ANNUAL REPORT, 1941 61 



were not significant. In the check plot there were 5 infested non-salable ears 

 and 5 infested but salable ears in a yield of 203 ears. Hills sprayed individually 

 with a mist nozzle showed 1 infested but salable ear in 219 ears, and the block 

 sprayed with a spray gun from the border showed 2 infested salable and 2 in- 

 fested non-salable ears out of 226. Powdered derris root 3 pounds and Ultrawet 

 }/2 pound in 100 gallons was used June 17, 24, 30, and July 7. 



The second generation planting at W'altham was not sprayed because of the 

 light infestation, and an examination on August 21 showed 15 infested ears or 

 1.34 percent In 1,118 ears examined. 



On August 12 a part of this corn was treated for protection against the corn 

 ear worm, by applying a standard lubricating oil-pyrethrum solution to the 

 dried silk of the ears. No corn ear worm infestation developed but the treatment 

 injured the ears by preventing pollination of the kernels in the terminal portion of 

 the ear, indicating that this treatment is not satisfactory under all conditions. 

 (See page 55.) 



Potato Spraying Experiments. (A. I. Bourne.) The weather conditions during 

 spring and early summer furnished a ver\' favorable start for potatoes and al- 

 lowed them to keep this initial advantage. The plots were planted on May 9. 

 The plants appeared promptly and growth was steady and rapid throughout the 

 summer. The plants were slightly damaged by a light frost on the night of 

 September 19-20 and were killed by a heavy frost on September 29-30. The 

 crop was dug September 30 to October 2. In all of the plots sprayed with bor- 

 deaux the plants were alive, green, and thrifty until killed by frost. 



Leafhoppers were very few and no outbreak occurred at any time during the 

 season. Potato aphids became abundant in early July but were controlled by 

 the addition of nicotine in the spray of July 16 and never threatened thereafter. 

 Flea beetles were abundant throughout June and early July; the late July infes- 

 tation was not so heavy. In the experimental plots 11 applications were made 

 between June 11 and August 27. A new method of determining flea beetle injury 

 was devised by which the number of feeding punctures was correlated with the 

 amount of leaf growth. The plan was designed to show the amount of injury from 

 week to week as well as the cumulative damage throughout the season. On this 

 basis the amount of flea beetle feeding in the plots given a commercial spray of 

 basic copper sulfate and sulfur was 103.1 feeding punctures per square inch of 

 leaf surface; plots which received a basic copper arsenate-sulfur compound 

 showed 45.1 feeding punctures per square inch of leaf surface; and the plot which 

 received a neutral insoluble copper fungicide (double copper) showed 88.6 punc- 

 tures per square inch. 



In all the plots sprayed with home-made bordeau.x mixture the damage from 

 flea beetle feeding was very much less than that in the plots receiving commercial 

 sprays. There was a slight advantage in favor of the low-calcium bordeaux, 

 and the addition of calcium arsenate in every case furnished added protection. 



The length of life of the plants in the different plots was in exact proportion 

 to this index of beetle activity. The plants sprayed with basic copper sulfate 

 and sulfur began to die early in August and by the end of the month practically 

 all were dead. Plants in the plot given the basic copper arsenate-sulfur compound 

 succumbed somewhat later. The plants given the neutral copper fungicide re- 

 mained alive until mid-September. In all of the bordeaux-sprayed plots most 

 of the plants were alive and green until the frosts of late September. 



The summer was marked by a prolonged drought, and the lack of sufficient mois- 

 ture interfered very seriously with the growth of the tubers and yields were 

 proportionally reduced. 



The yield records, however, showed a direct correlation with the amount of 

 flea beetle injur\'. In the plots which received the commercial sprays, yields 



