42 MASS. EXPERIMENT STATION BULLETIN 427 



Fungus Check Naphthalene Percent Increase 



Fusarium culmorum L5 2.0 33.3 



Fusarium dianthi _. 3.5 5.3 51.4 



Allernaria dianthi... ?.8 3.0 7.1 



When the plants are generally healthy, none of these diseases become estab- 

 lished under the conditions required for naphthalene fumigation. Spores of 

 Alternaria and Fusarium were exposed for 3 days in February in a greenhouse 

 section fumigated for 6 hours each day beginning at 10 a. m. No spore ger- 

 mination followed, whether the spores were exposed dry or previously sprayed 

 with water. In the latter instance evaporation of moisture followed shortly 

 after exposure. The concentration of naphthalene was not fungicidal. All of 

 the evidence is clearly in favor of fumigation to control the red spider mite. 



DISEASE RESISTANCE 



No studies have been reported on the genetics of resistance to carnation wilt 

 diseases and the development of disease-resistant types, although many investi- 

 gators have speculated on the economic importance of such studies wholly on 

 the basis of apparent differences in susceptibility of standard varieties to Fusarium 

 dianthi. 



Wight (79) advised, "grow resistant varieties" although none are defined. 

 White (72) stated, "The most satisfactory solution of the wilt problem is offered 

 in the possibility of the development of strains of plants immuneor highly resist- 

 ant to disease. There is no reason to doubt that resistant strains of the carnation 

 could be obtained." Van der Bijl (67) stated: "The question of the existence of 

 varieties more or less immune from disease has not received attention though a 

 problem well worth serious consideration and the breeding of disease-resistant 

 varieties may yet be the ultimate solution." Wickens (78) stated: "It is recom- 

 mended that a search for resistance be made amongst the numerous seedlings 

 raised by specialists in the development of new varieties and that the possibility- 

 of the occurrence of resistant sports in existing varieties be not overlooked." 



Some conception of the task involved in the development of a commercially 

 desirable type is conveyed by Weston (70): "Not only must the grower strive to 

 grow quality blooms but he must select varieties that grow and produce well. 

 They must have a reputation for giving a high average of good flowers; not be 

 prone to splitting at the sight of dull weather; produce good stems that have 

 some stamina in them; not be below average size and above all possess good color 

 and be free from a tendency to go to sleep under normal conditions"; and by 

 Laurie and Chadwick (40): "The ideal flower is of pleasing pure self color; non- 

 bursting calyx; a diameter of 4 inches, erect wiry long stem; petals hard enough 

 to withstand shipping; serrated, guard petals flat at right angles to calyx, center 

 to stand above calyx one-half the distance to make half a sphere; fragrant, 

 resistant to disease." 



However, judging from the limited utility of new carnation varieties in com- 

 mercial culture, it appears questionable whether the eflfort required to combine 

 resistance with other desirable commercial qualities is justified. The variety 

 or line of Mrs. C. W. Ward, from which by selection came Boston Ward and 

 then New Deal Ward, although highly susceptible to Alternaria blight and 

 Fusarium branch rot, has enjoyed the unique reputation ot many years of utility. 

 The introduction of this variety represented a great achievement. The desirable 

 qualities of Boston Ward or any of its improved selections combined with re- 

 sistance to Fusarium dianthi would appear to represent the nearest approach to 

 the ideal pink variety. 



