Natter’s Notes 

When Pesticides Change

Jean R. Natter, OSU Master Gardener

You know the rule about pesticides: “Read and follow label directions.”

Well, that catchy little phrase has become more critical than ever. Several popular home-use products have changed their formulations with minimal fanfare. There’s no indication of “new” on the label.

To compound the confusion, labels on the revised formulation closely resemble the old ones. Unless the user is more observant than average, it’s very likely something may go awry. The application method may have changed; the precautions may have been modified; and/or the end result may be different than expected.

The explanations below were published in “When Familiar Pesticides Change.” (“Pests in the Urban Landscape;” August 29, 2018.

When Sevin is no longer carbaryl

Sevin is a familiar insecticide brand name for home gardeners used to control insects in lawns, on ornamental plants, and on vegetables. Sevin and the active ingredient carbaryl are practically synonymous. Recently, the active ingredient in some Sevin products was changed from carbaryl (a carbamate) to zeta-cypermethrin (a pyrethroid).” . . .  This pyrethroid is less toxic to mammals but both carbaryl and zeta-cypermethrin are highly toxic to bees and aquatic species. The new label on Sevin Insect Killer states that it controls more pests than the old product containing carbaryl, which may seem great, but the product may also kill some of the good bugs like lady beetles (ladybugs).

Product labels often look very similar, even when the ingredients change. On the left is the recently released product containing zeta-cypermethrin; the former version on the right contains carbaryl.

Another very important difference is the time the products can safely be applied on fruits and vegetables before harvest (called preharvest interval or PHI). Following the PHI reduces your pesticide exposure when you eat the food. For fruits such as apples and peaches, the PHI for the zeta-cypermethrin Sevin is 14 days, but for the Sevin with carbaryl it’s 3 days. For other fruits and vegetables, the PHI for the new Sevin label may be shorter than the carbaryl label. Again, check the label.

When Roundup is no longer glyphosate

Another familiar pesticide name is Roundup, a product known historically for containing the herbicide active ingredient glyphosate. Monsanto, the manufacturer of Roundup, now produces an extensive line of Roundup products containing multiple active ingredients, rather than just glyphosate alone. Many of these products contain triclopyr or diquat in addition to glyphosate. Some don’t contain any glyphosate at all

“Roundup Landscape Weed Killer” is a new product which contains pendimethalin instead of  glyphosate. It’s both a non-selective herbicide and a pre-emergent.

When Corry’s Slug and Snail Killer is no longer metaldehyde

In 2012, the active ingredient of the well-known Corry’s Slug and Snail Killer was changed from metaldehyde to sodium ferric EDTA, but the general look of the product box didn’t change. This relatively new active ingredient is less toxic and less attractive to dogs and still effective against snails and slugs. However, the amount users apply and how quickly it works both differ from the previous active ingredient. If you are familiar with the old product you may have noticed a change, but unless you read the label, you may not know why.

A Bonus Snippet on a different topic

MGs who volunteered this summer probably received multiple inquiries about the seemingly overabundant wasps this summer.  Well, the general public is seriously confused concerning the differences among bees, yellowjackets, and paper wasps. When they see a somewhat elongated yellow and black insect, they assume “wasp;” that is, yellowjacket. (Don’t bother asking how I know.)

But yellowjackets have a near twin: European paper wasps, Polistes dominulus, invasive insects officially identified in Oregon years ago. Most paper wasps are mild-mannered whereas P. dominulus is nasty. To easily differentiate them from yellowjackets, check the antennae. Text and images are at “Invasive paper wasp responsible for increasing yellow jacket complaints.” ( )

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When Pesticides Change

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