53 



appears to be the same disease that attacks the apple-tree tent- 

 caterpillar mentioned in Bulletin 152, page 291. 



COMBATING THE INSECT. 



Owing principally to the fact that the caterpillars attack a large 

 variety of trees, this subject is a somewhat complicated one. In 

 badly infested localities, however, it has three distinct phases. 

 First, combating the insect in the forest ; second, combating the 

 insect when attacking shade trees ; and third, combating the 

 insect in the orchard. We will discuss the subject under each of 

 the three heads reversing the order given above. 



Combating the insect in the orchard : destroying the eggs. — After 

 the leaves have dropped the egg masses are somewhat con- 

 spicuous. When pruning the trees they should be carefully 

 looked for and destroyed. If the orchard has been badly infested 

 it will pay to make a special search for them. 



Destroying the caterpillars. — Many methods have been sug- 

 gested for destroying the caterpillars but there are three especially 

 feasible ones, which, if carefully carried out, will usually prove 

 effectual. 



First, spraying with an arsenical compound. — Any good arsenical 

 will answer the purpose if applied before the caterpillars are 

 half-grown. Some of the principal arsenical insecticides are 

 Paris green, green arsenite and arsenite of lime. For a discussion 

 of green arsenite and arsenite of lime see Bulletins 143 and 152 

 of this Station. A third arsenical, arsenate of lead, has been found 

 by the Gypsy Moth Commission of Massachusetts to be especially 

 effectual against the gypsy moth and to be almost harmless to 

 foliage. The formula is as follows: 11 ounces acetate of lead, 4 

 ounces arsenate of soda, 150 gallons of water. The directions for 

 making arsenate of lead as given by Professor C. H. Fernald^'are 

 as follows : ' ' Arsenate of lead is easily prepared ,by putting 1 1 

 ounces acetate of lead in 4 quarts of water, in a wooden (not metal) 

 pail, and 4 ounces of arsenate of soda (50 per ct.) in 2 quarts of water 

 in another wooden pail, and when entirely dissolved mixing them 

 in a hogshead containing 150 gallons of water, when a chemical 



3=Ann. Rpt. Mass. Bd. Agr, 1897. 



