528 Journal of Agricultural Research voi. v. no. 12 



tion of mid hawthorns in the immediate vicinity of the cherry orchard — 

 should leave few opportunities for the pest to develop to injurious 

 numbers. 



FUMIGATION WITH HYDROCYANIC-ACID GAS 



Of the various measures employing insecticides tested by this station 

 to protect cherry foliage from the work of the leaf miner, fumigation 

 with hydrocyanic-acid gas alone was effective. Most cherry growers in 

 New York are not equipped with suitable apparatus to undertake this 

 means of affording protection to their trees, and fumigation should only 

 be undertaken as an extreme measure and in an experimental way 

 under expert direction. 



CULTIVATION 



Cultivation, if done with care and at the proper time, is destructive 

 to many insects with subterranean habits. Species especially that un- 

 dergo pupal development in the ground are not only peculiarly sensitive 

 to disturbances of the soil, but plowing and cultivation, besides breaking 

 up the cells of hibernating larvae, exert another detrimental influence, 

 exposing the helpless insects to insectivorous birds and other foes. 

 Since it is the normal habit of the larvae of this sawfly leaf miner to live 

 in earthen cells for the greater portion of the life cycle of the species, such 

 practices as fall or early spring plowing or cultivation are to be recom- 

 mended from an entomological standpoint. These measures, fortunately, 

 are standard operations which are invariably practiced by the most 

 successful cherry growers. 



DESTRUCTION OF UNCULTIVATED HOST PLANTS 



The fact that the sawfly leaf miner is very partial to hawthorns, 

 especially of the group C. crus-galli, and breeds most abundantly on 

 them, suggests the desirability of destroying these plants when they 

 exist in the immediate vicinity of a cherry orchard. The value of this 

 operation is not known ; but until there is more knowledge of the breeding 

 habits of the pest the removal of wild plants along roadsides and hedge- 

 rows that are attractive to the insect for purposes of propagation would 

 appear advisable as a precautionary measure. 



SPRAYING OF HAWTHORNS 



For the protection of hawthorns in decorative plantings, spraying 

 seems to be preferred to any of the preceding measures. The insecticide 

 which has given the most satisfactory results is composed of i pint of 

 nicotine solution (40 per cent) to 100 gallons of water to which are added 

 4 pounds of soap. In making the treatment the liquid should be used in 

 liberal amounts and applied with rather high pressures at the time when 

 the insects first begin to mine the foliage. 



