1978 



ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 



ment by drying, freezing or excess of 

 water, and high temperatures, and tlie 

 methods of treatment are based upon our 

 knowledge of the influence of these fact- 

 ors upon the organisms. Drying the soil 

 has been employed in Europe on field 

 crops and is very satisfactory when ap- 

 plied on a small scale in the greenhouse. 

 Removing the soil and replacing it with 

 new, or freezing it, is quite ejBEective, and 

 the so-called catch crop method has 

 proved successful in some instances. The 

 method consists in planting some crops 

 like mustard or rape before the regular 

 crop is planted, and when the galls are 

 well formed the crop is dug up, and the 

 roots exposed to the drying action of the 

 sun, which kills the worms. By this 

 method the females are captured and de- 

 stroyed at the most advantageous time. 



One of the most practical methods of 

 ridding a house of eel worms, when the 

 proper facilities are at hand, consists in 

 sterilizing. With special appliances this 

 can be done effectively at no great cost, 

 and is on the whole the cheapest and 

 best method of destroying this pest. 



Where water is allowed to stand for 

 some time in the soil it becomes destruc- 

 tive to eel worms. 



G. E. Stone, 

 Massachusetts Bulletin 138. 



Eoot Bot, Rosette, Bamping-Off 



Bhimoctonia sp. 



Root root or rosette occurs frequently 

 in greenhouses where tomatoes are 

 grown following crops of lettuce. The 

 fungus produces various effects which 

 are commonly damping-off of the younger 

 seedlings or collapse of the older ones; 

 recently a basal constriction of the stem 

 of mature plants is traced to Rhizocto- 

 nia. In this case wilting of plants re- 

 sults. It seems to be propagated un- 

 der greenhouse conditions where much 

 organic matter is used and calls for soil 

 disinfection through steaming or for- 

 malin drench. In older plants the symp- 

 toms are a shortened development of the 

 axis, giving effects similar to that in let- 

 tuce. 



Rust. See Leaf BUgM, this section. 



Scab. See Leaf Mould, this section. 



Selerotium Blight 



This is a wilt disease first reported by 

 Rolfs from Florida but it is now general 

 in greenhouses. The first symptom is wilt- 

 ing of the terminal portion of plant. The 

 dead plants and diseased portions show 

 in them sclerotia of the fungus which 

 causes the trouble. These are of the size 

 of mustard seed or smaller, at first milk 

 white and finally mahogany red to black. 

 Sometimes these sclerotia grow together 

 in anvil-shaped masses. Burning diseased 

 plants is advised. 



A. D. Selby, 

 Ohio Bulletin 214. 



Sleeping Diseases. See Wilt, this sec- 

 tion. 



Summer Blight. See Wilt, this section. 



Surface Molds 

 White Fly Excretions 



Tomatoes under glass suffer to a con- 

 siderable extent from the excretions of 

 the greenhouse white fly (Aleyrodes). 

 When this fly becomes abundant and is 

 allowed to thrive in the house the plants 

 become coated with a sticky substance 

 (honey dew), which forms a favorable 

 medium for the development of surface 

 molds. The remedy is to destroy the flies. 

 Hydrocyanic acid gas is recommended and 

 the following formula has been used with 

 success. 



Ten gms. fused cyanide of potassium 

 (98-99% pure), 20 c.c. commercial sul- 

 phuric acid; 40 c,c. of water to 1,000 cubic 

 feet of space. 



Turn the acid into the water in an 

 earthen or graniteware jar and then, by 

 a loose bag and string, drop the cyanide 

 in, after tightly closing the place to be 

 fumigated 



Fumigate every two weeks as long as 

 the fly is present. Cyanide of potassium 

 is a virulent poison and the house should 

 be thoroughly aired before it is re-entered. 



Timber Rot 



Selerotmia Wbertiana Fckl. 

 The fungus causing what is termed 

 "timber rot" is occasionally found on 

 tomatoes, and the effects are similar to 



