Major outbreaks of the saddled prominent (Fig. 32) were first documented in New England in 1907. Since that time they have been reported in parts of the Northeastern United States or Canada at intervals of 10 to 12 years. During the most severe and widespread outbreak on record (1967 to 1971), nearly one-half of the northern hardwood forests in central and eastern New York were defoliated heavily. Extensive areas of Canada, Massachusetts, Pennsylvania, and Vermont also were affected.
Rarely during outbreaks is this species found alone. Rather, it is the dominant member of a defoliator complex. Apparently, conditions suitable for an increase in saddled prominent populations also favor other defoliators. The whitemarked tussock moth (Orgyia leucostigma) is a frequent associate in the Maritime Provinces of Canada. In Ontario, the greenstriped mapleworm (Dryocampa rubicunda), several loopers, and Heterocampa biundata (a species similar to saddled prominent) are common members of the complex.As many as nine species have been associated with the saddled prominent during outbreaks in Maine. Usually, H. biundata (Fig. 33) and D. rubicunda (Fig. 34) have been the primary associates.
On good sites, healthy dominant and codominant sugar maples usually survive 2 successive years of defoliation, though the understory trees may suffer heavy mortality. In Maine, tree mortality occurred in intermediate and suppressed crown classes, but crown damage occasionally was extensive on dominant and codominant trees after 2 years of defoliation. Crowns may recover within 3 years after the outbreak collapses. Diameter growth usually is reduced by at least 50 percent during the period of defoliation.
A recent episode of 2 years of heavy defoliation in New Hampshire resulted in serious deterioration of crowns. A favorable growing season (presumably adequate moisture) during the second year may have enhanced recovery.
Mortality and crown dieback of sugar maple in Vermont was significant after a single year of severe defoliation during 1980. The most extensive damage was in stands with predominantly pole-size (5.0 to 12.0 inches (12 to 30 cm) in d.b.h.) to young sawtimber-size (more than 12.0 inches (30 cm) in d.b.h.) sugar maple trees at high elevations. Despite some top kill, sugar maples with no more than 40 to 50 percent of their crown defoliated usually survived.
The principal short-term economic impact of defoliation by saddled prominent occurs in sugarbushes. Sap quantity and sugar content may decline following heavy defoliation. During the 1967-71 outbreak, New York syrup producers who did not spray their sugarbushes were unable to operate during the spring following defoliation.
It often is difficult to predict the immediate and long-term impact of a saddled prominent outbreak because many events determine the outcome. However, sugarbushes that have been stressed recently by thinning, drought, or severe defoliation should be protected.
This relatively large moth has a wingspan of approximately 2.0 inches (50mm). The mottled forewings are drab greenish or brownish-gray and marked with irregular creamy white splotches. The hindwings are light brown. All four wings usually have a broken dark to black band near the outer margin. Throughout June and early July, adults deposit eggs on leaves, especially of sugar maple, American beech, or yellow birch. Fully grown caterpillars are approximately 1.3 inches (33mm) long and usually are green with a reddish saddle-like mark in the center of the back (Fig. 32). The head is marked on each side with a series of distinct stripes: one dark brown, two yellow or white, and one pink. Some caterpillars may lack the saddle marking or are entirely reddish-brown.