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The Weekly Florists^ Review* 



Afbil 6, 1905. 



The Greenhouse White Fly. 



a, egg; b. young larva; c, pupa, top view; d. pupa side view; e. adult— c, d, e, about 26 times natural 



size; a, b. still more enlarged. 



THE GREENHOUSE WHITE FLY. 



The Division of Entomology of the 

 U. S. Department of Agriculture has is- 

 sued a bulletin on the white fly, from 

 which we reproduce the accompanying 

 illustration and the following matter: 



' * The damage by the greenhouse white 

 fly to tomato, cucumber and many other 

 plants growing under glass easily places 

 it in the front rank of greenhouse pests. 

 In many cases it would be impossible to 

 grow certain crops in forcing houses 

 without the aid of remedial measures. A 

 specific instance is on record where, in 

 a western Massachusetts town, the at- 

 tacks of this insect resulted in the total 

 loss of a greenhouse crop of tomatoes 

 and cucumbers, valued at $4,000. 



"During the past few years many ap- 

 peals for remedies have been made to 

 the editors of our horticultural journals, 

 to many state experiment stations, and 

 to the United States Department of Ag- 

 riculture; yet, although it is not, in real- 

 ity, -a difficult insect to control, the reme- 

 dial methods which should be followed 

 are far from being generally known 

 among the many greenhouse men who 

 suffer from its depredations. 



"The insect is notable for its very 

 general feeding habits, having already 

 been recorded as breeding on over sixty 

 different kinds of plants. Of these the 

 following are of the most economic im- 

 portance: Aster, chrysanthemum, salvia, 

 lantana, fuschia, coleus, ageratum, prim- 

 ula, geranium, heliotrope, rose, egg 

 plant, bean, melon, lettuce, cucumber and 

 tomato. The two last suflfer the most 

 serious injury from this insect, perhaps 

 more than the other greenhouse plants 

 together, although not infrequently there 

 are reported serious losses in greenhouses 

 devoted to one or more of the other 

 plants mentioned. 



Description. 



"The mature white flies of both sexes 

 are four-winged insects scarcely more 

 than three-fiftieths of an inch in length. 

 The adult white flies, as well as the scale- 

 like larvae, are provided with sucking 

 mouth parts. In a short time after the 

 emergence of the adult from the pupa 

 case, the body, legs, and wings become 

 covered with a white waxy substance 

 which gives this, as well as other species 

 of the genus, a characteristic floury ap- 



pearance. The adults feed nearly 

 continuously during their existence. 

 The number of eggs deposited per 

 day by an adult female white fly in 

 a laboratory has been found to average 

 very nearly four. Probably in the warm- 

 er temperature of a greenhouse this num- 

 ber is greater by one or two eggs per 

 dav. The eggs hatch in from ten to 

 twelve days. The majority of the adults 

 are found upon the upper and newer 

 leaves of the food plant. They are 

 almost invariably found upon the under- 

 side of the leaves, and it is here that 

 nearly all the eggs are deposited, al- 

 though many are found upon the tender 

 stems and leaf petioles and a very few 

 scattering ones on the upper surfaces 

 of the leaves. 



Appearance of Infested Plants. 



' ' On thoroughly infested plants we find 

 on the uppermost leaves only adults and 

 freshly laid eggs; a little lower on the 

 plants we find eggs in the process of 

 hatching; and, flnally, on the lowermost 

 parts of the plants we find discolored, 

 shriveled leaves with many pupse and 

 emerging adults and few, if any, un- 

 hatched eggs or young larvae. The larvae 

 and pupae secrete little globules of honey- 

 dew, so named after the material of a 

 like nature secreted by plant lice. Ow- 

 ing to the interference with the respira- 



tory processes of the leaf, both by the 

 bodies of the insects themselves and hj 

 the fungus growths due to them, badly 

 infested plants have a tendency to wilt 

 when exposed to the sun's rays. In seri- 

 ously infested greenhouses the leaves of 

 the plants gradually die, the lower leaves 

 first. 



Preventives. 



"The introduction of the insect into 

 non-infested floral establishments may be 

 prevented by avoiding the introduction 

 of infested plants unless first subject- 

 ing them to a fumigation in a tight 

 fumigating box, based on the directions 

 hereafter given for entire greenhouses. 

 Vegetable houses, which are not used 

 during the summer months, allow of a 

 practice which not only greatly reduces 

 the chances of the white fly appearing 

 in the house during the growing season, 

 but may result in the house being suc- 

 cessfully kept free from thrips and other 

 insect pests during the whole or a con- 

 siderable part of the season. Tho prac- 

 tice referred to consists in removing from 

 the house all vegetation, even the small- 

 est weeds, and fumigating the tightly 

 closed greenhouse with hydrocyanic-acid 

 gas at the rate of five or more ounces per 

 thousand cubic feet of space for a ten 

 hours' exposure. 



Fumigation with Hydrocyanic-add Gas. 



"This has been found to be the^most 

 successful means of controlling the white 

 fly in greenhouses. Its success in this 

 case is due to the susceptibility of the 

 adults and larvae of these insects to a 

 comparatively long exposure to a small 

 amount of the gas. Experiments thus 

 far have been with tomato and cucum- 

 ber plants, but as these plants are among 

 those most liable to injury from improper 

 fumigation with hydrocyanic-acid gas, a 

 wide range of usefulness is indicated by 

 the success thus far obtained. 



"Experiments have shown that the 

 white fly is destroyed in all except two 

 stages (egg and late pupal) by an 

 amount of potassium cyanide which is 

 extremely small as compared with the 

 amounts generally recommended for other 

 insect pests. As small an amount as 

 between one-fifth and one-sixth ounce 

 per 1,000 cubic feet, for three hours' ex- 

 posure, has been used with success, but 

 the greatest diflBculty attending the use 

 of hydrocyanic-acid gas, in greenhouses 

 containing plants as susceptible to in- 

 jury by it as are the cucumber and to- 



CERAMIQUES DE FLANDRES. 



During the Easter season the trade 

 should find an exceptionally ready sale 

 for the truly artistic hand-made art pot- 

 tery called "Ceramiques de Flandres" 

 which is produced in Belgium by the 

 Association of Flemish Craftsmen and is 

 offered in this country by the associa- 

 tion 's American representative, Edwin 

 A. Denham, at 430 PHfth avenue. New 

 York. No molds are employed in the 



production of this ware, the designs be- 

 ing applied by the inlaying or super- 

 imposition of variously colored clays, the 

 background being composed of a num- 

 ber of harmoniously blending shades of 

 some one color — green is the favorite. 

 Some of the best pieces, however, bear 

 no designs whatever, relying entirely on 

 their gracefulness and originality of 

 form and beauty of coloring. This ware 

 is very inexpensive. 



