169 



ON THE BEST MEANS OF DESTROYING ^INSECTS IN THE 

 STOVE AND GREENHOUSE. 



BY DAVID CAMERON, A.L.S., Botanic Garden, Edgbaston. 



All plants of a soft woody texture grown in greenhouses, and those of all 

 descriptions in stoves, are subject to the depredations of various kinds of insects, 

 either at particular seasons of the year, or from any irregularity of the tempera- 

 ture, such as a sudden transition from heat to cold, or the reverse ; by too much 

 water or too little ; the parching effects of fire heat in severe weather, and various 

 other causes which are sometimes unavoidable even under the care of the most 

 skilful gardener. In the greenhouse the green fly is most prevalent, particu- 

 larly in spring, and is readily destroyed by a fumigation of tobacco ; or what is 

 better, where it can be obtained genuine, is tobacco-paper obtained from the 

 manufacturing tobacconist. For fumigating houses, fumigating bellows &c. have 

 been invented ; none however are better adapted to that purpose than the old- 

 fashioned process of using strong flower-pots half filled with clear well-burnt 

 embers of wood or coal, on the top of which is lightly placed the tobacco or 

 tobacco-paper, and using one or more pots so filled, according to the size of the 

 house, taking particular care that the tobacco never bursts out into a flame. 

 Care should also be taken to place the pots so that the smoke may reach the 

 glass without coming into contact with any of the plants, which would be certain 

 to scorch the leaves. As the house fills, the cooler smoke descends and destroys 

 the insects without injury to the plants. For want of this precaution much 

 injury is frequently done to the foliage and laid to the charge of the tobacco ; 

 whereas it is the heat of the smoke that does the injury. To avoid scorching the 

 leaves, some gardeners select the infested plants and fumigate them in frames or 

 under hand-glasses ; but the smaller the space is where the operation is per- 

 formed, the greater is the danger of scorching the plants, so that where the 

 operation is done in a small space, the pots in which the tobacco is placed ought 

 to be small also, and the violent heat allowed to subside before the pots are 

 introduced. 



It is in the plant-stoves where a high temperature is kept up that the greatest 

 variety of insects is to be found ; such as the green fly, thrips, mealy bug, and 

 brown scales : any of these when they attack a sickly plant, if not speedily 

 destroyed, soon spread to the other plants. Where the collection is small and 

 not of choice species, the infected plant can be destroyed without much loss, but 

 in extensive and rare collections the most choice and valuable plants are too often 

 the weakliest, and therefore the gardener has both to endeavour to preserve the 

 plant and keep the insects under. The green fly must be destroyed by tobacco- 

 smoke as in the greenhouse ; the thrip, by tobacco mixed with damp hay ; the 

 mealy bug may also be considerably reduced by a, stronger fumigation of tobacco, 



VOL. II. NO. XXIII. JANUARY. Z 



