We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Birds

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What Is a Spruce Budworm?

By Phil Riddel
Updated: Jun 04, 2024
Views: 6,451
References
Share

Contrary to its name, the spruce budworm is not a worm, but the caterpillar of a moth. There are, in fact, a number of different species of spruce budworm, all belonging to the genus Choristoneura and all broadly similar in appearance, but the two most destructive insects are the Eastern Spruce Budworm, C. fumiferana and the Western Spruce Budworm, C. occidentalis. The caterpillars feed on various coniferous trees, such as spruces, firs and pines. The moths are found in many parts of the United States, including Alaska, and Canada; some species are found in Europe and Asia. It is the caterpillar that does the damage; the adult moth does not feed on plants.

The moths, which vary from grayish to brownish in color, lay their eggs late in the summer on the undersides of spruce needles. The larvae, after they hatch, do not begin feeding, but instead build structures out of silk among bark and small twigs, in which they hibernate through the winter. They emerge from hibernation the following spring, just before new growth begins on the host tree.

The caterpillars, which are brown with whitish spots — resembling small spruce twigs, initially feed upon old needles, but move on to budding new needles, which they seem to prefer, as soon as they are available. It is these attacks on the growing centers that cause the most damage. The larvae feed until they have matured, usually by late June. At this point, they build silk cocoons close to the feeding areas and pupate there. The moths appear about ten days later.

Obvious signs of attack by spruce budworm are brown-colored dead needles and stunted or deformed growth near the tips of branches. Closer inspection will reveal silk webbing spun between needles and twigs, and crumbly excreted material known as frass. Damage may be restricted to the growing tips, but in heavy infestations, other parts may be affected and severe defoliation may result. Trees that are stressed — for example, as a result of drought — are more vulnerable to attack by this insect and are more badly damaged. Healthy trees will normally recover, but repeated attacks on trees weakened by stress can eventually be fatal.

The spruce budworm has a number of natural predators, including birds, spiders and parasitic wasps. These usually limit budworm numbers, but from time to time, a combination of factors can produce a population explosion, resulting in extensive damage. Often, the best control policy consists of keeping the trees healthy and better able to resist or recover from attack by minimizing stress factors. In the event of a severe infestation, a number of common insecticides can be effective. The bacterium Bacillus thuringensis, which produces an insecticidal compound, has proved to be a successful method of biological control.

Share
All Things Nature is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Link to Sources
Discussion Comments
Share
https://www.allthingsnature.org/what-is-a-spruce-budworm.htm
Copy this link
All Things Nature, in your inbox

Our latest articles, guides, and more, delivered daily.

All Things Nature, in your inbox

Our latest articles, guides, and more, delivered daily.