Environmental Entomology (1994) 23, 396-405

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Gladwin Joseph and Rick G. Kelsey (1994)
Acceptability and suitability of Douglas-fir as a secondary host for gypsy moth (Lepidoptera: Lymantriidae)
Environmental Entomology 23 (2), 396-405
Abstract: Given free choice, first instar gypsy moth, Lymantria dispar (L.), larvae selected new flush Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, foliage over 1-yr-old fir needles, fir bud scales, or young expanding white alder, Alnus rhombifolia Nutt., leaves. Although new fir foliage was the most acceptable, it was not the most suitable for first or fourth instars. Fourth instars fed new fir foliage consumed more but did not grow any better than larvae fed 1-yr-old needles or alder. This was the result of a decreased efficiency of converting digested food to growth. Switching II, III, or IV instars from white alder to Douglas-fir reduced pupal weights compared with larvae fed white alder alone but it did not affect development rate. Switching to Douglas-fir increased instar duration and decreased relative weight gain for all instar switches, but this lasted only for the instar switched. As a secondary host for gypsy moth, Douglas-fir differs from northeastern pines. First instars ingest new fir foliage but not pine foliage because of its toughness. Larvae switched from a preferred host to fir do not perform as well as larvae remaining on the preferred host, whereas larvae switched to pine outperform those remaining on the preferred host. In Northwest forests, Douglas-fir could possibly maintain gypsy moth populations without the presence of other hosts.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Database assignments for author(s): Rick G. Kelsey

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Lymantria dispar Pine (Pinus) U.S.A. (NE)
Lymantria dispar Fir (Abies) U.S.A. (NE)
Lymantria dispar Douglas fir (Pseudotsuga menziesii) U.S.A. (NE)
Lymantria dispar Alder (Alnus) U.S.A. (NE)