THE ALDER "BLIGHT 



265 



The Fall Web Worm. The adult insect is a white moth 

 (Hyphantria cunea Dru.) with wing expanse of about one and one- 

 fourth inches. The wings are slightly spotted with black. The 

 pale yellow eggs, in clusters of a few hundred, are deposited on 

 the under side of the leaves during the summer. About ten days 

 are required for hatching. The young larvae are pale yellow with 

 brown markings. 



These feed upon the leaves of various trees, and spin a pro- 

 tective web as their feeding-ground enlarges, this nest enclosing 

 the leaves (Fig. 266). The active 

 larvae become full grown late in 

 summer. At this time the cater- 

 pillars are about one inch long 

 and are covered with black and 

 white hairs which project from 

 numerous black tubercles. These 

 caterpillars are somewhat vary- 

 ing as to color; some are uni- 

 formly yellow; others are almost 

 white. They attain full growth 

 in summer. 



After spinning light cocoons 

 in the ground or under the bark 

 or rubbish, they pupate and 

 emerge as adults the following 

 spring. The moth is a night flier. 



Control. Cut away and 

 burn branches containing colo- 

 nies of caterpillars. Spray badly 

 infested trees with arsenate of 

 lead, using three pounds to fift}> 

 gallons of water. Burn all rubbish on the ground beneath trees 

 which were infested the previous year. Do this before the adults 

 emerge in the spring and after their pupation in the fall. For- 

 tunately many enemies tend to keep this pest in check. 



The Alder "Blight." This is a woolly louse (Pemphigus tes- 

 sellata Fitch) which receives the above name because of the fact 

 that it secretes a honey dew which, falling on leaves beneath, 

 creates a favorable condition for the growth of the blight fungus. 

 The louse itself is dark in color, but is covered and hidden with a 

 white, flocculent growth. It infests limbs and twigs of the alder, 



FIG. 266. Nests of the fall web worm. 



