The Blackfoot optimist. [volume] (Blackfoot, Idaho) 1907-1918, 1916-08-10
THE ALFALFA WEEvIL
BECOMING WIDESPREAD

vii is spreading in a way which max es
it possible that sooner or later everv
section of the country will have to con
slider the problem Of guarding against
this pest During tic IL years since the
weevil was introduced into America it
has been confined to the limits of the
Great Basin of tie West, but it has
been found this yea. by the Bureau Of
Entomology at Malta, McCammon, Po-
catello and Blackfoot, Idaho, all well
within the Snake River drainage sys-
TEN, and at Duchesne, Utah, in the Col
orado River system, which, like that of
the Snake, slopes to the Pacific. Within
the Great Basin the weevil has spread
as far south as Richfield into the IL
falfa fields of central Utah. The insect,
in spreading across the continental di-
vide, Department entomologists say, is
to he regarded merely as passing con-
venient landmark rather than as sur
mounting a barrier, for experience has
not shown that it spreads faster along
rivers than across mountain ranges.
Nevertheless, it is now many miles
nearer to important alfalfa growing dis
tricts which have hitherto felt safe from
its attack.
Description Of Weevil
A description of the alfalfa weevil
and methods of combating its ravages
are contained in new publication of
the U. s. Department of Agriculture,
Farmers Bulletin 741. The spread Of
the pest has, as a matter of fact, been
slower than was at one time feared, but
its progress has been steady. In Utah
and in small portions Of Idaho and
Wyoming, where it now exists, it has
caused at times loss of SO per cent of
the first cutting Of alfalfa and total
loss of the second cutting.
In order that farmers in those sec
tions in which the weevil has not yet
appeared may be able to recognize the
pest and to protect their crops from it,
the bulletin already mentioned con-
tains details of it's habits and of its ap-
pearance in the various life stages. The
weevil is most easily discovered in the
form of the full grown larva. 1t is then
a green worm-like creature one fourth
of an inch long with black head and
a faint white stripe down the middle of
the back. 1t feeds upon the leaves Of al
falfa mainly during late May, June and
early July and may be found by sweep
ing the tops Of the plants with an in
sect net or by looking for the notches in
the leaves where it has fed. When the
larvae are numerous they destroy most
of the tender growth and cause the
tops to appear white, making the field
look as if frostbitten when viewed from
a distance.
The adult insect is an oval, brown
beetle three sixteenths Of an inch long
with a prominent snout. It's color fire.
quently is nearly black. This beetle is
harder to discover than the larva, but,
on the other hand, it is present in the
field the whole year around. In winter
it can be found by digging about the
crowns and roots Of the alfalfa plants.
Control Measures
The alfalfa weevil does not hibernate
definitely. When the weather is cool
the adults are quiet, but with warmer
temperatures they quickly resume their
activities. Egg laying begins in early
spring and is usually ended by June 10.
One etficacions method of controlling the
pest, therefore, is to destroy the eggs
by pasturing the first crop up to that
time. A similar result may be obtained
by cutting the alfalfa green and feed
ing it as soiling crop.
If this is not done the larvae hatch
in large numbers about the last week
of May or earlier and eat the alfalfa
leaves SO rapidly that the plant is un-
able to Outgrow the injury. After the
field is cut the larvae which have been
feeding upon the first crop gather upon
the buds of the stubble and frequently
consume all of the second crop. By
that time most Of the insects have com
pleted their growing period and have
gone into the pupal or resting stage.
The later growth Of the crop, therefore,
does not suffer from them.
TO protect the crop pasturing, as has
been said, is effective in the early part
of the season. The field should be di-
vided into two or three lots and each
lot should be pastured alternately, the
animals being left in it until the alfalfa
has been eaten down close to the
ground. The number and size of the
lots should be proportional to the pro-
ducing power of the REID and the num-
Der of animals to be pastured, so that
each lot may be grazed about once in
two weeks. Pasturing should be con
'tinucd until most of the weevil eggs
have been laid, which in practice means
little later than the usual cutting time
of the first crop. This method has the
additional advantage of providing an
economical method of fattening live
stock. Combined with the proper feed
of gain, alfalfa pasture is excellent foI
putting on weight and it is said that
many farms would probably be more
profitable if their management centered
about the pasturing of stock on alfalfa
with the growing of enough other crops
to provide grain and forage throughout
the year.
If the weevils are not killed early in
the year they may be destroyed after
the first crop has been removed by get
ting rid Of all the vegetation in the
field, crushing the clOds and filling thu
cracks SO as to expose the whole sur
face to the sun. This is best done 10y
covering the field with dust mulch
the aus. being an additional means o.
killing weevils. Success obviously lie
ponds upon doing the work when thu
ground is dry and the weather warn