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  • Jane Shellenberger



Marking trees with a “No Vacancy” sign for bark beetles, ISCA®’s SPLAT® Verb goes to work at Tahoe National Forest

As climate changes and weather patterns become increasingly unpredictable, some of the smallest pests can wreak large scale havoc on the magnificent trees of our forests. Fluctuations in temperature, drought and overcrowding contribute to unhealthy conditions for millions of acres of forested land.  Stressed by these conditions, large swaths of trees are left in a weakened state that can render them vulnerable to pests that a healthy tree would be able to resist.

Among the most damaging pests in the forest are bark beetles. Particularly the mountain pine beetle, Dendroctonus ponderosae. When these beetles successfully colonize susceptible trees, the beetle population flourishes, often leading to tree mortality.  When beetle damage affects large sections of forest the landscape can become increasingly vulnerable to wildfire.

Photo courtesy of ISCA

ISCA’s SPLAT® Verb helps resource managers protect high-value trees with an innovative solution that is inconspicuous to humans and animals but loudly communicates “no vacancy” to bark beetles. This species of beetle puts out its own pheromone signal once a tree is considered too full to handle more beetles, in essence, asking its species to move on to another tree.  SPLAT® Verb mimics this signal, causing the new approaching beetles to move on to more hospitable locations.

A recent U.S. Forest Service audio podcast details the research station’s use of SPLAT® Verb in combating mountain pine beetle, Dendroctonus ponderosae, in the Tahoe National Forest.

Adult mountain pine beetles can kill western pine trees by burrowing into trees and laying eggs into the bark, enabling the larvae to infest and destroy the tree. The mountain pine beetle is also a vector for blue stain fungus, which, combined with larval feeding, blocks water and nutrient transport within the tree. 

In forests throughout the West, mass attacks of bark beetles are part of a tapestry of environmental stressors that are killing millions of trees each year. They can do this because overcrowding, warming, drought and disease diminish the tree's defenses. Many forests have too many trees on the landscape, which creates competition for limited water and space to grow. Together, these environmental stressors weaken trees, making them more vulnerable to infestation.

Enter bark beetles, tiny brown insects that are about the size of a grain of rice. Bark beetles spend most of their lives within a tree, feeding and reproducing beneath the bark. There are approximately 200 native species of these tiny creatures in the U.S., and most support forest health by helping break down vegetation as part of the natural decomposition process. But around ten species prey on and kill some of our most desirable trees, which contributes to tree mortality. And most use pheromones to communicate with each other when they do it.

Photo courtesy of the USDA Forest Service: Danny Cluck, an entomologist with Forest Health Protection, State and Private Forestry for the Forest Service Region 5, applies the pheromone verbenone to a sugar pine that is genetically resistant to white pine blister rust to protect it from bark beetle infestation. Tahoe National Forest, June 2023. (USDA Forest Service photo by Andrew Avitt)

In the U.S. Forest Service podcast episode, Chris Fettig, a research entomologist with the U.S. Forest Service's Pacific Southwest Research Station, explains, “For a tree to die as a result of bark beetle attacks, it requires what we call a 'mass attack,' a whole bunch of beetles coming together in a very short period of time to overwhelm the tree's defenses. They facilitate that through the release of aggregation pheromone components that say, ‘come here,’ drawing other beetles into mass attack on that tree.”  

Once a tree begins to fill up, they switch to production of an anti-aggregation pheromone, which says, "Hey, this tree's filling up, please disperse.”

SPLAT® Verb is manufactured by ISCA.  It features the anti-aggregation pheromone verbenone and is available in an easy-to-apply, no mix, no dilution, ready-to-use tube.



Hinrichs, J. (2024) Bark beetles: The science of Scents, US Forest Service. Available at: (Accessed: 01 February 2024).

Forest Focus: Episode 35: Bark Beetles: The Science of Scents (2023) Forest Service National Website. Available at: (Accessed: 01 February 2024).

For more information or to purchase SPLAT® Verb:


ISCA, headquartered in Riverside, Calif., is committed to the research, development, and commercialization of innovative, safe, and eco-friendly management solutions for agriculturally detrimental pests and disease vectors. Harnessing the power of nature's biocommunication compounds, ISCA's groundbreaking products not only offer protection against destructive pests but also ensure the preservation of non-target species. In many scenarios, ISCA's solutions significantly reduce or eliminate the need for traditional pesticides. For a deeper insight into our sustainable approach to crop protection, please visit



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