60 MASS. EXPERIMENT STATION BULLETIN 355 



dust (.75 percent rotenone and 20 percent sulfur) was the least effective of the 

 dusts used. Wettable cube and derris sprays (4 pounds in 100 gallons) gave 

 83.4 and 84.4 percent protection and were slightly inferior to the dusts. 



On this basis the effectiveness of all the treatments is within the range of ex- 

 perimental error, indicating that the calcium arsenate-lime dust, which is the 

 cheapest, was the most practical under 1938 conditions. 



Control of Squash Vine Borer. (W. D. Whitcomb, Waltham.) The average 

 field infestation by the squash vine borer in the experimental planting of Hubbard 

 squash in 1938 was 6.67 borer tunnels per vine, which is much greater than has 

 been recorded here before. Many vines were killed before they had grown second- 

 ary roots at the nodes, and frequent and excessive rainfall during July reduced 

 insecticide treatments to about one-half their usual efficiency. Almost continuous 

 rainfall from July 18-25, which practically prevented dusting or spraying, only 

 slightly reduced oviposition by the borer moths and greatly aided the develop- 

 ment of an unusually severe infestation. 



Insecticides were applied July 6, 13, 22, 29, and under these conditions 40 per- 

 cent nicotine sulfate 1-250 permitted an average of 3.06 borer tunnels per vine, 

 which is a reduction of 54.12 percent over the infestation in the untreated plants. 

 Cube-clay dust (.6 percent rotenone), wettable cube spray (4 pounds in 100 gal- 

 lons), and a neutral copper-rotenone dust (.8 percent rotenone), all reduced the 

 infestation approximately 45 percent. Nicotine sulfate 1-500-foil emulsion 1 per- 

 cent and cube-clay dust (.75 percent rotenone) were less effective in the record 

 but obviously were affected by the unfavorable weather conditions. 



Potato Spraying Experiments. (A. I. Bourne.) Potato flea beetles appeared 

 in the fields almost as soon as the young plants appeared above ground, and were 

 so abundant that they constituted a major problem throughout the season. 

 Leafhoppers were late in appearing and were at no time very abundant. The 

 rainfall in July was 7.45 inches, a record exceeded only three times in the last 

 fifty years. This heavy precipitation during July very largely prevented aphid 

 attack, and no serious outbreaks in potato fields were noted or reported. 



The frequent rains during June and July made it difficult to hold to any definite 

 schedule of sprays, and applications were frequently interrupted. However, the 

 experimental plots were given 10 applications of copper sprays between June 14 

 and August 29. Six different insecticides were tested on the standard variety, 

 Green Mountain, each of them being used in combination with 5-5-50 and 5-3-50 

 Bordeaux mixture in the applications from July 14 to August 9. As thorough 

 coverage of the foliage as weather conditions permitted was maintained through- 

 out the season, and the plants remained green until killed by the frost of October 

 7-8. Weekly records of flea beetle damage were made in each plot throughout 

 the season. The ranking of each material with the two .strengths of Bordeaux 

 mixture was as follows: 



With 5-5-50 Bordeaux With 5-3-50 Bordeaux 



Derris 4 percent rotenone Cube 



Cube 4 percent rotenone Derris 



Calcium arsenate (Calrite) Commercial 2 percent rotenone 



Commercial 2 percent rotenone Calcium arsenate-arsenite mixture 



Calcium arsenate (Calgreen) Calcium arsenate (Calrite) 



Calcium arsenate-arsenite mixture Check (Bordeaux alone) 



Check (Bordeaux alone) Calcium arsenate (Calgreen) 



All of the materials gave better control with the 5-5-50 Bordeaux mixture, 

 indicating that in a year of frequent and heavy rainfall, as in 1938, the greater 

 persistence of the high calcium Bordeaux gave added protection to the foliage. 

 This was also borne out in the relative yields as shown in the following table: 



