8 NINETEENTH REPORT STATE ENTOMOLOGIST OF MINNESOTA—I9Q22 
Jack Pine Sawfly (Diprion abietis Harris) 
Many reports of injury to Jack pine by sawfly larvae were received 
during the season of 1922. The species responsible was not the com- 
mon pine sawfly but the fir sawfly (Diprion abietis). Several localities 
were examined where the trees were completely defoliated by this insect, 
and judging from reports received from other places not visited, injury 
occurred locally throughout the Jack pine region. Owners of summer 
hotels and cottages are urged to plant other species of trees and develop 
mixed woods about their property. This will tend to reduce the likeli- 
hood of a sawfly outbreak in these places, where the esthetic value of 
the trees is paramount. 
Birch Skeletonizer (Bucculatrix canadensisella Cham.) 
In August and early September of 1922, the birch skeletonizer 
destroyed the leaves in practically all the birch woods in the northern 
part of the state. This defoliation came after the trees had completed 
the season’s growth and did comparatively little permanent injury. 
In some cases, however, owing to the early loss of leaves and the 
late fall, the buds of the birches began to swell before cold weather 
set in. This will probably mean a considerable amount of winter 
injury. The larvae of this insect were so abundant that there was not 
sufficient green foliage to carry them all to maturity. A very large 
proportion of the caterpillars starved to death and many others spun 
cocoons in an under-nourished condition. As a result it is probable 
that the skeletonizer will not be very abundant in 1923. 
Many other insects were reported and many letters were written 
answering inquiries, but these mentioned were the most important. 
Spraying 
Experimental work in spraying orchards, comparing the regular 
formula of arsenate of lead and lime-sulphur with dusts, has been 
continued. Dust versus liquid sprays js a very live question with 
the orchardist as well as with the potato grower. The importance of 
spraying is being more and more recognized by the grower in this 
state and it 1s necessary that the different formulae be tried under 
Minnesota conditions. So far the dusts have not proved, either in 
results or costs, any better than the liquid formulae advised for several 
years, viz., arsenate of lead and lime-sulphur for orchard spraying, 
and arsenate of lead or calcium arsenate plus bordeaux mixture for 
potato spraying. 
