20 MASS. EXPERIMENT STATION BULLETIN 351 



Formic Acid 



According to Rideal and Rideal (76), formic acid has a higher antiseptic power 

 than acetic acid, and Uppal (90) found it more toxic to Phytophthora colocasiae 

 Rac. than acetic acid. 



As used in these experiments, 7 cc. of 90 percent formic acid, diluted to 250 cc. 

 and woriied into the soil immediately before seeding, controlled damping-off 

 very well. This efTect plus the better germination, as compared with checks, 

 resulted in marked improvements in the final stands: 



Increase in Final Stand 

 Percent 



Canterbury bells 100 



Beet 442 



Cress 377 



Thus applied, there was no injury to Anchusa aziirea, Canterbury bells, Cheiran- 

 thus Allionii, Galega, beet, and cress. 



This quantity and as little as 4 cc. if applied to soil after seeding, was injurious 

 to these species and to Felicia, Calendula, Linanthus, and celery. It is, however, 

 a real fungicide, harmless enough to plants if applied to soil before seeding and 

 its use in this way merits further investigation. It must, of course, be handled 

 with care, because of the danger of injury to the skin. 



Acetaldehyde 



Acetaldehyde is known to have fungicidal properties, and Tomkins and Trout 

 (87) found that it lessened the severity of a Penicillium rot of citrus. As used 

 here, it was less effective against damping-ofif caused by Pythium and Rhizoctonia, 

 than is formaldehyde; although dilutions of 1:30 to 1:50, applied at the rate of 

 2 quarts per square foot, resulted in considerable improvement in germination, 

 especially of sweet pea. 



It was also less toxic to plants than is formaldehyde, a dilution of 1:30 being 

 harmless to pasque flower, Canterbury bells, sweet pea, Drummond's phlox 

 and cucumber, seeds of which were sown 9 days after soil treatment. Growth 

 of sweet pea in soil inoculated with Rhizoctonia was improved almost 100 percent 

 by a dilution of 1 :40 and its use, at least with sweet pea, is deserving of further 

 investigation. On the whole, however, and as compared with formaldehyde, it 

 seemed to lack toxicity to both plants and fungi. 



Acetone 



Acetone was found by Tomkins (86) to inhibit the growth of some fungi in the 

 way that formaldehyde does; but, like acetaldehyde, it was less effective than 

 formaldehyde in controlling damping-off in experiments conducted here. This 

 was true of a dilution of 1:20 (2 quarts), and it is unlikely that heavier applica- 

 tions could be used safely — immediately before seeding, anyway — for even this 

 application, 3 days before seeding, was slightly toxic to some species. 



Ethyl Alcohol 



Ethyl alcohol (vapor) is known (86) to retard the growth of fungi, and Roberts 

 and Dunegan (78) found that it entirely prevented the growth of a Sclerotinia. 



