6 MASS. EXPERIMENT STATION BULLETIN 394 



square toot) was applied, immediately before seeding, to a soil having a pH value 

 of 5.8 and to the same soil after its pH value had, by the earlier use of hydrated 

 lime, been changed to 7.L There was no injury to growth of beet or cucumber 

 and vinegar was effective in both soils; but, as may be seen by reference to Table 

 3, it was considerably more effective in improving stands in the acid soil than it 

 was in the soil with a high pH value. 



Copper, Mercury, and Zinc Compounds 



Red cuprous oxide 1 pound or yellow cuprous oxide 12 ounces in 50 gallons 

 water is sometimes used (13, 14) as a seedbed spray, applied first when seedlings 

 emerge and later at weekly intervals although, for better results, such treptment 

 should be supplemented by treatment of seeds. Earlier investigators (15), re- 

 porting good results after spraying with red cuprous oxide, obtained better con- 

 trol with Bordeaux mixture 2:1:50, 1 quart per square foot, two applications at 

 intervals of 3 days, beginning upon the first appearance of damping-off. 



But Bordeaux mixture is sometimes injurious (13), seedlings of crucifers are 

 susceptible to injury by red cuprous oxide used in this way, and, in the work of 

 the writers, neither Bordeaux mixture nor a spray of red cuprous oxide controlled 

 damping-off as well as did seed treatments. Nor did these copper sprays, includ 

 ing copper zeolite, control damping-off as well as did treatment of soil with for- 

 maldehyde (see Table 2). 



Cuprocide, 0.2 ounce in 0.8 quart water per square foot, gave good results only 

 with lettuce, pepper, and pea, not with the other eight vegetables with which it 

 was used; and stands of all of them except cauliflower were more improved or 

 less injured by formaldehyde. 



Bordeaux mixture was also of some benefit to lettuce, pea, and pepper, but 

 stands were more improved by formaldehyde and even by red cuprous oxide. 



When red cuprous oxide was dusted on to seedbeds, first (at the rate of 0.9 

 gm. per square foot) as seedlings emerged and again (at the rate ol 2.9 gm. per 

 square foct) a week later, cabbage was injured but stands of lettuce seedlings 

 were improved. In another experiment, however, stands of lettuce and celery 

 were more improved b> seed treatment with red cuprous oxide than they were 

 by that treatment supplemented by soil treatment with red cuprous oxide. 



Semesan, 1 ounce in 3 gallons water (1 to 1.5 quarts for 10 square feet), has 

 been advocated as a supplement to seed treatment with Semesan. A much 

 heavier application, as used on seedbeds, was somewhat injurious and certainly 

 of no benefit to tomato, eggplant, radish, and spinach (see Table 2). 



Dusted on to a lettuce seedbed immediately after the seeds were covered and 

 again a week later, Semesan, Calochlor, Corona P. D. 7, and corrosive sublimate 

 were injurious. Thus used, calomel (0.47 and 1.8 gm. per square foot for the 

 first and second applications, respectively) caused no injury and improved the 

 stands, but red cuprous oxide (0.85 and 2.95 gm. per square foot) gave better 

 results. These materials were all somewhat injurious to cabbage. 



Blackleg and black rot of some crucifers have been controlled, although not 

 without some chemical injury, by a solution of corrosive sublimate, 1:1000, ap- 

 plied three times to the seedbed (2); and dilutions of 1:1280 or 1:1600, applied 

 directly to plants in the seedbed, have controlled Rhizoctonia wire stem (8, 9). 

 These results have been the basis for recommending the application of corrosive 

 sublimate solutions to cabbage and cauliflower seedbeds at weekly intervals be- 

 ginning when seedlings emerge, using 1 ounce to 10 gallons for cabbage and 1 

 ounce to 15 gallons for cauliflower. But this method is not widely used for the 

 control of damping-off. Preference is more generally given and, it seems, with 



