EXPERIMENT STATION BULLETINS. 579 



numerous can they be found at all easily. The number of plants on 

 which they can thrive renders their extermination still more difficult. 

 The following is a list of their food-plants taken from a treatise* on this 

 insect by Dr. L. O. Howard and C. L. Marlatt of the United States Depart- 

 ment of Agriculture: 



Tiluvcccn Saxifragacece 



Linden Gooseberry 



Celastraeece Currant 



Euonymus Flowering- currant 



Rosacece Ebenacece 



Almond Persimmon 



Peach LeguminosoB 



Plum Acacia 



Cherry Urticacece 



Spiraea Elm 



Raspberry Osage orange 



Rose Jaglandacece 



Hawthorn English walnut 



Cotoneaster Pecan 



Pear Betulaceaz 



Apple Alder 



Quince Salicaceoe 



Flowering quince Weeping-willow 



Laurel-leaved willow 



We have found it on grape also. 



REMEDIES. 



Numerous experiments have proved conclusively that the remedies 

 found to be effective on the Pacific coast are almost useless in the east, 

 and this seems to be due to a difference of climatic conditions. All the 

 experiments tried in the east seem to indicate that a wash of whale-oil 

 soap used at the rate of two pounds of soap to a gallon of water, is the 

 best and cheapest remedy. This must never be applied except when the 

 trees are dormant, for its effect is very injurious if used when the foliage 

 is on the tree. Two applications should be made, one in the autumn just 

 after the leaves fall and one during the winter. Too much stress cannot 

 be laid on doing the work thoroughly; every spot and every twig on the 

 entire tree should be thoroughly wetted. 



Whale-oil soap costs about four cents per pound if purchased direct 

 from manufacturer and in quantity; the cost is then eight cents per 

 gallon for the liquid ready to spray. If purchased in small quantities, 

 the cost is considerably more. Strong potash solution has been used to 

 some extent, but thus far it has seemed inferior to the soap, while its 

 cost is considerably greater. Kerosene-emulsion is inadequate, while 

 pure kerosene is pretty sure to kill the tree. 



Before spraying, it is best to cut back all that the tree will stand and 

 to burn the cuttings. If a small amount of stock is found infested, it 

 should be rooted up and burned. 



*B\ill. No. 3, New Series, 1896. 



