Outbreaks of the Forest Tent Caterpillar, Malacosoma disstria Hbn., and Their Effects on Stands of Trembling Aspen in Manitoba and Saskatchewan

1960 ◽  
Vol 92 (3) ◽  
pp. 199-209 ◽  
Author(s):  
V. Hildahl ◽  
W. A. Reeks

Stands of trembling aspen in Manitoba and Saskatchewan are frequently attacked by the forest tent caterpillar, Malacosoma disstria Hbn. The recent history of attack is reviewed in this paper to determine if there is evidence of a consistent pattern of outbreaks and if the latest of these had any appreciable effect on aspen stands in the two provinces.

1979 ◽  
Vol 111 (7) ◽  
pp. 841-846 ◽  
Author(s):  
Arthur Retnakaran ◽  
Larry Smith ◽  
Bill Tomkins ◽  
Jeffrey Granett

AbstractDimilin (25% wettable powder) was mixed in water and sprayed from a Grumman Agcat aircraft equipped with four micronair units at the rate of 70 g (active ingredients) / 4,67 L/ha (1 oz/0.5 U.S. gal per acre) on two stands of trembling aspen, Populus tremuloides Michx., heavily infested with forest tent caterpillar, Malacosoma disstria Hübner. The material was applied when the insects were in the first and second instars and the trees were starting to flush. Spray deposit analysis using a dye, Rhodamine-B, in the spray mix and spray plates in the plots indicated that conditions for spraying in the morning were better than those in the evening as expected. Total control of the forest tent caterpillar with very little defoliation of the trees was achieved.


2005 ◽  
Vol 137 (5) ◽  
pp. 615-619 ◽  
Author(s):  
Maya L. Evenden

Trembling aspen, Populus tremuloides Michx. (Salicaceae), is the most widely distributed tree species in North America (Perala 1990) and is considered to be an ecologically (Hogg et al. 2002) and economically important (Brandt et al. 2003) component of the boreal forest. Due to the recently increased economic value of trembling aspen (Brandt et al. 2003), the impact of native insect defoliators on tree growth and mortality has become commercially important. Two of the most significant defoliators of trembling aspen throughout its range in Canada are the forest tent caterpillar (FTC), Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae), and the large aspen tortrix (LAT), Choristoneura conflictana Walker (Lepidoptera: Tortricidae).


2002 ◽  
Vol 32 (11) ◽  
pp. 1929-1934 ◽  
Author(s):  
E H Hogg ◽  
M Hart ◽  
V J Lieffers

Recent studies of trembling aspen (Populus tremuloides Michx.) in western Canada have shown a correlation between past insect defoliation events and the formation of narrow, abnormally pale-coloured ("white") tree rings. The objectives of this study were to test the hypothesis that defoliation causes the formation of white rings and to examine how defoliation affects ring width and density. We experimentally defoliated 7- to 18-year-old aspen in June, July, or August 1997 and subsequently found that white rings were formed the same year in all aspen that were severely defoliated in early June. These white rings were much narrower than in adjacent trees left as controls, and mean xylem density of the white rings (0.27 g·cm–3) was significantly reduced relative to normal rings (0.35–0.40 g·cm–3). In the year following defoliation, the tree rings remained narrow, but their appearance and density had returned to normal. Aspen defoliated later in the season formed relatively normal rings in 1997, but ring widths were reduced in 1998. The results confirm that white rings in aspen can be a useful retrospective indicator of the severe, early season defoliation that is typical during major outbreaks of forest tent caterpillar (Malacosoma disstria Hbn.) and other insects.


2011 ◽  
Vol 41 (8) ◽  
pp. 1606-1617 ◽  
Author(s):  
Julien Moulinier ◽  
François Lorenzetti ◽  
Yves Bergeron

Forest tent caterpillar (FTC; Malacosoma disstria Hübner) outbreaks represent an important natural disturbance in broadleaf-dominated stands; however, their effects on forest gap dynamics are not well understood. To describe such effects on canopy gaps and tree recruitment patterns, we investigated 20 trembling aspen (Populus tremuloides Michx.) dominated stands defoliated severely over 0 to 3 years during the last outbreak (1998–2003) in the northwestern Clay Belt of Quebec. Results show that canopy opening more than tripled (12.3%–43.7%) from 0 to 3 years of severe defoliation, and mean gap size was more than 12 times greater (7.2–87.5 m2) over the same gradient. Regeneration patterns suggest that aspen recruitment is not sufficient to completely restore closed canopies in stands defoliated 0, 1, and 2 years, whereas it should be sufficient in stands defoliated 3 years, where large gaps allow trembling aspen establishment. Our results clearly indicate that FTC outbreaks represent an important factor of gap formation in trembling aspen stands. At the stand level, gaps create uneven stand structures, and at the landscape level, FTC defoliation duration creates a large range of even to uneven stand structures.


