20 MONTANA EXPERIMENT STATION BULLETIN 425 



and the larvae move down into the leaf sheath upon hatching. In 

 this position they feed on sap which exudes from injuries which 

 they make in the plant tissue. At full growth they develop into 

 the "flax seed" stage within the leaf sheath. There are probably 

 two generations a year in Montana, and the winter is spent only 

 in the "flax seed" stage. Wheat attacked in the fall does not grow 

 well, and usually takes on a bluish-green tinge. The leaves become 

 thickened and stand erect. When heavily infested the plants will 

 die during the winter. Spring infested plants are usually char- 

 acterized by weakened stems which break over as the head fills. 

 The break is not clean and usually occurs above the leaves, thus 

 differing decidedly from that of the wheat stem sawfly, where 

 the stems break completely off usually near the ground line. 



In controlling Hessian flies three methods of attack are suc- 

 cessfully employed. First, late planting of winter wheat, after the 

 fall generation of flies has appeared and disappeared, will elimin- 

 ate fall attack. In states to the east where the flies are a constant 

 threat this "fly-free" date has been worked out on a geographical 

 basis, delaying the planting later and later as one progresses 

 south. This fly-free period has not been ascertained for Montana, 

 for in years past it has not been necessary to consider this insect 

 as a pest. Second, all volunteer wheat in the fields, margins, around 

 straw stacks, granaries, etc. should be destroyed to reduce the 

 overwintering population. Third, where feasible, plowing under 

 the stubble as soon after harvest as possible is desirable. 



WHEAT JOINTWORM (Harmolita tritici Fitch). — An infesta- 

 tion of this insect in wheat, involving approximately 3000 acres 

 was examined south of Columbus in Stillwater County during 

 the summer of 1943. In places straws were up to 60 percent in- 

 fested and the reduction in yield was substantial. The infestation 

 in this area in 1944 had disappeared and there was no record of 

 loss in this area. According to County Agent Payne, farmers in 

 this area in the fall of 1943 did a considerable amount of fall 

 plowing and stubble burning and this may have had its effect 

 on the population. 



MISCELLANEOUS RECORDS AND OBSERVATIONS 



PEA WEEVIL (Bruchus pisorum (Linn.) ) . — A rather extensive 

 survey in 1944 in the intermountain valleys where peas are grown 

 for seed and dried peas showed the pea weevil to be present only 

 in the vicinity of Missoula. Ravalli County was surveyed under 

 unfavorable weather conditions but it is believed the survey was 

 valid. Survey of Lake and Flathead counties was extensive and 

 thorough but no weevils were found. An infestation of 2-5 per- 

 cent was reported in some peas grown in Flathead County in 



