Forest Insect and Disease Survey; Ontario, 1965 - NFIS

B 16
Cedar Leaf Miners, Argyresthia thuiella Pack. and
Pulicalvaria thujaella Kft.
Little change in the status of these leaf miners was noted in 1965. Heavy infestations
again caused premature shedding of the foliage of eastern white cedar in
a 40-mile wide band across the central part of the district. Severe defoliation in
recent years has reduced growth and caused some branch and tree mortality.
Jack-pine Resin Midge, Cecidomyia reeksi Vock.
Moderate and heavy damage of the shoots of jack pine recurred at many points in
the older plantations in the district. At many points in Sunnidale, Tosorontio,
.Essa, Whitchurch, and East Gwillimbury townships 75 per cent of the current shoots
were killed and the remainder severely damaged.
A Midge on Red Pine, Cecidomyia sp.
A little-known midge caused heavy damage to the current year's foliage of red
pine trees in late summer in plantations in Vespra, Essa, Tosorontio, Sunnidale, and
Oro townships. This minute insect feeds at the base of the needle within the needle
sheath. At some locations 75 per cent of the needles were killed and prematurely
shed in 1965.
Spruce Budworm, Choristoneura fumiferana (Clem.)
Spruce budworm infestations recurred at approximately the same intensity as in
1964 in Uxbridge Forest Headquarters Tract and declined for the second consecutive
year at Midhurst. Anew medium infestation occurred in West Gwillimbury Township
(Table 9).
A medium-to-heavy infestation caused 55 per cent defoliation of the current
year's foliage in a 35-year old white spruce plantation in Uxbridge Forest. The
egg density increased from 68 clusters per 100 square feet of foliage in 1964 to
almost 200 in 1965 indicating that population levels will greatly increase in this
plantation in 1966. Medium infestations recurred in younger trees in adjacent
compartments where 181 larvae were collected on 20-tray beating samples. Defoliation
averaged approximately 40 per cent of the current foliage.
Defoliation in a 35-year old white spruce plantation at Midhurst declined from
11 per cent in 1964 to five per cent in 1965. Egg density surveys carried out in
the fall revealed an increase in numbers of clusters from 1.4 in 1964 to '3.4 per
100 square feet of foliage in 1965.
A new medium infestation caused approximately 45 per cent defoliation on young
blue spruce ornamentals along Highway 400 in West Gwillimbury Township in 1965.