E-37 .... April 19136
United States Department of Agriculture
Bureau cf Entomology and Plant Quarantine
PRESENT STATUS OF THE ALFALFA WE:IVTL PROBLEM
WITH PARTICULAR REFERENCE TO QTAULArTINTES
By P. N. Annand, In Charge, Division of Cereal and Forage Insect Investigatior
The alfalfa weevil has been the subject of many discussions and of
frequent controversy with regard to its destructiveness and abundance in
its present area of distribution, as well as t6 the benefit or harm
attributable to certain quarantine procedures associated with its control.
It is not the purpose of the present discussion to enter into the
controversy on the merits or demerits of the weevil quarantines in par-
ticular or in general, but rather to present as complete a picture of the
economic status of the weevil as available information will permit, and to
furnish a brief review of some of the information bearing on quarantines
which has been accumulated through research by the Bureau of Entomology
and Plant Quarantine over a period of 25 years. But little information
on the means of spread of the weevil is available, in addition to that al-
ready published in technical journals and reports. It may be of some value,
however, to bring together such information as has particular bearing on
the quaranti-ne problem r.nd to indicate results obtained in work accomplished
by this Bureau but not previously reported.
K DISTRIBUTION AND ABU1TDANCE OF THE WEEVIL
No regular, extensive surveys of weevil distribution or abundance in
the infested areas have been conducted in recent years. Surveys to deter-
mine weevil abundance have usually been limited to those districts known
ti have experienced damage at fairly regular intervals. The earlier surveys
consisted mostly of observations on the prevalence tf injury, supplemented
by sweepings made in occasional fields to determine the larval population.
Most of such work was done.-in Utah. Estimates of the abundance of adult
weevils in the fall of thp year began in 1932, with the sampling cf fields
in 10 districts scattered throughout the weevil territory. In this first
fall survey, some 12 to 15 tons of samples were washed and examined. ,Thc
information thus obtained is serviceable both in indicating threatpnpd
damage and in providing a reliable record of the abundance of the weevil
and its parasites from year to year.
In 1935 a somewhat extensive survey of distribution was conducted, in
cooperation with a number of States, particularly in those areas contiguous
to known infestations. In a few cases ares-is were examined that were known
to have been Infested but where weevils had not been reported for many yearU-
and where determination of p-reent oicurr.ni, wan rf p-irtic-alar interest.
This survey added to the known infested area Wayne and Vane Counties in Utah,
Coconino County in Arizona, Montezuma County in.Colorado, Clark County in
Nevada, and Scotts Bluff County iin Nebraska, and confirmed the presence of
the weevil in Union and Baker Counties, Oregon, and in Sioux County,
Nebraska. The present known area of distribution is indicated on the map
(figure 1). This includes those records reported by State agencies and
by the Salt Lake City laboratory of the Bureau of Entomology and Plant
Quarantine. It does not agree in some respects with the map presented
by Essig and Michelbacher in 1933,. in their paper on the alfalfa weevil,.
Essig, E.O., and Michelbacher, A.E., The Alfalfa Weevil. Calif. Agr.
Expt. Sta. Bul. 567. 1933.
in that Harney County, Oregon, and Sublette and-Teton Counties, Wyoming,
are indicated as uninfested, and .in that-additional records .obtained since
1933 have been added. .If authentic records of the infestation in Harney,
Teton, and Sublette Counties are available they have escaped the writer's
search. Attention is directed to the fact that in this nap the county is
used almost exclusively as a unit of infestation. It should not be inferred
from this that all of each county indicated as infested is entirely infested.
The weevil has been unreported recently in a number of the counties shawn in
the map as infested. .
.. EXTENT OF JAMAGE RESULTING FROM THE ALFALFA WEEVIL
As with most insects, weevil damage is hard to estimate accurately.
That losses were extremely heavy in certain areas soon after establishment
and that the weevil continues to cause heavy commercial losses in certain
restricted areas cannot be doubted. It is also true, however, that con-
siderable portions of the infested area have never suffered much commercial
damage and that losses may now be so slight, as. to .be relatively insignifi-
cant in some of the areas where serious injury was recorded in the early
stages of the infestation..
