Aspen defoliators
Last Review/Updated: November 20, 2008
The following information summarizes the annual pest conditions for each year. For more detailed information, click here to download the annual reports.
If there is any discrepancy between the forest health information on this website and the original paper versions, the paper originals are considered to be the authoritative ones. Although every effort is made to ensure that all information posted on the forest health website is accurate and complete, its integrity is not guaranteed. This information is provided for personal use only and is not intended for commercial use. Written permission to publish this information must be requested from the Manager of Forest Health at (780) 427-8474; Fax (780) 427-0084, or Fh.Info@gov.ab.ca.
| Year | Description | Click Map to Enlarge |
|---|---|---|
| 2007 | Aspen defoliation, predominantly by the forest tent caterpillar, was scattered over an estimated 3,255,338 hectares of provincial forested Crown land. This was a 44.4% reduction compared to the 5,851,155 hectares affected in 2006. The extent of defoliation was significantly reduced in the Northwest but increased in the Northeast and Southwest Alberta. Bruce spanworm, linden looper and large aspen tortrix were among the other defoliators of aspen. No gypsy moths were collected in the pheromone-baited traps deployed by Alberta Sustainable Resource Development to detect this pest. |
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| 2006 | The forest tent caterpillar was the major defoliator of aspen forests in 2006. The extent of insect pest-caused aspen defoliation almost doubled in 2006 to reach 5.8 million hectares compared to the area defoliated in 2005. Most of this defoliation was of moderate intensity (30-60%). The large aspen tortrix and the aspen leafroller were the other aspen defoliators reported in 2006. Most of the aspen defoliation in 2006 occurred in northwest Alberta. |
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| 2005 | As expected, forest tent caterpillar (FTC) infestations expanded in 2005 at the expense of large aspen tortrix infestations. Insect pest-caused aspen defoliation expanded dramatically in northern Alberta in 2005; the gross area of defoliation was scattered over an estimated 2.8 million hectares, a four-fold increase, compared to 632,810 hectares affected in 2005. The FTC defoliation was prominent in the Northwest Corporate Region and perhaps was underestimated in the Northeast Corporate Region. Aspen defoliation is expected to increase in 2006. |  |
| 2004 | Keeping with the historical trends, populations of the large aspen tortrix also collapsed in most areas of the province in 2004. The total area affected by aspen defoliators was reduced to 654 886 ha compared to 5 447 089 ha affected in 2003. However, the forest tent caterpillar populations picked up especially in the NW Region. More widespread forest tent caterpillar defoliation is expected in the province in 2005. |  |
| 2003 | The large aspen tortrix was the predominant aspen defoliator in the province in 2003. This pest defoliated aspen stands scattered over an estimated 5.4 million hectares in the province. There was a shift in the defoliated area in western Alberta as the eastward movement of this pest continued in 2003. This shift of large aspen tortrix populations in western Alberta will continue if the eastward movement of the pest continues as expected. However, the forest tent caterpillar infestations are expected to pick up in the coming years in areas where large aspen tortrix populations decline. No gypsy moths were trapped during the annual survey carried out by Alberta Sustainable Resource Development (SRD) in 2003. However four gypsy moths were trapped by the City of Edmonton under the Canadian Food Inspection Agency's program. |  |
| 2002 | In 2002, the gross area defoliated by aspen defoliators increased to reach an estimated 4.2 million hectares. The large aspen tortrix continued to be the predominant defoliator of aspen stands in the province. Forest tent caterpillar was inter-mixed with large aspen tortrix in a few forest stands. No Bruce spanworm damage was observed in the province in 2002. Satin moth populations were reduced and confined to the peripheral areas of the infestation found in and around Edmonton. One gypsy moth was trapped during the annual moth surveys carried out by the Canadian Food Inspection Agency in collaboration with several agencies including the Forestry Division of the Department of Sustainable Resource Development. |  |
| 2001 | The large aspen tortrix (LAT), the predominant defoliator of broadleaf stands in 2001 in Alberta, defoliated an estimated 3.5 million hectares. Some forest tent caterpillar defoliation was observed but was overshadowed by the LAT defoliation. In 2001, the Bruce spanworm populations collapsed across the province. As well, the satin moth populations around Edmonton collapsed with the establishment of a parasitoid. No gypsy moths were trapped during the annual survey carried out by Alberta Sustainable resource Development (SRD) in 2001. |  |
| 2000 | The large aspen tortrix-defoliated area increased dramatically to reach 2.3 million hectares in 2000. The forest tent caterpillar-defoliated area decreased to 366 000 hectares, a considerable decrease compared to 600 000 hectares defoliated in 1999. The Bruce spanworm populations collapsed during 2000. The rate of spread of satin moth populations in and around Edmonton also decreased during this year. |  |
| 1999 | The forest tent caterpillar-defoliated area increased in extent and severity in 1999, compared to the previous year. The gross area of defoliation was estimated to be 584 260 hectares. This is nearly a five-fold increase in the defoliated area. Most of this defoliation was severe. The forest tent caterpillar defoliation was found in the northwest part of the boreal forest; none was reported from the northeast. Large aspen tortrix also defoliated aspen stands in northwestern Alberta. The total defoliated area was estimated to be about 780 000 hectares. Almost all of this defoliation was in the northwest part of the boreal forest; an estimated 4700 hectares were defoliated in the northern east slopes. The Bruce spanworm infestation in western Alberta also expanded in 1999. This pest defoliated an estimated 64 000 hectares in the northern east slopes and another 44 000 hectares in the southern east slopes. |  |
| 1998 | Among the aspen defoliators, forest tent caterpillar-defoliated area increased in the northwest part of the province in 1998 compared to the defoliated area in 1997. There was no aspen leaf roller defoliation in the northwest boreal forests. The large aspen tortrix defoliated aspen stands throughout the northwest. Satin moth infestations increased dramatically in and around Edmonton. The spearmarked black moth continued to defoliate white birch stands in the northwest part of the boreal forest. Four gypsy moths were collected during a provincewide ground survey carried out by using pheromone-baited traps. |  |
| 1997 | Among the aspen defoliators, forest tent caterpillar defoliation in the province in 1997 was significantly lower than in 1996. However, aspen leaf roller defoliation increased in the northwest part of the boreal forest. There was no large aspen tortrix defoliation in the province in 1997. Satin moth infestations are still localised around Edmonton. The spearmarked black moth, an occasional pest, defoliated white birch stands in the northwest part of the boreal forest. No gypsy moths were detected during a provincewide ground survey with pheromone-baited traps. |  |
