THE CANKEBWOBMS 33 



though, it was completed before the blossoms had opened to any 

 extent. Before the spraying was done practically every leaf was 

 being eaten by several larvse. A few days later it was difficult to 

 find a living larva, and practically impossible to find a healthy one. 



Quaintance (32) has reported almost perfect control of the spring 

 cankerworm in two orchards in Virginia. In 1905 a single applica- 

 tion of Paris green at the rate of 1 pound in 75 gallons of water, ap- 

 plied when the larvse were one-half to two-thirds grown, caused an 

 almost complete disappearance of the larvse within three days. The 

 following year part of a second orchard was sprayed twice with 

 arsenate of lead with similar results. 



No field tests were made at Wallingford with the fall species, but 

 results equally satisfactory could doubtless be obtained. 



In orchards which are well cared for, the cankerworm infestation 

 is seldom severe, and can usually be sufficiently controlled by the 

 calyx spray. This application is ordinarily put on about as the larvse 

 of both species are entering the fourth stage, and have at least 8 

 to 10 days yet to feed. During this time most of the larvse present 

 will be killed. This application alone will keep a light infestation 

 within bounds, although it will not prevent much of the injury of 

 the season when the application is made. 



Where spraying is consistently practiced there is little complaint 

 of cankerworm damage. In properly sprayed orchards banding and 

 other measures for cankerworm control are seldom necessary. 



MECHANICAL BARRIERS. 



When for any reason spraying is impracticable, the use of various 

 mechanical barriers, properly applied, will give complete protection. 

 At a very early date the wingless condition of the female moths was 

 recognized as a weak point in the life history of the cankerworm, 

 and a number of interesting and ingenious types of barriers were 

 devised and used in the effort to prevent the moths from ascending 

 the trees to lay their eggs. At present the most common method of 

 preventing the ascent of the moths is by means of sticky bands. For 

 applying any of the commercial tree-banding materials, Doctor Brit- 

 ton (33), of the Connecticut Experiment Station, recommends the 

 following procedure: First, place around the trunk of the tree a 

 strip of cotton batting 2 or 3 inches wide ; second, cover this with a 

 band of tarred paper 5 or 6 inches wide, drawing it tight and tack- 

 ing it at the ends, which should overlap; finally apply a smooth 

 coat of sticky material one-eighth of an inch thick and covering about 

 two-thirds of the width of the tarred paper. The cotton batting 

 serves to fill any irregularities in the bark and prevents the passage 

 of the moths under the tarred paper. The use of the tarred paper 

 makes possible a more economical use of the sticky material than 

 would be possible in applying it directly to the rough and irregular 

 bark, and eliminates possible injury to the tree. 



Directions for making a gipsy moth tree-banding material which 

 has been developed at the gipsy moth laboratory at Melrose High- 

 lands, Mass., are as follows (38) : 



Prepare a stock mixture by placing in a large kettle one part by weight of 

 hard coal-tar pitch [melting point about 49° C] and adding one part by 



