June, 1918 
WISCONSIN HORTICULTURE 
151 
Bacterial wilt is carried from 
plant to plant by the mouth parts 
of the insect; the twelve-spotted 
cucumber beetle also carries the 
infection in the same way. No 
other means of spreading this di- 
sease is known . A plant wilts down 
in a few days after infection. The 
wilting is presumably caused by 
the growth of becteria in the vas- 
cular tissues, which eventually 
shut off the water supply from the 
upper portion of the plant. 
The larvae also do considerable 
damage, when they exist in large 
numbers, by feeding at the bases 
of the plants, by tunneling up in- 
to the stems, and by feeding upon 
the fruits. An attack of the 
larva) at the base of a. plant may 
cause the plant to wilt, and the 
death of a plant caused by larvae 
in this manner is often erroneously 
attributed to bacterial wilt. 
Control 
The logical time to begin the 
fight against the beetles is in the 
fall several weeks before they go 
into winter quarters, for it is these 
beetles which emerge in the spring 
and cause all the damage to the 
crops. 
In the control measures outlined 
in the following, no special remedy 
is suggested for bacterial wilt ; 
there is no known remedy, except 
to control the beetles which spread 
the disease. 
Control Measures During the 
Fall 
The control measures during the 
fall are based on the fact that the 
beetles at this time exhibit a great 
greed for food. After the main 
vine crops have been killed by the 
first frost, large numbers of the 
beetles can be poisoned by com- 
pletely covering with poison a few 
squash vines which have been pro- 
tected from the frost. Hubbard 
or Boston Marrow squash plants 
are the best to use for this purpose, 
as the beetles prefer these to any 
of the other vine crops, including 
other varieties of squash. 
The poison may be dusted on the 
plants in the morning while the 
dew is on, or it may be applied in 
the form of a spray. If dusted on, 
it is best to use powdered arsenate 
of lead, for Paris green is liable to 
injure the foliage. If applied as 
a spray, the solution should be of 
double strength. Four pounds of 
the paste or 2 pounds of the pow- 
dered arsenate of lead should be 
used to each 50 gallons of water. 
Paris green when applied as a 
spray should be used at the rate 
of t /2 pound to 50 gallons of water. 
Paris green should be added to 
freshly slaked lime and the mix- 
ture diluted to the proper propor- 
tion. One pound of fresh stone 
lime should be used with each half 
pound of Paris green. 
Another method of killing the 
beetles in the fall is to leave a num- 
ber of immature Hubbard squash 
scattered about the field. The 
beetles will congregate on these in 
great numbers after the vines have 
been killed by a slight frost. Early 
in the morning while it is still cool, 
many of the beetles can be collect- 
ed by picking up the squash and 
brushing the beetles into some re- 
ceptacle from which they cannot 
escape. They will make very lit- 
tle effort to fly away when they are 
stiff from the cold. 
Large quantities of squash bugs 
and of the twelve-spotted cucum- 
ber beetle will also be collected in 
this way, as they congregate in the 
same manner. As the two latter 
insects spend the winter in the 
adult stage, their capture is a val- 
uable means of control for two 
more destructive cucurbitous pests. 
The writer has collected several 
quarts of a mixture of these three 
insects on different occasions, 
in less than fifteen minutes. Small 
boys could render valuable service 
in this kind of work. The princi- 
pal objection to hand picking is 
that a few of the beetles will still 
feed upon the partly green stems 
of the old plants and of course 
will be missed. This can be over- 
come to a certain extent by raking 
up the old vines and immature 
squash on piles of dry straw. 
After the beetles congregate, which 
will take a week or ten days, the 
vines may be burned. The straw 
placed under the vines hastens the 
burning so that few of the beetles 
escape. Dry straw placed over 
the top of the pile at the time of 
burning is an advantage. A few 
immature squash scattered over 
the field after the burning afford 
a means of collecting any beetles 
which have escaped. 
Control Measures Durixg the 
Spring and Summer 
In the spring the method of con- 
trol for the first five or ten days 
after the beetles appear on the 
plants is essentially the same as 
the method of applying poison 
described for the fall treatment. 
Advantage is taken of their rav- 
enous feeding habit during this 
period by applying poisons to the 
crops upon which they are feeding. 
If cucurbitous crops other than 
squash are the main crops, it will 
be advisable to apply the poison to 
a trap crop of Hubbard squash, 
driving the beetles from the main 
crop with air-slaked lime or Bor- 
deaux mixture. The beetles na- 
turally prefer the squash plants, 
(Continued on page 353) 
