Insect Notes For 1918 5 
Carpenter ants are responsible for an immense amount of damage 
to standing white cedar in the northern part of the state. The in- 
festation varies from 15 to 20 per cent of all swamp trees of pole size 
and from 40 to 75 per cent of the trees on higher ground. S. A. 
Graham, of this department, has investigated the injury. He believes 
that altho it is impractical to suggest methods of protecting the standing 
trees from injury by ants, the loss occasioned by them may be reduced 
to comparatively small proportions if we discourage wasteful practices 
in the woods. 
PoTaTo SPRAYING 
In an experiment to determine the comparative value of lead 
arsenate, calcium arsenate, zinc arsenite and paris green, it was found 
that when applied under favorable conditions, the poisons were equally 
effective in poisoning the colorado potato beetles. The favorable condi- 
tion necessary is dry weather such as we had in 1918 which makes it 
possible for the poison to remain on the plants for a long time. Under 
less favorable conditions, those materials which are easily washed from 
the leaves would have been the less effective. 
These results show that two factors determine the comparative 
value of the stomach poisons: (1) Ability to stick in spite of rains and 
a2 )e the Cost. 
Preliminary work in testing the power of adherence of these com- 
pounds indicates that both lead arsenate and calcium (lime) arsenate 
are resistant to washing, while paris green washes off very readily. 
Calcium arsenate (arsenate of lime) is the cheapest of these poisons 
and therefore is the most desirable for potato spraying. 
IXxperiments for the control of leaf hoppers on potatoes showed 
that the commercial tobacco extracts with soap were effective as con- 
tact sprays, provided the insects were hit with the material. The 
problem of leaf hopper control, therefore, is a problem of perfecting 
the mechanics of application. 
ORCHARD AND Nursery INSPECTION 
During the entire growing season 146 nurseries have been in- 
spected and 100 certificates issued. We have also given 11 certificates 
to dealers in nursery stock. For the most part the nurseries of the 
state were found to be in excellent condition. No dangerously in- 
jurious insect or disease was found, necessitating quarantining any 
nursery or refusing a certificate. In a few instances barberry eradica- 
tion and white pine blister rust called for extra precautionary measures, 
