Controlling grasshoppers in alfalfa with chlordane and toxaphene sprays

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Material Information

Title:
Controlling grasshoppers in alfalfa with chlordane and toxaphene sprays
Physical Description:
19, 2 p. : ill. ; 27 cm.
Language:
English
Creator:
Shotwell, R. L ( Robert Leslie )
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
U.S. Dept. of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:

Subjects

Subjects / Keywords:
Grasshoppers -- Control   ( lcsh )
Alfalfa -- Diseases and pests -- Control   ( lcsh )
Spraying and dusting in agriculture   ( lcsh )
Genre:
federal government publication   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliographical references (p. 19).
Statement of Responsibility:
by R.L. Shotwell.
General Note:
Caption title.
General Note:
"E-819."
General Note:
"May 1951."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030329393
oclc - 780436823
System ID:
AA00025218:00001

Full Text
STATi
May 1951 E-819

United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
i


CONTROLLING GRASSHOPPERS IN ALFALFA
WITH CHLORDANE AND TOXAPHENE SPRAYS
1/
By R. L. Shotwell,- Division of Cereal and
Forage Insect Investigations


The control of grasshoppers is an important problem to the alfalfa
seed grower in areas where these p!s 1-; are likely occur. In the last
15 to 20 years grasshoppers have become so well established in alfalfa-
seed fields in western South Dakota and Nebraska that they are an annual
threat to both hay and seed crops. For this reason alfalfa-seed growers
have used poisoned bait more consistently and more persistently than any
other group of farmers. Although these growers have sometimes obtained
excellent results with the bait, their failures have so far outnumbered
their successes that a more reliable method of control is needed.
The alfalfa field is an ideal place for using the spray method to
destroy a grasshopper infestation. The plant growth is sufficient to
catch and hold the spray, and the margins, whether ditch banks or fence
rows, are usually lush with vegetation in which grasshoppers concentrate
during any movement out of or into the alfalfa. Thus a field of alfalfa
or the areas bordering it can be used as traps where chlordane and toxa-
phene can be applied to destroy grasshoppers moving in from much larger
areas when the small grains are harvested.
Entire farms and fields in the alfalfa-seed areas around Buffalo
Gap, S. Dak., in 1948 and Crawford, Nebr., in 1949 were utilized for
testing both chlordane and toxaphene sprays to protect the alfalfa-seed
crop from grasshoppers and reduce local infestations to a minimum.
These two areas were selected because of their long history of grass-
hopper damage to alfalfa, and because large quantities of poisoned bait
had been used in them at various times without giving very effective
control. The investigation was continued in 1950 with treatments of
lightly infested marginal areas.


/ This work was done in cooperation with the Division of Grasshopper
Control of this Bureau and the Sugar Loaf Soil Conservation District,
Crawford, Nebr.









