HANDBOOK OX IXSECT ENEMIES OF FLOWERS AND SHRUBS 



CUCUMBER BEETLES 



Spotted Cucumber Beetle 



The spotted cucumber beetle (Dia- 

 brotica undecimpunctata howardi Barber 

 may be found destroying many plants 

 grown in both flower and vegetable gar- 

 dens. Among the flowering plants 

 attacked are aster, calendula, canna, 

 chrysanthemum, cosmos, dahlia, daisy, 

 rose, sweet pea, zinnia, and several 

 others. It feeds on the leaves, buds, 

 and flowers, although its chief injury 

 consists in eating holes in the blossom 

 petals. If many beetles are present, 

 their excrement may discolor the blos- 

 soms even when they do no other dam- 

 age. This insect often causes serious 

 damage in late summer or early fall, 

 when many of its more favored host 

 plants have matured or become unpal- 

 atable and the beetles have therefore 

 migrated to asters, dahlias, and other 

 late-season garden flowers. The beetles 

 are about % inch long, yellowish green, 

 with 12 black spots on the wing covers 

 (fig. 12). They pass the winter in the 

 adult, or beetle, stage. The eggs are 

 laid in the ground in the spring, and the 

 larvae feed on the roots of various 

 garden plants and weeds about a month 

 before the adults emerge. 



Western Spotted Cucumber Beetle 



The western spotted cucumber beetle 

 (Diabrotica undecimpunctata Mann.), 

 which is similar in appearance to the 

 spotted cucumber beetle, attacks chrys- 

 anthemum, daisy, rose, and zinnia. 



Striped Cucumber Beetle 



Another species, the striped cucumber 

 beetle (Acalymma vittata (F.)), eats 

 holes in the leaves and flower petals of 

 aster and rose. This beetle (fig. 13) is 

 pale yellow, with three stripes on its 

 wing covers. 



Figube 12. — The spotted cucumber 

 beetle, and feeding injury and dis- 

 colored areas on aster caused by it. 

 About twice natural size. 



Figure 13. — Striped cucumber beetle. 

 About twice natural size. 



Treatment. — Since these beetles are 

 generally distributed and are likely to 

 be a recurrent problem, they should be 

 destroyed on the first evidence of injury 

 to plants. Spraying with enough py- 

 rethrum to wet the beetles is recom- 

 mended. It is usually necessary to 

 repeat the spray applications, since the 

 beetles may continue to fly in from 

 surrounding areas. 



Dusting with cryolite (p. 97), rote- 

 none (p. 99), or nicotine dust (p. 98), 

 or with a mixture of 1 part of calcium 

 arsenate and 15 parts of gypsum (land 

 plaster) by weight once or twice a week, 

 is also of value. Spraying with bor- 

 deaux mixture (p. 97) repels these 

 beetles. 



Prevention. — Choice plants and 

 flowers, especially asters, dahlias, or 

 roses, may be protected by covering 

 them late in the summer with cheese- 

 cloth. 



BLISTER BEETLES 



Blister beetles are general feeders that 

 chew and devour the foliage and flowers 

 of many kinds of plants. At times the 

 adult beetles occur in enormous numbers 

 and often travel in swarms, devouring 

 nearly all plants in their path. They 

 usually appear about the middle of June 

 and continue their feeding until early 

 fall. They are about 3 4 inch long, 

 slender, rather soft-bodied, and of 

 various colors. Some species are en- 

 tirely black, some are brown or yellow 

 with black stripes or spots, whereas 





