CARNATION WILT DISEASES 25 



after May 30 until the old plants and soil can be cleaned out and the benches 

 resoiled. Labor shortage requires planting the new stock in old soil, and the 

 continuation of some of the flowering stock for two or even three years. The 

 abuses which the young stock receives, and the loss attendant upon the delay 

 would, in more normal times, justify a plant house wholly for growing the young 

 plants (Fig. 11). A plant house should simplify the classification and segrega- 

 tion of the stock, make it easier to recognize disease and to exclude inferior or 

 unhealthy stock from the planting, and enable the grower to realize more fully 

 the potentialities of healthy, well-grown plants. It would eliminate much of the 

 hard work of lifting the flats onto elevated supports and removing them again 

 for planting. 



GREENHOUSE MANAGEMENT 



The intelligent management of the greenhouse atmosphere, and the judicious 

 use of water, are intimateh' involved in the successful control of disease. During 

 the course of these studies frequent instances of serious occurrences of the Alter- 

 naria blight disease were observed in places kept excessively wet b\- water drip- 

 ping onto the planted beds through leaks in the greenhouse roof. The same condi- 

 tion may arise from careless watering practices and too much water. 



Fusarium root rot, Fusarium branch rot, and Rhizoctonia stem rot are favored 

 by high temperatures and a high water table. These diseases are epidemic only 

 in the warmest months of the year. 



The grower can encourage the prevalence of carnation foliage diseases in the 

 greenhouse by tolerating continual moist and stagnant conditions. E.xchanges 

 of greenhouse air with the outside air are required to avoid, or to remove, moist 

 stagnant atmospheric conditions. Both heating and ventilating require careful 

 regulation to meet the changes created by the outside weather, and the effect 

 of both upon the greenhouse atmosphere can be seriously impaired by the misuse 

 of water. 



Some growers believe that carnations do best by an alternate drying and wet- 

 ting of the soil. Wiggin (80) states that carnations do best when the soil is uni- 

 formly moist but not saturated. It is his experience that newly benched plants 

 should be kept as dry as possible without producing a wilted condition. Peltier 

 (53) reported that the temperature should be kept as low as possible and no 

 more water applied than is necessary for good plant growth. 



Carnations are grown best at a temperature range of 50°-68° F. Low tem- 

 peratures inhibit infection and the progress of disease, but they are difificult to 

 maintain in Massachusetts greenhouses because of the warm weather prevailing 

 in the first few months after the fielded plants are benched. Continued low 

 temperatures correlated with a humid atmosphere encourage occurrence of 

 Botrytis bud rot. These conditions are paired when heating is delayed or lacking 

 in the fall months. An epidemic infection of the flowers b\- Alternaria in 

 November and December, unusual as it is, occurs where both heat and ventila- 

 tion are not properly managed. Similarly, the only devastating occurrence of 

 Heterosporium echinulatum (Berk.) Cke., the fungus causing fairy ring spot, to 

 come to the writer's attention was brought about by confined humid conditions 

 and wet foliage. The same conditions apply to serious occurrences of carnation 

 rust, Uromyces caryophyllinus (Schrank) Wint., and to bacterial leaf spot, 

 Phytomonas woodsii (Smith) Berge>- et al. These diseases become serious only 

 as sound watering and management practices are seriously violated. In every 

 instance the immediate correction of the contributing conditions has checked 

 these diseases. 