SL i' -RIAL'S ANI .METHODS


The chlordane sp.ray used in the Buffalo Gap area consisted of 1
pound of technical chlordane dis:.-:>lved in 1 quart of No. 1 petroleum dis-
tillate with 25 ml. of Ig,'pal CA Extra High Concentrate (a condensation
product of ethylene oxide and an alkylated cresol) and water to make 4
gallons. Some of the chlordane spray used in the Crawford area was the
same formulation, except that in place of the Igepal a granulated com-
mercial soap substitute was used at the rate of a handful per gallon of
distillate. However, in most of the tests an emulsion concentrate con-
taining 8 pounds of chlordane per gallon was used. One pint of this con-
centrate in water sufficient to make 4 gallons of spray was applied per
acre with a mist blower.
Some of the toxaphene spray used in the Buffalo Gap area consisted
of 2 pounds of technical toxaphene dissolved in I gallon of No. 1 petroleum
distillate with 100 ml. of Igepal CA Extra High Concentrate and sufficient
water to make 4 gallons. Other sprays were concentrates containing
either 4 or 6.9 pounds of technical toxaphene per gallon. In the Crawford
area a concentrate containing 8 pounds of technical toxaphene per gallon
was used. Enough water was added to make a spray that would give the
desired dosage.
All the sprays were applied with a mist blower. A side-delivery
nozzle was used in all the spraying. Although a level field -night best
be sprayed with a rear-end-delivery nozzle, in these alfalfa fields the
interspersed variety of marginal areas could be reached only with a
side-delivery nozzle. Considerable maneuvering and retracing of distances
were thus avoided. Furthermore, the side-delivery nozzle on this blower-
type sprayer was much preferred by the farmers to their own boom-type
sprayers.
The sprayer was calibrated to deliver 8 gallons of liquid with the
truck traveling 1/2 mile at 10 miles per hour and covering a strip 2 rods
wide, or at the rate of 4 gallons per acre. At this calibration the recom-
mended dosage per acre for either insecticide determined the quantity of
emulsion concentrate that went into the 50-gallon sprayer tank. Since a
sp.eedr of 10 miles per hour could not always be maintained, records were
kept of the quantity of spray used on a known acreage.
In all areas 1 pound of chlordane or 1. 5 pounds of toxaphene per acre
was generally used for early spraying of grasshopper nymphs in the first
four instars and for spraying entire fields, and 1.5 pounds of chlordane or
2 pounds of toxaphene per acre for spraying late nymphal and adult infes-
tations and barrier strips. In theCrawford area in 1949, lighter dosages
of both sprays were tested in the initial applications.
The dosages of technical material were the same as those that the
farmer would use in his own spray operations. From the strength of the
concentrate he could calculate the amount needed for use in his spray tank.
















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delay in s, ray opration--w;-.'"-f until the hay was dry enough to be
taken off fi- fields and for the road',ays to become passable--allowed
some of the grasshopper-- to --pread from the alfalfa into adjacent small-
grain fields, and dubled the area to be treated.
General observations ird, catc that, to protect an alfalfa-seed crop
adequately from grasshopper damage, the numbers of grasshoppers in the
field must be held to less than 5 per quaree yard. This means that where
there are 50 or more grasshoppers per square yard 90 percent or higher
mortality must be obtained, prefe-nbly with one application of in ;ecticide.
To prevent movement of grasshoppers ,-,ut of the alfalfa or reinfestation
of the crop from hatching grasshoprPr- or from some outside infestation,
the insecticide should show a marked residual effect over a period of
1 to 3 weeks. Chlordane and toxaphene sprays have this quality.

Pi sults

Table 1 summarizes the results with chlordane and toxaphene sprays
applied for the control of grasshoppers in seed alfalfa at Buffalo Cap in
1948 and the effect of residues from these sprays on infestations in 1949.
Altogether 255 pounds of chlordane v"-re sprayed on 50 acres of alfalfa
and on 132 acres of margin and adjacent cropland at the average rate of
1.4 pounds per acre. This rate was high, mostly because in one 55-acre
contoured wheatfield (NW 1/4, sec. 10, fig. 1) the ground was rough and
slowed up the speed of the truck. The heavy dosage was intentional
where a long residual action was desired (NE 1/4, sec. 8, fig. 1). On the
contoured wheatfield, the north half of which was first sprayed with
1.3 pounds of chlordane per acre on July 8 when the wheat was in the
dough stage and the foliage was drying up, the kill was only 85 percent,
whereas 95 to 100 percent is usually obtained with this dosage of
chlordane. The lower kill was attributed to the lack of succulent green
foliage in the wheat. Previous tests in ripening small grain had given
similar results. A hailstorm during the night of July 11 destroyed over
half of the wheat crop in this field, but on July 13 grasshoppers were
dying from the effects of the spray. On August 12 chlordane was applied
to the south half of this field, where grasshoppers had concentrated in
a heavy growth of sweetclover covering a third of the field, and the
infestation was practically eliminated. In sections 8, 9, and 10 where
chlordane was used, the infestations were reduced 94 to 100 percent.
About 650 acres of alfalfa and 338 acres of adjacent land, approxi-
mately 85 percent of the total area sprayed at Buffalo Gap, were treated
with 1,607 pounds of toxaphene at the average rate of 1.6 pounds per acre.
Populations were reduced 90 to 100 percent.






