136 THE CULTIVATED EVERGREENS 



latter part of October they migrate from the leaves to the 

 twigs, where they fasten one end of the case to the bark and 

 hibernate in this condition. 



No practical method of control is known for this pest in 

 forest areas. In ornamental plantings, however, a dormant 

 spray of lime-sulfur solution, testing 32 degrees Baume, diluted 

 at the rate of one part of lime-sulfur to eight parts of water, 

 has given good results. It is advisable to make this application 

 just as late as possible in the spring before the buds start 

 growing. 



The larch sawfly {Lygceonematus erichsonii, Hartig). 



The larch, both under cultivation and in the forest, is 

 subject to severe defoliation by the larva of a sawfly. The 

 insect hibernates as a larva in tough brownish cocoons on the 

 ground under the litter beneath the trees. The sawflies appear 

 in late May or early June. The female inserts her eggs in the 

 young, green, terminal twigs, causing them either to die or to 

 become bent and distorted. The eggs hatch in about a week 

 and the larvae become full grown in three to four weeks. When 

 abundant, the tree is completely defoliated and the growth 

 seriously checked. The young larvae are pea-green in color, 

 with dusky heads. When full grown the head is black and the 

 body is glaucous-green. There is only one generation a year. 

 On reaching maturity the larvae descend to the ground and 

 spin their cocoons under trash or in the ground very near the 

 surface. 



The larch sawfly can be controlled effectively on orna- 

 mental trees by spraying with arsenate of lead — three pounds 

 of powder in one hundred gallons of water. The application 

 should be made late in May just as the eggs are hatching. 

 When only a few trees are to be protected and when spraying 



