129 
Sterilization of the soil by steam is the most efficient measure 
of controlling the eel-worm, as well as many insect pests ordinarily 
introduced into the greenhouse with the soil, and various ways of 
accomplishing this have been devised by hothouse gardeners. Per- 
haps the earliest record of this soil treatment is that of Mr. W. N. 
Rudd,* of Chicago, who used it successfully in 1893. The most 
practical and economical method with which I am acquainted, is 
that of Mr, J. F. Ammann, of Edwardsville, Illinois. Into a steril- 
izing bin of rough boards, measuring two feet high, 10 feet wide, 
and 20 feet long, about a foot of soil is placed, and a heating ap- 
paratus of five "runs" of old perforated two-inch pipe is laid and 
connected with the steam supply. Another foot of soil is added, 
and potatoes are placed in the bin, one at each end and another in 
the center. The bin is then covered with a tarpaulin, and 80 
pounds of steam are turned into the pipes for about an hour and 
a half, or until the potatoes are well cooked. 
LETTUCE 
The cultivation of lettuce, tho carried on thruout the year, is 
confined to hothouses during the cooler months. The hothouse 
product is far the most important, and it is to this that insect pests 
are the most troublesome. Cutworms, the lettuce plant-louse, and 
the cabbage-worm are usually abundant enough to do it much 
damage, and need the close attention of the lettuce grower. 
The Variegated Cutw^orm 
Pcridroma uiargaritosa Haw. 
(Pcridrouia saiicia, Agrotis saucia) 
Young lettuce, cabbage, and other plants, are often cut off, or 
otherwise eaten, by some unseen insect, and later the leaves may 
be so badly eaten as to ruin them for market. In such cases if one 
searches near the plant, just beneath the surface of the soil, he is 
almost certain to find a grayish or dark fleshy cutworm. 
The only cutw^orm I found feeding on lettuce and other vege- 
tables in the greenhouses and out-of-doors in 1908 was the species 
named above. The egg (Fig. 22, e) from which it hatches is 
about one-fiftieth of an inch in diameter, dome-shaped, with ver- 
tical ribs. When first laid it is creamy white with a pearlv luster, 
but it soon changes to a pinkish tint, and finally to lilac or darker. 
The parent moth may deposit 500 eggs, or even more, in masses 
of 60 and upwards (Fig. 22, /). The larva hatches in five or six 
days, and after eating the egg-shell from which it has emerged, 
*Killing Grubs in Soil. American Florist (Chicago), Vol. IX, Sept. 28, 1893, 
p. 171. 