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Protection of Area Sprayed


A total of 1,170 acres were sprayed in this area in 1948 to protect
915 acres of seed alfalfa, or 1.28 acres sprayed for every acre protected.
In practically ever-y test the initial spraying eliminated the infestation.
When the alfalfa was first cut, some of the grasshoppers moved to the
margins and adjacent fields. This migration reduced the numbers of
grasshoppers 30 to 50 percent in alfalfa fields 20 to 60 acres in size, and
50 to 100 percent in smaller fields. Grasshoppers escaping into adjacent
fields were either sprayed in these fields or were kept out of the alfalfa
by the use of sprayed barrier strips consisting of weedy margins or the
first 8 or 10 rods of the alfalfa itself. From two to four applications on
these barriers at 5- to 10-day intervals were required to keep them
effective until all threatening reinfestation was eliminated.
Three small alfalfa fields in the eastern half of section 19 totaled 20
acres. The weedy banks of a creek formed the margins of these fields.
After the first alfalfa cutting all the !'-shoppers from the alfalfa con-
centrated in these weedy margins, where they averaged about 300 per
square yard. A single application of toxaphene to 6 acres of these weeds
on June 14 destroyed nearly all the infestation originating in these three
fields.
At the other extreme the infestation on a 30-acre alfalfa field in the
SE 1/4 of section 4 was not eliminated until 163 pounds of toxaphene had
been sprayed on 93 acres in seven treatments. The hay was cut on June 14,
buit was not raked until June 23 because of heavy rains. A small part of
the field had been sprayed on June 3, but the largest part was not treated
until June 25. Because it was not possible to spray the entire field soon
after the first cutting, the original infestation spread over about three
times the area it originally occupied. The increase in the area requiring
treatment, including most of the wheatfield adjacent on the east, explains
why on an average 1.28 acres had to be sprayed to protect 1 acre of alfalfa.
Most of the survey to determine the numbers of eggs laid in 1948 was
made in the spring of 1949. Egg deposition for the entire area was
extremely low, the number of egg pods averaging a maximum of 0.1 per
Square foot in the fields and 0.8 in the margins (table 1).

Effect of Spraying on Subsequent Infestations

To determine the effect of the 1948 spraying operations on the
populations in the Buffalo Gap area, a survey was made on July 16, 1949,
when most of the grasshoppers were in the late nymphal or adult stage.
The greatest number of grasshoppers withinthe fields was 1 and in the
margins, 6 per square yard. It thus appears that the spraying in 1948
gave almost complete control of grasshopper infestations that year and
the following year.








