Forest Insect and Disease Survey; Ontario, 1965 - NFIS

B 17
TABLE 9
Defoliation of White Spruce by the Spruce Budworm
in 1964 and 1965, Egg Densities, and
Corresponding Forecasts for 1966
Per cent
Egg density per 100 feet
defoliation
of foliage
Forecast for
Location 1964 1965 1964 1965 1966
Uxbridge Forest 55 55 68 196.6 Heavy
Midhurst Forest 11 5 1.4 3.4 Light
.111•101■•■0
Larch Casebearer, Coleophora laricella Hbn.
knew but small heavy infestation of this insect occurred in a European larch
compartment in Vivian County Forest in 1965. Severe discolouration of the foliage
due to larval feeding was observed over the entire crowns of the infested trees.
No larvae were found on branch samples from plots in Vespra, Uxbridge, and Whitchurch
townships in 1964 and 1965. The number of larvae per sample increased slightly in
a plot in Albion Township but decreased in Medonte Township (Table 10).
TABLE 10
Summary of Larch Casebearer Larval Counts
in 1964 and 1965
Location
to shi
Medonte
Albion
Av. d.b.h. in
inches in 1
5
4
Av. no. of larvae
per 18-inch branch
1 16
6 1.5
1
4.6
Pitted Ambrosia Beetle, Corthylus punctatissimus (Zimm.)
Sample plots were established in 1962 to study the effects of infestations of
this beetle on sugar maple reproduction. The plots were located in various degrees
of exposure to light in or adjacent to mature sugar maple stands. All reproduction
in square-yard quadrats in the study areas has been uprooted and examined annually.
Infestations have declined for the second consecutive year in all quadrats.
In plots 2A and 2C, located in an undisturbed stand in Oro Township no infested trees
were found. In plot 3k in a partially thinned stand in Oro Township, the incidence
of attack declined from 10 per cent in 1964 to 5.8 per cent in 1965.
In a mature sugar maple stand in East Gwillimbury Township, part of which was
heavily thinned in recent years, the incidence of attack declined by 1.7, 22.5 and
17.8 per cent in shaded, fringe and open quadrats respectively.