The present reduction in annual loss experienced in some of the
districts longest infested, as compared with the earlier losses, when the
entire first crop was destroyed over considerable areas, is reasonably
well explained by the recent adoption of improved cultural practices,
such as maintenance of more vigorous stands, earlier cuttings, and timely
irrigation. To these must be added the benefits conferred by the estab-
lishment of the introduced hymenoptrous parasite Bathyplectes curculionis
Thrmrns., and possibly by the intervention at harvest time of climatic
conditions that were less favorable to the weevil.
On the map (fig. 1) an attempt has been made to classify the infested
area into three categories according to frequency of damage to the alfalfa
crop. This classification is based on data furnished by J. C. Hamlin and
G. I. Reevec, of-Salt Lake City, and on information obtained directly from
State agencies. The classification into areas of frequent, occasional, and
rare damage is more or less arbitrary but it represents the best informa-
tion available. It may be noted that frequent damage has been limited to
two States--Utah and Nevada. It is probable that portions of western
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Colorado might well be included in this category as well as a few other
areas shown on the map as areas of occasional damage. In some of the
rarely damaged areas commercial loss has never been experienced.
Considering the rather extensive region in which t'.e weevil now
does little or no damage, the important loss of extra-State hay markets,
due to the enforcement of ouaranitines, must be considered as chargeable
to the alfalfa weevil, and in some of the areas unier consideration this
is the mrna.ior loss resulting from weevil infestation.
Last fall a reouest was made of some of the entomologists in the
infested States that they furnish an estimate of the losses caused by the
weevil in 1935, and the losses from this cause that occurred in their
respective States over a previous 10-year period. Not all replied and
some of the replies received are not complete, but the information thus
obtained has been combined with other available data to cc-'orise an
estimate indicative of the importance of this insect as a pest, exclus-
ive of any loss attributable to interference with alfalfa markets, due
to the enforcement of quarantines. ablee 1.)
Table 1.--Losses from the alfalfa weevil
State Losses during Past 10 Yebrs Loss In 1935
Average 2 1/2 per cent
$25,000 to $160,000 per
year. Always noticeable
injury on first crop in
valley sections. Sometimes
as high as 40 per cent of
first crop in Delta and
and Montrose Counties.
Practically none in south-
ern and southwestern Idaho,
Moderate injury in upper
Snake River Valley where
soil fertility is low.
Annual loss to Grinmm
alfalfa growers in eastern
Idaho $5,000 per year.
Severe damage to first
crop in 4 fields.
Delta County, 25 per
cent cf first crop,
County, 25 per cent of
first crop, $20,7"Y0;
1'esa County, Grand
Junction Section, 50
per cent of first crop,
$100,000. Also retarda-
tion of second crop.
Moderate damage in
Canyon, Ada, Payette
dr:iae An Adams -County,
li iht. damage in
Table l.--Losses from the alfalfa weevil
State Losses During Past 10 Years Loss in 19355
Nebraska------------- ITone (except for 1935).
Nevada--------------- No figures available. Con-
siderable damage in western
Oregon--------------- Very slight, except in Jackson
County, where loss has been
moderately heavy recently.
Utah----------------- Annual loss tc hay conserva-
tively 5 per cent of annual
production, or 60,000 tons.
valued at $600,000; 5 per
cent loss to seed crop.
Slight damage to a few,
fields in Sioix Oounty.
33 1/3 per cent on first
and second crops in
Jackson County. Approx-
imate loss, $100,000.
Approached 10-year aver-
age. Severe damage in
Box Elder, Salt Lake,
Utah, Duchebne, Sevier,
and Sanpete Counties.
DISSET'!TATIOIT THROUGH COI:I-:PRCE TIN AGRICULTURAL PRODUCE
Before reviewing the information available on the artificial trans-
portation of alfalfa weevils in agricultural produce, it will be interesting
to tabulate the commodities suspected of being most important .-in this regard,
as indicated by the quarantines maintained by.25 States against the alfalfa
weevil. The information given in table 2 has been provided by the Division
of Domestic Plant Quarantines of the Bureau of Entomology and Plant Quarantine
frcm the most recent information available in that office.
Tab.e 2.--Commodities included in quarantines of 25 Stateg
against the alfalfa weevil.
Number of States
Commodity quarantine Pro-isions of quarantine
All kinds of hay
and cereal straw------------- 25
Alfalfa meal----------------- 22
v Cho pped hay--- ---------25
Alfalfa seed------------- 4
Salt-grass pacVing--------- 8
Nursery stock---------------- 3
Greenhouse plants------------ 2
Used machinery--------------- 6
Railway cars----------------- 7
Emigrant movables----------- 3-
Prohibited in part and
restricted in part.........
Restricted, an )rovnl of
mills or periait required...
Prohibited in summer,
restricted in winter.......
Prohibited in part,
restricted in part.........
Prohibited, except as
Included in hay restrictions.
Prohibited in summer,
restricted in winter.......
Restricted all year..........
Restricted .................. .
require certification as
A large amount of wor was done during the early years of investiga-
tion of the alfalfa weevil to determine what commodities may be responsible
for weevil distribution. More recent wor, which has been reported else-
where, was done on railway cars, alfalfa meal, and baled hay as mediums for
the movement of this insect. The work on dissemination of weevils with
commodities is herein reviewed only in sufficient detail to indicate the
extent and present state of our information on the importance of the
transportation of various commodities in weevil spread.
Fruits and Vegetables.
Most of the work of the Bureau of Entomology and Plant Quarantine
specifically aimed at determining the importance of the movement of fruits
and vegetables in transporting the weevil was done in the early days of the
weevil quarantines, although observations incidental to other work have
been made almost continuously. In 1913, from July until October 1, one
entomologist was employed at -Brigham, and other localities in Utah, one at
Pocatello, Idaho, one at -Helena and Butte, Montana, and one at Rock Springs,
Wyo., and Denver, Colo., constantly observing the handling of produce at all
stages, from its harvest in the fields in the infested area to its delivery
to the consumer. Examinations were made of fields, orchards, packing houses,
freight and.exoress shipments, and freight, express, and passenger cars, at
the Utah point of origin, in transit, and at the destination points in
Idaho, Montana, Wyoming, and'Colorado, mentioned above. During the period
of this project the weevils were active throughout the infested territory
and conditions were at the best for finding them on fruits and vegetables.
These observations were very extensive and included examination by
S. J. Snow, at Brigham, Utah,- and other Utah shipping points, of hundreds
of cases of apples, apricots, peaches, plums, cherries, strawberries,
raspberries, blueberries, corn, cucumbers, beans, and other vegetables.
'No weevils were.actually found on the corrmodity at the shipping point,
although one weevil was found in a case of apricots in transit to Sugar
City, Idaho,.and one in cherries in transit to Dillon, Mfont. S. J. Snow
and T. R. Chamberlin examined 10 cars of potatoes at Oden, Utah, and
discovered a total of 26 weevils. Desla Bennion examined 50 cars of
fruits and vegetables at Pocatello, Idaho, and numerous shipments of
potatoes, but found no weevils. C. W. Creel examined numerous cases of
apricots, cucumbers, beans, plums, and cabbages at Butte, Mont., and
found no weevils in them, but discovered a total of 51 weevils in 7 car-
loads of potatoes. At Rock Springs, Wyo., C. W. Creel examined hundreds
of cases of fruits and vegetables without finding any weevils but found
20 weevils in 2 carloads of potatoes. P. B. Miles, at Dei.ver, Colo.,
examined 67 carloads of prunes, pears, mixed fruit, peaches, and apples
and found no weevils, but he found 7 weevils in 3 cars out of 67 carloads
of potatoes examined. Mr. Miles' traced the cargoes of these cars as they
were unloaded at Denver and examined them in the commission houses. lHe
met practically all of the trains that carried express and examined
individual packages containing produce from Utah points. All of the
weevils found at Denver in the course of the two months, covering the
most active season, were 7 living and 7 dead weevils--all in potato
During July T. R. Chamberlin was assigned to examine produce wagons
at the Salt Lake City market. These examinations included large ouantitles
of raspberries, alfalfa seed, tomatoes, potatoes, turnips, onions, corn,
cauliflower, beets, melons, cherries, radishes, carrots, cucu.ib-rs, in3 n
variety of other truck: crops and fruits. No weevils were found at the
market, even on potatoes. Weevils were found on potatoes at the Ogden
market, however, apparently as a result of the handling of potatoes with
alfalfa hay, a practice conmaon in that area but not followed in the
Salt Lake City market.
