AN ATTACK BY THE LARGE LARCH SAWFLY. 43 



branches were burned on the ground during the last week in 

 May, in the hope of destroying the emerging sawflies, but this 

 was not quite a success. 



The methods now adopted are, in the younger plantations, 

 crushing by hand, and in those which are above reach and 

 up to 20 feet in height, spraying. Handcrushing is most 

 rapidly and economically done when the larvae are about half- 

 grown ; they will then be found congregated in masses, as many 

 as sixty having been counted in one group, and these can be 

 easily destroyed by a single closing of the hand, ordinary leather 

 gloves being used by the operator. Where women's and 

 boys' labour is available, this method will be found to be very 

 effectual and economical. 



Spraying, which is resorted to in plantations between 6 

 feet and 20 feet in height, is very effectual, and has been 

 found to cost on an average about 6s. id. per acre where the 

 stock was practically pure larch. This operation is carried out 

 with Knapsack sprayers and a solution of arsenite of copper. 

 The arsenite of copper is mixed in equal proportions with 

 wheaten flour and made up into i-oz. packets, one packet being 

 sufficient for four gallons of water, which is the capacity of the 

 Knapsack sprayers in use here. The reason for mixing the 

 arsenite of copper with flour is to make it adhere better to the 

 foliage. As spraying has no effect upon the larvae until after 

 they have eaten of the poisoned foliage, care should be taken 

 to thoroughly spray all the foliage. One application is generally 

 sufficient for a season, as there is only one annual brood of 

 sawfiy, although, owing to the long period of emergence, which 

 extends over several weeks, both full-grown and recently-hatched 

 larvae are frequently found on the same tree. 



I am pleased to say that all the young plantations which have 

 been treated by spraying or handcrushing, have made good 

 growth during the past season, and are at present looking very 

 healthy. 



When the larvae are three parts grown they are easily dislodged 

 from the trees, and frequently after sudden showers of rain or 

 strong wind they are to be found on the ground in great 

 numbers. Some American writers recommend the shaking of 

 the trees, in order to cause the larvae to drop off; it is said that 

 they will not get up the trees again, and they are thus starved to 

 death. But this is not the case, as I have frequently seen the 



