Jeffrey Hahn, Asst. Ext. Entomologist
Now that we are leaving the doldrums of winter behind us, the promise of a new growing season beckons and we can start preparing to work in our gardens and landscapes again. Although we hope we don’t encounter insect pests, we should be prepared to act if it becomes necessary. When using integrated pest management (IPM), we explore any non-chemical methods that could be effective first. However, there may times when some of us may need to consider applying an insecticide in our garden or yard.
Photo 1: Look for the active ingredient on the pesticide label. Jeff Hahn
The following is a list of common garden and yard insecticides that homeowners may find in stores. This is not meant as a complete list of every insecticide available to home gardeners that can be found in Minnesota but should include many of the most common active ingredients. Also, the listing of any specific trade names is not meant as an endorsement of these products but to just point examples of pesticides with a particular active ingredient.
When examining product labels, look carefully for the active ingredient which is often in small lettering. Also be sure to examine product labels carefully to be sure the plant you wish to treat is listed on it and the product is used correctly.
Lower Impact Insecticides
Bacillus thuringiensis (B.t.) variety kurstaki is a naturally occurring bacterial disease of insects. It is specific to caterpillars (butterfly and moth larvae). It is a stomach poison, killing insects after they have consumed it. It is most effective against young larvae. Examples include Bonide Bacillus Thuringiensis (BT), Hi-Yield Dipel Dust, and Green Light Dipel Dust.
Note: Bacillus thuringiensis var. tenebrionis, an insecticide effective against Colorado potato beetle larvae, does not appear to be available to home gardeners. The Bonide product Colorado Potato Beetle Beater which used to contain this active ingredient now contains spinosad.
Horticulture oils are either derived from petroleum oil, plant oils (typically derived from the seeds), or even fish oils. Oils are used to suffocate certain insect and mite eggs. It can also suffocate certain immature and adult insects, especially soft-bodied ones like aphids and scale crawlers, as well as mites. Examples include Bonide Mite-X (cottonseed oil, clove oil, garlic extract) and Ortho Volck oil spray (petroleum oil)
The active ingredient of insecticidal soap is listed as potassium salts of fatty acids. They are generally effective against small, soft-bodied insects, such as aphids. They are usually believed to affect insects by penetrating and disrupting the cell membranes. Examples include Bonide Insecticidal Soap, Natural Guard Insecticidal Soap, and Garden Safe Insecticidal Soap.
Neem and Neem Derivatives are derived from the neem tree, a plant found in arid tropical and subtropical areas. There are many compounds that can be synthesized from neem and different extraction methods can produce different products. Neem products are generally divided into one of three groups: azadirachtin-based products, neem oil-based products, and neem oil soap products. Neem can deter insect pests in one of several ways. They can inhibit their feeding, repel them, or disrupt their life cycle preventing them from successfully molting. Neem is generally effective against a wide array of insects, such as aphids, caterpillars, beetles, leafminers, and thrips. Examples include Green Light Fruit Tree Spray and Green Light Neem II.
Photo 2: There are many insecticide options on the market. Jeff Hahn
Pyrethrins are made from the ground flower blossoms of the chrysanthemum plant, especially Chrysanthemum cinerariaefolium. It is a fast-acting contact insecticide that affects the nervous system, paralyzing the insect. Some products may be mixed with a synergist, that is, a product that makes the pyrethrins more effective, although by itself it does not have any insecticidal properties. This insecticide is effective against a wide spectrum of insects. Examples include Bonide Japanese Beetle Killer and Garden Safe® Brand Rose & Flower Insect Killer.
Spinosad is produced by the fermentation of a soil-dwelling bacterium, Saccharopolysora spinosa. It is quick acting, attacking the nervous system of insects. It is most effective against caterpillars, flies (mostly leafminers), and thrips and is also reasonably effective against leaf beetles and grasshoppers and similar insects that consume a lot of foliage. Examples include Garden’s Alive Bulls-EyeTM, Bonide Captain Jack’s Deadbug Brew, and Green Light Lawn and Garden Spray.
