Cranberry Girdler; Sod Webworm Chrysoteuchia Topiaria

44 MAJOR INSECTS: Cranberry Girdler

CHAPTER TWENTY Cranberry Girdler; Sod Webworm Chrysoteuchia topiaria

David L. Overhulser

Insect and hosts The larval stages of the cranberry girdler commonly feed on the crowns and roots of grasses. Cran- berry girdler feeding damage to the root-collar area of conifer seedlings has been reported in Oregon, Wash- ington, and Idaho. Two-year-old Douglas-fir, noble fir, larch, and spruce stock are frequently damaged. Other stock types occasionally damaged are 1+0 and 3+0 Douglas-fir and 1+0 larch.

Cranberry girdler damage may be confused with: Lower stem canker Mechanical damage Rodent feeding Root weevil damage Figure 20-1. Cranberry girdler damage to 2+0 noble fir seedlings. Oregon Department of Forestry photo. Symptoms jerky movements for short distances. of the effects of predation and In late summer and early fall, Female moths deposit eggs on and disease on overwintering larvae. cranberry girdler larvae eat patches around nursery stock. Eggs hatch in of bark and cortex from the root 3 to 5 days. Larvae feed in nursery collars and roots of seedlings beds from June to October. The Loss potential (Figures 20-1 and 20-2). Damage is feeding of late-instar larvae from Nurseries next to grass fields, detected when stock is lifted and August to October causes the most graded or when severely damaged which are prime cranberry girdler damage to seedlings. In late fall, habitat, are most vulnerable. When seedlings still in the beds turn yellow larvae spin a cocoon in the soil in the fall. the moth population is high, 15 to 20 where they overwinter (Figure 20-4). percent of the seedlings in a single lot Cranberry girdler larvae and can suffer below-ground girdling. Insect biology cocoons usually cannot be found by Since many foresters will not accept searching nursery soil. Moths are seedlings with cranberry girdler Adult moths (Figure 20-3) emerge easily detected in the spring with damage, the cull rate for infested from May to July in grass fields in or traps baited with a commercially seedlings can be high. next to nurseries. Moths are visible available attractant. Moth popula- during daylight; they fly in quick, tions vary from year to year because MAJOR INSECTS: Cranberry Girdler 45

igure 20-4. Late-instar cranberry girdler larva in hibernaculum. Larvae ire generally 25 mm (1 inch) in length. J.S. Department of Agriculture photo.

September kills small larvae feeding tear the soil surface.

Selected references Figure 20-2. Cranberry girdler damage to 2+0 Douglas-fir. Note that callus has not formed around wounds, indicating that damage took place in late summer and fall. Berry, R.E. 1978. Insects and mites of Oregon Department of Forestry photo. economic importance in the Northwest. Corvallis, OR: Oregon State University, Department of BIOLOGICAL Entomology. 189 p. Birds such as starlings, killdeer, sandpipers, and blackbirds feed on Kamm, J.A.; Robinson, R.R. 1974. Life overwintering larvae. These birds history and control of sod are common in bareroot nurseries webworms in grass seed and grass fields. A naturally occur- production. Extension Circular ring soil fungus, Beauveria bassiana, 851. Corvallis, OR: Oregon State also kills overwintering larvae. University, Extension Service. 2 p.

CHEMICAL Kamm, J.A.; Morgan, P.D.; Traps placed in grassy areas next Overhulser, D.L.; McDonough, to the nursery will help in timing the L.M.; Triebwasser, M.; Kline, L.N. applications of insecticides. Figure 20-3. Moth stage of cranberry 1983. Management practices for girdler is present from May to July. Diaz-inon, applied to nursery beds 3 and 5 cranberry girdler (Lepidoptera: Moths are generally 25 mm (1 inch) in Pyralidae) in Douglas-fir nursery length. U.S. Department of Agriculture stock. Journal of Economic photo. Cranberry girdler symptoms Entomology. 76:923-926. appear: Tunnock, S. 1985. Suppression of Management 2+0 cranberry girdler damage in beds Late summer to lifting of Douglas-fir seedlings, Coeur CULTURAL d'Alene nursery, Idaho Panhandle Removing grasses in noncrop National Forest. Report 85-4. areas by cultivating or applying Missoula, MT: Northern Region. herbicides will eliminate prime weeks after the male moths are U.S. Department of Agriculture, habitat and therefore reduce infesta- detected in traps, is effective against Forest Service. 7 p. tion of nursery beds. ovipositing female moths. Applying chlorpyrifos to the soil in August and