The detailed investigations of 1913, together with more or less
continuous observations over a period of 10 years, have been tle basis
for the conclusion that the transportation of the various commodities
listed--with the possible exception of potatoes, for which screening is
required by a number of the state quarantines--is of little or no
importance in weevil dissemination. It is probable that much of the
infestation in potatoes was the result of hauling them in wagons
cushioned with alfalfa hay and with a few forkfuls of hay carried on
top of the load as feed for the team. The extensive use of auto trucks
and the improvement of roads has now undoubtedly changed this practice
to a large extent.
Alfalfa Hay in Stacks
It has been adequately demonstrated, by observations extending over
a period of years, that weevils may occur in stacked alfalfa hay, and that
the numbers are dependent (1) on the intensity of the field infestation,
(2) on the amount of handling between the harvesting in the field and the
time of examination; and (3) on the lapse of time between the stacking
and the date of examination. A detailed examination of 15 stacks by
Chamberlin, Miles, and Snow, in 1913-14, indicated that in first-cutting
stacks weevils may survive in the stack proper as late as January 13 and
around its base as late as March 14, and in stacks containin:- second or
S third cuttings, as late as April 7, both in the stack and around its base.
Similar results were obtained by Hamlin, Hawley, and others in 1927 and 192?,
when it was determined that weevils may survive in excess of 111 days in
stacks of second cuttings. It must be recognized, however, that, although
weevils can be recovered in stacks, the numbers present are small and the
moTtality extremely high. In view of these findings alfalfa hay must be
considered as infested material, because no one can be sure that the stacks
are absolutely free of weevils where the hay is produced in an infested
That weevils occur normally in hay baled from the stack has been
inferred from their occurrence in stacks and from their discovery in rail-
way cars that have contained baled hay. The only detailed work by the
Bureau of Entomology and Plant Quarantine on the effect of baling on weevil
survival and longevity in baled hay has been reported by Larrimer and
Reeves in the Surnal of Economic Entomology for June 1929 and by Hawley
in California State Department of Agriculture Special Publication 115
(1932). In this work the effect of the baling process upon the alfalfa
weevil was tested and a determination-made of .the. longevity of. weevils in
baled hay. This hay was baled on September 22, 1927, from a stack of the
same year's production. During the baling process 1,Q00, weevils were
introduced into each of; three bales--a number enormously in excess .'of that
which would occur normally. 'The essential results of this experiment are-
(1) that at least 39 per cent Qf the weevils were injured during the baling
process, (2) that living weevils were readily found for a period of 60 days
in one bale broken open 4 days after baling, (3) that live .weevils emerged
for at least 39 days after baling, and (4) that on February 15 no live
weevil was found inside a bale that had remained unbroken for 146 days
The results of these limited observations indicate that a few weevils
may live in baled hays, under late fall and early winter temperatures for
over 2 months, but that all die in less than 5 months after baling. When
it is considered that these results were obtained under conditions of ex-
tremely high infestation, the danger of transporting weevils in baled hay,
if it is baled early in the winter and held for 4 or 5 months for shipment,
would seem to be slight. This" is Iparticularly evident when the normal
infestation of box cars, as discussed later, is taken into account. It
would not be possible, however, to state that such hay would be absolutely
free from weevils, and .the small number of recorded observations will not
permit the definite statement that under some conditions of storage weevils
will not survive more than 5 months in baled hay.
The observations of Titus, Parks,'and Henderson on the absence of
infestation in alfalfa seed is corroborated by: the results of observations
over a period of years made by the Bureau laboratory at Salt Lake City.
Alfalfa Meal' ..
The work of the- Bureau on the liability of transportation of alfalfa
weevils in alfalfa meal was reviewed by Larrimer and Reeves in June 1929,
and by Reeves, Iawley, Hamlin, and others, in 1932, in the publications
previously referred to. The examinations reported in these publications
were of the larger stationary mills.' On the basis of careful experimenta-
tion this wor]- established the fact that few weevils reached the mill
premises and that those which did' were so located that they constituted
little menace to recontamination of the meal prior to shipment; and,
further, that this slight chance could be eliminated by the erection of
screened runways between the sacker and the car, or by blowing the meal
directly into the car. It also established the fact that the mills under
investigation produced weevil-free meal.
