ANNUAL REPORT, 1941 27 



lime, for loss of sulfur by weathering, for scab control, and for chemical injury. 

 There were no apples to harvest from the untreated row because cf a complete 

 June drop caused by the plum curculio. In this row 20.3 percent of the leaves 

 were scabby and only a small amount of this was primary infection. In the 

 sprayed rows, irrespective of whether the sulfur was coarse or fine, there was 

 no scab. 



The results confirm the work of previous years to the effect that sulfur particle 

 size and concentration of sulfur are not as important in scab control as good 

 spraying. Chemical determinations of the residues after spraying revealed that 

 the loss of sulfur by weathering was greater with Magnetic Spray Wettable Sulfur 

 than with dry wettable Flotation Sulfur, eaily in the season. In both cases more 

 sulfur was retained on the foliage when the combination of sulfur and lead arsenate 

 was used without lime. Fish oil added to Flotation Sulfur, lead arsenate, and 

 lime increased the deposit and retention of sulfur. No improvement was shown 

 by substituting So^-a flour for fish oil in the first and second cover spra^^s. No 

 consistent benefit in the deposit and retention of sulfur otherwise could be shown 

 with the t3'pes of sulfur used by the addition of Soya flour. 



2. Copper Dusts for Cucumber and Muskmelon. Fifteen proprietary and two 

 home-mixed copper dusts containing different sources of metallic copper were 

 tested on cucumber and muskmelon planted in rows of 5 hills of 5 plants per hill. 

 The copper content of the dusts varied from 4.75 to 7 percent. Some contained 

 an insecticide (either 20 percent cryolite, 0.75 percent rotenone, or 5.75 to 10 

 percent calcium arsenate) added for the control of striped cucumber beetles. 

 The dry summer was unfavorable for the usual foliage diseases, but bacterial 

 wilt and mosaic were present on cucumber. 



A proprietary dust containing 5 percent metallic copper and 20 percent cryolite 

 was injurious to both muskmelon and cucumber. On the basis of plant condition 

 and yield, the five best treatments on cucumber were: 



6 percent Cu in tri-basic copper sulfate and 0.75 percent rotenone 



6 percent Cu in tri-basic copper sulfate 



5 percent Cu in copper oxychloride sulfate and 1 percent rotenone 



7 percent Cu in tri-basic copper sulfate and 0.75 percent rotenone 

 5.16 percent Cu in red copper oxide and 0.75 percent rotenone 

 The best treatments on muskmelon were: 



6.5 percent Cu in tri-basic copper sulfate and 0.75 percent rotenone 



6.5 percent Cu in tri-basic copper sulfate and 10 percent calcium arsenate 



6 percent Cu in tri-basic copper sulfate and 0.75 percent rotenone 

 5.16 percent Cu in red copper o.xide and 0.75 percent rotenone 



5 percent Cu in copper ox) chloride sulfate and 7.5 percent calcium arsenate 

 4 percent Cu in copper hydroxide and 7 percent calcium arsenate 

 The differences between the best copper treatment combinations and a 0.75 

 percent rotenone dust on muskmelon were not significant in 1941. 



3. Mercury Compounds for Control of Club Root of Crucifers. In a preliminary 

 exploratory experiment calomel and mercuric bichloride in varying amounts 

 were used for the control of club root of cabbage and cauliflower. Applications 

 were made to seed flats and in the field at different times and by various methods. 

 Because of uneven infestation in the experimental block, the results were in- 

 definite and no conclusions can be made. 



4. Vegetable Seed Treatments for Damping-off Control. For the second suc- 

 cessive year cooperative tests of vegetable seed treatments were conducted under 

 the auspices of the committee for coordinated seed treatment research of the 

 American Phytopathological Society. Weighed amounts of treated seed (treat- 



