The Weekly Florists^ Review, 



813 



<^ 



Wreath Sent to the Funeral of Queen Victoria by Mrs. Garfield. 



Effects of Heating the Soil Upon Other 

 Greenhouse Pests. 



Besides the destruction of nematode 

 worms, and the gaining of robust and 

 vigorous plants which steaming the soil 

 gives rise to, there are other beneficial 

 effects worthy of being taken into con- 

 sideration. Many of the fungous and 

 insect pests to which our greenhouse 

 plants are subject find their normal 

 habitat in the soil. In our experiments 

 upon heating the soil in the beds we 

 killed thousands of red spiders, and we 

 presume that we did the same with the 

 cucumber aphis, or with the eggs, as we 

 were remarkably free from them, al- 

 though the soil had previously been used 

 for cucumber crops, which were badly 

 contaminated with aphis. This latter 

 statement, however, in regard to killing 

 the aphis, is nothing more than a con- 

 jecture, as entomologists tell us that 

 they do not know where the aphis breeds, 

 but thev surmise that it breeds upon par- 



ticles of organic matter in the soil or 

 upon the old cucumber vines thrown out 

 upon the compost heap. The soil un- 

 doubtedly harbors many of the spores 

 of the mildews which are common to 

 cucumbers, tomatoes and lettuce. 



One of the most common and trouble- 

 some diseases to young cucumbers is the 

 so-called "damping fungus," Pythium De 

 Baryanum, which attacks the young 

 plants at the surface of the ground and 

 causes them to wilt and collapse. We 

 have repeatedly found as a result of heat- 

 ing that this did not make its appear- 

 ance when they were subjected to a tem- 

 perature which was over 140 or 150 de- 

 grees F. ; when, however, the temperature 

 went below these points the fungus ap- 

 peared to be accelerated in its growth 

 and development and damping was more 

 likely to show itself than in normal pots. 

 Tliis fungus must be distinguished from 

 the ordinary "damping fungus" (Botry- 

 tis) which attacks begonia cuttings, etc., 

 in the propagating pit. Sterilizing the 



soil for this fungus would be of no ac- 

 count, as the spores (conidia) of this 

 species are everywhere and only await a 

 favorable opportunity to germinate and 

 develop tljemselves, whereas with the 

 Pythium the conditions of dissemination 

 are much more restricted. What is true 

 in regard to the Botrytis is probably true 

 in regard to some of the mildews, as 

 there is no reason to doubt that the 

 spores can thrive in the house for some 

 time without coming in contact with the 

 host, although sterilizing the soil would 

 undoubtedly kill many of them. The so- 

 called "drop" in the lettuce which is 

 caused by a facutative parasite, a species 

 of Botrytis, is also completely controlled 

 bv sterilization. This fungus causes no 

 eiid of trouble to some lettuce growers 

 and is confined entirely to the soil where 

 it propagates only by means of its myce- 

 lium, but it frequently becomes dissem- 

 inated from one part of the house to the 

 other by means of the gardener's tools. 

 Sterilizing the soil has also an effect upon 



