Mugo Pine Pest

Asked November 1, 2019, 4:22 PM EDT

Yesterday, 10/31/19, noticed the egg sac looking nests on crowns of Mugo Pines. Do you know what this pest is and how to treat it? Have 25 mugos on property, have cut out area infected but most likely missed some. Mugo's in part shade, sprinkled beds, Southern Maryland, sand/loom soil, and do not fertilize.

Calvert County Maryland

1 Response

Good morning. This looks like frass produced by a boring insect. Nantucket pine tip moth and European pine shoot moth both can affect mugo pines. The larvae bore into the stem, causing the shoots to die. They may prune back but rarely kill established pines.

The best method of removal is to prune out the affected branches, cutting several inches below where you see the frass. Remove the cuttings off-site (in the trash) so that they do not serve as a source for re-infestation. Manual pruning would be more practical and effective than using an insecticidal spray.