20 



MISC. PUBLICATION 6 2 6, U. S. DEPT. OF AGRICULTURE 



sweet honeydew excreted by the aphids, 

 or by the sooty mold that develops in 

 the honeydew on the foliage, giving the 

 plant a sooty appearance. 



Treatment. — See treatment for 

 aphids (p. 9). 



Arborvitae Leaf Miner 



The tips of arborvitae twigs in the 

 Eastern States sometimes become dis- 

 colored (fig. 33) and gradually turn 

 brown as a result of having the interior 

 of the needles eaten out or mined by the 

 small caterpillars of the arborvitae leaf 

 miner (Argyresthia thuiella (Pack.)). 

 The reddish-green caterpillars, about x /% 

 inch long, pass the winter in the infested 

 tips, and the small moths emerge late in 

 May and during June to deposit their 

 eggs on the foliage. 



Treatment. — Cut off and burn the 

 infested tips during the fall or winter. 



Spray with nicotine sulfate or pyre- 

 thrum a number of times during June 

 to kill the moths and newly hatched 

 larvae. Spraying with a combination 

 of nicotine sulfate and lead arsenate 

 late in June or early in July is also 

 useful. 



Other Pests of Arborvitae 



Juniper scale. 

 Spider mites. 



Page 

 . 55 

 . 11 



Figure 33. — Discolored tips of arbor- 

 vitae tunneled by leaf miners. 



ASTER 

 Six-Spotted Leafhopper 



The six-spotted leafhopper {Macro- 

 steles divisus (Uhl.)), also known as 

 the aster leafhopper, causes injury by 

 extracting the plant juices from the 

 leaves, which may turn brown and die. 

 On asters it also transmits, as a result 

 of its feeding, a virus disease known as 

 aster yellows from diseased to healthy 

 plants. Often an entire planting may 

 become so badly infected that all the 

 plants are worthless. Practically all 

 horticultural varieties of asters of the 

 genus Callistephus are susceptible. 

 After feeding on infected wild plants in 

 the spring the leafhoppers carry the 

 disease with them to asters. Other 

 flowering plants on which the leafhop- 

 pers feed include African marigold, 

 calendula, chrysanthemum, cosmos, 

 dahlia, and gailiardia. The adult leaf- 

 hoppers are greenish gray and slightly 

 less than Y% inch in length. They are 

 rather robust and not so slender as most 

 other species (fig. 19, p. 11). The 

 young, or nymphs, are grayish. The 

 insects feed on the under sides of the 

 leaves and mostly on the lower foliage. 

 The leafhoppers usually spend the 

 winter on weeds in nearby fields. 



Treatment. — See treatment for leaf- 

 . hoppers (p. 11). 



Prevention. — The only satisfactory 

 way of preventing infection by the aster 

 yellows disease is to grow the asters 

 under a cloth shelter, wherever this is 

 feasible. Better flowers are produced 

 in this way. Another preventive meas- 

 ure is to burn over all nearby weed 

 patches in early spring, where this is 

 practical, before the insects can reach 

 the garden plants. 



Black Blister Beetles 



Blister beetles are especially fond of 

 the petals of flowers, on which they 

 chew. They feed on the foliage also. 

 The black blister beetle (Epicauta 

 pennsylvanica (Deg.)) is commonly 

 known as the black aster bug because 



