HANDBOOK OX INSECT ENEMIES OF FLOWERS AXD SHRUBS 35 



Treatment. — There is no effective 

 way of poisoning the stalk borer, a- it is 

 an internal feeder. Individual plant- 

 can often be saved by splitting the stem 

 lengthwise, removing the borers, and 

 then binding the stem together again. 

 Cutting and crushing or burning the in- 

 fested stems having wilted tips is 

 effective in reducing the borer popula- 

 tion. A small amount of pyrethrum 

 spray injected into the burrows may kill 

 such borers as are actually reached by it. 



Prevention. — The best remedy is 

 clean cultivation and the burning of all 

 stems and plant remains that are likely 

 to harbor overwintering eggs. The 

 growth of large weeds, especially the 

 giant ragweed, should be prevented, or 

 the weeds should be cut, raked together. 

 and burned before the caterpillars con- 

 tained within them can escape and mi- 

 grate to garden plants. 



Potafo Leafhopper 



The potato leafhopper (Empoasca 

 fabae (Harr.)) sometimes seriously in- 

 jures dahlias. Its sucking of the plant 

 juices causes a whitening of the potato 

 foliage and gives it a fine stippled ap- 

 pearance. A more serious effect is the 

 so-called hopperburn which it causes, 

 wherein the edges of infested leaves turn 

 pale, curl, and finally become brown and 

 die fig. 19. p. 11). This insect also 

 attacks African marigold (p. 5 s . . 

 aster, gladiolus, hollyhock, rose, and 

 zinnia. The adult leafhopper 'fig. 95. 

 p. 59' is wedge-shaped, pale yellowish 

 green, and about % inch long. 



Treatment and prevention. — Same 

 as given for leafhoppers 'p. 10). 



Tarnished Plant Bug 



The tarnished plant bug (Lygus 

 oblineatus (Say)) is particularly injur- 

 ious to dahlia, aster, calendula, cosmos, 

 and marigold. It is a general feeder 

 and has been recorded as attacking 50 or 

 more economic plants, besides many 

 weeds and grasses. This habit greatly 

 complicates the effective use of insecti- 

 cides and the protection of flowering 

 plants. Both the nymphs and adults. 

 when feeding, sting the young tips, and 

 especially the buds of dahlia, and cause 

 them to become "blasted" and die 

 (fig. 56). They also puncture the leave- 

 so that small spots appear in the areas 

 fed upon. While feeding, the tarnished 

 plant bugs seem to inject a poisonous 

 substance into the plant, killing the 

 surrounding tissue. The adult is a 

 small, brownish, flattened bug. about 

 % inch long (fig. 57). It has a brassy 



Figure 56. — Injury to terminal growth 

 of dahlia by the tarnished plant bug. 



Figure 57. — The tarnished plant bug. 

 About 4 times natural size. 



appearance and is marked with yellow- 

 ish and black dashes. The adults 

 hibernate under leaf mold, stones, or 

 bark of trees, or among leaves of clover, 

 alfalfa, and mullein and in other pro- 



I tected places. They appear in early 



•' spring, and the bugs are most numerous 

 by late summer. Their eggs are laid 

 in the stems, petioles, buds, and tender 

 growths of many herbaceous weeds and 

 garden plants. 



Another species, the four-lined plant 



I bug (p. 94). which is a little larger, also 

 attacks the leaves of dahlia, giving 

 them a spotted appearance (fig. 159. p. 94) 

 similar to that caused by the tarnished 



i plant bug. 



Treatment. — Since most adult plant 

 bugs are extremely active, it is difficult 



I to reach them with -pray- or dust un- 



