52 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 



10. An Attack by Sawfly Larvae. 



{With Plate.) 



By Fred. Moon. 



On the 23rd of June 1906, while inspecting a young Scots 

 pine and larch plantation, I found it very badly infested with 

 sawfly larvae, and trust the following particulars and means 

 taken to combat the attack may be of interest. 



The plantation in question is about four and a half miles S.W. 

 from St Boswells station. The elevation is about 700 feet above 

 sea-level. The area of the plantation is about 15^ acres. The 

 south half is ten years old and the north half nine years. 



When first noticed, the larvae would be about three weeks 

 hatched, and the attack was by far the most severe met with in 

 my experience, many of the plants being simply loaded with 

 larvae. I at once got a Vermorel sprayer, and after a few 

 experiments with Paris green, had 10 lbs. of this and 10 lbs. of 

 wheat flour mixed and put up in i oz. packets, each packet 

 being mixed with 3^ gallons of water, this being the capacity of 

 the knapsack-sprayer. The infested plants were sprayed with 

 this mixture, the result being that after about twelve hours the 

 insects lost their appetite, and in about three days died and 

 shrivelled up. 



The strength of the mixture was the maximum that could be 

 used with safety. In fact, during a spell of very bright sunshine^ 

 a few of the sprayed plants were more or less scorched. This 

 method of destruction was very efficacious, but as the water 

 supply was from 100 to 200 yards distant, it had the dis- 

 advantage of being rather slow. I was therefore obliged to 

 send two more men to crush the larvae by hand. The plan 

 adopted in the latter case was to put the infested branches into 

 a small sack without severing them from the plant, and to rub 

 the bag containing the larvae between the hands, thereby crush- 

 ing the pests. They could of course be crushed between gloved 

 hands without using a bag, but the advantage of using the 

 latter at this advanced stage of larval growth, was that it 

 prevented the escape of large numbers which dropped off" when 

 the branch was touched. 



Of the two plans tried, crushing by hand is certainly the 

 quicker method and the most certain, as, though in this parti- 



