HANDBOOK OX INSECT ENEMIES OF FLOWERS AND SHRUBS 33 



must be taken when using this chemical, 

 because it is poisonous, highly inflam- 

 mable, and explosive when mixed with 

 air in certain proportions. 



Prevention. — Thorough raking and 

 working of the soil around the base of 

 the plants early in the spring has been 

 suggested to destroy the overwintering 

 eggs. 



Cambium Curculio 



Another boring insect, the cambium 

 curculio (Conotrachelus anaglypticus 

 (Say)), has recently been found to injure 

 columbine seriously. In nature this in- 

 sect is rather common and feeds in a 

 variety of situations. The beetles often 

 occur in company with those of the plum 

 curculio. The larvae, which are small, 

 whitish, legless grubs, have been found 

 attacking peaches, cotton bolls, and the 

 cambium and inner bark (fig. 53, A) of 



Figure 53. — Cambium curculio: A, 

 Larvae, or grubs, exposed bv removal 

 of bark; B, adult. Both about l l/ 2 

 times natural size. 



many fruit, shade, and forest trees. 

 They work around the edges of wounds, 

 retarding the healing processes and 

 enlarging the injured areas. In colum- 

 bine they seem to prefer the crown and 

 roots. Their feeding results in a wilt- 

 ing and dying of the plants attacked, 

 and the injury is usually not discovered 

 until these symptoms appear. The 

 adult is a small weevil, or snout beetle 

 (fig. 53, B), less than V 4 inch long. 



Treatment. — No satisfactory treat- 

 ment is known except to remove and 

 burn the infested parts. This opera- 

 tion destroys the insects contained 

 therein and in this way reduces the 

 chances for future reinfestation. 



Prevention. — Clean culture late in 



the fall is useful in that it destroys the 

 overwintering quarters of the adults, 



which are among the debris and litter 

 on the ground. 



Columbine Leaf Miner 



The columbine leaf miner (Phytomyza 

 minuscula Clour.) is rather abundant 

 throughout the United States. The tiny 

 whitish maggots feed between the leaf 

 surfaces of columbine (fig. 54) and aster 

 and produce a whitish, tortuous or 

 serpentine trail or mine, which is visible 

 on the upper leaf surface. The mine 

 frequently crosses itself and ends in a 

 spot about % inch wide. This miner 

 attacks the lower leaves first and then 

 continues upward on the plant. The 

 small, shiny, black, two-winged flies 

 emerge in May or June, feed, and de- 

 posit eggs in the under side of the leaf. 

 The larvae hatch, feed for about 10 days 

 to 2 weeks, and then form small foot- 

 ball-shaped puparia on the leaf. Eight 

 or ten larvae may develop in a single 

 leaf. The last, or fourth, generation 

 appears about the middle of September 

 and passes the winter as pupae in the 

 soil about the base of the plants. 



A closely related species (P. aquilegine 

 Hardy) also occurs on columbine but 

 differs from the one discussed above in 

 that it forms a blotchlike mine. 



Treatment. — Spray with a nicotine 

 sulfate and soap solution. An infesta- 

 tion may often be checked if all infested 

 leaves are promptly removed and burned. 



Prevention. — Spade the ground 

 thoroughly about the base of the plants 

 early in the spring to destroy the pupae 

 before the flies have a chance to emerge. 



Figure 54. — Work of the columbine leaf 

 miner. 



