528 
Journal of Agricultural Research 
Vol. V, No. 12 
tion of wild 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. 
