Lodgepole pine seedset increase by mesh bagging is due to Leptoglossus occidentalis (Hemiptera: Coreidae) exclusion.

Authors

  • Ward Strong BC Ministry of Forests, Lands and Natural Resource Operations

Keywords:

Heteroptera, Hemiptera, Coreidae, foraging behaviour, crop loss, internal cone temperature, relative humidity,

Abstract

Lodgepole pine (Pinus contorta  Dougl. ex. Loud. var latifolia) seed orchards in British Columbia, Canada, suffer from low seedset problems. Seedset can be improved by installing mesh bags over the 2nd-year cones. One mechanism of improved seedset has been shown to be exclusion of the seed-feeding Western Conifer Seedbug, Leptoglossus occidentalis, but the possibility of microclimate alteration leading to improved seedset has not been carefully explored. We measured the internal cone temperatures of cones both inside and outside mesh bags, as well as the relative humidity around cones both inside and outside bags. We also installed time-lapse cameras that, every 5 minutes, photographed unbagged cones situated near bagged cones, and examined the photographs for feeding by L. occidentalis. Internal temperatures of cones inside bags were warmer, accumulated more heat units, and had higher peak temperatures than cones outside bags. Humidity was slightly higher inside bags in late-season, particularly during rainy days. The evidence did not support the hypothesis that microclimate change is the cause of improved seedset inside bags. On the other hand, the cameras showed extensive feeding by L. occidentalis on unbagged cones, and showed a strong correlation between the amount of time a cone was fed upon and the subsequent seedset. Therefore the increase in seedset due to the mesh bags is not related to microclimate change, but is caused by exclusion of L. occidentalis.

Author Biography

Ward Strong, BC Ministry of Forests, Lands and Natural Resource Operations

Tree Improvement Branch

Research Scientist, Reforestation Entomology

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Published

2016-02-25