10 Eighteenth Report State Extomoeoc.ist ok Minnesota — 1920 



and Murray counties, and the soutliern parts of Lyon and Redwood 

 counties was badly damaged, as was another section lying on the boun- 

 dary between Pipestone and Rock counties. Isolated outbreaks were 

 reported from Canby, Yellow Medicine county, Hutchinson, Mc- 

 Leod county, and Northfield, l\ice county. 



The damage was done principally to oats, and consisted in the 

 cutting oft of the heads. This was seen to a considerable extent even in 

 fields in which the oats were cut and shocked. In one or two places 

 flax and corn were attacked, and at Northfield a pasture was slightly 

 damaged. Clover and other legiuninous crops were rarely eaten, and in 

 no case were thev badly damaged. Where oats and wheat were planted 

 together, the oats were always more badly damaged than the wheat. 



There is little probability of an attack in this region in 1921, but 

 fall conditions seem to indicate the possibility of an outbreak through 

 the central portion of the state, near the Twin Cities and northward 

 to St. Cloud. This, however, can not be definitely determined initil 

 next July. 



Onion insects. — The onion maggot and onion thrips were much in 

 evidence last year, particularly the latter. Considerable experimental 

 work was done with these insects but the exceptionally dry summer 

 prevented experimental control work. 



Orchard spraying. — The experimental work on orchard spraying 

 was continued and the data are being worked over at this time. The 

 results this year, owing probably to the season, were slightly different 

 from those of last year. This year it was found, as in 1918, that lime- 

 sulphur controlled scab better than any of the other mixtures, while 

 of the arsenicals used, arsenate of lead and arsenate of lime were 

 equally eltective in controlling the codling moth or leaf-eating insects. 

 Further experimental spraying work must be carried on before dust- 

 ing can be unhesitatingly recommended. • 



Hasal leaf galls of cottonwoods, and squirrels. — At the base of 

 Cottonwood leaves in June there occurs very often a swollen oval en- 

 largement from a ((uarter to half an inch in diameter. These are galls 

 caused by a plant louse, Ponphigiis popnlicaulis Fitch. Another closely 

 related leaf-stem gall is caused by Pcmpliigifs popnUtranst^crsns Riley. 

 These galls on the leaf stems of cottonwoods are very common in this 

 state. During the early part of the summer complaints came to the office 

 that the cottonwoods were losing their leaves. The same thing was hap- 

 pening on my own lawn. Upon examination of the fallen leaves it was 

 found that they had broken ofif or had been cut straight across the center 

 of the gall. In freshly fallen leaves the cut areas were still fresh and 



