Pesticide Toxicity Profile: Neonicotinoid Pesticides
Click here to view a PDF version of this document.
Home Search What's New Products Survey Help
Pesticide Toxicity Profile: Neonicotinoid Pesticides

   

Pesticide Toxicity Profile: Neonicotinoid Pesticides1

Frederick M. Fishel2

This document provides a general overview of human toxicity, provides a listing of laboratory animal and wildlife toxicities and a cross reference of chemical, common and trade names of many neonicotinoid pesticides registered for use in Florida.

General

The mode of action of neonicotinoid pesticides is modeled after the natural insecticide, nicotine. They act on the central nervous system of insects. Their action causes excitation of the nerves and eventual paralysis which leads to death. Because they bind at a specific site (the postsynaptic nicotinic acetylcholine receptor), they are not cross-resistant to the carbamate, organophosphate, or synthetic pyrethroid insecticides, which was an impetus for their development. As a group, they are effective against sucking insects, but also chewing insects such as beetles and some Lepidoptera, particularly cutworms. All neonicotinoid products are classified as general use.

Acetamiprid is for use against sucking insects, such as aphids and whiteflies, on leafy vegetables, cole crops, citrus, cotton, ornamentals, and fruiting vegetables. Ready-to-use formulations are available in addition to wettable powders and water-dispersible granules.

Imidacloprid was first registered for use in the U.S. in 1992 and is possibly the most widely used insecticide of the group. It has a wide range of target pests and sites, including soil, seed, structural, pets, and foliar treatments in cotton, rice, cereals, peanuts, potatoes, vegetables, pome fruits, pecans, and turf. It is a systemic with long residual activity and particularly effective against sucking insects, soil insects, whiteflies, termites, turf insects, and Colorado potato beetle. Products are available in dusts, granules, seed dressings as flowable slurry concentrates, soluble concentrates, suspension concentrates, and wettable powders. The application rates for neonicotinoid insecticides are much lower than older, traditionally used insecticides.

Thiamethoxam's chemical structure is slightly different than the other neonicotinoid insecticides, making it the most water soluble of this family. Because of its greater water solubility, it moves readily in plant tissue. Products are labeled for soil, seed, and foliar treatments to a wide range of vegetable and field crops. Product formulations include emulsifiable concentrates, water dispersible granules, and soluble concentrates.

Toxicity

Neonicotinoids are classified by the EPA as both toxicity class II and class III agents and are labeled with the signal word "Warning" or "Caution." Because the neonicotinoids block a specific neuron pathway that is more abundant in insects than warm-blooded animals, these insecticides are more selectively toxic to insects than mammals. The most available toxicity data of the neonicotinoids is with imidacloprid. These data indicate that it is less toxic when absorbed by the skin or when inhaled compared to ingestion. It causes minor eye reddening, but is non-irritating to the skin. Signs of toxicity in rats include lethargy, respiratory disturbances, decreased movement, staggering gait, occasional trembling, and spasms. There are no accounts of human poisoning, but signs and symptoms of poisoning would be expected to be those similar for rats. A chronic toxicity study showed that rats fed up to 1,800 ppm resulted in a No Observable Effect Level (NOEL) of 100 ppm. The EPA categorizes imidacloprid as a "Group E" (no evidence of carcinogenicity). In animals and humans, imidacloprid is quickly and almost completely absorbed from the gastrointestinal tract, and eliminated via urine and feces within 48 hours. Of the neonicotinoids, imidacloprid is the most toxic to birds and fish. Both imidacloprid and thiamethoxam are highly toxic to honeybees. Mammalian toxicities for neonicotinoid pesticides registered in Florida are shown in Table 1 . Table 2 lists the toxicities to wildlife by the common name of the neonicotinoid pesticide. Table 3 provides a cross listing of many of the trade names that these products are registered and sold by in Florida.

Additional Information

Tables

Table 1. Neonicotinoid pesticide mammalian toxicities (mg/kg of body weight).

Common name

Rat oral LD50

Rabbit dermal LD50
Acetamiprid

450

>2,000 (Tristar®)
Imidacloprid

4,870 (Gaucho®)

>2,000 (Admire®)
Thiamethoxam

>5,000

>2,000

Table 2. Neonicotinoid pesticide wildlife toxicity ranges.

Common name

Bird acute oral LD50 (mg/kg)*

Fish LC50 (ppm)**

Bee LD50†
Acetamiprid

PNT

PNT

MT

Imidacloprid

MT

MT

HT
Thiamethoxam

ST

PNT

HT
*Bird LD50: Practically nontoxic (PNT) = >2,000; slightly toxic (ST) = 501 - 2,000; moderately toxic (MT) = 51 - 500; highly toxic (HT) = 10 - 50; very highly toxic (VHT) = <10.
**Fish LC50: PNT = >100; ST = 10 - 100; MT = 1 - 10; HT = 0.1 - 1; VHT = <0.1.
†Bee: HT = highly toxic (kills upon contact as well as residues); MT = moderately toxic (kills if applied over bees); PNT = relatively nontoxic (relatively few precautions necessary).

Table 3. Cross reference list of common, trade and chemical names of neonicotinoid insecticides.

Common name*


 Trade names**


 Chemical Name
Acetamiprid


 Acetamiprid®, Assail®, Tristar®


 (E)-N-(6-chloro-3-pyridinyl)methyl)-N1-cyano-N-methylacetamidine
Imidacloprid


 Admire®, Advantage®, Gaucho®, Merit®, Premise®, Touchstone®


 1-(6-chloro-3-pyridin-3-ylmethyl-N-nitroimidazolidin-2-ylidenamine
Thiamethoxam


 Cruiser®, Platinum®


 3-(2-chloro-1,3-thiazol-5-ylmethyl)-1,3,5-oxadiazinan-4-ylidenene(nitro)amine
*Basic molecule; isomers not listed.
**Does not include manufacturers' prepackaged mixtures; major agricultural brands for basic manufacturers.

Footnotes

1. This document is PI-80, one of a series of the Pesticide Information Office, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date October 2005. Visit the EDIS Web Site at http://edis.ifas.ufl.edu.

2. Frederick M. Fishel, Associate Professor, Agronomy Department, and Director, Pesticide Information Office; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition. Use pesticides safely. Read and follow directions on the manufacturer's label.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other extension publications, contact your county Cooperative Extension service.

U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.


Copyright Information

This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.