INSECTS ON GREENHOUSE PLANTS 219 



Carnation plants in benches along the sides of the houses are 

 especially liable to be attacked by red-spiders. It is difficult 

 to syringe the back rows of plants, and the warm, dry, atmos- 

 pheric conditions near the glass favor their development. It is 

 always advisable to place the benches away from the side-walls. 



252. Effects of fumigation with hydrocyanic acid gas. 

 Fumigation with hydrocyanic acid gas seems to have no effect 

 on red-spiders. After an all-night application of this fumigant 

 in sufficiently strong proportions to kill all plant life in the houses, 

 they have been found as lively as ever, when examined under 

 a microscope. 



253. Effects of water sprays and salt solutions. Water, 

 thoroughly syringed over both surfaces of the leaf, seems the best 

 remedy. Recently, a salt solution has come into quite general 

 use for red-spiders on carnation plants. C. W. Ward, 1 in his 

 book on the carnation, says, " During the past three years we 

 have been using a solution of salt made as follows : Eight six- 

 inch potfuls of common salt, dissolved in fifty gallons of water. 

 When using this solution, always stir the bottom of the barrel 

 in order to insure an even strength throughout. Give the 

 foliage a thorough spraying both underneath and above, using 

 a fine hose, with water under considerable pressure. After 

 syringing with the salt solution, this should be allowed to remain 

 from three to four days in bright weather, and from one to two 

 days in dark, cloudy weather, after which the salt should be 

 thoroughly washed off the plants by a strong syringing with 

 clear water. Care must be taken not to syringe with the salt 

 solution too often. The carnation plant loves a certain amount 

 of salt, and is not injured by what will reach the soil, provided 

 the applications are not too frequent or the solution too strong. 



" Do not spray the plants with the salt solution unless the 

 foliage is in a firm, well-hardened condition, for if applied to 

 plants that are in a soft state, that is to say, those which have 

 been grown under too high a temperature or in soil that has 

 been kept too moist, the tender foliage will be injured or 

 burned, and as the salt keeps the foliage constantly wet during 

 the night, there is some danger of developing spot upon very soft 

 plants. 



" An application of salt should generally be made no oftener 

 than once in two weeks ; however, we occasionally syringe with 

 the salt mixture upon alternate days, using the weaker solution 

 of salt. The red-spider does not thrive upon the carnation 



1 "The American Carnation," by C. W. Ward. 



