United States. They tested them for 

 virus by grafting a runner of each to 

 a runner of a plant of the little wood 

 strawberry [Fragaria vesca) . The 

 little wood variety was chosen be- 

 cause it shows virus symptoms 

 clearly. 



A few virus-free plants from each 

 of 40 to 50 varieties were found by 

 this method. These were multiplied 

 and distributed to nurserymen for 

 further increase and sale. Great care 

 was taken to prevent reinfection. 



Screenhouse Protects Plants 



Massachusetts growers received the 

 first virus-free plants in the Spring 

 of 1953. Tests were immediately un- 

 derway in several places in the state 

 to compare the plants with ordinary 

 nonvirus-free plants. They found that 

 runner formation in virus-free plants 

 is two to five or more times that of 

 ordinary plants. If a grower cares 

 for the new plants properly, they 

 will not degenerate or, as the growers 

 express it, "run out." 



The best way to produce virus-free 

 foundation stocks of high quality is 

 to grow the plants in a screenhouse. 

 This frame structure can be of any 

 convenient size, high enough to walk 

 in. It is covered with a fine screen 

 to keep out aphids. 



Soil in the screenhouse must be 

 thoroughly fumigated before plants 

 are set. Later, some of the founda- 

 tion stock is set in the nurserymen's 

 fields for further increase. The rest 

 of the foundation stock remains in 

 the screenhouse to be a nucleus for 

 more virus-free stock. 



Three Massachusetts nurserymen 

 have already built screenhouses and 

 are producing virus-free foundation 

 stock. It may take two or three years, 

 however, l>efore the nursery stock has 

 increased sufficiently so that enough 

 plants are available to meet the ever- 

 increasing demand. Strict control 

 measures in the field keep the nursery 

 stock free of virus-carrying insects. 



Nematode Control Possible 



A screenhouse will also assure 

 nematode-free as well as virus-free 

 plants. Meadow nematodes are micro- 

 scopic worms that burrow into and 

 feed on the roots of the strawberry. 

 They are related to black-root rot, a 

 wide-spread disease which is very 

 serious in southern Massachusetts, 



Through this protective measure, 

 the aim of researchers to control, and 

 perhaps eliminate, some of the more 

 serious strawberry diseases may be 

 realized. 



Virus-free stock really pays 

 off. Right: superior vigor 

 and runner development of 

 selected Sparkle strav/- 

 berries. Left: regular stock. 

 Photo courtesy of New York 

 State Agricultural Experiment 

 Station, Form Research, Jan- 

 uary, 1954. 



