52 
WISCONSIN 
HORTICULTURE 
December, 1916 
BUY YOUR TICKET FOR 
Some Common Pests of Greenhouse 
By S. B. Fracker at Summer Meeting, 
rofessor Sanders has asked 
me to express to you his 
great regrets that he could 
not take part in this meeting and 
to tell you of the pleasure he has 
had in his work with you during 
the last six years, as well as his 
appreciation of your co-opera- 
tion in his work. He requested 
me yesterday evening to talk in 
his place and to discuss the in- 
sects affecting ornamental plants 
and those found in greenhouses. 
I shall consider only those which 
the greenhouse men have ac- 
tually asked about in our in- 
spection trips and those which 
we know are occasionally trou- 
bling them in their greenhouse 
or on their ornamental shrubbery. 
First, it seems advisable to go 
briefly into the primary prin- 
ciples of insect control. As most 
of you know, insects from the 
control standpoint are divided 
into two groups, — those with 
chewing mouth parts and those 
with sucking mouth parts. The 
former include caterpillars, 
beetles, grubworms, insects 
which chew the leaf tissue and 
which take into their stomachs 
the leaf material in some solid 
form. The other group consists 
of plant lice, scale insects and a 
few others of less importance. 
These insects do not eat the 
surface of the leaf tissue but 
take into their stomachs only 
the liquid food which consists of 
the sap of the plant. 
On account of the difference 
of these two groups, it is neces- 
sary to use different control 
measures, and sprays are there- 
fore divided into two kinds, the 
first consisting of arsenicals or 
stomach poisons which operate 
through the digestion, and the 
second including contact poisons 
which operate through the ex- 
terior of the insect. 
It happens that the injurious 
insects with sucking mouth parts 
are in almost all cases smaller 
insects which can readily be 
combatted through the exterior. 
It is impossible, regardless of 
the mouth parts, to control 
caterpillars and beetles, as well 
as insects with a harder covering, 
with any kind of a contact in- 
secticide. Stomach poisons are 
mainly forms of arsenic, or 
arsenicals, as these are the 
cheapest poisons which we can 
use for this purpose. The com- 
mon arsenicals, as you know, are 
Paris green and arsenate of lead. 
Arsenate of lead comes in two 
forms, — the powder form and the 
paste form, the latter consisting 
of water and powdered arsenate, 
half and half. Twice as much 
of the paste must be used as is 
needed of the powder. At the 
present time we are advising the 
use of the powder form almost 
entirely, both in sprays and in 
dry applications. The reason 
for this is merely a climatic one, 
as it is almost impossible under 
ordinary circumstances to keep 
the paste over winter. If it has 
an opportunity to freeze it will 
crystalize, and its further use- 
fulness will be gone. 
The contact insecticides in 
most common use are Black Leaf 
“40,” or some other 40 per cent 
nicotine sulfpte, and kerosene 
emulsion. The former is mixed 
with 800 to 1200 times its bulk of 
water and is very simple to ap- 
ply. Kerosene emulsion is made 
with hot soapsuds and necessi- 
tates mixing the kerosene with 
the soap suds very carefully. 
Mixing kerosene and tobacco 
solutions together, as is some- 
times done, is not necessary and 
it is not desirable to invest in 
commercial preparations of this 
nature. 
Fumigation may also be con- 
sidered as a form of contact in- 
secticide because in this case we 
are using a gas which operates 
on the exterior of the insect, in 
place of a liquid. Fumigation is 
carried on in almost every green- 
house, in fact, in almost every 
commercial greenhouse in the 
state with which I am familiar. 
Publications describing the 
preparation and use of these 
spray materials will be sent, on 
request, by the State Entomolo- 
gist’s office. 
* * 
INSECTS AFFECTING SHRUBBERY. 
Fortunately, there are few 
chewing insects on the orna- 
mental shrubs which we are com- 
monly using in the state at pres- 
ent. It is seldom that any ar- 
senical spray is needed on such 
shrubs as Spiraea, Dogwood, 
Viburnums, and others of the 
same nature. An exception is 
in the case of roses which have a 
full supply of slugs and cater- 
pillars. These may be controlled 
by the ordinary lead arsenate 
spray. 
White hellebore may be used 
in place of arsenic when one does 
not wish to put poison on the 
plant. It is not recommended 
more often because of the greater 
expense. Hellebore should be 
used fresh and it is sometimes 
