An Ergonomic Evaluation of Douglas Fir Manual Pruning in New Zealand

Douglas-fir seed chalcid (DFSC) Megastigmus spermotrophus, a small (3 mm long) host-specific seed-predatory wasp, was accidentally introduced into New Zealand in the 1920s. Concern over DFSC reducing Douglas-fir seed production in New Zealand led to an attempt at biocontrol in 1955 with the release, but failed establishment, of the small (2.5 mm long) parasitoid wasp, Mesopolobus spermotrophus. We investigated why DFSC causes little destruction of Douglas-fir seed in New Zealand (usually <20%) despite the apparent absence of major natural enemies. Douglas-fir seed collections from 13 New Zealand sites yielded the seed predator (DFSC) but also potential parasitoids, which were identified using morphology and partial COI DNA sequencing. DFSC destroyed only 0.15% of Douglas-fir seed. All parasitoids were identified as the pteromalid wasp, Mes. spermotrophus, the host-specific biocontrol agent released in 1955. Total parasitism was 48.5%, but levels at some sites approached 90%, with some evidence of density-dependence. The discovery of the parasitoid Mes. spermotrophus could indicate that the biocontrol agent released in 1955 did establish after all. Alternatively, Mes. spermotrophus could have arrived accidentally in more recent importations of Douglas-fir seed. The high level of parasitism of DFSC by Mes. spermotrophus is consistent with DFSC being under successful biological control in New Zealand. Suppression of DFSC populations will benefit commercial Douglas-fir seed production in New Zealand, but it also represents the likely loss of a potential biological control agent for wilding Douglas-fir.

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Megastigmus spermotrophus. [Distribution map].

Distribution Maps of Plant Pests ◽

10.1079/dmpp/20056600378 ◽

1977 ◽

Author(s):

Keyword(s):

New Zealand ◽

North America ◽

Host Plant ◽

Geographical Distribution ◽

Pseudotsuga Menziesii ◽

Douglas Fir ◽

Distribution Map ◽

New Distribution ◽

Distribution In Europe

Abstract A new distribution map is provided for Megastigmus spermotrophus(Wachtl.) (Hymenopt., Torymidae) (Douglas Fir Seed-Fly). Host Plant: Pseudotsuga menziesii. Information is given on the geographical distribution in EUROPE, Austria, Belgium, Britain, Czechoslovakia, Denmark, France, Germany, Hungary, Ireland, Netherlands, Poland, Yugoslavia, AUSTRALASIA, New Zealand, NORTH AMERICA, Canada, U.S.A.

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Phaeocryptopus gaeumanii. [Distribution map].

Distribution Maps of Plant Diseases ◽

10.1079/dmpd/20056500042 ◽

1976 ◽

Author(s):

Keyword(s):

British Columbia ◽

New Zealand ◽

North America ◽

Northern Ireland ◽

Geographical Distribution ◽

Pseudotsuga Menziesii ◽

Douglas Fir ◽

Distribution Map ◽

Irish Republic ◽

New Distribution

Abstract A new distribution map is provided for Phaeocryptopus gaeumanii (Rohde) Petrak. Hosts: Douglas fir (Pseudotsuga menziesii). Information is given on the geographical distribution in AUSTRALASIA & OCEANIA, Australia (Tasmania), New Zealand, EUROPE, Austria, Belgium, Britain & Northern Ireland, Denmark, France, Germany, Irish Republic, Italy, Netherlands, Romania, Sweden, Switzerland, Yugoslavia, NORTH AMERICA, Canada (British Columbia), USA.

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