175 PKACTICAL FLOKICULTUKE. 



We now come to the insects which are troublesome 

 under glass ; here we have the means within our control 

 to entirely prevent the two leading insects, Green Fly and 

 Red Spider. In both cases, I have always contended 

 that " an ounce of prevention is better than a pound of 

 cure." There is no neglect of the gardener or foreman in 

 charge of green-houses which is so little excusable as 

 allowing insects to injure his plants. 



Green Fly (Aphis) is prevented, (for I contend that it 

 should never be seen, so that it need be destroyed), by 

 fumigating with tobacco smoke, not less than twice each 

 week. We do it in a manner much more simple and 

 agreeable to the operator than is often practiced. Two 

 or three times each week during the entire season at 

 which our green-houses are filled with plants, we use a 

 small handful of shavings, on top of which we place about 

 half a pound of tobacco stems, previously made damp. 

 The shavings are lighted, and the fire being on the brick 

 flooring, is left to take care of itself. We use this quanti- 

 ty of tobacco to every 500 square feet of glass ; we burn thus 

 five to six tons of tobacco stems every season, but we rarely 

 see a green fly. We have occasionally seen this insect in- 

 crease to such an extent in its different conditions, that fu- 

 migation was powerless to destroy it, or rather it would 

 have required it to be applied so strong, to dislodge the vast 

 number of the enemy, that the plants would have been in- 

 jured. The safer way to treat a desperate case of this 

 kind is to brush the insect off, by hand, or with a soft 

 brush ; this is a slow process, but an effectual one. This 

 condition of the plants can only be the result of utter neg- 

 lect. The green fly sometimes injures plants which stand 

 too near together, so that the leaves get matted so closely 

 that the fumes of the tobacco cannot penetrate. This is 

 a condition, where recourse must be had to brushing the 

 insects from the leaves, and, if possible, spreading the 

 plants, so that the air can pass freely among them, 



