18 MASS. EXPERIMENT STATION BULLETIN 203 



nematode galls from tomato roots. Orthodictilorobenzene adsorbed bydiatoma- 

 ceoiis earth and lacking calcium cyanide has little nemacidal value. Calcium 

 cyanide alone will materially reduce the injury caused by nematodes, but the 

 addition of orthodichlorobenzene prolongs the nemacidal activity of the cyanide 

 and has effected eradication. 



The most effective mixture from the standpoint of eradication without subse- 

 quent injury to seed germination and plant growth proved to be, by weight: 1 

 part orthodichlorobenzene (12.5 grams) adsorbed by 4 parts diatomaceous earth 

 (50 grams) and then mixed with 2 parts calcium cyanide (Cyanogas) (25 grams). 

 Two treatments of the soil are necessary with this mixture, with an intervening 

 interval of a week, and a final interval of 10 days before seed is planted. 



Acetic Acid and Pyroligneous Acid as Soil Disinfectants. (W. L. Doran.) 

 It was found that either of these chemicals can be substituted for formaldehyde 

 for soil disinfection to prevent damping-off, and at less cost than formaldehyde. 

 A description of this work has been published in the Journal oj Agricultural Re- 

 search 44:571-578, April 1, 1932, under the title, "Acetic acid and pyroligneous 

 acid in comparison with formaldehyde as soil disinfectants." Undistilled pyro- 

 ligneous acid was more effective than the distilled. 



Germination of onion seeds was not injured by pyroligneous acid 6:100, 65 

 gallons per acre, applied to soil in the open row at the time of seeding. This treat- 

 ment did not entirely prevent onion smut, however. 



A dust containing 6 per cent glacial acetic acid (in diatomaceous earth), when 

 applied to soil at the rate of 42.5 grams per square foot, afforded less complete 

 protection against damping-off than did acetic acid applied in water to the soil. 

 This dust applied to soil immediately before seeding did not injure the germina- 

 tion of beet and tobacco seeds. 



Carnation Blight (Alternaria dianthi S. SaU.). (E. F. Guba, Waltham.) 

 Production of the best blooms was lowest with December cuttings and highest 

 with March cuttings when benching was done on July 20, and this was influenced 

 by a corresponding difference in the prevalence of both Alternaria blight and 

 Fusarium wilt. E.\tensive observations in carnation nurseries in 1931 indicated 

 a correlation between greater prevalence of disease and early propagation. Heavy 

 rains in the summer of 1931 were an important factor influencing the losses from 

 these diseases, but benching in advance of the heavy rains in July contributed 

 greatly to their effective control. 



In a test of the control of blight in the field with fungicides, Bordeaux 4:4:50 

 containing one pound of calcium arsenate and one-half pint of fish oil gave the 

 best control. A spray of nicotine sulfate, salt, and fish oil, which is used occasion- 

 ally to combat red spider on carnations under glass, was not an effective treat- 

 ment for blight, and a spray of zinc sulfate, lime, aluminum sulfate, and fish 

 oil, recommended in the Middle West for controlling the bacterial spot of carna- 

 tions (Bacterium woodsii EFS), was of no value. 



With the present crop, results have been obtained which show the value of using 

 Bordeaux in the field. Results also show that early housing is of far greater value 

 in the control of blight, and where practiced the use of fungicides in the field 

 would appear not to be warranted. 



Strawberry Gold Leaf. (K. F. Guba, Waltham.) This trouble is genetic 

 and non-infectious, subject to modification by the environment. Seedlings of 

 Howard 17 develop the characteristic symptoms o'f chlorosis. Degeneration of 

 chlorophyll which is associated with this disease accounts for weak growth and 

 often death. Badly chlorotic seedlings succumb soon after the leaves appear. 



