chlo·​ro·​thal·​o·​nil | \ ˌklȯr-ə-ˈtha-lə-ˌnil How to pronounce chlorothalonil (audio) \

Definition of chlorothalonil

: an organochlorine fungicide C8Cl4N2 that protects against a wide range of fungal diseases and is used especially on agricultural crops (such as peanuts and tomatoes) And, although chlorothalonil is an excellent home garden fungicide, and oil sprays are highly effective against mites and other soft-bodied insects, the two are not compatible and cannot be combined or used within several days of each other.— H. S. Stevens, Dallas Morning News, 28 May 1999 … one of the most widely used fungicides on crops in the United States, chlorothalonil, raises mortality rates among frog tadpoles at low concentrations.— Susan Milius, Science News, 11 Sept. 2010

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

  • More than 250,000 words that aren't in our free dictionary
  • Expanded definitions, etymologies, and usage notes
  • Advanced search features
  • Ad free!

First Known Use of chlorothalonil

1973, in the meaning defined above

Keep scrolling for more

Learn More about chlorothalonil

Time Traveler for chlorothalonil

Time Traveler

The first known use of chlorothalonil was in 1973

See more words from the same year

Statistics for chlorothalonil

Cite this Entry

“Chlorothalonil.” Dictionary, Merriam-Webster, Accessed 26 Jan. 2021.

Comments on chlorothalonil

What made you want to look up chlorothalonil? Please tell us where you read or heard it (including the quote, if possible).


Test Your Vocabulary

Slippery Words Quiz—Changing with the Times

  • ducreux self portrait yawning
  • What is an earlier meaning of nice?
Name That Thing

Test your visual vocabulary with our 10-question challenge!

 AlphaBear 2

Spell words. Make bears.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!