Green-scaled willow (Salix chlorolepis) COSEWIC assessment and status report: chapter 8

Limiting Factors and Threats

Most plants are generally inaccessible and no human threats are anticipated, except at the site of the largest population in the westernmost part of Vallée du Diable. This site, where CDPNQ estimates there are 200 specimens of the willow, is adjacent to the International Appalachian Trail on Mount Albert and is very exposed to human foot traffic. The author took the shortcuts taken by some hikers to get around obstacles in the trail. In the long term, such diversions from the trail cause it to be widened resulting in damage or destruction of adjacent specimens. At most, perhaps 10-20 specimens could be impacted by hiker foot traffic. The managers of Gaspésie Provincial Park are attempting to control the widening of the trail.

Off-trail downhill skiing is a sport that is gaining in popularity and skiers may eventually want to use other sectors of Mount Albert. At that time, the significance of the potential disturbances to green-scaled willow habitat caused by avalanches would have to be studied, but the threat appears to be minimal, if not non-existent.

Herbivors

During the 2004 inventory, the rusty tussock moth (Orgyia antiqua (Linnaeus, 1758)) of the family Lymantriidae (Lepidoptera), was observed on several occasions on green-scaled willow and short-fruit willow (Figure 7). The foliage of some individuals of green-scaled willow was severely affected. At present, it is impossible to know the impact of herbivory by rusty tussock moth on the green-scaled willow population; however, it is likely relatively limited (pers. comm., McIntosh, 2006). Dr. McIntosh, an insect and disease specialist, has indicated that based on the known behaviour of this moth and the ability of willows to sucker and survive even severe herbivory, the moth, by itself, would be unlikely to kill individual willow plants. This moth is also prone to a rapid population crash after an outbreak due to the fast buildup of fatal viruses (pers. comm., McIntosh, 2006).

Figure 7. Rusty tussock moth caterpillar on a green-scaled willow.

 Rusty tussock moth caterpillar on a green-scaled willow

An unidentified gall (Figure 8) was observed a number of times on the green-scaled willow and short-fruit willow (Salix brachycarpa). The galls are irregular and are likely caused by mites or aphids (Goulet, 2005). Its impact on green-scaled willow is unknown, but Sacchi et al. (1988) report that flower bud production is reduced by 43% by comparison with intact stems and that seed production per individual is reduced by between 10% and 50% in the case of Salix lasiolepis.

Figure 8. Galls on green-scaled willow.

Galls on green-scaled willow

On the specimen cultivated in the private garden, aphids were observed during the first year of planting (1994), but no other infestations have since been observed. No observations of this type were made on individuals from Mount Albert.

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