June, 1918 
WISCONSIN HORTICULTURE 
149 
The Imported Cabbage Worm 
In Wisconsin 
By H. F. Wilson ; L. G. Gentner, 
University of Wisconsin, Madison, 
Wis. 
There is a general belief among 
Wisconsin canners and growers 
Young unsprayed cabbage plant showing in- 
jury from cabbage worms. (This and following 
pictures by courtesy of Prof. H. L. Wilson, 
Agr. College.) 
that it is dangerous to use cab- 
bage that has been sprayed with 
poisons of any kind. Both can- 
ners and growers recognize the 
fact that the cabbage worm is a 
serious pest but the growers have 
not been free to use essential com- 
bative measures because they con- 
sisted of spraying with arsenicals. 
Other investigators have already 
shown that cabbage sprayed with 
arsenicals may be eaten without 
danger to the consumer but in or- 
der to more thoroughly convince 
Wisconsin growers of these facts, 
the investigations from which the 
included data was secured were 
planned. 
The life-history work of two sea- 
sons has shown that there are three 
distinct generations each year and 
sometimes a partial fourth. There 
is normally more or less overlap- 
ping of generations, especially to- 
ward the latter part of the season. 
The maximum emergence of adults 
from overwintering chrysalids oc- 
curs somewhere from the first to 
the middle of May, depending upon 
the season. The maximum emer- 
gence of adults of the first genera- 
tion occurs during the first two 
weeks of July; and of the second 
generation during the first two 
weeks of A u grist. 
In the southern half of the state 
generally speaking, both early and 
late cabbage are grown while only 
late cabbage is grown in the north- 
ern sections. The early cabbage 
usually matures without much in- 
jury from the cabbage worm, but 
the late cabbage is often seriously 
injured and as many as 35 per 
cent to 40 per cent of the heads 
may be made unfit for market. In 
very severe cases entire fields are 
wiped out. In the northern half 
of the state the late cabbage some- 
times matures in good condition 
without a single application of 
spray while at other times the 
losses are very serious. 
In the experiments carried on 
at Madison during the past year 
Longitudinal section of cabbage bead injured 
early in the season by th? cabbage worm. 
the following insecticides were 
used: Paris green, lead arsenate 
(powder and paste), zinc arsenite, 
calcium arsenate (powder and 
paste), tobacco dust and finishing 
lime. When applied in the liquid 
form the sprays were applied at 
the rate of one pound of the pow- 
der or two pounds of the paste to 
fifty gallons of water. The follow- 
ing materials were used as 
“spreaders” or “stickers:” com- 
mon yellow laundry soap (resin) 
Longitudinal section of uninjured cabbage 
head. 
at the rate of one or two pounds 
to fifty gallons of spray; molasses 
at the rate of one or two quarts; 
and molasses and lime at the rate 
of two quarts of molasses and three 
pounds of lime to each fifty gal- 
lons of spray used. When ap- 
plied as a dust spray, the materials 
were diluted from three to ten 
times by weight with lime. 
The results of the experiments 
showed that Paris green (this was 
used only in liquid form), lead 
arsenate and calcium arsenate 
gave entirely satisfactory control, 
while, contrary to expectations, 
zinc arsenite failed to give con- 
trol in any of the four plats to 
which it was applied. In fact 
some of the plats sprayed with 
zinc arsenite were practically as 
severely injured as the unsprayed 
check plat. In comparing the li- 
quid sprays with the dust sprays, 
results showed that the liquid 
sprays gave slightly better control 
