Current research on quarantine aspects of the alfalfa weevil problem


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Current research on quarantine aspects of the alfalfa weevil problem
Physical Description:
Hamlin, J. C
Bunn, R. W
United States -- Bureau of Entomology and Plant Quarantine
U.S. Dept. of Agriculture, Bureau of Entomology and Plant Quarantine ( Washington, D.C )
Publication Date:

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Resource Identifier:
aleph - 030261217
oclc - 778357678
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Full Text

E-404 April 1937

. ,United States Department of Agriculture
Bureau of Entomology and Plant Quarantine


By J. C. Hamlin and R. W. Bunn,
Division of Cereal and Forage Insect Investigations *


The status of the alfalfa wevil problem with particular reference
to quarantines was discussed by P. N. Annand before the Central Plant
Board at its meeting a year ago and was subsequently published. a That
review centered attention upon needed research, which the alfalfa weevil
laboratory of the Bureau of Entomology and Plant Quarantine has since

Last August a project was undertaken to determine the facts rel-
ative to contamination of baled alfalfa hay, native grass hay, and
cereal straw by the alfalfa weevil and thereby to learn whether and
under what conditions baled hay might be shipped out of weevil-infested
regions without increasing the possibility of transporting the insect
into uninfested territory. To give the project a broad and practical
foundation, inquiry will be made into various practices and conditions
affecting the hay business in different parts of the weevil-infested
territory. Importance in this regard attaches to the relation of local-
ities producing surplus hay to variations in regional abundance of the
weevil and to the effect ,upon weevil contamination, of differing prac-
tices in regard to production, baling, storing, and time of shipment.
This inquiry will also take into account the bearing of the weevil's
biology upon the danger of weevil spread through shipment of baled hay
and, finally, will relate these findings to other constant hazards of
weevil dissemination.

i The work on which this report is based was carried out, under the gen-
eial direction of the senior author, by R. W. Bunn, assisted success-
ively by H. F. Cline and W. E. Peay, anI intermittently by W. C. McDuffie
ani J. C. Hamlin.

a Annand, P. N. Present status of the alfalfa weevil problem with par-
ticular reference to quarantines. U. S. Dept. Agr., Bur. Ent. and P1.
Quar., E-378 (mimeographed), April 1936.

2 -

The immediate attack has been directed toward determining the
lcngevity of weevils in baled alfalfa hay and the frequency with which
they occur naturally in it. All work to date has been performed in Salt
Lake Valley, Utah, which is a heavily infested area. Consequently, the
results relating to natural occurrence in baled hay have no reference to
conditions of infestation that may exist in those portions of the weevil-
infested territory where the insect occurs more sparingly. Notwithstand-
ing the limitations within which present results must be construed, it is
considered desirable to make them available at this time in order that
Bureau workers may benefit from suggestions of interested persons for the
future guidance of the investigation.

Development of Methods

At the very outset we were confronted with the necessity of de-
veloping a technique making possible rapid examination of large quanti-
ties of hay in order that a sufficient number of bales might be included
to provide trustworthy results. Looking for weevils in hay is on the
same plane with searching for the proverbial "needle in a haystack", and
earlier experience had demonstrated the impracticability of hand-collect-
ing weevils by picking over the hay bit by bit, or even by shaking out
the chaff and examining all of this by careful visual methods. Such
examination requires ,on the average, one day for a man to examine three-
fourths of a cubic foot of chaff and, at this rate, from two weeks to a
month would be required to examine a single bale of hay. Moreover, even
the most competent men will occasionally miss a weevil. This problem
has been solved by following the suggestion of Dr. Annand that the
Berlese funnel be used to drive living weevils from hay chaff, after
having removed the stems and very fine particles by means of a motor-
driven shaker.

The shaker used (figs. 1 and 2) was constructed by R. W. Bunn,
following the one devised by Campbell and Stone. S It is provided with
two screen-bottom trays, the upper screen having 2 meshes and the lower
one 16 meshes per inch. In the upper tray the flakes of baled hay are
thoroughly torn apart, one at a time, and the loosened hay is churned
repeatedly. These manual operations, combined with the reciprocal action
of the shaker, effect the desired separation. The stems are caught on
the upper tray and are discarded. The very fine particles pass through
the fine screen of the lower tray, leaving the hay chaff, together with
any weevils, in the lower tray. The shaker operation removes approximate-
ly two-thirds of the volume that was in the bale originally,

3 Campbell, R. E., and Stone, M. W. Soil Sifters for Subterranean Insects.
U.S. Dept. Agr., Bur. Ent. and Pl. Quar., ET-49 (multigraphed), May 1935.


