Alternatives to conventional insecticides are available for use against certain insect pests of woody landscape plants. The ambiguous term "biorational" is often used for this group of chemicals; however, its meaning is unclear and ill defined. Here we discuss insecticides that are natural products, microbials or botanicals (of plant origin), and soaps and oils which cause mortality to insects mechanically through suffocation or desiccation. We also discuss insect growth regulators that kill insects by interfering with specific insect physiological processes such as molting or chitin synthesis. Most of these chemicals have a narrow spectrum of activity and are relatively safe to mammals.
Inorganics. Sulfur has been used to control mites for a long time and still is effective against certain species, although conventional acaricides are much more efficacious.
Botanicals. Probably the best known "alternative" pesticides are plant extracts which were discovered and used long before the advent of conventional chemical pesticides in the mid-twentieth century. Rotenone and pyrethrin are the best known extracts from plants that have broad spectrum toxicity to insects. Azadirachtin (neem) has also been widely used in Asia for a long time, but only recently been available in commercial products such as Neemix (Margosan-O), Bioneem and Azatin.
Microbials. Insects, as with all organisms, are attacked by disease-causing pathogens (called entomopathogens). Two groups of pathogens, bacteria and fungi, are readily available commercially for use against insect pests of woody landscape plants. Many strains of Bacillus thuringiensis produce endotoxins that are effective against caterpillars, beetle grubs and other insects. Many brands are available for use: Dipel is probably the best known, newer brands are Stewart, Foil and Javelin. One fungus, Paecilomyces, is available commercially to control mites and other soft-bodied insects.
Insect Growth Regulators (IGR's). IGR's are a more recent discovery that target the immature stages of insects and interfere with molting or chitin synthesis. Kinoprene (Enstar II) and Dimilin are the brand names available. Kinoprene is labeled for whiteflies, aphids and scale, while Dimilin is effective against caterpillars.
Oils. Horticultural oils, either petroleum or vegetable based, kill insects mainly through suffocation. Because of this mechanical method of toxicity, they do not induce resistance in the pests. Highly refined oils can be used under most growing conditions without fear of phytotoxicity. Sunspray Ultrafine spray oil and Volck oil are well known brands of horticultural oils. There are several other similar products available.
Soaps. Insecticidal soaps also kill insects mechanically by desiccation. Like oils, they do not induce resistance in the target pests, and are safe to mammals. M-Pede and Safer's soap are readily available brands for control of soft-bodied insects such as aphids and mites. See the table below for specific recommendations for use of soaps.
Advantages of Oil and Soap:
Disadvantages:
Mode of Action:
Proper Use:
Known Causes of Phytotoxicity:
Tank Mixes: