August i, 1882.] 



THE TROPICAL AGRICULTURIST. 



T7r 



frnit, or express the oil, or utilise the fibre. Thus 

 any selector thiukiug to go in for cocoa-nut growing 

 will see that it is entirely owing to the circumstance 

 of Mr. Barnes being so close to a large town that 

 the industry has been made to pay. 



lu these gardens there are many other trees as well, 

 the most noticeable being date palms, of which there 

 are .300 planted. These grow quite as well as the 

 cocoa-nuts, and are equally handsome. Between 300 

 and 400 orange trees also are planted out, most of 

 which are in full bearing ; some of these were evidently 

 suffering from dryness or poverty of the soil, and a 

 great many were injured from having been planted 

 too near the date trees, which rival the bamboo in 

 the way in which their roots ramify and rob the 

 moisture from every neighbouring plant or tree. — 

 Quecnsla ndu; 



PYRBTHRUIVI INSECT-POWDER. 



BY C. V. EILET. 



Application of Pyrethbum in Fumes. — The powder 

 burns freely, giving off considerable smoke and an 

 odour which is not unpleasant. It will burn more 

 slowly when made into cones by wetting and moulding. 

 In a closed room the fumes from a small quantity 

 will soon kill or render inactive ordinary flies and 

 mosquitos, and will be found a moat convenient pro- 

 tection against these last where no mosquito bars are 

 available. A series of experiments made under our 

 direction indicates that the fumes affect all infects, 

 but most quickly those of soft and delicate structure- 

 This method is impracticable on a large scale in the 

 field, but will be found very effective against insects 

 infesting furs, feathers, herbaria, books, &c. Such can 

 easily be got rid of by enclosing the infested objects 

 in a tight box or case, and then fumigating tliem. 

 This method will also prove useful in green-houses, 

 and, with suitable instruments, we see no reason why 

 it should not be applied to underground pests that 

 attack the roots of plants. 



Alcoholic Extract of Pyrethrum Powder. — The 

 extract is easily obtained by taking a flask fitted 

 with a cork and a long and- vertical glass tube. Into 

 this flask the alcohol and pyrethrum arc introduced 

 and heated over a steam-tank or other apparatus, 

 The distillate, condensing in the vertical tulie, runs 

 back, and at the end of an hour or two the alcohol 

 may be drained off, anel the extract is ready for use. 

 Another method of obtaining the extract is by repercol- 

 ation after the manner perscribed in the American 

 Pharmacopreia. The former method seems to more 

 thoroughly extract the oil than the latter ; at least, 

 we found that the residuum of a quantity of pyrethrum 

 from which the extract was. obtained by lepercolation 

 had not lost a great deal of its power. The first 

 method is apparently moi'e expensive than the other, 

 but the extract is in either case more expensive than 

 the other prcpar.itious, though very conveniently pre- 

 served and handled. The extract may be greatlj 

 diluted with water, and then applied by means of 

 an atomiser. Professor E. A. Smith, of Tracaloosa, 

 Ala., found that, diluted with water at the rate of 

 one part of the extract to 15 of water, and sprayed 

 on the leaves, it kills cotton-worms that have come in 

 contact with the solution in a few minutes. The 

 mixture in the proportion of one part of the extract 

 to 20 parts of water was equally efficacious ; and even 

 at the rate of 1 to 40 it killed two-thirds of the worms 

 upon which it was sprayed in 15 or 20 minutes, and 

 the remainder were subsequently disabled. In still 

 weaker solution, or at the rate of 1 to 50, it loses 

 its efficacy, but still kills some of the worms nnd dis- 

 ables othe; B Professor Smith experimented with the 

 extract obtained by distillation, and another series 

 of experiments with the same method was carried on 



last year by Professor R. W. Jones, of Oxford, Miss. 

 He diluted the extract with twenty times its volume 

 of water, and applied it by means of an atomiser 

 on the cotton-worm and the boll-worm with perfect 

 success. Mr. E. A, Schwarz tried last summer the 

 extract obtained by repercolation, and found that 10 

 drachms of the extract, stirred up in two gallons of 

 water and applied by means of Whitman's fountain 

 pump, was sutEcient to kill all cotton. worms on the 

 plants. Four drachms of the extract to the sn.me 

 amount of water was sufficient to kill the very j'oung 

 worms. 



Pyrethrum in Simple Water Solution. — So far 

 as our experiments go this method is by far the 

 simplest, most economical, and efficient. The bulk of 

 the powder is most easily dissolved in water, to which 

 it at once imparts the insecticide power. No constant 

 stirring is necessary, and the liquid is to be applioel 

 in the same manner as the diluted extract. The finer 

 the spray in which the fluid is applied the more 

 economical is its use, and the greater the chance of 

 reaching every insect on the plant. Experiments with 

 pyrethrum in this form show that 200 grains of the 

 powder stirred up in two gallons of water is amply 

 sufficient to kill the cotton-worms, except a very few 

 full-grown ones, but that the same mixture is not 

 sufficiently strong for many other insects, as the boll- 

 worm, the larva of the Terias uicippe, and such species 

 as are protected by dense long hairs. Young cotton- 

 worms can be killed by 25 grains of the powder 

 stirred up in two quarts of water. The pyrethrum 

 water is most efficacious when first made, and loses 

 power the longer it is kept. The powder gives the 

 water a light greenish colour, which after several 

 hours changes to a light brown. On the third day 

 a luxuriant growth of fundus generally developes in 

 the vessel containing the fluid, and its efficacy is 

 then considerably lessened. 



The Tea, or Decoction.— Professor E. W. Hilgard, 

 of Berkeley, Ca!., is the only one who has experi- 

 mented with pyrethrum in this form, and he expressi-s 

 himself most favourably as to the result. He says : — 

 "I think, from my experiments, that the tea, or in- 

 fusion, prepared from the flowers (which need not be 

 ground up for the purpose) is the most convenient 

 and efficacious form of using this insecticide in the open 

 air ; provided that it is used at times when the water 

 will not evaporate too rapidly, and that it is applied, 

 not by pouring over in a stream, or even in drops, 

 but in the form of a spray from a syringe with fine 

 holes in its rose. In this case the fluid will reach 

 the insect despite of its water-shedding 6urfac>-s, 

 hairs, &c., and stay long enough to kill. Thus appl'°d 

 I have found it to be efficient even aj^ainst the 

 armoured ecale-bug of the orange and I nion, which 

 falls off in the course of two or three days after the 

 application, while the young brood is almost inslan.ly 

 destroyed. As the flower tea, unlike whale soap and 

 other washes, leaves the foliage perfectly clean, and 

 does not injure even the most tender growth, it is 

 preferable on that score alone ; and in the future 

 it can hardly fail also to be the cheaper of the two. 

 This is the more likely as the tea made of the leaves 

 and stems has eimilar, although considerably weaker, 

 effects ; and if the farmer or fruit grower were to 

 grow the plants, he would save all the expense of 

 larvcsting and grinding the flower-heads by simply 

 using the header, curing the upper stems, leaves, and 

 flower-heads altogettier, as he would hops, making 

 the tea of this material by the hogshead, and dis- 

 tributing it from a cart through a syringe. It should 

 be diligently kept in mind that the least amount of 

 boiling will seriously injure the strength of this tea, 

 which should be made with briskly b"ding water, 

 but then simply covered over closely, so as to allow 

 of as little evaporation as possible. The details of its 



