282 



THE CANADIAN ENTOMOLOGIST 



Another system classed under the dry method of control was 

 tried on a small scale in France in 1908 and on a large scale in 

 1909. This method consisted in suspending in the tree a canvas 

 sac (10-14 inches in length and about 2 inches in diameter), which 

 contained about \ x /i lbs. of a mixture of poisoned molasses, saw- 

 dust and bran (Fig. 24). The insecticide transudes directly 

 through the canvas and when a rain washes off the bait, the 

 poisoned molasses filters through again. The proportion of the 

 ingredients used in the canvas sacs was as follows: 



Arsenical molasses 71% 



Sawdust 21% 



Bsan 8% 





s-v — %ln 



An excess of bran gives too much porosity to the mixture and 



favors evaporation. The addition 

 of water to the molasses acceler- 

 ates dessication, a thing to avoid 

 most. To lessen dessication it is 

 necessary to tightly stuff the sacs. 

 After filling the bags, drops of 

 liquid ooze out and this loss can 

 be avoided by allowing the sacs 

 to drain over a vessel for several 

 hours or even two days. 



The sacs thus prepared are 

 placed in the interior of the trees 

 at a region as accessible as pos- 

 sible. Once during the summer, 

 water was added to the bags on 

 account of the sacs becoming dry 

 at their upper end; this was due 

 to the oozing of molasses through 

 the canvas and to evaporation. 

 Later when the first rains and dew 

 of September occur, the atmos- 

 pheric humidity insures excellent conditions. The cost, including 

 all expenses, amounted to $4.00 per sac. The results obtained in 

 two isolated olive gardens are given in tables V and VI. 



h • if-'.- -£."•'-" 



'■ 



Fig. 24. — Canvas sac stuffed with a 

 mixture of bran and poisoned molasses. 

 (After Berlese). 