Considerable preliminary study -,as required to 4etcrrnine vh~t
type of funnel would be most suitablA for extracting weevils from hay
chaff. Because of its poor heat-ccnuuctiig qualities, the- chaff had
to be spread out in a fairly thin layer, with the heat applied from
above. Consequently f.he funnels used are large and shallow (fi,-s 3 and
4). These funels were constructed by W. C. McDuffie, fo)lowlf' the
general plan used by L. D. Christensen 4 They are 53 inches hiph,
and the upper ,cylindrical .part has a diameLer of 47 inches. The chaff
is spread on a tray, made of 4-mesh hardware cloth, which rests upon
brackets flush with the upper edge of the cone. The inner surface ot'
the cover is fitted with 13 electric globes so that the heat and LLIt
are directly above the chaff. As the heat within this tray increases,
the weevils crawl deeper into the loose chaff until they fall through
the screen meshes onto the sloping si ,,s of the funnel and thence into
a catch bottle placed at the bottom of the cone.

Careful tests of these funnels, extending over several weeks, were
necessary to work out, empirically ,the proper thickness of the chaff
layer and the current consumption or amount of heat required to drive out
all living weevils within a reasonable time. Thermoregulators were used
initially but they were found to be unnecessary since, with proper wat-
tage, the input of heat came into balance with losses from radiation. It
was found that complete extraction of normally active weevils introduced
with chaff could be obtained by any one of three operating conditions,
shown in table 1. Detailed results of the experiments are presented in
table 2.

Table 1. Successful operating conditions in Berlese funnel
established experimentally ,Salt Lake City, Utah, 1936.

Electric ___ Chare of chaff
light Volume Averave depth without Time
wattage .c.(u. f_. ompactig.Jinchesi minutes
1,000 0.5 0.75 30
1,000 1.0 1.25 90
1,300 1.5 1.75 123

The 90-minute exposure with 1,000 watts s, current consumption and 1
cubic foot of chaff was adopted as the standard. Chaff treated under these
conditions was found to have a mass temperature of 1200 F. at the end

4 Christensen, L. D. A. Berlese funnel for collecting smaller soil ani-
mals, U. S. Dept. Agr., Bur. Ent. and Pl. Quar., ET-81 (multigraphed),
May 1936.

s Slightly lower wattage was required in the two newer funnels, which
were fitted with wood tops and so radiated less heat than the original,
metal-top funnel in which extraction tests were made.


Table 2. Summary of experiments with 4-foot-diameter Bsrlese
funnel, Salt Lake City, Utah, September 1936.

Experi- Heating Charge Weeyis Recover Final
ment unit of chaff Num- Condi- Per- Time temp.
No. (watts) (cu. ft.) ber tion cent (mins.) (IF.)

1 650 0.5 100 Subjected 100 30 170.6
to baling
2 650 .5 100 do. 97 40 --
3 650 .5 100 50 normally, 60 35 163.4
50 subnormal-
ly active
4 650 .5 -- do. 61 46 --
5 650 .5 100 do. 76 41 168.8
6 650 .5 100 Normally 99 47 171.5
7 650 .5 100 do. 95 41 169.7
8 650 .5 100 do. 96 45 171.1
9 650 .5 100 do. 97 53 168.8
10 650 .5 100 do. 100 39(a) 167.0
11 525 .5 50 do. 98 152(b) 172.4
12 1000 .5 50 do. 100 30 185.0
13 1,000 1.0 100 do. 100 113 194.0
14 1,000 1.0 50 do. 100 90 215.6
15 1,300 1.5 100 do. 100 123 --

(a) Weevils put on chaff in hopper 31 minutes before lights were turned
on to allow time for them to crawl into chaff.

(b) 100 percent recovery when catch bottle was removed the following
morning, 15 hours and 50 minutes later.

of the exposure. The 90-minute interval yielded the greatest efficiency
when one man was operating three funnels and one shaker. With this
equipment one man can examine from 1 to 1 bales of hay daily.

Experimental Determination of Weevil Longevity in Baled Alfalfa Hay

An experiment was designed to determine the longevity of weevils,
artificially introduced into hay, to serve as a check upon natural oc-
currence of weevils in baled hay. On September 3, 1936, 2,000 living
weevils were placed in each of seven bales of alfalfa hay that was being
put up from third-cutting haycocks. The weevils for a given bale were
divided into 10 lots of 200 each and were sprinkled into the hay as it
was being compressed, so they would be distributed throughout the bale.
The weevils used had recently been collected from the bottoms of hay-
stacks, mostly of second-cutting hay.

