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New Over-the-Counter Pesticides

By Whitney Cranshaw, Colorado State University Extension Entomologist

There are a couple of changes - for the better I think - in insecticide options available over-the-counter.

IMIDACLOPRID

Newest are imidacloprid formulations for home landscape and houseplant use. Imidacloprid is the active ingredient in Merit/Marathon. It is a systemic insecticide with excellent activity against most phloem-feeding Homoptera (e.g., aphids, soft scales, mealybugs, whiteflies) and leaf beetles. There is also some evidence that it can assist in control of certain borers (e.g., some metallic woodborers/flathead borers) and there is anecdotal evidence that it works on sawflies.

Four new products should be available, all sold under the Bayer Advanced Garden line.

"2-in-1 Plant Spikes" contain fertilizer and 2.5% imidacloprid and is sold for use on potted plants. It is an alternative to the plant food/insecticide stakes of the past which had the insecticide DiSyston. It should be an excellent product for houseplant problems involving whiteflies and soft brown scale.

"3-in-1 Rose and Flower Potting Mix" is a potting mix with fertilizer and 0.015% imidacloprid.

Perhaps most useful is "Tree and Shrub Insect Control", a 1.47% granular formulations for use as a soil applied systemic insecticide to control tree and shrub insects.

The Bayer Advanced Garden line also carries a sprayable formulation of imidacloprid, combined with the pyrethroid cyfluthrin (a.k.a. Tempo) as "Rose and Flower Insect Killer".

Positive points of imidacloprid in addition to effectiveness against the above mentionned insects include low toxicity (particularly when compared to DiSyston) and quite long persistence. Disadvantages include lack of activity against certain insects (e.g., caterpillars) and spider mites. Regarding the latter, imidacloprid has been shown to sometime actually increase problems with spider mites.

(Note: Imidacloprid formulations for control of white grubs and billbugs were on the market last year, under the trade name Season-Long Grub Control under the Bayer Advanced Lawn trade name.)

PERMETHRIN AND PYRETHROIDS

Finally some pyrethroids have begun to filter down to the garden centers. Several of these insecticides have been used for over a decade in landscape pest management and for two decades on fruits and vegetables.

Probably of greatest use for yards and gardens is permethrin. There are numerous permethrin formulations available, some of which are labeled for a wide variety of fruits and vegetables as well as ornamentals. Examples include: Bonide Eight Insect Control, Ford's InterCept Insect Control, Ortho Bug-B-Gon Multipurpose Garden Dust, and K-Gro Multi-Purpose Garden and Pet Dust. Other formulations are sold for control of ants and household/nuisance pests.

Less commonly available is esfenvalerate, sold as Ortho Concentrate Bug-B-Gon Multi-Purpose Insect Killer. Esfenvalerate is listed for control of a variety of garden insects, including some on fruits and vegetables.

I think that the permethrin/esfenvalerate products are equivalent to or superior to the organophosphates for almost all insect control purposes (including borers). Not only are they highly efficacious but are considerably less hazardous than Dursban and diazinon and can be adequate substitutes for these insecticides - which have been pulled from the market. Downsides are that they are often weak on aphids (at least some aphids) and mites.

There are also other pyrethroid insecticides on the market as alternatives to Dursban for household pest control - particularly tralomethrin-containing insecticides.

Photo: Judy Sedbrook

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Date last revised: 01/05/2010