REPORT ON INSECTS INJURIOUS TO FLOW¬ 
ERING AND ORNAMENTAL GREENHOUSE 
PLANTS IN ILLINOIS 
By J. J. DAVIS 
Pursuant to an assignment by Dr. Forbes, the winter of 1907- 
08 was largely spent in making a general survey of insects in¬ 
jurious to greenhouse plants in Chicago and vicinity. Since then 
the more prominent of these injurious insects have been studied, 
and experiments have been made with measures for their control. 
Importance oe Floriculture in Illinois 
According to the Census of 1900 the amount invested in flori¬ 
culture in the United States was $52,075,558, while in Illinois it 
was $4,626,466. The number of square feet of glass surface in 
florists’ establishments in Illinois (the third state in this respect) 
was 8,414,541, 5,855,612 feet being in Cook county alone. The 
total wholesale value of the floricultural products of Illinois (the 
fourth state in this particular) was $1,865,722, and the retail 
value could hardly be estimated at less than $3,000,000. Since 
1899, the year this census was taken, this industry in Illinois has 
developed enormously, one conservative estimate being that it has 
more than doubled in the past nine years. At the present time 
several florists in the vicinity of Chicago have from 1,000,000 to 
1,500,000 square feet of glass each.* 
The expense of growing flowers under glass is. much greater 
than that of any other kind of crop, since it involves a large 
outlay—first for the houses, and then continually for labor, fuel, 
water, soil, fertilizers, etc. Because of this, very intensive methods 
of culture must be practiced to realize a fair profit from the in¬ 
vestment. Insect pests are one of the greatest drawbacks, and 
the losses resulting from their attacks are frequently large. For 
example, it is estimated that two Illinois florists lose annually 
*At the fifty-fourth annual convention of the Illinois State Horticultural 
Society (see Transactions of the Society for 1909, page 139) Mr. H. B. 
Dorner said: “Illinois now produces more flowers than any other state in 
the Union. Within the borders of the State are plant houses covering an 
area of over eighteen million square feet, or over three hundred and sixty 
acres.” 