These bales, together with any loose chaff remaining on the floor
of the baling chamber, were wrapped in canvas as soon as baled and trans-
ported to the laboratory, where their exteriors were swept free of loose
material. Six bales wcre then put into individual sheet-metal storage
cabinets so constructed that any weevils leaving the bales would collect
in oil-pan traps for counting (fig. 5). The cabinets were located in the
Salt Lake City Federal Building basement, where the air temperature was
remarkably even and averaged 701 F.

The other bale had its wires cut shortly after arival at the
laboratory in order that the percentage killed by compression might be
distinguished from any mortality due to confinement in stored bales.
Examination results were as follows: 38 weevils, 27 living and 11 dead,
were obtained from the loose chaff swept from the exterior of the bale
before it was opened. The shaker-funnel treatment yielded 1,611 living
weevils. After removal of each charge of chaff from the funnels, one-
eighth of it was examined by careful visual methods for dead weevils,
and on this basis it is estimated that there were 216 dead weevils in
the bale. These operations accounted for a total of 1,865 weevils, of
which an unknown, but Coubtless small, fraction occurred naturally in the
hay when it was baled. These figures place the compression kill at only
11.82 percent.

Results of the entire series, opened at intervals of from zero to
153 days after baling, are summarized in table 3. As shown in column 3,
from 38 to 199 weevils, or roughly from 2 to 10 percent of those placed
in the bales, were swept from their surfaces shortly after baling. The
fifth column shows that from 7.80 to 22.74 percent of the recovered
weevils crawled out of the bales and dropped into the catch pans. Of
these an average of 57 percent appeared during the first 10 days of stor-
age, 71 percent in 20 days, and 82 percent in 30 days. The last weevil
was caught 109 days after baling, but this does not necessarily mean
that this individual had just emerged from the bale, since it may have
remained on the bale surface for some time before dropping into the catch
pan. Small numbers of weevils crawled from the interior of bales and
died on bale surfaces without dropping into catch pans, these numbers
ranging from 6 to 37 weevils per bale and averaging 21.8.


Table 3.--Summary of results from experimentally stored bales
of alfalfa hay.

_ Number of Total number Proportion Proportion
I Iweevils brushedlof weevils re- that crawled surviving
Bale I Storagelfrcm exterior Icovered from out during I storage
No. i period Ibcfore bale wasIhale during andj storage f period in
I (days) Iset in storage after storage I period bale
I cabinet period I (percent) 1 (percent)

1 0 38 I 1,827 88.18
2 10 84 1,628 7.80 64.82
3 31 103 1 1,327 11.76 25.53
4 61 60 1,816 8.92 0.73
5 91 199 1,118 21.11 0.45
6 123 161 J 1,082 22.74 0
7 153 73 1,081 13.88 0

The sixth column of table 3 shows that the initial survival of the
baling process was 88.18 percent, declining to 25.53 percent at the end
of 31 days. After 61 days 0.73 of 1 percent survived, and this was not
appreciably reduced at the end of 91 days, when 0.45 of 1 percent re-
mained alive. No weevil survived after 123 days' storage and none was
alive in the final bale, examined 153 days after the hay was baled.
The survival curve is shown in figure 6. A check lot of weevils of the
same origin and history, except that they had not been through the baling
process, was kept with dampened chaff near the storage cabinets. These
weevils, too, died off, but not so rapidly as those in the bales, for
whereas the survival in bales had dwindled to less than 1 percent at the
end of 2 months, approximately this same percentage survived in the check
after 5 months.

Weevils recovered from bales dismantled after intervals of zero,
10, and 31 days' storage were placed with dampened chaff and kept at
approximately 700 F. to learn how long they would live. From 50 to 72
percent died within 10 days, the mortality bein- proportioned to the
storage period. From 65 to 79 percent were dead after a month, and there-
after the decline was quite gradual until over 99 percent were dead
after 5 months,

Natural Occurrence of Weevils in Baled Alfalfa Hay

Supplementary studies were undertaken to determine, from farm-col-
lected samples, the frequency of occurrence of living weevils in alfalfa hay
of the three normal cuttings, baled both from cocks in the field and frcm
haystacks; also how long such contamination endures, and whether the con-
tamination is contained chiefly within the bales or located on their sur-
faces. Three bales were taken from each lot of hay studied, the pile
of bales being sampled to give the best distribution possible with three

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bales. These bales were put into individual canvas bags immediately
after being taken from the bale pile. At the laboratory the bale was
removed from the bag and its surface swept with s room to dislodge any
weevils that might be merely resting on the surface. The bale was then
returned to the canvas bag and placed beside the shaker, where the
baling wires were broken. It then passed through the shaker-funnel
process already described. Seventy-two 6 bales of alfalfa hay, totaling
3j tons, have been examined since October 20, 1936.

