MONTANA INSECT PESTS. 1947 AND 1948 17 



YELLOW JACKETS (Vespidae) 



Various species of Vespidae are minor pests in the Flathead 

 and other areas in the western part of Montana. Some damage 

 occurs to the ripe fruit each year due to the feeding activities of 

 the yellow jackets. Equally important is the nuisance value they 

 have during the picking season. 



PEAR SLUG (Caliroa cerasi) 



The pear slug is widely distributed throughout the state and 

 is not confined to a single host. Severe defoliation may occur on 

 plums, pears, quince, hawthorne, Juneberry, etc. In general, there 

 are two broods a 3^ear, the first appearing in June and the second 

 in August. The second brood usually causes the most damage. In 

 1948, the slug populations did not build up early in the season 

 because of a high mortality, presumably induced by the cool, wet 

 weather which prevailed during June and July. 



RUST MITE (Phyllocoptes sp.) 



A 1947 survey of sweet and sour cherry trees in western Mon- 

 tana showed that nearly all plantings were heavily infested with 

 a species of rust mite. This was the first authentic record of the 

 rust mite damaging fruit trees in Montana. However, from all 

 indications, this pest has been present for several years but has 

 been overlooked. The trees that are heavily infested have the 

 general appearance of trees suffering from drouth. The leaves 

 become curled longitudinally and show a bronzed discoloration. 

 Sour cherry leaves generally show a more pronounced bronzing 

 than do the sweet cherry leaves. Preliminary life history observa- 

 tions indicate that this pest overwinters as an adult, hidden behind 

 leaf bud scales and in cracks in the bark near the terminal and 

 lateral buds. In the spring, feeding activity begins as soon as the 

 buds show green. Generally, population levels are low throughout 

 the early growing season and a build-up does not occur until the 

 advent of hot, dry weather. In 1947 this build-up occurred early in 

 July whereas in 1948 populations did not build up until late 

 August. 



RASPBERRIES 



RASPBERRY CROWN BORER (Bembecia marginata) 



A preliminary survey of raspberry plantings in western Mon- 

 tana shows the crown borer to be present throughout the Bitter- 

 root and Flathead Valleys. In general, infestations are heavy in 

 many of the older plantings throughout both areas. Where vigorous 

 plantings are maintained, a loss of canes has not been severe, 

 however, in areas where the growth is less hardy due to soil 



