Browning of Colorado Blue Spruce

Asked July 4, 2018, 12:29 PM EDT

The top and half of my blue spruce is quickly turned brown with loss of needles and pine cones. What are possible causes and how can I treat this so I don't lose the entire tree.

Howard County Maryland

3 Responses

We can see in your photo that your tree has bagworms. They can be a serious pest in conifer trees if left unmanaged. You can treat bagworms with a pesticide containing Bacillus thuringiensis (Bt), which is a type of bacteria that only kills certain insects and does not affect humans or animals. Bt must be applied between mid-June and mid-July because it works well only on young bagworms. Additional options for mechanical and chemical control of bagworms are provided on our website:


Thank you for your prompt response. How often should the solution be placed on the tree.

You will have to read and follow the pesticide product label for instructions on how often to apply the product during the period between mid-June -- mid-July. Bagworms have just one generation per year. You can apply treatment now. In fall and winter, continue to check the tree and manually remove/destroy any bags you see. They may contain up to 1,000 overwintering eggs. In June next year, begin looking for new bags, and treat again with Bt if needed.