ORCHARD INSECTS OF THE PACIFIC NORTHWEST 



39 



CONTROL 



Many of the egg masses may be found and destroyed when the 

 trees are pruned. If the small caterpillars are numerous, a spray of 

 lead arsenate, 2 pounds to 100 gallons, applied just before the trees 

 bloom, is very effective. If the spraying is done later, the quantity of 

 lead arsenate should be doubled, as the larger 

 caterpillars are more resistant to the poison. 

 Very often the tents can be pruned out 

 and destroyed or burned out with a torch, 

 moving the flame rapidly so as not to injure 

 the tree. The tents should be destroyed at 

 night when most of the caterpillars are con- 

 gregated in them. 



A FALL WEBWORM 



Although the habits of the fall webworm 

 Hyphantria textor Harris are somewhat simi- 

 lar to those of the tent caterpillar, there is 

 enough difference to remove any difficulty 

 in distinguishing the two insects. As the 

 name implies, the fall webworm appears late 

 in the summer and constructs a loose and 

 very unsightly nest of webbing about a num- 

 ber of twigs (fig. 48). These nests are 

 extended as the caterpillars grow and often en- 

 close entire branches. The caterpillars feed 

 within the webs, devouring the leaves and fruit. When full grown the 

 caterpillar is about l}{ inches long, covered with long, whitish hairs, 

 and with a dark band along the back. It constructs a flimsy, brown 



cocoon in trash on the ground; from 

 this cocoon the moth emerges late in 

 the spring. The moth is usually 

 pure white or spotted with dark- 

 colored dots. It lays pale-green eggs 

 in a flat mass on a leaf, covering them 

 with white hairs from its body. The 

 eggs hatch in about 10 days. There 

 is only one brood annually in the 

 Pacific Northwest. The insect occurs 

 in the area west of the Cascade 

 Mountains and in Idaho. 



Apple and pear trees that are regu- 

 larly sprayed with arsenicals are not 

 harmed by the fall webworm, as the 

 caterpillars appear after some of 

 these sprays have been applied, and 

 the small worms succumb readily to the poison on the foliage. On 

 shade trees or fruit trees not ordinarily sprayed, a special application 

 of lead arsenate, 2 pounds to 100 gaUons, is effective if applied while 



Figure 47.— Larvae and nest of the 

 eastern tent caterpillar (Malaco- 

 soma americann Fab.). 



Figure 48.— Nest of a fall webworm. 



