DISTRIBUTION AND IMPACT OF LEPTOGLOSSUS OCCIDENTALS HEIDEMANN (HEMIPTERA: COREIDAE) IN SEED ORCHARDS IN BRITISH COLUMBIA

Abstract

Leptoglossus occidentalis Heidemann (Hemiptera: Coreidae) is considered to be an important cone and seed pest in seed orchards in British Columbia; however, no impact studies have been done in Canada. Surveys to determine the distribution of L. occidentalis were conducted over a 3-year period in three coastal seed orchards of Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, and over a 2-year period in two seed orchards of lodgepole pine, Pinus contorta var. latifolia Engelmann. Leptoglossus occidentalis was found to distribute itself in patches, coinciding with a clonal preference. Seed losses were assessed for 2 years in the coastal Douglas-fir orchards and for 1 year in one lodgepole pine orchard. The percentages of partially filled seed that could have been caused by feeding of L. occidentalis or by a number of other factors were < 5% in coastal Douglas-fir for both 1992 and 1993 and ~14% in lodgepole pine in 1993. Apparently because populations of L. occidentalis were low, there was no correlation between the percentage of partially filled seed and number of insects per tree. Except in unusual circumstances, management measures in Canada are judged not to be necessary as populations of L. occidentalis are consistently below the calculated threshold levels required to cause ≥5% loss in seed production.

Host colonization patterns, cues mediating host selection and calibration of field surveys with estimates of population abundance of leptoglossus occidentalis in a seed orchard.

“…Consistent with Blatt and Borden's (1996) Blatt and Borden (1996) also reached the same conclusion. However, other highly ranked clones, including the most highly infested clones in both 2008 and 2009, were not highly ranked in 1993 or 1994 (Blatt and Borden 1996).…”

“…However, other highly ranked clones, including the most highly infested clones in both 2008 and 2009, were not highly ranked in 1993 or 1994 (Blatt and Borden 1996).…”

“…Cones have significantly stronger infrared radiation than foliage, and this differential may also provide a strong short-range navigation cue for L. occidentalis searching for feeding and oviposition sites Blatt and Borden's (1996) finding that L. occidentalis clonal preference on lodgepole pine is consistent from year to year, and; 3) assess clonal differences among several candidate host-selection cues identified from the literature.…”

Assessment of cues potentially mediating host selection of Leptoglossus occidentalis on Pinus contorta

“…Carr. (DeBarr et al , ; Blatt & Borden, ; Bains et al , ). Blatt and Borden () found that L. occidentalis exhibited pronounced clonal preferences in seed orchards of lodgepole pine and Douglas‐fir, and that the preference was relatively consistent from 1 year to the next.…”

“…The present study aimed to (i) identify and rank the clones of lodgepole pine favoured by L. occidentalis in 2008 and 2009 at the Kalamalka Seed Orchard in Vernon, British Columbia, Canada; (ii) test the finding of Blatt and Borden () suggesting that L. occidentalis clonal preference on lodgepole pine is consistent from year to year; and (iii) assess whether or not host preference could be explained by monoterpene emission, infrared radiation, cone number and/or size.…”