dairy and seed improvement meetings. 255 



Rhizoctonia Stem Injury and the "Little Potato 



Disease." 



In central and southern Maine in certain seasons, much 

 damage, the nature and amounts of which are not even sus- 

 pected by the average grower, is caused by the attacks of the 

 Rhizoctonia fungus upon the parts below ground. Young 

 shoots are cut off before they reach the surface, older ones ana 

 the roots are more or less injured, resulting in premature ripen- 

 ing, and the young tubers are cut off from the parent stem by 

 the destruction or girdling of the stolons upon which they are 

 borne. Observations made in Aroostook last season indicate 

 that the same form of injury is more common there than had 

 been previously suspected. 



Recent studies indicate that it is probably impossible to en- 

 tirely control this disease, for the fungus appears to be present 

 in potato soils, universally. It can attack a wide variety of 

 plants and apparently can live equally well on various kinds of 

 decaying vegetable matter. 



Our studies have shown that disinfecting seed tubers with 

 formaldehyde or corrosive sublimate helps to control it — the 

 latter being the most eft'ective. Applying sulphur to the soil 

 made a marked increase in the virulence of the disease for two 

 successive seasons. It is probable, however, that the amount 

 of sulphur used for drying seed after cutting is not sufficient 

 to produce any deleterious effect. Seed tubers free from the 

 sclerotia or resting bodies of the fungus — the closely adhering 

 brownish or black bodies which look like dirt on the skin, but 

 which cannot be washed off — should be used if possible. Plant- 

 ing infected land less frequently to potatoes would doubtless 

 prove helpful. It looks now as if the most hopeful results 

 would be obtained from planting resistant varieties, or from 

 breeding resistant strains of those varieties which, like the 

 Irish Cobbler, are relatively susceptible. 



Blackleg of the Potato. 



A little over nine years ago or during the first summer I 

 spent in Maine I discovered that the blackleg disease was rela- 

 tively common here, more especially in Aroostook county, al- 

 though it was not generally recognized by the potato growers 