Subsequent work, which has not been reported, was cc-'.T-tcd by
G. I. Reeves and J. C. Hamlin, at Medford, Oregon, in I'-O, io detemine
the insecticidal action of three different'makes of small, portable ,i:al
mills. The results of these investigations' Indicate that not all portable
mills produced weevil-free hay, even with fans operating at a speed of 3,000
revolutions per minute. This work on portable mills' also indicated that,
so far as these mills are concerned, the insecticidal action cannot be
expressed solely in terms of speed of the fan but that other features of
the mechanical design may be more important. The results of tests of the
insecticidal action of portable meal mills are given in table 3.
Table 3.-Tests of insecticidal action of portable alfalfa
of Approx. Weevils dead Meal
machine speed -used Screen Survival weevils texture
Inch Number P.ct.
A 3,000 200 3/4 8 4.0 2 Variable;
A 3,000 200 1/2 9 4.5 Finer;
A ,31000 300 1/4- 4 1.3 3I S Fine
B 2,000- 200 1/2 0 0 0 Medlium;
C 2,250 300 7/16 0 0 2 Medium;
C 2,250 300 1/4 0 0 0 Fine;
The insects escaping the action of these mills may be of little practi-
cal importance in view of the frequent contamination of the freight cars into
which -I-e hay is loaded--cars that are used also in the transportation of
No detailed information is available on the infestation of cereal straw
or of its possible importance in weevil transportation, nor would it seem
feasible to obtain sufficiently detailed information to determine beyond
doubt that such straw is absolutely free of weevils. It is known, however,
that weevils do not normally feed on cereals, and such contamination as
might possibly occur would necessarily be due to the production of the
straw in close proximity to alfalfa fields or other sources of contamina-
tion, or the utilization of straw from fields in which the cereal is used
as a cover crop for alfalfa. The baling of straw in balers previously
used for alfalfa is also a conceivable source of contamination. So far
as present information goes, weevils have never been taken in straw that
was uncontaminated by alfalfa, and the available facts suggest the possi-
bility of permitting its shipment under certificate or other safeguard.
In 1913, in connection with the detailed study of the transportation
of weevils in various agricultural produce, extensive observations were
made of railway cars to determine, if possible, the danger of transporting
weevils in or on cars in transit. S. J. Snow examined the outside of 230
freight cars placed at different times on side tracks at Brigham, Utah.
He also examined rather thoroughly the inside of 25 box and baggage cars,
and the outsides of the cars of 1S trains that stopped temporarily at the
depot. No living weevils were discovered. Desla Pennion, at Pocatello,
Idaho, examined the outsides of 56 freight cars, the -outsides of the cars
of 37 through-passenger trains coming from the weevil-infested territory,
and the insides of the baggage and express cars on most of these trains,
without discovering any weevils. C. W. Creel, at Butte, Mont., examined
the contents of 24 baggage and express cars, inspecting their interiors,
especially the floors, besides examining the Outsides of through trains,
the interiors of passenger coaches, and the sides and top of coal, coke,
and other freight cars, without discovering weevils. These examinations,
however, were of necessity more or less cursory, and weevils have been
reported by other investigators on passenger cars, notably in 1910 by
Titus, who observed that it was not uncommon to find weevils in the cars
of railway trains, and who reported the definite finding of a number of
weevils in the vestibule of one sleeping car in Salt Lake County, Utah.
The most significant evidence of the importance of railway cars in
transporting weevils is found in the result of investigations, conducted
in 1928 by the Salt Lake City laboratory, on weevils occurring in empty
hay cars. This work was reported in 1929 by Larrimer and Reeves in the
Journal of Economic Entomology for June, and in 1952 by Beeves, Hawley,
Hamlin, and others, in California State Department of Agriculture Special
Publication 115. A total of 130 empty hay cars were examined during June,
July, August, September, and November. Living weevils were found in nearly
40 per cent of the cars that carried hay baled from the stack, while of
those that hauled hay baled in the field from the cock nearly 55 per cent
were infested. Of all the cars examined, 40.5 per cent carried the
alfalfa weevils. As these examinations were limited to an examination
of only a fraction of the chaff on the floor, many of the cars listed as
ininfested undoubtedly carried weevils. Sixty-six weevils were found in
one car examined. Additional investigation of the movement of these cars
indicated that, during a 60-day period following the original examination,
only 11.5 per cent remained within the region for a 60-day period. The
remaining 115 cars traveled as indicated in figure 2 in an average of 3
out of a possible 9 regions. One of the traced cars traveled over the
lines operated by 14 different railroads. Within 15 days after the
examination was made at Ogden, every one of 9 regions of the United
States was visited by one or more of the cars.
