18 MONTANA EXPERIMENT STATION BULLETIN 384 



during the past two years. In 1939 these insects invaded a wheat 

 field on Reece Creek north of Bozeman, causing the usual mottling 

 of the leaves. The wheat was about eight inches high at the time, 

 and soon outgrew the damage. Conostethus americanus Knight 

 has not been reported as injurious since 1938. 



The Potato and Tomato Psyllid. — A survey was made June 19- 

 27, 1939, of all Montana potato areas except those in Flathead and 

 Lake counties. Specimens of Paratrioza cockerelli (Sulc) were col- 

 lected in Lewis and Clark, Cascade, Blaine, Phillips, Valley, Rich- 

 land, Dawson, Custer, Rosebud, Yellowstone, Carbon, and Still- 

 water counties. Despite the presence of psyllids at this early date, 

 the subsequent 1939 psyllid losses dropped far below those of 1938. 

 In many parts of the State light psyllid infestations were obscured 

 by heavy Rhizoctonia infections which were very prevalent. How- 

 ever, slight potato losses directly attributable to Paratrioza cock- 

 erelli were observed at Trident in Gallatin County, at Malta in 

 Phillips County, and in the Yellowstone Valley (Park City, Bill- 

 ings, Huntley, Custer). 



A survey was made June 22-27, 1940, of potato plantings in 

 the eastern two-thirds of Montana. Neither adults nor immature 

 stages of Paratrioza cockerelli were found west of a line connect- 

 ing the western borders of Phillips and Yellowstone counties. 

 Adult Paratrioza cockerelli were collected in Phillips, Valley, 

 Richland, Dawson, Custer, Rosebud, Big Horn, and Yellow- 

 stone counties. Subsequent summer observations of infestations in 

 Yellowstone County snowed a gradual increase in populations of 

 psyllids until harvest time, afer which a general migration oc- 

 curred to tomatoes, egg plant, and peppers. Slight losses in po- 

 tato yields, unnoted by growers, probably resulted from these 

 infestations. A few farmers sprayed their potatoes (1 gal. liquid 

 lime sulfur testing 28° Baume, in 35 gallons of water) early in 

 the season as a precautionary measure. No reports of psyllid 

 damage were received from growers in the State. 



Pear Psylla. — The pear psylla (Psyllia pyricola Forst.) is a 

 small, pale-orange to reddish-brown sucking insect. It is one of 

 the most important pests of the pear. When abundant, the leaves 

 turn brown, the fruit drops prematurely or is of poor quality, and 

 both the leaves and fruit may be covered with sticky honeydew 

 which the insects produce. This insect was introduced into Con- 

 necticut from Europe in 1832 and has spread over the eastern 

 states. Recently it was introduced into the Spokane area in Wash- 

 ington, and it now presents a threat to the western part of Mon- 

 tana at least. Ravalli, Missoula, Lake, Flathead, and Sanders 

 counties were surveyed from July 23rd to 30th to discover wheth- 

 er or not the insect had reached the State. The following is a 

 tabulation of the results of the survey: 