This is a common group of related insecticides that are based on the chemistry of naturally occurring pyrethrum. They are long residual insecticides killing a wide range of pests. One of the more common pyrethroids is permethrin. Examples include Bonide Eight Garden and Home, Bonide Borer - Miner Killer, Hi-Yield Kill A Bug II, Ortho Bug-B-Gon Garden Insect Killer. Other common pyrethroids are bifenthrin, an example is Bug B Gon Max Lawn and Garden Insect Killer; cyfluthrin, examples include Bayer Advanced PowerForce® Multi-Insect Killer and Bayer Advanced Triple Action Insect Killer for Lawns and Gardens; lambda cyhalothrin, examples include Bonide Beetle Killer and Bonide Caterpillar Killer; deltamethrin, examples include Bonide Delta-Eight Granules and Hi-Yield Turf Ranger Insect Control; and esfenvalerate, an example is Ortho Bug B Gon Max Garden & Landscape Insect Killer.
The following are products that were available when I started at the U of M (long ago) that can be still be found, although in some cases they are much less commonly available.
Acephate, an organophosphate, kills on contact and is also a foliar systemic with moderate residual activity. It is effective against a wide range of insects, such as caterpillars, sawflies, and leafminers. An example include Bonide Systemic Insect Control. Malathion, another organophophate, is a broad spectrum, contact insecticide with short residual. Examples include Spectracide Malathion and Bonide Malathion. Trichlorfon is another organophophate. It is effective against beetle grubs and caterpillars in turf. Examples include Hi-Yield Dylox 6.2 Granular and Bayer Advanced Lawn 24 Hour Grub Control. Carbaryl (generally thought of as Sevin), is a carbamate. It is a contact insecticide with moderate length residual. It is effective on many insects, especially beetles. However, they are not effective against aphids. Examples include Hi-Yield Carbaryl Garden & Pet Dust and Bayer Advanced Complete Insect Killer For Gardens.
This is a new class of insecticides. It has a similar chemistry to and is modeled after nicotine. These insecticides affect the nervous system of insects, paralyzing them. It has a generally wide spectrum of insects it is effective against. The most common active ingredient in this class is imidacloprid. It has both systemic and contact modes of action. Many products are applied to the soil while some are applied foliarly. Imidacloprid is effective against beetles, including borers and grubs, sawflies, and aphids and other sucking insects. It is not effective against butterfly or moth caterpillars. Examples include Bayer Advanced Tree and Shrub Insect Control, Bonide Annual Grub Beater, Hi-Yield Grub Free Zone, SpectracideE Grub Stop2 Once & Done, and Ultra Stop Tree & Shrub Insect Killer. Another insecticide in this class is acetamiprid. An example is Ortho Max Flower, Fruit and Vegetable Insect Killer.
This class of insecticide is represented halofenozide. It is an insect growth regulator, preventing target insects from finishing their development. It is effective on caterpillars and beetle grubs found in the soil. Examples include Hi-Yield Kill-A-Grub 0-0-7 and Spectracide Grub Stop Once & Done!
There are two common pesticides sold for the management of slugs. Metaldehyde is labeled around flowers but not around vegetables or other edible plants. It is generally considered to be hazardous to dogs. It is more effective during warm, dry weather. It is best to apply metaldehyde after a rain storm but when sunny weather is predicted. Examples include Hi-Yield Improved Slug and Snail Bait, Ortho Bug-Geta Snail & Slug Killer, and Vigoro Snail & Slug Killer Meal 2.
The other common pesticide for slug management is iron phosphate. It is labeled for both flowers and vegetables and other edible plants and is not considered dangerous to dogs. Examples include Bayer Advanced Dual Action Snail and Slug Killer Bait and Spectracide Snail & Slug Killer Bait.