2008 ◽  
Vol 38 (6) ◽  
pp. 1349-1356 ◽  
Author(s):  
Rongzhou Man ◽  
Gordon J. Kayahara ◽  
James A. Rice ◽  
G. Blake MacDonald

The growth response and mortality of trembling aspen ( Populus tremuloides Michx.) were monitored 1, 3, 5, and 11 years after partially harvesting an aspen-dominated mature mixedwood stand in northeastern Ontario. Both diameter and height of aspen trees responded positively to harvesting. However, 3 years after harvest, the growth rates of residual aspen were severely suppressed by 3 years of moderate to severe defoliation by forest tent caterpillar ( Malacosoma disstria Hbn.). The diameter growth of surviving trees almost recovered, but due to continuous crown dieback in the 6 years after defoliation ceased, height growth did not. Over the 11 years after harvest, 70% of residual aspen died, with 80% of that mortality occurring in the 6 years after defoliation. Trees in the lower canopy and in the partial cut had higher mortality rates than those in the upper canopy and in the uncut control. Increased mortality at the individual tree level was generally associated with greater foliage loss. Aspen growth and mortality were associated with defoliation levels, particularly for trees in partial cut treatments. Partial cutting and crown class strongly influenced the response of aspen trees to insect defoliation and should be considered when selecting residual trees during harvesting.


2003 ◽  
Vol 135 (3) ◽  
pp. 359-378 ◽  
Author(s):  
Melanie J. Filotas ◽  
Ann E. Hajek ◽  
Richard A. Humber

AbstractFuria gastropachaecomb. nov. (= Furia crustosa MacLeod et Tyrrell) has long been associated with declines in populations of the forest tent caterpillar, Malacosoma disstria Hübner; however, its prevalence and impact on host populations have never been documented. We clarify the nomenclature for this species, which has previously been called F. crustosa, and describe the morphology of F. gastropachae isolates from Maryland and New York. Epizootics of F. gastropachae were studied in M. disstria populations in New York and Maryland, United States of America. Prevalence (mean ± SE) of F. gastropachae in late fifth instar larvae in New York was 25.6 ± 7.8% compared with 22.2 ± 11.3% infection by virus and 23.3 ± 8.4% parasitism. In Maryland, F. gastropachae was not found in early instars and its incidence in fourth and fifth instars was 14.5 ± 7.3 and 21.6 ± 17.6%, respectively. Dipteran parasitoids were also important natural enemies with 38.3 ± 3.0 and 17.9 ± 1.4% parasitism in fourth and fifth instars, respectively. Virus was found in fewer than 5% of larvae collected. Furia gastropachae showed a marked tendency toward resting spore production in infected larvae, with 100% of larvae collected in New York and >80% of larvae collected in Maryland producing resting spores, either alone or in combination with conidia. The appearance of cadavers of larvae dying from fungal and viral infections was similar. Of 13 species of Lepidoptera exposed to F. gastropachae conidia in host-range bioassays, only 3.3% of Danaus plexippus (L.) (Lepidoptera: Danaidae), 5.6% of Pieris rapae (L.) (Lepidoptera: Pieridae), and 3.7% of Manduca sexta (L.) (Lepidoptera: Sphingidae) were successfully infected by this fungus.


1953 ◽  
Vol 85 (8) ◽  
pp. 297-310 ◽  
Author(s):  
C. R. Sullivan ◽  
W. G. Wellington

The forest tent caterpillar, Malacosoma disstria Hbn., and the eastern and western tent caterpillars, M. americanum (Fab.) and M. pluviale (Dyar), are common pests of several species of deciduous trees in Canada. All are colonial during the larval stage, but M. disstria differs from the others in one respect: it does not construct a communal tent. This difference in habit merits special consideration in any comparative study of larval behaviour, particularly in one concerned with the effects of physical factors upon the insects, since a tent modifies the effects of the physical environment considerably. Recently, a series of such studies was carried out, and one part of the work consisted of laboratory and field observations on the light reactions of larvae. The results obtained have raised a number of new questions which unfortunately cannot be answered now, hecause two of the species have been difficult to obtain in quantity since 1950. Nevertheless, the findings are presented here without additional delay, since they are of general interest, and other workers may wish to use them.


1993 ◽  
Vol 71 (8) ◽  
pp. 1511-1515 ◽  
Author(s):  
T. D. Fitzgerald ◽  
F. X. Webster

Behavioral assays show that the steroid 5β-cholestan-3-one, isolated from the abdomen of the larva of the forest tent caterpillar (Malacosoma disstria), constitutes the chemical basis of trail following in this insect. Caterpillars follow artificial trails prepared from solvent dilutions of the compound at rates as low as 10−11 g∙mm−11 of trail, though the true threshold sensitivity is likely to be one or two orders of magnitude lower than this. Fourth-instar caterpillars store an average of 58 ng of the pheromone. Field and laboratory studies indicate that the compound is fully competitive with their authentic trails. The caterpillars are highly sensitive to differences in the concentration of the pheromone, preferring stronger trails to weaker trails. The caterpillars also respond to 5β-cholestane-3,24-dione, a chemical not found in M. disstria but known to be a component of the trail pheromone of the eastern tent caterpillar, Malacosoma americanum.


2005 ◽  
Vol 11 (4) ◽  
pp. 588-599 ◽  
Author(s):  
Jep Agrell ◽  
Brian Kopper ◽  
Evan P. McDonald ◽  
Richard L. Lindroth

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