TOMATO LEAF MOLD 13 



Table 10. — Relation of Automatic Humidity Regulation and Automatic 

 Temperature Regulation to the Control of Tomato Leaf Mold 



Fall Cropping Season 1931. 



Percentage of Diseased Leaflets 



Date of 



Foliage Counts House A House B 



Humidity Temperature 



Control Control 



October 29, 1931. 

 December 2, 1931 

 January 4, 1932. . 

 January 13, 1932. 



Total 69.0 78.9 



In general, the benefit from control measures in these experiments was too 

 insignificant to justify the installation of costly air-conditioning apparatus. 

 The conditions imposed always gave a lower yield. The commercialization of 

 greenhouse air control systems seems to have been too sudden and speculative. 

 Installations involving the forced introduction of outside air and its distribution 

 throughout the growing area through a piping system proved a fallacy. The 

 conveniences of minimum thermostatic temperature control over hand-valve 

 control in greenhouse heating are recognized and several such installations are 

 in use in Massachusetts. The cost of further controlled air conditioning is at 

 present prohibitive and unjustified in commercial practice. 



GREENHOUSE DESIGN AND LOCATION 



Greenhouse design and location are closely bound up with the problem of 

 disease control. Both govern the means for providing adequate ventilation and 

 air circulation. It has been noted in Ohio (5, 55) that north and south houses 

 with ridge-hinged ventilation have less leaf mold. Multiple houses in a con- 

 tinuous series are objectionable. This type of range is considered more desirable 

 from the viewpoint of ventilation if built in sections of three houses each with 

 side ventilators and the sections connected by a covered alley (5). Judging from 

 experience in Massachusetts, single houses without the connecting covered alley 

 are more acceptable (Fig. 6 A, B). The alley does not permit good air movement 

 about each individual house. 



The need for adequate ventilating area in greenhouse design is generally rec- 

 ognized (33, 47). The modern high-ridged, even-span-roofed house all of glass 

 with continuous ventilation on sides, ends, and spans offers a remarkable contrast 

 to the low-span-roofed house with its row of single-pane ridge-hinged ventilators 

 and its back or north side of wood. The earliest construction showed a strong 

 disregard for light and normal atmospheres (Fig. 6 C, D). It has been stated that 

 the best type of greenhouse for tomato culture is one which permits the removal 

 of the greenhouse roof in the summer (15). The improvement in the provision 

 for light and air shown in the evolution of greenhouse design suggests an approach 

 to this end (Fig. 7 A). The inadequacy of ventilating area is still an evil of much 

 of the recent greenhouse construction for tomato culture, and reveals the desira- 



