i8gS. 



HARDENING. 



267 



lar minute spider-like creatures. The 

 gases given oft by its decomposition seem 

 to be deadly to them. To the plants it is 

 harmless unless used in unreasonable 

 quantity. Exactly where the reasonable 

 line ends is a question which the experi- 

 ence of the gardener must ascertain for 

 each line of plants; but ordinarily there is 

 no risk in sowing the sulphur so as to 

 yellow the soil very perceptibly. 



The sulphur acts only when the insects 

 are in the active stage, and does not 

 injure the eggs, hence infestation may 

 continue for some time after the sulphur 

 is applied, and so long as any unhatchcd 

 eggs remain. 



Against plant lice sulphur is of little use 

 as compared with tobacco. Tobacco in 

 all forms is a good thing. It is a fer- 

 tilizer; the nicotine as it is gradually 

 extracted by the moisture of the soil kills 

 almost all insect life contained in it, and 

 when vaporized it is death to plant lice. 

 The mere smell of the tobacco while appa- 

 rently unpleasant to many insects is not 

 poisonous to them. But an extract in 

 water so applied that the insects become 

 covered is rapidly fatal. So tobacco 

 smoke when breathed by insects is fatal 

 to many, while it stupefies a yet greater 

 number. I need not speak on this point 

 to practical florists, all of whom have 

 probably had experience in this direction. 



A very good way to use tobacco where 

 pipes are sufficiently hot is to smear them 

 with a tobacco extract and moisten from 

 time to time until it has all evaporated. 

 This will penetrate everywhere and will 

 settle on everything in almost invisible 

 globules, killing all the aphides that come 

 under its influence. 



This leads naturally to another very 

 important point that must be considered 

 and whose neglect accounts for many 

 failures. Mo-t insects have the bodies 

 cither pubescent, very polished, or pow- 

 dery or somewhat wax}' on the surface, 

 so that they shed water quite readily 

 and any application of a coarse spray 

 simply rolls oft' without effect. So also 

 the spiracles or breathing pores are fur- 

 nished with protecting screens of hair or 

 bristles which serve to keep out foreign 

 material. A large drop of water or 

 watery decoction has not the least chance 

 of penetrating th-ough this protection 

 and the application is useless as an insect- 

 icide. Use the same mixture with an 

 atomizer and the result will be quite dif- 

 ferent. The minute globules adhere read- 

 ily to the insect because they are not 

 heavy enough to roll off; they penetrate 

 between the protecting screen or under 

 it, and enter the body with the in-breath- 

 ing. Therefore when tobacco or any 

 other watery mixture is to be applied it 

 should be put on in as fine a spray as can 

 be secured. 



For cleaning house plants of all save 

 scale insects a tobacco soap-suds put on 

 with an atomizer, is almost perfect. 

 This brings me to soaps as insecticides 

 and they act in a somewhat different 

 way. When put on very strong they are 

 of course very caustic and as dangerous 

 to plants as to insects. Put on at a 

 strength safe to the plants they clog the 

 spiracles and thus choke the insects to 

 death. 



Some of you in days gone by may have 

 made soap-bubbles, and if you did not 

 you have probably seen others make 

 them. This is a good example of the ten- 

 acity of a soap film, and if such a one 

 forms over the spiracles of an insect the 

 creature simply chokes to death. That 

 explains how soaps act and' the one that 

 forms the stickiest film is the best. Tar 

 soaps, or fir-tree oil soaps arc particu- 



larly good for that reason, and fish-oil 

 soaps come next. You can readily test 

 the difference between these and the com- 

 mon hard soap-suds if you make a solu- 

 tion of equal strength. The common 

 soap-suds will feel clean and smooth and 

 crisp to the hand, while the others will 

 feel more or less slimy. These soapy 

 mixtures should also be put on in a fine 

 spray and from what I have said you will 

 realize that thoroughness is essential, for 

 no insect not actually hit by an applica- 

 tion will be in the least affected by it. 

 Soap-suds have an advantage over more 

 watery mixtures, because they adhere 

 better. The insect surface that will shed 

 a droplet of water will retain and become 

 covered by one of soap-suds — hence a 

 tobacco soap is better than a tobacco 

 tea, though neither is equal to a tobacco 

 smoke. 



There is another point worthy of atten- 

 tion in the greenhouse. If soaps are to 

 lie used, those made with potash rather 

 than with soda should be selected. Pot- 

 ash is a plant food and when washed into 

 the soil acts as a fertilizer and is taken 

 up and removed by the vegetable growth. 

 Soda on the contrary in the form used in 

 soaps is actually deleterious to the plants 

 when present in any quantity, and a fre- 

 quent use of suds made with a soda soap 

 may easily impair the value of the soil for 

 plant growth. In general, hard soaps 

 are soda soaps, while soft soaps are pot- 

 ash soaps. 



Dry powders are rarely used in the 

 greenhouse, but whenever they are to be 

 employed the reasons that call for a fine 

 spray, call for the finest possible dust. 

