pine needles off, black worms on the porch

(Question)

HI: after a week of absence I noticed that my10-year old previously quite healthy pine ‘shrub’ tree has lost all needles except for this-year’s growth (some brown ones still stayed on the branches), and in 2 m from it I saw plenty of 2-cm black worms on my porch.
Please advise if there is a way to save the shrub? Should i alert the city? Many thanks.

(Answer)

It sounds like you could have an infestation of sawfies and their larvae. According to The Online Gardener’s Handbook 2010These insects feed in colonies, defoliating one branch then moving to the next. Many species exist, and they attack both coniferous and deciduous trees and shrubs.

The larvae of sawflies that attack conifers feed on needles and mine buds, or bore into the pith of young shoots. Fir, larch, spruce, pine and hemlock are most susceptible. The larvae look like caterpillars but have more than 5 pairs of prolegs and lack hooked spines.”

European pine sawflies have dark-greenish bodies with longitudinal stripes and black heads and appear in late May and June.

Ontario Ministry of agriculture, Food & rural Affairs (OMAFRA) recommends removing individual colonies by hand and destroying whenever possible. Some of these insects have natural enemies which help keep populations in check.

 For more in-depth information see https://omafra.gov.on.ca/english/crops/gardbk/gh-ch6-2ins.htm#13 In your situation, it would probably be a good idea to consult a tree expert.