VictorÆ Mosquito Barrier (39% garlic) have had labels approved (and exempted from registration) for sale in Texas. With this new regulation, some products like Garlic Barrier, technically no longer require EPA registration. I forecast that this new EPA regulation will result in the introduction of a number of other "new", non-registered products marketed with claims to repel or control pests.
There has always been, and there will continue to be a challenge for growers to select the "best" method(s) to manage pests in their greenhouse/nursery operation. With so many plants, pests, and "control" alternatives available, combined with major differences in production facilities and growing practices, there is probably not a single "best" management approach anyway. However, the need for scientific studies will continue to a vital source of information; and the results of these efforts will likely remain more reliable than most testimonials or rumors. In the absence of data from scientific studies to support a particular pest control practice, the best information a grower will always be that which is generated in his/her own operation!
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