19 1 a] Distribution of the Large Larch Saw-fly. 991 



the trees with' a draw-knife, and a layer of Archangel tar put 

 on with a brush. In this way a large number were caught, 

 although it is probable that the number was small compared 

 with the total number on the trees. 



It has been found that with trees of about 7 cu. ft. contents, 

 four men can tar about 700 trees in a working day of nine 

 hours. One man can shave off the rough bark with a draw- 

 knife, while three men apply the tar with brushes. This 

 works out at 4s. to 5s. per acre. The tar remains moist 

 enough to retain the caterpillars for about a fortnight. 



Various other remedies have been suggested in the case of 

 mature trees, such as raking up the cocoons, jarring the trees 

 to shake down the caterpillars, and hand-crushing and hand- 

 picking from young trees. 



Of these, raking up the cocoons and burning or treating 

 with lime is likely to be effective if it can be economically 

 accomplished. Usually this will not be the case, owing to 

 the tangled grass and the large area to be raked over. The 

 risk of re-infestation from adjoining plantations which remain 

 untreated must also be considered. 



It is found that jarring the trees does not dislodge the 

 caterpillars unless they are nearly full-grown, and even then 

 a vigorous shaking of the crown is necessary. Trials 

 of jarring, combined with tar-banding to prevent re-ascent, 

 are necessary to prove the utility or otherwise of this 

 treatment. 



Hand-crushing is an excellent means of treatment in young 

 plantations, and should be resorted to as long as the cater- 

 pillars can be conveniently reached. 



Distribution of Saw-fly Caterpillar Parasites— The in- 

 efficacy of the foregoing remedies is obvious where trees of 

 any size are concerned. It is proposed to breed out cocoons 

 from woods where ichneumons have been noticed at work, 

 with a view to determining the percentage parasitised, and 

 if a satisfactory result is obtained, to distribute numbers of 

 the cocoons among woods where the attack is just beginning. 

 By hatching the cocoons under a net the saw-fly can be 

 retained and killed and the parasites allowed to go. It is 

 hoped that in this way the parasites will obtain a much wider 

 distribution than by natural means, and that the spread of 

 the saw-fly will be checked and its attacks minimised. 



