| True firs | Balsam twig aphid | - Look for trees with curled last season’s needles.
- On undamaged shoot, look for silvery,
oval-shaped eggs on underside of twig within 1–2 inches of buds.
- Light green stem mothers feed on undersides of needles, excreting honeydew droplets. |
| Colorado blue spruce | Cooley spruce gall adelgid | - Look for brown, pinecone-like galls from the previous season.
- Gray-black overwintering nymphs are found at the base of the new season’s buds. |
| Douglas-fir | Cooley spruce gall adelgid | - Look for crooked needles.
- Black nymphs will be on undersides of needles (may be covering over with white wax). |
| Norway spruce | Eastern spruce gall adelgid | - Look for brown galls at the base of previous year’s growth; needles may be missing beyond gall.
- The black overwintering nymphs will be found at the base of the new season’s buds. |
| Pines, spruces, true firs | Eriophyid mites | - Look at 20 trees per acre that exhibit a gray or rusty coloring.
- Tiny, peach-colored eggs are found in clusters or rows at the needle base (underside).
- Pale, oblong adult mites move along the needles. |
| Pines | Pales weevil | - Look for trees showing “flagging,” or browning, of needles at the ends of branches that have shown signs of chewing on stem bark.
- Pull duff away from base of last year’s stumps to look for adult weevils that are becoming active. |
| Douglas-fir | Rhabdocline needle cast | - Scout trees in areas likely to hold extra moisture such as shaded areas along a woodlot or tight plantings.
- Examine current season’s needles for orange-rust discoloration. |
| Spruces | Rhizosphaera needle cast | - On the lower half of the tree, look for purple-brown needles with visible black fruiting bodies. |
| Spruces | Spruce needle rust | - On cloudy days, look for needles with yellow bands containing an orange spot.
- Focus scouting in low or shaded areas. |
| Arborvitae, Douglas-fir, spruces, true firs | Spruce spider mites | - Look for discolored (brown or yellow) needles.
- Red eggs are found on the undersides of twigs, needles, and at base of buds.
- Reddish-brown adult mites move along needles and twigs.
- Tap symptomatic branches over a white surface to dislodge eggs or mites. |
| Douglas-fir | Swiss needle cast | - In shady or tightly planted areas, look for trees with needles that are browning from the tip down.
- On the underside of these needles, rows of tiny, black fruiting bodies will be visible with a hand lens.
- Also look for fruiting bodies on healthy, green needles. |
| Douglas-fir, pines, spruces | White pine weevil | - Set out baited pyramidal traps (see Appendix E for instructions).
- Check soil temperature daily on unshaded side of a tree in susceptible block.
- Once soil temperatures near 50°F, check traps daily.
- On sunny days, look for sap droplets on tree leaders as feeding evidence. |