Thirty-six $bales were examined between October 20, 1936, and Jan-
uary 9, 1937 to determine the relative infestation of cock-baled and stack-
baled hay from each of the three normal cuttings. These bales came from
12 farms in the Salt Lake Valley, Utah. The bales were stored in the
open or in barns, sometimes in close proximity to loose hay of the 1936
harvests. The results are summarized in table 4.

Table 4. Summary of results from examinations of 36 bales of
alfalfa hay, October 20, 1936. to January 9, 1937,
Salt Lake Valley, Utah.

Days in Days in Bales examined Weevils
Baled stack bale Num- Percent per bale
from Harvest (Approx.) (average) ber Infested Range Average

1st 165 14 6 100 1-71 20.0
Stack 2nd 101 8 3 100 40-47 43.7
3rd 15 31 3 100 14-47 33.3

Tot. or Avg. ill 17 12 100 1-71 29.3

1st 0 186 12 33 0-2 0.5
Cock 2nd 0 115 6 50 0-3 1.2
3rd 0 1C5 3 0 -- 0

Tot. or Avg. 0 154 21 33 0-3 0.6

"Pile" 2nd 14 90 3 100 5-20 10.7

The averages (table 4), which do not distinguish between different
cuttings, show that 100 percent of the bales put up from haystacks were
infested as against 33 percent of those baled from cocks in the field.
Moreover, weevils were 49 times as numerous in stack-baled as in cock-
balEd hay, the respective averages being 29.3 weevils and 0.6 weevil per
bale. This differential infestation is borne out by the figures for

* Exclusive of one bale from an exceptional fourth cutting.


each crop. Thus, first-cutting hay averaged 20.0 weevils per bale of
hay from stacks as contrasted with 0.5 weevil per bale from haycocks.
Similarly, second-cutting hay had respective averages of 43.7 and 1.2,
while third-cutting hay showed comparable averages of 33.3 and 0.

It is noteworthy that weevils were most numerous in second-cutting
hay, whether stack-baled or field-baled. This condition doubtless re-
flects the fact, determined in recent ecological studies in Salt Lake
Valley, that the new generation of adult weevils is produced in two
divisions, one appearing about June 15 and the other in the latter half
of July. Both divisions of new-generation adults are present when second-
crop hay is baled or stacked.

Data on one exceptional lot of hay have been appended to table 4.
Original inquiry indicated that it had been baled in the field, and the re-
sults were originally tabulated among lots baled from haycocks. However,
its high level of infestation was entirely out of line with those of
other lots baled from cocks and suggested that it might actually have been
baled from a haystack. Further investigation revealed that it was an
anomalous lot of hay, the haycocks having been put into a loose pile and
left in the field for about 2 weeks before being baled. All three bales
were infested, and the average of 10.7 weevils per bale was intermediate
between the averages of stack-baled and cock-baled lots.

The above results very clearly indicate that weevil contamina-
tion continued longer and at a higher level in hay that was first stacked
and then baled in fall or early in winter than in hay baled directly from
haycocks. The reason for this difference is not known,

The loose material swept from the surfaces of bales prior to
shaking and funneling yielded living weevils from 7 of the 22 bales that
were infested. In five instances only a single weevil was thus found, two
in another instance, and in one exceptional case six living weevils were
recovered from a bale 7 that had been stored in a barn in close proximity
to loose hay of the first and second cuttings in 1936. These findings
indicate that considerable importance attaches to conditions of storage.

