Forest Insect and Disease Survey; Ontario, 1965 - NFIS

G2
TABLE 1 (continued)
Per cent egg mortality
Av. no. Per cent caused by
of eggs of eggs Para- Unsuccess. Sterile Degree of
Location er band hatched site emer:ence e s infestatioi
Fort Frances Dis ri ct
Atikokan 255 88 1 6 5 H
N.E. Bay Rainy Lake 192 70 1 12 17 H
Redgut Bay Rainy
Lake 184 87 2 6 5
Kenora District
Dyment 135 69 8 19 4 H
Macintosh 179 71 0 11 18 H
Despite the abundance of forest tent caterpillar larvae in the early instars,
very few insects reached the pupal stage in areas where heavy infestations have
occurred for four to five consecutive years. This resulted in part from a spectacular
polyhedral virus epizootic. Almost total mortality of forest tent caterpillar
larvae occurred in the third to fourth instars near Sioux Lookout and Redditt.
Thousands of dead larvae were massed in the upper portion of tree trunks and branches
but few were found on the understory. In contrast, near English River where the
larval population was infected with a virus in the fourth and fifth instars, the
majority of the dead insects were found adhering to the undergrowth.
Parasitism was the most important control factor in the cocoon stage but the
incidence of disease also increased compared with previous years. To assess these
control factos and their effect on moth emergence large numbers of cocoons were
examined at 26 points in the region (Table 2).
TABLE 2
Summary of Forest Tent caterpillar cocoon Dissection
in the Western Region in 1965
Location
Per cent
parasitized
196 196
Per cent
diseased
1 6 196
Per cent
emerged
1964 196 5
Sioux Lookout District
Skey Twp. - 56 17 27
Savant Lake _ 63 17 20
Wapikaimaski Lake - 56 6 38
Harris Bay Sturgeon
Lake _ 56 - 20 - 24
Baird Twp. - 81 - 8 - 11