DORMANCY IN BUDS 



233 



diseases, especially those carried in the tubers. It is now common practice 

 to force northern-grown seed potatoes in the greenhouse during the winter 

 to determine whether the seed is virus-free. This gives a preview of the 

 next year's crop. This control of tuber dormancy is also useful m practice, 

 not merely because it enables southern growers of the fall crop to produce 



Figure 86. Second crop of potato tubers in same year in 

 Institute gardens from tubers treated with ethylene chlorhydrin. 



(Left) Check 

 not treated. 



lot 



from northern-grown disease-free tubers, but also to produce a second crop 

 from the small tubers of a first crop. 



Many other chemicals were found more or less effective in forcing dor- 

 mant potato tubers, but ethylene chlorhydrin and the thiocyanates showed 

 advantages over the others for one or more of the following reasons: high 

 effectiveness in forcing; wide margin between forcing and killing dosages; or 

 cost of the chemical for treatment. Among the other chemicals that Denny 

 early found to be more or less effective were di- and trichloroethylene, 



