INSECTS FEEDING ON RHIZOMES AND ROOTS

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INSECTS FEEDING ON RHIZOMES AND ROOTS

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1. Plants cut-off at or slightly below the soil surface in the spring (April, May, early June). Lower foliage with ragged-edged holes. Cutworms found beneath soil surface during the day and feeding on above-ground foliage at night. REDBACKED CUTWORM {bmc larvai.bmp} and other Euxoa species (Figs. 1, 2 PNW Pub. #182) and BLACK CUTWORM. Redbacked cutworm occurs only east of the Cascade Mountains.

2. Plants show wilted appearance above ground during August, September and early October. Rhizomes with tunneling around the nodes or rhizomes hollow. MINT ROOT BORER LARVAE {bmc larvai.bmp} if 1/2 inch long with three pairs of true legs (pg 3 PNW Pub. #322, Fig. 9 PNW Pub. #182). If larvae smaller, 1/8 inch long, C-shaped, white legless grub found feeding inside mint stems near the soil surface in Idaho or eastern Oregon, then MINT STEM BORER LARVAE {bmc larvai.bmp} (Fig. 15 PNW Pub. #182.)

3. Plants slow to grow in the fall and early spring. Surface feeding injury on the rhizomes, roots and stems. Small C-shaped white legless larvae1/4 to 1/2 inch long with brown head may be found inside roots or in the soil around or beneath roots. STRAWBERRY ROOT WEEVIL LARVAE{bmc larvai.bmp} (Fig. 13 PNW Pub #182). Also includes other weevil species such as black vine weevil, obscure root weevil, and rough strawberry root weevil.

4. Plants slow to grow in the spring. Feeding injury evident on surface of roots or just beneath root epidermis, brown "tracking" evident just beneath root epidermis Very small white larvae 1/8 inch long with three pairs of legs and a brown head may be found inside the roots or in the soil around roots. MINT FLEA BEETLE LARVAE {bmc larvai.bmp} (Fig. 11 PNW Pub. #182).

5. Plants stunted in irregular spots in the field, plants often very slow-growing in the spring. Small, 1/8 to 1/4 inch long, white centipede-like animals feeding on small roots leaving few root hairs, roots stunted and discolored with prunned appearance. Found principally west of the Cascade Mountains. GARDEN SYMPHYLAN {bmc symphi.bmp} (Fig. 21 PNW Pub. #182).

6. Plants appear stunted and slow growing from feeding injury on roots and rhizomes. Tan or dark brown, shiny, segmented larvae, 1/2 to 3/4 inch long, with three pairs of legs and key-hole-like structure on the last abdominal segment. WIREWORM LARVAE {bmc larvai.bmp} (Fig. 19 PNW Pub. #182).