APPLE INSECTS — BUDS AND FOLIAGE 83 



of destructive outbreaks of canker-worms is usually due more 

 to certain obscure climatic or other local conditions. Early 

 spring frosts often kill large numbers of the young caterpillars. 



Remedial measures for canker-wortns. 



Although among the most destructive of the insect pests 

 of orchards, canker-worms can be rc^adily controlled. Well 

 cultivated orchards are rarely injuriously infested with canker- 

 worms. Thorough cultivation during June or later kills, or 

 turns out for the birds or other enemies, many of the pupse in 

 their earthen cells or cocoons near the surface. Thus orchards 

 can be kept practically free from the devastating hordes of 

 these caterpillars by simply practicing one of the most essential 

 factors in modern fruit-growing ; namely, thorough cultivation. 



Barriers of various sorts have long been used to prevent their 

 ascent or to trap and kill the wingless female moths when they 

 attempt to crawl up the trunks of the trees to lay their eggs. 

 To get the best results with these barriers it is necessary to 

 know which species of canker-worm infests the trees. If it is 

 the spring canker-worm, the barriers need not be applied until 

 late in February or during March, depending upon the early 

 occurrence of a warm spell. But in the case of the fall canker- 

 worm the barriers must be put on late in October and kept in 

 working order until the ground is well frozen ; in some of the 

 more southern or warmer localities in this insect's range, where 

 many of the moths often do not emerge until early spring, it 

 will be necessary to maintain the barriers during March and 

 April also. 



Among the mechanical barriers, there are two simple devices 

 that have been found effective. But few of the moths can get 

 over a band of cotton batting several inches wide placed around 

 the trunk, tied tightly with a string near the bottom edge, 

 and the upper portion of the band then turned down over the 

 lower, thus forming an inverted funnel-shaped barrier. When 

 not kept matted down by frequent rains these cotton bands 