 The finer the dust, the more effective the 

 application. Coarse particles are readily 

 silted out, but fine fragments penetrate 

 and get into the body cavity where the}' 

 can produce their characteristic effect. 



Of the oils, kerosene only has been used 

 to any extent, and this is a most valua- 

 ble insecticide where its use is allowable. 

 It is very effective even when greatly 

 diluted, but it must be first emulsified 

 before it can be mixed with water. This 

 emulsion is prepared as follows: 



Hard soap shaved fine, Vi pound. 

 Water, 1 gallon. 



Kerosene, 2 gallons. 



Dissolve the soap in boiling water and 

 pour the kerosene, which should also be 

 slightly warm into the boiling hot suds 

 — churn rapidly with a force pump for a 

 few minutes, and you will get a beautiful, 

 snow-white butter which will keep in a 

 cool place for weeks, and will dissolve 

 readily in water to any extent. 



Thus much for insecticides in general, 

 and now a few words concerning a very 

 few kinds of insects. Of course the same 

 conditions that favor the growth of 

 plants also favor the development of cer- 

 tain kinds of insects, and particular]}' 

 plant lice or aphides, commonly called 

 "greenfly" or "blacVfly" according as 

 they vary in color. 



These are peculiar in several respects 

 and particularly their mode of multipli- 

 cation. Their appearance I will not 

 undertake to describe, but if a single - 

 large individual be observed for a few 

 days in succession, it will be noted that a 

 colony of small specimens, daily increas- 

 ing in size and number, forms round her 

 and, as these attain full size in a few days 

 they move off a little distance and in 

 turn become centers of new colonies. If 

 the watch be continuous and close, it may 

 be observed that every few hours the 

 mother of the colony gives birth to a liv- 

 ing young and all her descendants are 

 apt to be like herself, viviparous, par- 



thenogenetic females. Some of them be- 

 come winged, but that is not necessary 

 to enable them to begin reproduction. 

 Under greenhouse conditions no males 

 are produced as a rule, and multiplication 

 goes on with great rapidity. It is against 

 such insects that the florist is most fre- 

 quently called to battle, and besides the 

 methods already mentioned, it may be 

 in place to say that single plants may be 

 often completely cleaned by the use of 

 bisulphide of carbon. Bisulphide of car- 

 bon is a clear liquid like water which vol- 

 atilizes rapidly, giving oft" an extremely 

 foul odor which is poisonous to insects 

 when confined in it. A dram is sufficient 

 to poison one cubic foot of closed space, 

 si 1 as to kill plant lice without harming 

 plants in one hour. In a closet con- 

 structed for the purpose, a number of 

 plants might be placed at one time and 

 completely cleaned, whenever such clean- 

 ing was desirable, as before sending to a 

 customer. As the vapor is heavier than 

 air and sinks, the bisulphide should be 

 evaporated in a shallow dish secured in 

 some way near the top of the closet. The 

 objection to this materialis its inflamma- 

 bility, but so long as this peculiarity is 

 kept in mind it can be used with entire 

 safety. 



A somewhat similar process has of late 

 been the subject of experiment in cleaning 

 entire houses of insects by the use of 

 hydrocyanic acid gas. This is secured by 

 the action of dilute sulphuric acid on 

 cyanide of potassium, and it is exceed- 

 ingly poisonous to animal life of all kinds. 

 The proportions are: 



Fused cyanide of potassium, 



98 per cent, pure, 1 oz. weight. 

 Sulphuric acid, 1 oz. measure. 



Water, 3 oz. measure. 



Use a glazed earthenware vessel and 

 put in first the necessary water, then add 

 the acid; and when all is prepared drop in 

 the cyanide in small lumps. The forma- 

 tion of gas begins at once and the 

 amounts above given will thoroughly fill 

 100 cubic feet of space. Plant lice suc- 

 cumb in a few minutes, scales in from one- 

 half to one hour — plants very soon there- 

 after. I do not know enough of the prac- 

 tical use of this gas to say much of its 

 possibilities. I know that it has been 

 used in some large houses; but I do not 

 know the details. It is an exceedingly 

 dangerous thing in careless hands, yet it 

 may develop into a valuable method 

 when we become better acquainted with 

 its range and its possibilities. 



Among the most troublesome green- 

 house pests are scales; soft and armored. 

 Soft scales are usually of considerable 

 size; of the texture their name implies and 

 brown in color. The young are smaller, 

 much flatter and paler; usually quiescent, 

 but capable of motion. In some species 

 the young are produced alive, in some 

 eggs are deposited under the female scales. 

 Whichever is the case the florist must 

 study the species until he knows when 

 the young larvae are being produced. 

 Then he should apply his washes 

 promptly and thoroughly and at short 

 intervals, for the larvae scales are easily 

 killed, and once out of the way the plants 

 will remain clean. Soap washes are best 

 in this case, although tobacco will do it 

 frequently used. The main point to be 

 observed is the time when the young 

 appear and prompt application as soon 

 thereafter as possible. 



The armored scales differ from the soft 

 scales or lecaniums in that the scale is 

 separate from the insect itself which lies 

 free beneath it. The armored scales have 

 no power of motion when they are once 