From January 12 to 27, 1937, five lots of baled hay were re-
sampled to learn what changes, if any, had occurred in the weevil in-
festations existing before Christmas. The data, summarized in table 5,
show that the two lots of stack-baled hay continued to be 100 percent in-
fested, but the averages of 33.3 and 43.7 weevils per bale which existed
within a month after baling had declined to 7.3 and 4.7 weevils per bale,
respectively, in 101 and 71 days after baling, In bales originating from
hay "piled" in the field for a fortnight the percentage infested declined
from 100 to 33 as the interval after baling lengthened from 111 to 169
days. The average infestation also declined from 10.7 weevils to0.3weevil
per bale, or one weevil to the three bales examined. This bale was one
of a lot stored in a barn with loose hay. The two lots of cock-baled hay
were originally sampled 109 and 188 days after baling, and again after

71t was also one from the anomalous lot of hay just mentioned.

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184 and 225 days. Between examination the infestation in one lot de-
creased from 67 percent infested and an average of 1.3 weevils per bale to
zero infestation, and in the other it decreased from 67 to 33 percent
infested and an average of 0.3 weevil per bale. These three lots of hay,
comprising nine bales, yielded only two weevils after having been baled
in excess of 169 days. However, attention is directed to the fact that
the two weevils came from lots of baled hay which had been stored with
loose hay in barns, and in one instance the weevil was recovered from
the exterior of the bale.

Table 5.-- Resampling data on five lots of baled alfalfa hay,
Salt Lake Valley, Utah, 1936-1937.
(3 bales in each sampling)

from Harvest

First examination, fall
and early winter, _1936___
Average Percent Averzge
number of number
of days bales of
in bale infested weevils

Second examination,
January 1937
Average Percent Average
number of number
of days bales of
in bale infested weevils

Stack 3rd 31 100 33.3 101 100 7.3
Stack 2nd 8 100 43.7 71 100 4.7
"Pile" 2nd il 100 10.7 169 33 0.3(a)
Cock 2nd 109 67 1.3 184 0 0
Cock Ist 188 67 1.0 225 33 0.3(bI

(a) Bale stored in a barn with loose hay.

(b) This weevil was swept from the exterior of the bale. The bales were
stored in a barn with loose hay.

In order to learn whether hay baled from stacks in midwinter would
be free of living weevils, four lots of bales wer examined between Janu-
ary 29 and February 11, 1937. Moreover, the three bales of each lot were
selected at the time of baling to represent top, middle, and bottom
locations in the haystacks. The results, shown in table 6, demonstrate
that small numbers of weevils may live 71 months in haystacks a and then
survive the mechanical process of baling. This result is particularly
informative in view of the exceptionally low temperatures experienced in
Salt Lake Valley this winter (1936-37). Weevils in these haystacks were
too few to supply worth-while information on distribution within the stacks,
but the results do show that a few weevils are to be found in the middle
and bottom parts of haystacks after extended periods in the stacks.

S Christensen (unpublished notes) found 1.9 percent of the weevils alive
in a sample of hay taken from a first-cutting haystack on January 31,
1928, almost 8 months after it was stacked. He also found 8.1 percent
living weevils in "the very center" of a second-cutting haystack on Jan-
uary 25, 1928, and 8.3 percent alive in about the center of a third-
cutting stack on February 9, 1928. On March 26, 1928, he found 11.1
percent living weevils in a sample of hay taken about one-third of the
way down from the top of a third-crop stack.

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Table 6. Data from examinations of hay cut and stacked in the mid-
summer of 1936 and baled in the following miCwinter,
Salt Lake Valley, Utah

Harvest cut

in stack Baled
(approx.) (date)


in bale

Weevils Origin of
per bale weevils in-
(average) haystack

2nd Aug. 1 179 Feb. 3 Feb.8-9 6 0.3(a) Bottom center
1st June 222 Jan. 27 Jan.29-30 2 0
ist June 15 225 Jan. 30 Feb.1-3 3 0.7 Middle
ist June 15 228 Feb. 4 Feb.10-1l 7 0

(a) This weevil was dead when found, but its condition showed that it had
died very recently.

The latest examinations, made February 12-20, were of bales from
second-cutting hay (table 7). One of these lots, which was baled from the
stack at the end of September 1936, showed 33 percent infestation and aver-
aged 0.3 weevil per bale after 137 days in the bale. The other two lots were*
baled fi'om haycocks 192 to 198 days before examination. One lot was free
cf weevils while the other was 33 percent infested and averaged 1.0 weevil
per bale.

Table 7. ,$ur.warvzed results on nine bales of second-crop alfalfa
hay examined February 12-20,1937
Salt Lake Valley, Utah.

