Annual District Reports: Forest Insect and Disease Survey ... - NFIS

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2.34 Leaf and Twig Blight, Pollaccia radiosa (Lib.) Bald & Cif.:-
This disease of aspen was reported from several localities. The highest
incidence of infection occurred on the west end of Black Island in Lake
Winnipeg where stands of aspen reproduction were moderately damaged.
Elsewhere, light infection was noted 5 miles south of Gypsumville, and
at Gretna, Swan Lake, Glenboro and in the Spruce Woods Forest Reserve.
2.3.5 Ink Spot of Aspen, Ciborinia bifrons (Sear.)Sear.:- Light
infection of trembling aspen was common throughout the Spruce Woods
Forest Reserve, and in isolated patches in the Riverton, Pine Dock,
Hodgson, Lake St. George and Devil's Lake area. Only a few leaves were
affected on individual trees at the locations where the disease was
detected.
2.3.6 Industrial Fume Damage:- Fumes from an oil refinery in the
Greater Winnipeg Municipality of East St. Paul caused considerable coloration
of the foliage of several tree species over an area of about 2 1/2
square miles immediately north of the refinery. The affected area
extended in a northeasterly direction across Henderson Highway (No. 9)
to the Red River and north as far as Hoddinott Avenue. The foliage of
bur oak was most seriously affected and damage ranged from 10 to 95 per
cent of the leaves discolored on about 85 per cent of the trees. Lesser
damage occurred (in descending order) on Manitoba maple, trembling aspen,
green ash, balsam poplar, white elm, caragana, dogwood, chokecherry
and Canada plum. Observations later in the season (about mid-August)
indicated that the trees were recovering satisfactorily and very little
permanent damage would result.
2.3.7 Hail Damage:- A localized hailstorm south of Fraserwood in
early July caused heavy damage over an area of about 1 1/2 square miles.
Approximately 25 per cent of the foliage was stripped-off trembling
aspen, balsam poplar and green ash, and breakage of the leaders and
branches was common.
2.3.8 Malformation of Manitoba Maple Shoots and Foliage:- Surveys
were continued throughout the Interlake section and southwestern Manitoba
to determine the severity of damage to Manitoba maple by the use of
2,4-D for weed-control in field crops. Of fourteen shelterbelts examined
only three yielded typical symptoms of malformed shoots and leaves, and
damage was confined to, either a few isolated twigs or parts of the tree.
Results of the survey are shown in the following table.