The only control needed in the entire area during 1949 was accomplished
with 17 pounds of toxaphene sprayed on 10 acres of spotted infestations in
sections 9 and 10. The survey in July 1949 did show a 6-acre infestation
averaging 15 grasshoppers per square yard in a grove of trees in the
NE 1/4 of section 4. It had been the intention of the owner to spray this
area, but by the time he got around to it the grasshoppers had moved south
into the 30-acre alfalfa field in the SE 1/4 of section 4 and damaged about
15 percent of the northern two-thirds of the alfalfa. The species, mostly
Melanoplus differentialis and M. bivittatus, had laid their eggs along the
fence rows forming the northern and northwestern margins of the alfalfa
field. The number of egg pods averaged 4 per square foot. From 10 to
15 pounds of toxaphene and 1 hour of time would have wiped out the
original infestation. However, this inft'stFtion -,.vs wiped out in 1950,
when these margins were sprayed with 10 pounds of toxaphene soon after
the eggs had hatched. Other spotted infestations on the area were eliminated
by the use of approximately 15 pounds of toxaphene.
The tests at Buffalo Gap (table 1) indicate ;hat 90 to 100 percent
reduction in infestation in one year by early-season sprays will carry over
into the following year. On the other hand, experience has shown that any
reduction less than 90 percent offers no assurance that grasshoppers will
not be a threat the following season.
This situation was evident in Lyman County, S. Dak., where a large-
scale experiment to compare the efficiency of baiting and spraying was
conducted in 1947 (Shotwell 1). In 2 fields 3 or 4 baitings between July 29
and August 10 reduced the numbers of grasshoppers 70 and 85 percent.
Just before the baiting in the first field, which was then in corn, the
population was 3 hoppers per square yard within the field and 25 along
the margins. In August of the following year there were 10 hoppers per
square yard within the field, then in wheat, and 20 along the margin. In
the second field, which was then in strips of wheat and corn, the population
just before the baiting was 20 hoppers per square yard within the field and
40 along the margins. In August 1948 there were 10 hoppers per square
yard in this field, which was then in strips with the corn and wheat reversed,
and 30 along the margins, although some control work was done early in
the season. In the field where the reduction was 70 percent in 1947, the
infestation was greater in 1948. In the second field where the reduction
was 85 percent in 1947 and some control work was done in 1948, the
infestation in 1948 was still more than half as much as in 1947.
In the same area of Lyman County 7 fields were sprayed with chlordane
or toxaphene in 1947. The populations ranged from 1 to 200 per square
yard in the fields and 20 to 1,000 along the margins, and were reduced
94 to 100 percent by the treatments. In August 1948 the populations
averaged less than 1 per square yard in the fields and 7 along the margins.
On 2 sections containing 4 of these fields, 58 pounds of toxaphene was
sprayed on 35 acres of marginal infestations. The other 3 fields were





-8-


not treated. Al hough no complete ur,.-L- of the sprayed fields was made
in 1949, the owners reported that few grasshoppers were present. In
1950 the only control needed to hold down infestations in the 7 fields was
sprayir- 23 acres of light marginal infestations on 2 farms. It is now
stated positively by the farmers in this area that, because of the new
insecticide sprays, J.z.-. no longer worry about grasshopper damage to
the corr. Before 1947 all the fields and the general area had had a long,
continuous record of g, asshopper infestations dating back to 1930.
At Buffalo Gap in 1949 the yield of alfalfa seed fromt the area sprayed
in 1948 was estimated to average more than 2 bushels per acre. The
year 1950 was a poor alfalfa-seed year throughout this region. The work
and observations carried on in the Buffalo Gap area in 1948-50, and in
Lyman County in 1947-50 show that very satisfactory results can be
obtaine,, by the proper use of toxaphene and chlordane sprays for the
control of grasshopper infestations.

TESTS AROUND CRAWFORD, NEBR_

In the Crawford area in 1949 single alfalfa fields 15 to 60 acres in
size were used. These fields were scattered throughout an area of range
and farm land, 15 miles square, lying north of Crawford, where the
combined acreage of small grain and corn was much greater than the
alfalfa acreage. The 12 fields where the tests were made are shown in
figure 2.
Melanoplus bivittatus was the dominant species in the alfalfa and
M. mexicanus was second in numbers. A few M. differentialis hoppers
were present in spots. Some spraying of young and hatching nymphs
was done in June, but most of the tests were made in July in fields con-
taining late-instar and adult grasshoppers. Little previous information
was available concerning the location of infested fields, and spray
operations had to await the reports of farmers. The populations in these
fields numbered 10 to 60 grasshoppers per square yard and in the margins,
20 to 300.
In addition to these tests, a close record was kept of some of the
grasshopper-control operations conducted by farmers on the Sugar Loaf
Soil Conservation District lying north and west of Crawford. This
district comprises about 220,000 acres of privately owned and 75,000 acres
of government-owned land, with about 5,000 acres of alfalfa scattered
throughout. A spray-control campaign against grasshoppers, sponsored
by the district board of supervisors, was conducted here in 1949. Bureau
personnel making the spray tests helped in this campaign.




