The National tribune., 1881-12-24

PYRETHRUM AS AN INsECTICIDE-The Per
sian insect powder, which has been for many
years used in destroying insects in dwellings is
now becoming OF great importance for the de-
structOn of most, if not all, insects which pjure
the crops of the farm, orchard, and garden. It
is expected TO take the place of Paris green and
LondOn-purple, which are dangerous p0isons to
all animal life, whereas the pyrethrum powder
is entirely harmless to vertebrate animals.
Persian insect powder consists of the powdered
flowers Of Pgrethrum r0seun an herbaceous plant
a native Of the Caucasus Mountains. OF late
years another article called Dalmatian insect
powder has been introduced and found to be
equally effective, if, indeed not more potent than
the Persian. This Dalmation article is the pow
dered blossoms Of Pgrethrum ciaerGrjB foIium
and is now cultivated to a considerable extent in
California, where the powder is manufactured
and sold under the name of "Buhach." This
powder is reputed as being of superior quality
TO the imported article The value of these
powders as insecticides is said to depend upon
volatile Oil, SO that they deteriorate by long
standing or exposure. The California article can
be had comparatively fresh that its value is
not impaired by undergoing long transportation.
Professor {. V. Riley, Entomologist of the
United States Agricultural Department, has
during the past three years experimental largely
with the powder Oh many species of injurious
insects, and he has recently published several
articles on its preparation and use which we find
in the American Naturalist, and from which it is
proposed to make copiOus extracts from time to
time, being convinced that there are but few
subjects OF more Importance to the farmer and
gardener than that of the best method of DESTROY
ing the insects which injure their crops.
Professor Riley remarks that, while he fully
appreciates the value OF the powder as a general
insecticide, he does not consider it a universal
remedy for all insects, as has sometimes been
stated. No such universal remedy exists. and
pyrethrum has It's disadvantages as has any
other insecticide now in use The following are
It's more serious disadvantages /. The action OF
the powder, IN whatever form it may be applied
is not permanent one in the open air. If it is
applied TO a plant Il Immediately affects the
insects that plant with which it comes in
contact but it will prove perfectly harmless to all
insects which come on to the plant half an hour
Tor even less after the application. =. The pow
der acts in the Opon air-unless, perhaps, applied
in very large quantities only upon actual con-
tact with the insect. If it is applied TO the upper
side of cotton lear the worms that may be on
the under side are not affected by it. 3. II has
no effect On insect eggs nor on pupae that are in
any way protected or hardened.
Ihese disadvantages render pyrethrum in some
respects inferior to arsenical poisons; but On the
olher hand, it has the one overshadowing ad-
vantage that II is perfectly harmless TO plants or
10 hlgher animals; and if the cultivation Of the
Pi"n' Id TINS country should prove success, ard
the price OF the powder become low enough, the
aforementioned disadvantages can be overcome
10 certain degree 10y copious and repeated ap- /,
plicatiOns.
IN closed room the effect of pyre.hrun, On