25 



before feeding to any great extent on the exposed surfaces. Later they feed 

 under the protection of the webbed leaves and blossoms where it is very 

 difficult to reach them with the poison spray. By the time the fruit is at- 

 tacked the caterpillars are nearly half grown and very resistent to arsenical 

 poisons. Attempts to destroy them by the use of arsenate of lead at this 

 time have been generally unsuccessful. Fortunately very effective work 

 can be done against the eggs. While the varnish-like covering of the egg 

 masses is impervious to the lime-sulfur solution it is readily permeated by 

 the miscible oils. Experiments conducted in Colorado and more recently 

 in New York have shown that more than 75 per cent of the eggs can be killed 

 by spraying with a miscible oil, one part in fifteen parts of water, making 

 the application just before the buds open and therefore just before hatching 

 would take place. This is also the safest time of the year to use miscible 

 oils, there being less danger of injury to the trees in the spring when the sap 

 is moving than in the fall or winter when the activity of the tree is dormant. 

 One cannot expect to entirely prevent injury by leaf-rollers by spraying 

 to destroy the eggs. There will always be some eggs that are not hit by the 

 spray and from these caterpillars will develop. The oil treatment should 

 always be supplemented by careful and thorough spraying with arsenate 

 of lead, 5 to 6 pounds in 100 gallons of water, making one or two applica- 

 tions just after the buds open and before the caterpillars have been able 

 to find protection under their webs. The system of spraying adopted in 

 any particular orchard will depend on the severity of the infestation. Where 

 only a few scattering egg-masses are present it would not pay to use the mis- 

 cible oils and reliance should be placed on thorough work with arsenate of 

 lead. In case of severe infestation it is necessary to use the miscible oils sup- 

 plemented by thorough spraying with arsenicals. 



Dusting Experiments on Apple. 



The protection of our fruit trees from their numerous insect and fungous 

 enemies by means of spraying with liquid substances has been in vogue for 

 more than forty years and has reached a refinement of detail that would seem 

 to leave little to be desired. The manufacturers of spray machinery are con- 

 tinually devising new and better types of nozzles, pumps, and engines. 

 Manufacturers of chemicals are ever finding new spray materials or discover- 

 ing new combinations of those already on the market. It has been the same 

 with our official entomologists and plant pathologists. The main trend of 

 their thought and endeavour has been along the line of liquid spraying. 

 Under these circumstances it is no wonder that the possibilities of the dry 

 or dust method of applying insecticides and fungicides has been neglected. 

 Nor is it any wonder that when we begin to talk seriously of dusting as a 