-9-


Objectives

An important factor to be determined in the Crawford area was the
effect of grasshopper infestations in adjacent range land on attempts to
protect the alfalfa-seed crop from damage. Large expanses of open
range land surrounding crop land have always caused some farmers to
consider grasshopper control in crops as hopeless. The usual reasoning
has been that when the range grasses dry up all the grasshoppers will
move into whatever crop is still standing and destroy it, thus nullifying
any good accomplished by earlier control measures in that crop. Harvested
small-grain fields are notable sources of reinfestation of late crops,
including alfalfa, but in northwestern Nebraska infestations on open range
land are seldom a threat to such crops.
Collections were made in both grass lands and alfalfa to determine the
species found in each type of infestation. Each test was conducted with
the idea of destroying first the initial infestation in the field and then any
reinfestation from outside, whether adjacent crop or grass land. All
infestations were therefore fought from within the alfalfa field except in
field 12 (fig. 2), where an attempt was made to wipe out the entire infesta-
tion on a single farm. Most of the spraying on this farm was done along
the margins and in weedy places adjacent to the crop land.
To determine how light a dosage could be safely used in a general
spray-control program, on some fields light dosages of both chlordane
and toxaphene were used until heavier dosages were needed to save
the crops.
Another objective of the work in the Crawford area was to determine
the quantities of residue from the chlordane or toxaphene sprays present
in the threshed straw from the treated fields of seed alfalfa. Alfalfa straw
is used as feed, and it is important to know how much insecticide remains
in the pile after threshing.

Results

The results of the tests made at Crawford in 1949 are recorded in
table 2. Any single treatment of a whole or part of a field is considered
as one application. The numbers of grasshoppers shown before the
spraying are representative figures for peak infestation which developed
during the field test, and the reduction of infestation is based on a com-
parison of the population left at the end of the field test with that shown
before the spraying.
From June 9 to July 8, 502 pounds of toxaphene and 330 pounds of
chlordane were sprayed on 326 acres of alfalfa and 108 acres of margins
and weedy spots to protect 390 acres of alfalfa. Field populations of 10
to 60 grasshoppers per square yard were reduced to 0 to 5 and marginal
infestations of 20 to 300 per square yard to 1 to 10, a reduction of 80 to
99 percent. The egg survey in the fall showed a maximum of 0.4 egg
pod per square foot in the field and of 0.6 in the margins, which are
extremely light infestations.














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Economy of Minimum and Heavier Dosages of Toxaphene and Chlordane

As indicated in table 2 all or part of seven fields received a minimum
dosage in the first spray application, followed by heavier applications if
necessary to protect the field.
Field 2 (fig. 2) was 32 acres of sweetclover, half of which was cut for
hay and the other half saved for seed. Melanoplus bivittatus in the second
to fifth instars was the dominant species in the infestation, which averaged
27 grasshoppers per square yard in the field and 40 along the margins
(table 2). On June 28 the half cut for hay, and its margins, were sprayed
with toxaphene at the rate of 0.75 pound per acre. Six days later no
evidence of residual action was noted and the riumrber of grasshoppers was
reduced 40 percent. On July 20 and again on July 26 the same half was
sprayed at the rate of 2 pounds of toxaphene per acre. It was fairly windy
on July 20 and only a 30-percent kill was obtained. The poor results were
probably due to the small amount of foliage on the sweetclover stubble.
The total reduction in numbers was 80 percent for the entire 32 acres.
Four acres on the east end of field 9 (fig. 2) was sprayed with 0.75
pound of toxaphene per acre on June 23 (table 2). A 35-percent reduction
in the numbers of grasshoppers was obtained, and no residual action was
indicated after 6 days. The rest of this field to the west, about 22 acres,
was sprayed on the same day at the rate of 1 pound of toxaphene per acre.
A reduction of 80 percent in numbers was obtained, and the residual action
lasted 10 days. On July 13 the entire field was again sprayed at the rate
of 1 pound per acre, because the infestation then averaged 10 grasshoppers
per square yard. On July 30, 4 acres was given a third treatment at the
rate of 2 pounds of toxaphene per acre. As a result of all applications the
infestation was eventually reduced 92 percent.
On the same farm, just 1/4 mile east of field 9, field 11, containing
18 acres of alfalfa and 9 acres of crested wheatgrass and margins, was
sprayed on July 13 with 36 pounds of toxaphene at the average rate of
1.3 pounds per acre. There were 25 to 40 grasshoppers per square yard
in this field, mostly Melanoplus bivittatus adults. The one application
reduced the numbers to 2 per square yard. Since this field was completely
surrounded by open range land, no reinfestation occurred and the one
application was considered sufficient.
In fields 5, 7, and 12 (fig. 2) the first application of the toxaphene
spray was at the rate of 1 pound per acre. Field 5 was first sprayed on
July 6 (table 2), when the alfalfa was 18 inches high and the grasshoppers
were in the last two instars and adult stage. Of the population, which
numbered 40 to 70 per square yard, 78 percent were Melanoplus
bivittatus and 12 percent M. mexicanus. An 80-percent kill was obtained
with the first treatment, the residual action lasting 9 days. A wheatfield
adjacent on the south was a source of continuous reinfestation as the wheat
ripened and was harvested. Two more applications of toxaphene were








