Long-Term Effects of Defoliation of Aspen by the Forest Tent Caterpillar

Abstract

A second study of the effect of aspen of defoliation by the forest tent caterpillar in Minnesota was conducted 6 years after the conclusion of an initial comprehensive investigation. Results indicate increasing mortality in other than suppressed trees with increasing defoliation intensity. Hypoxylon, Nectria, and insect incidence increased with defoliation intensity. Growth is significantly reduced 1 year beyond the cessation of defoliation in stands where three successive heavy defoliations have occurred. Growth of the dominants increases significantly, however, the third year after defoliation in such stands.

Aspen: Ecology and management in the western United States

“…Various workers, for example Churchill et al (1964). have documented the severe diameter growth reduction in aspen caused by outbreaks of defoliating insects.…”

“…Stelzer (1968) reported that during 3 years of complete defoliation, ring widths of surviving stems in New Mexico were less than the average of the six preceding years by 2.4%, 52.2%, and 74.6%, respectively. In Minnesota, aspen defoliated for as little as 1 year by M, disstria grew much less in diameter than normal during that year and the next year (Churchill et al 1964, Duncan andHodson 1958). Pollard (1972b) studied a mature Ontario stand after a 3-year outbreak of M. disstria, and found that growth scarcely improved at all during the first post-outbreak year, and to only about 50% of their preoutbreak level by the third year.…”

A Revision of the Genus Malacosoma Hübner in North America (Lepidoptera: Lasiocampidae): Systematics, Biology, Immatures, and Parasites

“…Hildahl and Reeks (1960) 1956. Beginning in 1957, however, and continuing to the present time (1964) Wellington (1952) (1958), Ghent (1958), Rose (1958), Hildahl and Reeks (1960), and Barter and Cameron (1955) (Churchill et al, 1964), drought (Duncan and Hodson, 1958), overgrazing (Clark, 1956a), or bark beetles and borers (Barter and Cameron, 1955) to cause higher mortality rates.…”

Preliminary hazard rating for forest tent caterpillar in British Columbia

“…Mortality usually occurs after the trees are weakened by severe defoliation and are subsequently attacked by opportunistic diseases and secondary insects (Duncan et al 1956, Churchill et al 1964, Moody and Amirault 1992. Drought can hasten this process (Cooke and Roland 2007 (Callan 1998).…”

“…Trees weakened by defoliation are also susceptible to wind breakage, and often endure secondary insect attacks by wood borers such as the poplar and willow borer (Cryptorhynchus lapathi [L.]) (Coleoptera: Curculionidae) or longhorn beetles (Saperda spp.) (Coleoptera: Cerambycidae) (Duncan et al 1956, Churchill et al 1964 (McGugan 1958, Van Sickle et al 2001. Because the FIDS reports are well known, all such reports on insects will be referred to as the FIDS reports in this paper.…”