In 1929 additional world: was conducted with three cars to determine
mere accurately the length of time weevils would remain in empty railroad
cars' that contained chaff. Details of this work have not been published.
Each car was prepared by covering the floor about 1 inch deep with
alf- fa chafff an4 (,O00 weevils were liberated in each car in 10 lots
of IO0 eAh, jp he floor along its longitudinal axis. After being in
After interval of Region number
1 : 2 :3 4 5 : 6 7 : 8 : 9
15 days............. 57.7: 13.1 : 3.9 : 8.5 : 0.8 : 0.8 : 1.5 : 4.6 : 9.2
"0 days.............: 38.5: 13.1 : 6.9 : 11.5 : 3.1 : 2.3 : 2.3 : 10.0 : 11.5
60 days............. 29.2: 10.8 : 3.9 : 12.3 : 3.1 : 3.9 : 6.2 : 16.9 : 13.9
_________; _:_ : : : - : 111111
Figure 2.--Distribution of freight cars (130), shown in percentages for the nine
regions of the United States indicated on the map.
transit for the number of days indicated in table 4, the chaff was
examined, the cracks in the floor cleaned out, and the floor removed
in one case and the side walls in another, in order as nearly as possible,
to obtain all of the weevils present. The results are given briefly in
Table 4.--Summary of railway transportation of alfalfa weevils in chaff
in empty cars.
Duration of Weevils recovered out of 1,000 per car
Car No. trip Total Living
Days Percent Percent
1-- 0.25 37.3 32.0
2-- 6.og 14.g 11.2
3-- 3.09 41.6 35.5
Ninety-four living weevils were obtained from car 3 by removing the
floor boards, indicating that, where cracks are present in the floor, the
cars-cannot be adequately cleaned by sweeping out the chaff. No weevils
were obtained by removing the side walls of car 2.
The results obtained for cars 1 and 2 more nearly reflect actual
conditions that prevail in empty hay cars than do the results of the
'third, as the last was a much better car than those ordinarily used for
hay. In the case of car 2, the larger floor cracks were filled before
the experiment was started and the percentage recovered, 11.2, is
probably considerably higher than would normally occur. Thus the
best indications from this study are that approximately one-third of
the weevils remain alive in an average "hay-class" car during a fourth
of a day, while less than 11 per cent remain alive for 6 days. The
1,000 weevils used in each car is 50 to 100 times the average number
found under commercial conditions, as indicated in the study of the
130 cars previously referred to. It is therefore probable that rela-
tively few living weevils would remain as long as 1 week in the average
hay car when this is transported empty and uncleaned. An examination
of the data on the 130 cars studied in 1928 shows that 19, or 14.6 per
cent, left the region of origin (region 1) within 7 days after examina-
tion. Of these, 13 moved empty into the Pacific 1Torthwest (region 2),
5 into the region extending from southern Wyoming to Omaha (region 9),
and 1 into the region comprising Tevada, northern California, and
Although these additional data suggest that the danger of movement
in b6x'cars is not.as great as indicated by the data of 1928 taken alone,
there is in these figures still abundant evidence of the movement of
weevils from one region to another in cats recently used for hay shipment.
It has been pointed out previously that this movement of infested
railway cars may be a source of common and general transportation of al-
falfa weevils and that, because- of the apparent volume of this unrestrained
movement, it would tend to render, valueless many of the quarantine restric-
tions placed on the transportation of commodities, On the other hand, the
occurrence of weevils in cars used for the shipment of baled alfalfa hay
indicates that such hay, at least under some conditions, may be responsible
for the movement of a considerable number of weevils. In this connection
it should be noted that these cars were examined during the summer and
fall period and that most of the hay transported therein, produced under
maximum seasonal infestation, undoubtedly contained a much Hfigher in-
festation than would hay baled and transported during other periods of
the year. The summer movement of the alfalfa weevil in. empty hay cars
into noninfested areas would most favor its establishment and this
further emphasizes the importance of this.movement as compared with
the movement of haylor hay products during the winter, after the heavy
mortality -in the stacks and bales has occurred.
