'. "^^ 1^ 



«^ *< 



Tomato plants showing contrast between complete susceptibility and high resistance to 

 Cladosporium leaf mold disease. Inset: Tomato leaflet showing nature of disease. 



rtcM- iO^K€it<^C^ . . . result of twenty years of research 



TOMATO LEAF MOLD, (Clad- 

 osporium fulvum) still hovers 

 like an obstinate ghost to haunt 

 Massachusetts greenhouse tomato 

 growers. Unquestionably the leading 

 destructive disease of greenhouse 

 tomatoes, leaf mold has been a long- 

 standing problem of study because 

 of its importance in tomato culture 

 under glass. 



The loss of foliage caused by this 

 disease yields an inferior grade of 

 tomato and results in significant 

 production losses. The disease is 

 destructive in June and July toward 

 the end of the spring cropping sea- 

 son, whi'n returns are high, and 

 throughout the fall cropping sea- 

 son, wluMi returns are low. 



Control Through Breeding 



When customary disease-control 

 measures fail or prove impractical, 



* Researcli Professor, Botany, W.iltliam Field 

 Station 



By EMIL F. CUBA* 



then breeding for resistance and im- 

 munity can be the answer to prac- 

 tical and successful control. Of 

 course, the efTort required in breed- 

 ing is long and persevering. 



During breeding work at Wal- 

 tham, relating to the control of 

 tomato leaf mold, the varieties Bay 

 State and Improved Bay State were 

 successively introduced to the trade. 

 Improved Bay State is immune to 

 all e.xcept one strain of the fungus 

 and resistant to that one. Recently, 

 another acceptable red tomato, the 

 Waltham Mold-Proof Forcing, has 

 been developed totally immune to 

 the disease. 



South American Ancestry 



The high resistance of Improved 

 Bay State is derived from a strain 

 of the currant tomato native to 

 Ecuador, South America. The fruits 

 are round, red, about one-half inch 



16 