Days Days Bales examined
Baled in stack in bale Num- Percent
from (approx.) (average) ber infested



Weeyils per bale






It may be noted that whereas longevity of weevils in storage-cabinet
tests was less than 4 months, the studies of natural occurrence showed that,
in bales put up from haycocks, contamination persisted beyond 6 months.
This discrepancy may be due to higher temperature and perhaps lower humidity
in the experimental installation, but it may represent the effect of secon-
dary contamination. It is a common practice in Utah to store baled hay of
one crop in barns containing loose or baled hay of other cuttings, or to
store it in the open air next to haystacks or sheds, and in many cases to

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cover the pile of bales with several inches of loose hay as protection
against rain and snow. An effort wps made to segregate this factor of
secondary contamination by sweeping the surfaces of bales before opening and
examining them, and some weevils were thus obtained as already mentioned.
Nevertheless ,it is recognized that weevils may readily crawl into crevices
zf the bale where they cannot be removed by sweeping.

Let us reexamine the data on cock-baled hay of the first and second
cuttings (table 4) in the light of storage conditions. Of the 12 first-
cutting bales, 4 were contaminated. Two of these 4 originated in a lot
of hay that stood in the field 2 days after baling and when piled in the barn-
yard was covered with 5 inches of loose, first-cutting hay; the other 2 in-
fested bales came from a lot which was stored in a barn and then had bales of
third-cutting hay piled upon it. Of the second-crop hay baled from haycocks,
3 of the 6 bales had weevils. Two of the infested bales came from a lotof
hay stored in a barn with loose hay, and the other contaminated bale was one
of a lot that had been first stored in a barn free of other hay but later
was moved to another farm and stored near other baled hay. In some ex-
ceptional instances, however, bales were not contaminated with weevils
although stored next to other hay. The importance of secondary contamina-
tion cannot be estimated from the present data but will receive close at-
tention during the coming season.

Summarizing, these preliminary results indicate that, in a heavily
infested region such as Salt Lake Valley in Utah, hay stacked in summer
will not become free of infestation in time to take advantage of the winter
market in uninfested territory. On the other hand, it appears that even
with heavy infestation, hay of the first and possibly the second cutting,
baled from the cocks immediately after harvest, and stored away from sources
of secondary contamination, may possi.bly become weevil-free in time for
midwinter shipment.

Biological Background of Hay Studies

In the foregoing discussion attention has been directed only to the
number of living weevils in baled hay, and it is possible that the practical
problem may satisfactorily be solved on this basis. Notwithstanding, the
biology of the weevil in relation to harvest, baling, and storage may also
vitally affect the possibility of spread of the pest.

Overwintering adult weevils are of little concern here since they
are all dead by fall and therefore would not be a factor in winter shipment
of hay. The new generation of adults is produced in two divisions, the one
coinciding roughly with the first harvest in the first half of June and the
other with the second harvest late in July. Ordinarily the second divi-
sion is more numerous. A negligible number of adults may be produced dur-
ing the third-crop growing period.

Now, most of the first-division weevils have just recently emerged
when the first hay crop is cured and, consequently, have had little oppor-
tunity to feed and thereby to build up their food reserves when some of
them are carried from the fields in bales of hay or into haystacks. When

second-crop hay is put up toward the end of July, there are in the field
both recently emerged second-division weevils and first-division weevils
which have had an opportunity to feed for about 6 weeks. Weevils in third-
crop hay are partly those which have been in the field about 6 weeks and
partly those which have been there 3 months.

Weevils carried into haystacks or imprisoned in bales of hay are
without food and so must subsist on energy already stored in their bodies.
Consequently new-generation adult weevils present in each of the three
hay crops are believed to possess differential capabilities for survival.
Those removed from the field with first-crop hay in mid-June are believed
to have the smallest food reserves and so have the least likelihood of
surviving prolonged starvation.

Finally, it must be stressed- that the investigation has not pro-
gressed to the stage where any conclusion can be reached. Further results
in Salt Lake Valley and in a sparsely infested region will be obtained dur-
ing the coming year. Attention will also be directed to native grass hay
and cereal straw.

Figure 1.-Detail of Shaker.

Figure 2.-Shaker Operation .

Figure 3.-Battery of Funnels.

Figure 4.-Inside of Funnel.

Figure 5.-Hay Storage Cabinets.


a a a i -i -ii -ii i a .... wii wiiiw

0 4.AW

0 10 20 30 4o 50 60 70 so 90 100 110 1

Storage Period (Days)

Figure 6.-Longevity of alfalfa weevil adults in baled al.












'10 110 iO 150

faia hay.


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