36 



MISC. PUBLICATION 626, U. S. DEPT. OF AGRICULTURE 



less treatments are applied very early 

 in the day. The adults may be col- 

 lected early in the morning, however, 

 by beating them into a pan containing 

 water covered with a film of kerosene 

 or other oil. To control the insects, 

 especially the nymphs, which do not 

 have fully developed wings, dust with a 

 mixture of 9 parts of dusting sulfur 

 and 1 part of pyrethrum (containing 

 0.9 to 1.3 percent of pyrethrins by 

 weight) ; or spray with pyrethrum, der- 

 ris, or nicotine sulfate. Since these 

 treatments kill only the insects present 

 at the time, it is necessary to repeat the 

 applications as the bugs appear. 



Prevention. — For the tarnished 

 plant bug, one of the most important 

 practices is clean culture in and about 

 the garden. All weeds and trash, 

 which may serve as winter hibernating 

 quarters for the adults, should be 

 gathered and burned. The four-lined 

 plant bug, however, winters in the egg 

 stage. The small white eggs are in- 

 serted in slits in the tender shoots of 

 current and other plants, with one 

 end protruding. Wherever groups of 

 these eggs can be detected, clip and 

 burn the twigs. 



European Corn Borer 



The European corn borer (Pyrausta 

 nubilalis (Hbn.)) is an important enemy 

 of corn, but it also burrows in the stems 

 of many kinds of plants and weeds. 

 The stems of dahlia seem to be the most 

 susceptible of the flower crops attacked, 

 although aster, chrysanthemum, cosmos 

 (fig. 58), geranium, gladiolus, holly- 

 hock, zinnia, and other plants are also 

 tunneled. Sometimes the borers are 

 found feeding in flowers of dahlia, 

 chrysanthemum, and gladiolus. If an 

 infested dahlia stalk is cut open, a 

 grayish-pink caterpillar (fig. 59) with a 

 dark head will be found in the debris 

 of its tunnel. When full-grown it is 

 about an inch long. The corn borer is 

 easily distinguished from the stalk 

 borer (p. 34) by the absence of con- 

 spicuous bands or stripes characteristic 

 of the latter, although the injury it 

 causes is somewhat similar. Moreover, 

 the burrows of the corn borer are smaller 

 than those of the stalk borer. The corn 

 borer larvae hibernate in stems during 

 the winter, whereas the stalk borer lives 

 over in the egg stage. The first indica- 

 tion of infestation in dahlia is when the 

 new foliage and new blossom buds begin 

 to wilt. In severe injury the blooms 

 are greatly reduced in size and numbers, 

 and sometimes the affected plants are 

 destroyed before the propagating roots 



Figure 58. — Cosmos stems cut to show 

 the European corn borer and its 

 injury. 



Figure 59. — Larvae of the European 

 corn borer. Slightly enlarged. 



