29 



BULLETIN OF 



Massachusetts Boakd of .Agriculture. 



GREENHOUSE PESTS AND THEIR CONTROL. 



By H. T. Febnald, Ph. D., Professor of Entomology, Massachusetts Agricultural College. 



The value of crops raised under glass in Massachusetts is increasing 

 each year, and new houses are continually being added to those already 

 in use. Two classes of products are obtained in this way, — flowers 

 and other ornamental plants, and vegetables which during some por- 

 tions of the year could be produced out of doors, but which when raised 

 out of season command high prices. 



Both of these classes of crops, if they may be called such, occasion- 

 ally suffer severely from the attacks of insects of various kinds, some 

 of which may cause injury to but one kind of plant, while others may 

 affect nearly everything. Losses resulting from the presence of in- 

 jurious insects in greenhouses are frequently large, and Httle is generally 

 known as to methods of preventing them. Many kinds of insects may 

 be found at work at different times, and unless the grower knows what 

 the insect is with which he has to deal, he is uncertain as to the proper 

 treatment, for it is now becoming quite generally understood that the 

 nature of the treatment depends to a large degree at least upon the 

 kind of insect to be controlled. 



On forcing crops, plant lice, the white fly, thrips and occasionally 

 cutworms, snails and other pests appear. On florists' crops these 

 insects and scales are also too often in evidence. Accounts of some 

 of these pests, and reliable methods for their control, follow. 



Plant Lice. 



There are many different kinds of plant lice or aphids, most of which 

 are green in color, and are frequently called "green fly." A black 

 species known as the "black fly" is common on chrysanthemums", 

 and a brown species occurs on violets. All kinds of plant lice, how- 

 ever, suck the juices from the leaves, tender stems and flower buds 

 of the plants they are on, and in this way check the growth, blight 

 the blossoms, and if sufficiently abundant kill the plants. They 

 multiply rapidly, the young being generally brought forth alive, and 

 at first clustering around the mother, sucking the sap from the plant. 

 But after a few days, when more young appear and this region be- 

 comes too crowded, they move away to other parts of the plant and 

 continue their feeding. 



The mother louse (in one species at least) produces from four to 

 sixteen young every two or three days until about two hundred have 

 thus appeared, and when these young have fed till full grown they in 