RESEARCH AS APPLIED TO PRO3LE1'S OF QUARAITTI]'E
With the primary ..objective of.imp 'Ving control methods, much infor-
mati:6n has been accumulated in. the last 7 years 6n the climatic factors
controlling the abundance of the weevil. Studies along this line.'have
been conducted in the more heavily infested sections in the center of the
infested area, including the States of Utah, Nevada, Idaho, and, more
recently, Colorado. The information pertaining to the section around
Salt- Lake is now practically completed, and this explains to a large
degree the factors responsible for periods of high and low population
of the weevil in that section, and has established the basic method for
this type of research applicable to weevil work in other localities.
In 1932 this method of study was extended to the recently infested
area at Tedford, Oregon, which presents a very different climatic complex
and demonstrates additional applications of the limiting factors to the
control of weevil abundance. In addition to supplying information on
which cultural-control programs can be based, this type.of study furnishes
information that will lead to a more definite understanding of the probable
geographical limits of weevil spread and that will be of possible signifi-
cance when scientific quarantine procedures are being formulated.
It is planned to extend this study to the regions of more recent infes-
tation toward the margin of the infested area, with the idea of obtaining
information on the climatic limitations present in the areas subject to in.-
freauent outbreaks. It is hoped that information obtained from these
localities will afford data of significance as to the probable damage
to be expected as the weevil invades new territory.
Experience in predicting probable damage in new territories by other
insects does not encourage the belief that the data obtained by this method
of study can give an unequivocal answer to questions of distribution. The
careful, detailed method of procedure utilized in these studies, however,
can provide a much more positive basis for judgment than any body of
information now existing.
The review which has been given of the situation with regard to
portable meal mills indicates the desirability of developing definite
specifications, if this can be done, for certification of meal mills
as safe, provided this possible source of infestation still remains a
problem from the quarantine standpoint. The review of the information
available on survival in baled hay, given above, indicates the lack of
information on this sub.iect, as the data presented were based on cnly
3 bales the data on only 1 of which are applicable in determining sur-
vival of weevils actually in the bales. No information has been ob-
tained on the survival of weevils when the hay is baled during cold
weather, the possiblem7rtality in the bale as affected by exposure to
warm temperatures in the fall, or--as these studies were conducted on
single bales--of the rrtality occurring in the baled hay in stacks.
These problems deserve further consideration from a research standpoint.
A survey to determine relative abundance and limits of infestation
is an expensive procedure and is unsatisfactory so far as determination
of freedom from infestation is concerned. To be of value, it must be
performed during a relatively short period of time and hence light in-
festations may readily escape detection. As funds and opportunity permit,
however, it would seem desirable to make an occasional check on areas in
which the weevil has not been observed recently, reporting the findings
in quantitative terms, so that Quarantine officers may have data on
which to base conclusions regarding the extent of occurrence of the
weevil in the various areas.
Scouting around the margins of the infested territory at periodic
intervals, in order to detect the development of new infestations, would
also appear desirable.
A special effort will be made to obtain additional data on these
and other problems that may be suggested.
It must be recognized that quarantine action must frequently pre-
cede the accumulation of a body of scientific facts on which it can be
based and that delay in action in order to obtain all of the facts might
in itself defeat the purpose of the Quarantine. The accumulation of
facts on which quarantines can be scientifically based, is, however,
as truly a function of the research agencies as the development of
control methods in areas already infested.. It should be no concern
of the research worker whether the facts obtained invalidate present
procedures, support them, or indicate that modifications are desirable.
His primary function is to obtain the facts and to make them available
to others. Once the facts are established, it is certainly the function
and duty of the agencies responsible for the formulation of Quarantines
to strengthen, modify, or cancel requirements so that they are in accord
with the best available information.
UNIVERSITY OF FLORIDA
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