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How to identify it
- The first clear symptom is browning of the current year's needles in September, followed by early needle drop through fall and winter.[1][2]
- Affected needles are much shorter than normal. The needle sheath at their base is hardened and dead because the needle base inside has been hollowed out, forming a gall-like swelling at the base of the needle bundle.[1][2]
- Pull a bundle apart in summer and the small larvae are between the two needles inside the sheath, or on the needle surface between sheath and needles.[1]
Where it lives
Natural Resources Canada records it in eastern Canada, and the USDA Forest Service reports it from red pine in Wisconsin. It has been known in North America since 1932, mostly in red pine plantations.[1][2]
Biology and life cycle
Adults emerge between late May and early June and lay eggs, singly or in small clusters, at the base of new needle bundles on shoots still covered by bud scales.[1]
The young larvae bore into the needle sheath before it hardens and feed there through the summer. In October they drop to the ground and overwinter as larvae in the litter.[1]
A shady, cold site delays adult emergence, and vigorous trees whose new shoots elongate quickly give the females less chance to lay eggs.[1]
Damage and signs
- Major damage is occasional and very local. In a heavy infestation, lateral and terminal shoots may die if they lose more than 75 percent of their needles, and the USDA manual notes that laterals and terminals of heavily infested trees may be killed.[1][2]
- The midge does not threaten the tree's survival, but growth is reduced when large populations persist for two or three years. Heavy infestations appear to be confined to slow-growing trees.[1][2]
Health risk
Neither source mentions any effect on people; the midge is a pest of red pine needles only.[1][2]
Control
Prevention
Keep red pines vigorous. Fast-elongating shoots on healthy trees hinder egg-laying, and heavy infestations appear confined to slow-growing trees, so site and care matter more than any treatment.[1][2]
Early scouting of the new shoots in summer helps detect the larvae, especially during heavy infestations, before the browning shows in September.[1]
Common questions
- Why are this year's needles on my red pine short and turning brown in September?
- Short current-year needles with a hardened, dead sheath at the base that brown in September and drop over winter point to the red pine needle midge, whose larvae feed inside the sheath through summer.[1][2]
- Will the red pine needle midge kill my tree?
- No. It does not threaten the tree's survival. Shoots can die if they lose most of their needles, and growth slows if heavy populations persist for two or three years.[1]
Sources
- Natural Resources Canada, Canadian Forest Service, “Red pine needle midge, Trees, insects and diseases of Canada's forests.” tidcf.nrcan.gc.ca/en/insects/factsheet/3741 (accessed 2026-11-10)
- USDA Forest Service, “Eastern Forest Insects, Miscellaneous Publication 1175 (W. L. Baker, 1972; scanned copy).” archive.org/details/easternforestins1175bake (accessed 2026-11-10)
- iNaturalist, “Thecodiplosis piniresinosae taxon page (order and family).” www.inaturalist.org/taxa/1273374 (accessed 2026-11-10)