BOOK IV. OF DISEASES. 437 



Edinburgh, has almost completely cleared his trees of caterpillars by the following mode: " I examine," he 

 says, " the trees I wish to clear, in the beginning of June, that being the time the moths begin to leave the 

 chrysalis state. When I find one of those of a dark color, I am aware the insect will make its appearance 

 in the course of a few days. That chrysalis I examine daily until the insect comes out ; and although I do 

 not see the insect emerging from the shell, yet I am sure to find it in the neighborhood of the covering 

 which it has left, exhausted with fatigue in consequence of the exertion in extricating itself from 

 confinement. At first I put a few of the chrysalids into paper bags, which gave me an opportunity 

 of examining them minutely. I also watched some of the chrysalids of the bore-worm, which causes 

 gooseberries to fall off in great quantities by boring into the berry, and I found that fly to be of the same 

 class with those which infest the apple, pear, and cherry trees. I was also able to prove decidedly, that 

 the females come into existence full of the rudiment of eggs, which I found by dissecting several of them, 

 and examining the ovarium. I also found, by carefully noticing every insect which I caught, that the 

 greater number were females." 



Having made himself completely acquainted with the enemy with which he had to contend, he con- 

 tinued his labors : " going over a number of wall-trees which I fixed upon for the experiment, with a 

 branch of a willow-tree in my hand, with which I switched the leaves and branches, for it is amongst the 

 leaves and branches of the trees the insect secretes itself; but in order that it may be done with more ex- 

 pedition and success, I would recommend a birch-besom to be used in preference. There should be two 

 persons, one to go over the leaves and branches of the trees, in order to make the insect leave its retreat 

 and one with a net attached to a pole to catch the fly, or to destroy it if it should alight on the ground, as it 

 will be apt to do, if the day is clear and sunny, for these insects cannot bear the bright rays of the sun, which 

 is the cause of their remaining amongst the leaves during the day ; but should the day be dull, the net 

 will be highly necessary to catch the insect, as it will then likely fly to some distance before it alights. 

 This operation must be continued until all the insects are destroyed ; but it is not needful that it should 

 be performed every day, but every other day, as the insects are some days from the chrysalid state before 

 they are ready to deposit their ova, which is done during night. 



The method followed with standards is as follows : The time for going over them is generally two or 

 three weeks later than the wall-trees. It is a singular fact, that the insect keeps pace with the leafing of 

 the tree. With the standards nothing will be required but the net, as the branches can be gently shaken 

 which is sufficient to cause the fly to leave its nestling-place ; but as it might be the means of bringing too 

 many down at one time, if the tree was shaken all at once, care must be taken to shake the branches one 

 by one. Where the trees are lofty, a pole with a hook attached to the end may be used. 



The net used is made of strong black gau-ze, that color being best for the purpose. It is a yard and a 

 half in circumference, a foot deep, and attached to a whalebone rim. The handle is made of common 

 wood, about a yard and a half long. With regard to the manner in which it should be used, all I have 

 to say is, that I kept the net in my right hand ; and the moment an insect was driven from its place, I 

 swung the net in the direction opposite to that in which it flew. If I missed in the first attempt, the 

 second generally succeeded. 



The success of this plan of destroying moths has' succeeded equal to my expectations ; indeed it carries 

 conviction on the face of it. It is not only simple, and can be performed at very little expense ; but it is 

 sure, and can be acted upon in the most extensive orchards. When we consider the great number of 

 eggs one destroys by killing a single female in the beginning of the season, the utility of the plan I think 

 will at once appear. Supposing, then, that any person, by going over twenty or thirty trees each day, 

 which can be done easily in a few hours, kills 00 insects ; there will be no fewer than 10,000 eggs destroyed 

 or prevented. If the operation be carried on for a month only, every alternate day over this number of 

 trees, the amount of eggs destroyed will be 150,000. This is actually what I have done myself: there 

 is surely, then, very little reflection necessary, to convince any unprejudiced person, that by following 

 the same plan, he might soon be able to bid defiance to such a formidable foe. When we also take 

 into consideration how much the success of the crop depends upon an uninjured foliage, and a free and 

 strong expansion of blossom, the propriety of adopting this method must be obvious : hitherto all the 

 plans of liming, oiling, peeling, &c. have failed." (Caled. Mem. iii. 333.) 



281. Catching the winged insect, or hand-picking the eggs, or larva?, are the only certain modes of pre- 

 venting the ravages of the gooseberry caterpillar. As soon as the eggs which are white, and no thicker 

 than hairs, appear on the under side of the leaf, they should be rubbed off, or the entire leaf gathered. 

 It is true, watering the leaves well, and then dusting them with powdered quick-lime, will destroy all 

 those eggs which are wet at the time the lime falls on them ; but will it fall on the under sides of the leaves ? 

 Watering with lime-water is better ; but even that operation is less certain, more troublesome, and not much 

 more expeditious than hand-picking taken in time. In extreme cases, both modes may be combined. 



28. The aphides may be destroyed by the fumes of tobacco from the fumigating bellows, or by 

 excessive watering. 



283. The red spider and most insects may be destroyed by the fumes of sulphur, produced by flues, the 

 tops of which have been washed with it ; or from hot plates, or by burning sulphurated paper and rags, 



or distilling it with a retort. Ammoniacal gas, produced either from urine, recent stable-dung, or 

 tillation from bones, or other substances, is also, where the air is charged with it for sometime togeth 

 an effectual mode of destroying all animals. Watering, and a moist and warm atmosphere, will destroy 



tillation from bones, or other substances, is also, where the air is charged with it for sometime together, 



jstroying all animals. Watering, and a moist and warm atmosphere, will destr 

 the red spider and keep under all insects. Heat and moisture combined, indeed, are what the gardener 



has chiefly to depend on, especially in every description of plant-habitation. This will appear more fully 

 in the practical parts of this work, where the particular application of these general remarks is made to 

 the culture and treatment of particular plants. 



84. Snails and slugs, as already observed, are most effectually destroyed by lures of decayed leaves or 

 haulm and hand-picking. (275.) 



The earth-worm is most effectually kept under by watering with lime-water. Salt, vinegar, alum, or 

 other acrid waters, will have the same effect, but are injurious to vegetation, and besides less economical. 

 The lime-water, as Forsyth directs, is to be prepared by pouring water on quick-lime, and letting it stand 

 till it settles clear, the ground infested with worms should have their casts scraped off, and then the water 

 should be applied from the rose of a watering-pot. The evening, and early in the morning, or on ap- 

 proaching rain, are the best seasons. 



2285. The young gardener should carefully and assiduously study the nature, names, and classification 

 of insects ; and make himself acquainted with all the species he can pick up, either in gardens, houses, or 

 fields. Besides being of material use to him in his profession, he will find it a never failing source of 

 interest and enjoyment, at least equally so with the study of botany. For this purpose let him read the 

 articles on insects in such Encyclopsedias as come within his reach, and borrow, or otherwise procure, a 

 reading of the Essays and Works of Dr. Skrimshire, of Wood, Kirby and Spence, Donovan, Samouelle, and 

 other authors that he will find quoted and referred to in this and other books which mention the subject. 



SUBSECT. 3. Operations relative to Diseases and other Casualties. 



2286. The subject of the accidents and diseases to which plants are liable has been 

 treated at length in the "study of the vegetable kingdom" (Part II. Book I. Chap. IX.); 

 and it there appeared, that very little could be done by art in curing diseases ; but that 

 much might be done to prevent them by regimen and culture, and something to the 

 healing of wounds by amputation and exclusion of air. 



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