798 ANNUAL REPORT OF THE Off. Doc. 



theory was abimdant in gardens where the plants were frequently 

 and thoroughly syringed. 



"Keferring again to greenhouse work, in former articles on this 

 subject, I Lave noted the experiments in the plant houses at the 

 Wisconsin Experiment Station, where live steam was allowed to es- 

 cape into tlie houses for periods ranging from eight to tweuty-four 

 hours, completely filling the houses and without causing any lujury 

 or apparent inconvenience to the red spiders. 



''In order to obtain more evidence on the subject an experiment 

 was conducted last March in one of our plant houses as follows: A 

 closed frame, sides, roof and ends glass, was placed on a side bench 

 over steam pipes. In this frame was placed a variety of plants in 

 pots, including Clothilde Soupert roses, Coleus, Heliotrope, Tomato 

 and other plants. The plants had all been carefully syringed for sev- 

 eral days and were all apparently free from spider when placed in the 

 frame. The air was kept moist almost to the point of saturation for 

 several days with no bad results to the plants. 



"At the end of a week red spider was introduced by dropping on 

 the plants several badly infested leaves from a rose plant growing 

 in another house. Kow, according to the commonly accepted opinion, 

 the excessive moisture in the aii' in this frame should have prevented 

 any increase of the spider. The actual results, however, were w'holly 

 different, the plants becoming quickly infested and at the end of 

 three weeks were wholly destroyed by countless millions of red 

 spiders. Both temperature and moisture were maintained at a high 

 point throughout the experiment, the glass sides of the frame and the 

 foliage of the plants being almost constantly moist. 



"While these experiments do not furnish conclusive evidence that 

 red spider will thrive in a moist atmosphere there is in it 'food for 

 thought.' Is it not true that the spider is kept in check wholly 

 by the force used in syringing? Does any gain result from the 

 daily wetting down of walks, etc., practiced by greenhousemen?" 



Sulphur in its different forms is believed to bother red spider more 

 than any other one thing. A combination insecticide, known as Sul- 

 pho-Tobacco Soap, which, as its title implies, is made of sulphur, to- 

 bacco extract and soap, I have found about the best and most effec- 

 tive in stopping the ravages of this little pest; but to do any good it 

 must be used nearly daily among plants when badly affected if we 

 would have it produce the desired effect and restore our plants to 

 health and vigor again. 



A good force of water, say with at least thirty-five pounds pressure, 

 applied directly beneath the leaves where red spider finds its resting 

 and working place will be found to keep it from making much 

 headway. The great disadvantage we are laboring under, especially 



