452 GARDEN FARMING 



phosphoric acid, and potash. A 'good fertilizer for this purpose 

 consists of the following : I ^ parts of nitrate of soda, I part of 

 sulphate of potash, 2 parts of acid phosphate. Apply this at the 

 rate of 2 ounces per plant as soon as the plants have become well 

 established, and when the first fruits begin to color, make a second 

 application, using the same amount of the mixture per plant. 



Insects and diseases. Forced tomatoes, as a rule, are not seriously 

 injured by the common insect pests of the greenhouse. The mealy 

 bug and the white fly are the most annoying pests to the tomato. 

 The mealy bug can be destroyed by spraying the plants with fir- 

 tree oil or with a solution of ivory soap in water. The white fly, 

 Aleyrodes vaparorum, is easily held in check by fumigation with 

 tobacco or with one of the modern tobacco smudges. 



Nematodes, or eelworms, are minute organisms which frequently 

 infest soil in subtropical climates and under greenhouse conditions, 

 and are sometimes very destructive to the tomato. This organism 

 attacks the roots of the plant, causing abnormal swellings, or galls, 

 which interfere with the development of the roots and prevent 

 them from performing their normal functions. Infested plants are 

 weakened through lack of nourishment, the growth is abnormal, 

 and fruit production ceases. An examination of the roots reveals 

 the deformed, knotty condition shown in figure 1 70, which is char- 

 acteristic of this trouble. The only remedy is to root out and 

 destroy the plants, discard the soil for greenhouse purposes, and 

 after disinfecting the benches refill them with clean soil or steri- 

 lized soil, as described on pages 24-25. 



The one disease which is a menace to the forcing of tomatoes 

 is the mildew, Cladosporium fulvum. The first indications of this 

 disease are slight yellow discolorations on the surface of the leaf 

 and velvety brown patches of the fungus on the underside. This 

 stage is rapidly followed by the distortion and drying of the leaflets. 

 The spores of this disease ripen quickly and spread from leaf to 

 leaf. It usually appears first on the lower and older leaves, which 

 have partly lost their vitality. The plants should therefore be care- 

 fully watched for the appearance of this mildew, and when its 

 presence is detected immediate steps should be taken to eradicate 

 it. One of the best methods is to spray the plants at intervals of 

 a week or ten days with a solution of ammoniacal carbonate of 



