TWENTY-SEVENTH REPORT OF STATE ENTOMOLOGIST 29 



the "purple-top", and produced very small tubers which in 

 many cases did not justify the cost of digging. 



The adult potato psyllids are about 1/16 of an inch long 

 and have stout hind legs which enable them to jump when 

 disturbed. They are sometimes called "jumping plant-lice." The 

 females lay tiny oval, orange eggs which are supported on short 

 stalks. Each female may deposite 300 or more eggs. The eggs 

 hatch into tiny, scale-like, wingless nymphs, which feed on 

 the plants, moult five times at 3 or 4-day intervals, and emerge 

 as winged adults. There may be several generations during the 

 summer season. 



Experiments carried on during the past season indicate that 

 young psyllid nymphs are easily killed by a lime-sulphur spray, 

 or by various sulphur dusts, but the older nymphs and the adults 

 are more resistant to the action of these insecticides. The use 

 of the standard lime-sulphur spray is therefore successful only 

 when the following conditions are met: 



a) Spray must be of the proper strength (1 gal. 33° Baume' 

 lime-sulphur to 40 gallons of water, or equivalent 

 strength) . 



b) Spray must be forcefully applied to the under surface of 

 foliage. 



c) Plants must be sprayed early in the season, before the 

 nymphs have had a chance to produce the "purple-top" 

 disease. 



d) Most of the insects should be in the younger nymphal 

 stages, since the older nymphs and adults are not easily 

 killed. 



Considerable spraying was carried out by growers in Yel- 

 lowstone County, but the "purple-top" disease was already too 

 far advanced to permit recovery of the plants. 



GRASS PLANT BUGS 



(Labops hesperius Uhl. and Conostethus n. sp.) 



In the spring of 1936 two species of plant bugs were noticed 

 attacking range grasses on the Crow Indian Reservation. In the 

 spring of 1938 these pests were again abundant and some inva- 

 sion of winter wheat occurred east of Crow Agency and south 



