TOMATO LEAF MOLD 3 



to the open, it seems that outside conditions and boiler heat can be advantageously 

 utilized, and in a manner consistent with good growth, in greenhouse management 

 to control the disease, especially when aided by other useful contributory cultural 

 and sanitary measures. 



GREENHOUSE PLANTING DISTANCES AND PRUNING 



The suppressive effect of light, low relative humidity, and dr\- foliage conditions 

 on the fungus and infection is recognized. Close planting and abundant plant 

 growth encourage excessive moisture b>- interfering with the circulation of air. 

 The>- cause undue shading and poor light. The influence of pruning and adequate 

 spacing on air circulation and moisture removal and the penetration of light can 

 be significant and very useful in contributing to the control of the disease. The 

 lowest leaves of the plants always show the first signs of disease and their early 

 removal is a desirable sanitary practice. 



A planting distance of 3 feet by 14 inches in the spring growing season is com- 

 monly used in commercial practice. In the fall growing season with light con- 

 ditions less favorable for plant growth and moisture conditions very favorable 

 for the fungus, wider spacing is essential to the control of the disease. Double 

 rows of single leader plants or single rows of double leader plants are objectionable 

 in the spring growing season unless a generous amount of space is provided 

 between the rows, and they are not recommended for the fall growing season. 

 For double rows of single leader plants a distance of at least 15 inches inside 

 between the rows and Z]4. feet outside between the double rows is desirable. 

 If the plants are grown in single rows to two leaders a distance of 4 feet between 

 the rows and 15 to 18 inches between the plants in the rows is desirable. Wider 

 spacing than the foregoing distances would be excessive. Whether a system of 

 double rows of single leader plants or single rows of double leader plants is adopted, 

 light and air conditions about the leaders will be greatly improved by staggering 

 every other leader away from the row. Close planting or crowding does not 

 increase yield per square foot of space. Sufficient spacing to permit light and air 

 currents is also essential to pollination and ripening. On the other hand, the cost 

 of excessive spacing is prohibitive. It also encourages the curling of the leaves 

 exposed to the bright rays of the sun for long periods during the day. This un- 

 healthy condition has now and then aroused the fear and curiosity of the grower. 



After the plants have made a strong growth and before they have grown to 2 

 feet, the lowermost leaves can be removed. If the growth above is dense and 

 rank, an occasional leaf on the stem can be removed. When the fruit on the lower 

 trusses has reached full size the plants will stand more pruning below the fruit. 

 The practice of removing the leaves below the trusses that are ripening off is 

 desirable. (Figs. 1 and 2.) If the lower leaves are infected with leaf mold, drastic 

 bottom pruning can aid in retarding the progress of the disease. These bottom 

 leaves at any rate eventually turn yellow and become of no use to the plant, 

 and might as well be dispensed with earlier. Stone (49, 50) regarded the lack 

 of light as favorable to disease attacks in the greenhouse and advocated the 

 removal of foliage to improve light conditions. Dyke (14) advocated the removal 

 of foliage to improve light and undercurrents of air. 



Excessive foliage pruning can be harmful to the swelling of the fruit and to good 

 yields. Therefore good judgment is needed in providing the right balance of 

 foliage to fruit. The heavy, free-setting varieties require vigorous, healthy foliage 

 to insure good-sized tomatoes, so that with these types pruning must be practiced 

 with discretion. 



