CARNATIONS— THEIR PESTS AND DISEASES. 



235 



light. In the spring of the year these yellow blotches are much more 

 noticeable on the leaves, particularly in certain varieties. This disease 

 is caused in the first place by green-fly, thrips, or other sucking insects, 

 which leave a poison in the leaf when the proboscis is withdrawn. If 

 the constitution of the plant is weak this poison permeates the whole 

 plant, and is increased by propagation of the cuttings or layers, but 

 if the plant is constitutionally strong it can throw off the poison. 

 It continues to grow freely and healthily, providing all other cultural 

 details are correctly carried out. Of course, it is not a contagious 

 disease, but it is idle folly to propagate from affected plants. To 

 stamp out Bacteriosis it is not only necessary to select strong, healthy 

 cuttings, but to propagate from vigorous healthy plants only. 



Red Spider (Tetranychus telarius). — This pest, which is so well 

 known, has ruined more stocks of Carnations than any other insect 

 pest. It attacks Carnations as a rule under glass during June, 

 July, and August, owing to the atmosphere being too hot and dry ; 

 weakly, unhealthy stock invites it. Again, if the growth of the plant 

 is checked through improper feeding or lack of potting, and neglect to 

 syringe the plants thoroughly and periodically in hot, dry weather, 

 the best and only really effective remedy is to syringe the plants at 

 very high pressure on bright mornings, particularly the under sides 

 of the leaves, with clear cold water, and once every fourteen days 

 with Nicotine Extract, specially prepared for Carnations, avoiding 

 preparations which contain soap extracts or similar compounds, which 

 leave a deposit upon the leaves and are more harmful than beneficial 

 to the plants. 



The common green Aphis and black-fly are the simplest of all 

 pests to eradicate. A single application of the nicotine preparation 

 is sufficient to cleanse the plants entirely. The antiquated system 

 of fumigating, so far as Carnations are concerned, has proved with 

 us more harmful than effective, inasmuch as the life of the flower 

 is shortened, the growth of the plant is checked, and only the active 

 pest is destroyed. Furthermore, we are of opinion that the fumes 

 have certain detrimental actions upon the soil, and we are extending 

 our experiments on a large scale to test this theory. 



The common summer thrips (Heliothrips tabaci), which is the only 

 one that troubles the Carnation-grower, and appears to be Nature's 

 gift to all horticulturists, disfigures the flowers during the summer 

 and early autumn, and is effectively destroyed by periodically spraying 

 with the same Nicotine Extract which I have previously recommended 

 for red spider. 



Split Calyx. — This, of course, is not caused by any pest or disease, but 

 in the case of proved varieties is the result of irregular growth caused 

 by irregular conditions in the soil, affecting the growth of the roots, 

 or irregular climatic conditions affecting the growth of the plant, 

 or, as is too often the case, the use of unsuitable fertilizers. The ideal 

 calyx with well-rounded calyx claws — which act as a spring, as seen 

 in the two outside buds (see fig. 38) — rarely if ever split, while the tube- 



VOL. XLV. R 