:1" de on 12 acres of the margins -d on a barrier across the south end
of the field, 18 pounds on July 15 and 24 pounds on July 25, to obtain the
final 98-percent red-.'ction in numbers.
In field 7 some early spraying of third to fifth instars of Melanoplus
bivittatus and M. mexicanus mexicanus vas done on June 14 and 15 on
6 acres of alfalfa and 10 acres of margins at the rate of 1 pound of toxa-
phene per acre. The residual action lasted 9 days, with 95-percent
reduction in population. Before the spraying there were 15 grasshoppers
per square yard in the alfalfa and 75 alor the margins. On July 18 a
second spray was applied at the rate of 2 pounds of toxaphene per acre
on 10 acres of old alfalfa and also on 12 acres of newly seeded alfalfa
and 2 acres of margins, all of which had not been previously sprayed.
St this time the populations were 15 to 25 per square yard in both the
fields and margins, and all were adults. The field sprayed on June 14
did not need a second treatment. Infestations on this farm were reduced
90 percent by the two applications.
Tests in field 12 were begun on June 9 and 10, when 36 acres of
margins and weedy places were sprayed at the rate of 1 pound of toxa-
phene per acre. Melanoplus bivittatus was the dominant grasshopper and
was in the first to fourth instars. A few first to third instars of
M. mexicanus mexicanus were also present, while M. differentialis was
either just hatching or in the first instar. At this time few grasshoppers
were in the alfalfa on this farm, but the margins and weedy places con-
tained 10 to 300 per square yard. Almost 100-percent kill was obtained
with the first treatment, and the residual action lasted 6 days.
As a result of heavy infestation in the weedy creek bottom and some
infestation in the small grain, field 12 was partially reinfested after the
residual action of the toxaphene had ceased. On July 19, when all the
grasshoppers were adults, 72 pounds of toxaphene was sprayed on 36
acres of creek bottom and field margins and on 6 acres of alfalfa at the
rate of 2 pounds per acre. Most of this area had not been sprayed
previously, and the grasshoppers numbered 50 to 100 per square yard.
This second treatment reduced infestations to 1 per square yard in the
weedy creek bottom, which had been a source of infestation on this farm
for several years. A third spraying of 24 pounds on 12 acres of previously
sprayed margins was made on July 28 to eliminate infestations still
existing on the farm.
Light dosages of chlordane were tried out in fields 4 and 10. On
June 14, 8 acres of the margins of 60 acres of alfalfa in field 4 were
sprayed with chlordane at the rate of 0.5 pound per acre. The grass-
hoppers xrere hatching and the alfalfa hay was being cut. Populations
in half of the field averaged 10 per square yard and 20 to 150 in 1/8 mile
of margin. A 95-percent kill was obtained in the areas actually sprayed,
but 6 days later the residual action had ceased.






