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Timbor Fungicide, Insecticide & Wood Preservative

-A low toxicity wood treatment for insects and rot fungi-

Summary: Timbor is a natural insecticide/fungicide that is widely used as a wood preservative for protection against both insects and fungi. It is composed of nearly pure sodium borate, a crystalline salt form of boric acid. It is applied as a dry powder to wall voids or as a water solution to dry, unfinished wood surfaces.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Timbor is an insecticide/fungicide/wood preservative composed of 98% sodium borate (borax), a sodium salt of boric acid. Timbor itself is a white, fluffy powder that can be puffed in to wall voids for carpenter ant control, or dissolved in water and applied as a course spray* to surfaces. See the fact sheet and specimen label below for additional technical and product use information.

As an insecticide/fungicide Timbor is labeled for use against termites, wood destroying beetles, carpenter ants, and wood decay fungi. It is very effective against many of the most important wood destroying organisms and exhibits relatively low toxicity compared to other pesticides.

When used as a spray borate crystals are deposited on the wood when the water dries and may even penetrate a short distance into the surface. Borate acts as a stomach poison to any insect that comes into contact with this layer. Keep in mind that since borate is water soluble it must be used in dry situations or sealed over to make it waterproof. Often, water proof stains are applied once the spray dries.

* Timbor dissolves completely in water to make a true solution.

Timbor is made from borax (borate) crystals

Borax (sodium borate) crystals from which Timbor and other borate products are made. Photo by Aram Dulyan, Wikipedia


Timbor label and fact sheet

A specimen label (see below) contains all of the information for using and registering a pesticide product in the US but it is not attached to an actual product therefore specimen labels should only be used for general reference. The label attached to the product you are using has the final, often amended information.

The main ingredient in Timbor, borax, is mined as a crystal of nearly pure sodium borate. Borax itself has many commercial uses including water softening, flame retardant, glass additive, and as an insecticide/fungicide. See the Related Articles below for more information.


Purchasing and using Timbor

Timbor is sold as a water soluble powder in 1 lb bags and 25 lb pails. A 1 lb bag makes 1 gal of working solution. Two coats, applied with a pump sprayer or paint roller, are often needed, see label instructions. The dry powder can also be used to treat wall voids for carpenter ants. Like other borate-based wood preservatives Timbor is generally not available in stores but is available here (DoMyOwnPestControl).

Related Articles

Tim-Bor specimen label

Boric acid fact sheet - The National Pesticide Telecommunications Network (NPTN) fact sheet for the active ingredient in Timbor.

What are the Important Wood Destroying Insects?

Other Wood Preservatives That Contain Borate


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Jack DeAngelis, PhD,  , email:  [email protected]

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