56 TREE INSECTS. 
method consisted in pruning the tips of all the infested branches 
on a tree and burning them. When the infection is abundant, this 
means a tremendous amount of work and it may not pay even if it 
proves an efficient remedy. 
The poplar beetle has been doing considerable damage to the 
poplars and willows in the nurseries of the State. We are inves- 
tigating the life cycle of this insect and propose to perform a 
considerable number of experiments on spraying against it. We 
believe that a thorough spraying at least twice during the season 
with arsenate of lead paste at the rate of 3 or 4 pounds to 50 
gallons of water will be effective. So far, the most interesting 
phase of the work has been the discovery of a parasite, a Tet- 
rastichus sp. according to J. C. Crawford, which destroys over 
sixty per cent of the grubs in certain localities. 
The spiny elm caterpillar has done considerable damage to 
the elms and willows. Spraying with arsenate of lead 4 pounds in 
50 gallons of water will keep them in check. A bacterial disease 
has been noted killing many of the caterpillars. 
As mentioned in the article on spraying, scale insects in Min- 
nesota have not, up to the present time, caused any alarm. To be 
sure, from time to time, the oyster-shell scale and scurfy bark- 
louse causes considerable anxiety, but it is only rarely that these 
two scale insects have caused trouble. During the last year or 
so, however, the dread San Jose scale has made its appearance. 
With these three armored scales and perhaps more, capable of 
doing considerable injury and even causing death to orchard and 
shade trees, everyone must be on guard to stop the ravages of the 
pest in its incipiency. 
The remedy for all scale insects is the dormant spray of lime- 
sulphur. The lime-sulphur is the commercial concentrated ma- 
terial and is diluted in proportions of about one part of the lime- 
sulphur with nine parts of water. This is sprayed on the trees 
just after the leaves drop in the fall or in the spring before the 
buds swell. A warm day in midwinter is also suitable. Some- 
times two applications are desirable. During the summer months 
no insecticide will kill the mature scales without destroying the 
fohage. However, if in each case the time can be definitely deter- 
mined in which the young are crawling around in numbers, spray- 
ing with some contact insecticide like kerosene emulsion, dilute 
lime-sulphur or whale-oil soap will kill many and prevent serious 
injury until the dormant spray can be applied. 
