HANDBOOK ON INSECT ENEMIES OF FLOWERS AND SHRUBS 19 



top of the body are covered with a white, 

 waxy powder. Superficially, it resembles 

 a tiny white moth. The immature form, 

 or nymph, attached to the leaves, is 

 about the size of a small pinhead, oval, 

 flattened, and light greenish. The 

 nymph looks somewhat like a small, 

 soft scale insect and remains attached 

 to the leaf until it matures. 



Treatment. — Spray thoroughly, es- 

 pecially the under sides of the leaves, 

 with a combination of derris and pyre- 

 thrum, or with a nicotine sulfate and 

 soap solution, making two or three 

 applications at weekly intervals. A 

 white-oil emulsion can often be used 

 with success on the hardier shrubs, al- 

 though frequent applications at such 

 short intervals may not be advisable. 



Prevention.— Do not set in the 

 garden any cuttings or plants that are 

 infested, and take special precautions 

 with those originating in greenhouses or 

 conservatories. 



Other Pests of Ageratum 



Page 



Red spider 11 



Greenhouse leaf tier 5 



Mealybugs 28,31 



Corn earworm 29 



Asiatic garden beetle 21 



Stalk borer 34 



ARBORVITAE 



Bag worm 



The bagworm (Thyridopteryx ephe- 

 meraeformis (Haw.)) is a caterpillar that 

 lives in a silken, cocoonlike bag, to which 

 are attached bits of leaves from the host 

 plant. The bag is dragged about by the 

 caterpillar as it feeds on the foliage. " The 

 caterpillar gradually increases the size of 

 the bag as it grows. By late summer it 

 reaches a length of 1% to 2 inches and it 

 is then attached by one end to a twig 

 (fig. 32). In early fall the male emerges 

 as a winged moth, whereas the female is 

 wingless and remains in the bag, where 

 she lays a mass of eggs. These eggs pass 

 the winter in the bags attached to the 

 twigs, and by removing these bags the 

 eggs may be destroyed before they 

 hatch. Hatching occurs in May in the 

 South and late in May or early in June 

 in the North. The bagworm is distrib- 

 uted over the eastern half of the country 

 except in the more northern States. It 

 prefers to feed on arborvitae and juniper 

 but also infests pine, spruce, willow, 

 black locust, maple, and many other 

 evergreen and deciduous trees and 

 shrubs. 



Figure 32. — Bag or case of the bag- 

 worm attached to a twig. Natural 

 size. 



Treatment. — Spray with lead arse- 

 nate soon after the caterpillars hatch — 

 in the first half of May in the South, late 

 in May or early in June in the North — 

 using 2 ounces of the poison to 3 gallons 

 of water. If spraying is delayed until 

 July, when the insects are more than 

 half grown, increase the dosage to 3 

 ounces to 3 gallons. In the case of 

 small shrubs, pick off and destroy the 

 bags containing the feeding caterpillars. 



Prevention. — Remove and burn all 

 bags during the winter, thus destroying 

 the enclosed eggs and preventing their 

 hatching the following spring. 



Arborvitae Aphid 



The arborvitae aphid (Cinara tuja- 

 filina (DelG.)) feeds in colonies, sucking 

 the sap from twigs and small branches 

 of arborvitae, Italian cypress, and re- 

 tinospora (Chamaecyparis). It is widely 

 distributed over the country and when 

 numerous it weakens the branches or 

 the entire tree. The aphid is a small, 

 brownish insect, about y% inch long, with 

 the body partially covered with a whit- 

 ish, hairy pattern. Its presence can 

 often be detected by the occurrence o( 

 numerous bees and riies attracted by the 



