Greenhouse Pests. 309 



tobacco are excellent, for they are as efficient as the stems, and 

 are almost free from smoke and leave no offensive odor. If 

 powders are preferred for destroying aphis, pyrethrum will be 

 found efficient, especially if the plants have been wet previous 

 to the application ; tobacco dust will also answer the same 

 purpose. 



Foliage-eating Insects, of which there are many kinds, should 

 be treated by making applications of such insecticides as Paris 

 green, hellebore, etc., but the foliage of many plants is easily 

 injured by the arsenites, so these should be used cautiously. 

 Picking the insects off by hand is another means of clearing 

 the plants. 



Mealy-bug (Dactylopius adonidum, Linn.). Description. 

 Mealy-bugs are familiar to all who have grown plants under 

 glass. They are sucking insects, and are covered with a whitish 

 powder from which they have received their common name. 

 There is also a considerable quantity of a cotton-like material 

 present where these insects have been allowed to multiply, and 

 thus they may be easily recognized. All the green parts of 

 affected plants are susceptible to their attacks. 



Treatment. Although the mealy-bug is one of the oldest and 

 best known of greenhouse pests, still no very satisfactory remedy 

 for it has yet been discovered. The most practical plan is to 

 throw forcible streams of water against them, so that they may be 

 dislodged. If this practice is persisted in, it will prove very effect- 

 ive. But all plants will not bear such treatment, and it is not 

 always possible to throw the water, so that the remedy has a 

 somewhat limited application. Where it cannot be employed, 

 the alcoholic decoction of pyrethrum will be found of great 

 service. It should be applied by means of a small atomizer, 

 and the insect should be treated until it is seen that the liquid 

 has penetrated the woolly covering and has reached the body. 

 The latter then turns yellowish-brown. Comparatively few 

 plants are injured by this remedy, and its adoption is recom- 

 mended. Kerosene emulsion, and commercial insecticides, as 

 fir-tree oil, are also of value. Plants should be treated early, so 

 that the insect may not obtain a foothold. 



Mite; Verbena Mite (Tetranychus bimaculatus, Harvey). 

 Description. This mite is as yet not very well known in green- 

 houses. It is very similar to the red spider in size, shape, and 



