^2O Minnesota Plant Diseases. 



O 



Onion smut (Urocystis cepulae Frost.}. This is a leaf -smut 

 and is due to a fungus somewhat similar to that of the rye 

 smut. The smut masses appear in lines on the foliage leaves 

 and may later appear on the scale leaves of the bulb. The spores 

 are aggregated into true spore-balls, of which the outer spores 

 are sterile and incapable of germination, while the inner are fer- 

 tile and well protected by the outer ones. The infection of the 

 host plant takes place in- the seedling stage. 



Diseased plants should be destroyed. Care should be taken 

 not to plant seed in smut-infected soil, since the smut spores re- 

 tain their power of germination for many years. Care should 

 also be taken to prevent the transference of smutted plants or 

 smut-infected soil from one bed to another. When seeding in 

 infected soil, "apply in the drills per acre one hundred pounds 

 of sulphur thoroughly mixecl with fifty pounds of air-slacked 

 lime. Formalin (one pound to thirty gallons water) thorough- 

 ly sprinkled over the seed before covered with the soil, or ap- 

 plied by drip attachment to the seeder, is an efficient remedy. 

 Ground lime, drilled in the land with a fertilizer drill, at the rate 

 of 75 to 125 bushels per acre, is helpful in keeping the trouble in 

 check." (Conn. Ag. Ex. Sta. Bull. No. 142 1903.) 



The currant pore-fungus rot [Fames ribis (Schum.) Fr.]. 

 This disease of currant bushes is probably not common but has 

 been observed in this state. The fungus mycelium is parasitic 

 in the root of the currant, producing its fruiting bodies at the 

 surface of the ground, particularly around the base of the stem. 

 The affected portions of the root-tissue turn black and the 

 roots, and subsequently the remainder of the currant bushes, 

 are finally killed. The fruiting bodies are dark-yellow-brown, 

 woody, thin, saucer-shaped shelves and live from year to year. 

 The pores are small and line the under surface of the fruiting 

 body. The latter are sometimes six inches in diameter. It is 

 said also to attack gooseberry bushes. 



All fruiting bodies and infected plant-parts should be re- 

 moved and burned as soon as discovered. 



The sclerotium disease of cucumbers and other garden plants 

 (Sclerotinia libertiana Fckl.}. The fungus cause of this disease 

 is a sac fungus with a peculiar life history. When the sac 

 spores germinate at the surface of the soil they produce a my- 