On July 1, when !h tif'.2 1: -en rnumbered 25 fr-asshoppers per square
yard in t1- field and 50 in the margins, chlordane was sprayed on the 60
acres of alfalfa and on 12 acres of m.arg;is at the rate of 0.5pound per
acre. Melanoplus bivittatus, in all :'-3'es of development, was the
dominant species. This ap)lication killed 70 percent of the grasshoppers,
and the residual action lasted 8 days. On July 12 another 30 pounds of
chlordane was sprayed on the 60 acres, which then had a population of 15
grasshoppers per square yard. A reduction o; only 65 percent was obtained.
At this time the wheat to the no--.h and the oats to the west had been or were
being cut. Reinfestation from these small-grain fields plus the poor kills
obtained by the light dosages made a fourth spraying necessary on the
margins and parts of the field where the numbers had again increased to
10 to 15 per square yard. On July 25 chlordane was applied at the rate of
1.5 pounds per acre on 24 acres of the south, west, and north parts of the
field. This treatment completed 98 percent reduction of the infestations--
no grasshoppers in the field and only 3 per square yard along the margins.
The treatments enabled the owner to obtain 48 bushels of alfalfa seed from
45 acres of the alfalfa in this field. Dry weather conditions cut his seed
production, but there was no damage by grasshoppers.
In field 10, 16 acres of alfalfa containing 25 to 35 fourth and fifth
instars and adults of Melanoplus bivittatus per square yard were sprayed
with chlordane at the rate of 0.5 pound per acre on June 23. By June 29
50-percent reduction in numbers and some evidence of residual action were
observed. On July 6 the population was 10 to 15 per square yard. On
July 13 a second spray at the rate of 1 pound of chlordane per acre reduced
the infestation to 5 grasshoppers per square yard. At this time a small
wheatfield on the western edge was harvested, and a reinfestation from
this field kept the population in the alfalfa up to 5 per square yard. To
prevent any further reinfestation, the owner sprayed 12 acres of the
western end and margins with 24 pounds of toxaphene. The population
dropped to 3 per square yard for an over-all reduction of 88 percent of
the original numbers. The last two applications were made when all the
grasshoppers were adults.
Better results were obtained and fewer applications were made where
a heavier dosage of chlordane was used in the first application. In field
6, 24 pounds of chlordane was sprayed on 25 acres of alfalfa on the west
side of the farm on July 15. An infestation of 60 grasshoppers per square
yard was mostly Melanoplus bivittatus from the third instar to adults.
The stages indicated a late hatch. The alfalfa was 1-1/2 to 2 feet high,
dense, and beginning to bloom. The one application reduced the numbers
to 3 per square yard--95-percent kill. On July 27, 4 acres of the eastern
edge was sprayed again with 6 pounds of chlordane to take care of a small
reinfestation from a harvested wheatfield in the creek bottom.
Of 100 acres of alfalfa on the east side of the creek in field 6, 10 was
sprayed with 15 pounds of toxaphene on July 14 and 20 acres with 30
pounds of chlordane on July 27, the combined sprays reducing the infesta-
tion 95 percent.









Fields j, 3and 8 wre sprayed at the rate of 1.5 pounds of chlordane
per acre r. alfalfa 1 tJo 2 feeL high afr r the grasshoppers had become
adults.' *The one application was sufficient in fields 1 and 8, but a second
&.,plication was necessary in field 3 because of a reinfestation from a
harvested., wheatfield.
In all tests the lighter dosages of toxaphene or chlordane were not
sufficiently effective. Repeated applications and increased dosages were
essential to save the alfalfa seed crop. Heavier initial dosages, however,
reduce i the number of applications by at least one and gave more satis-
factory results. On an average, three applications were necessary in
fields where light dosages were used at the beginning and only 1.4 in
fields where heavier dosages were used in all treatments.

Effect of Range Land Infestations on Grasshopper Control in Alfalfa

As previously mentioned, one objective of the tests at Crawford was
to study the effect of native grassland infestations on the control of
grnshoppers ir alfalfa. Most of these tests were made in alfalfa
partially or wholly surrounded by native grasslands (fig. 2). The species
of grasshopper collected in four alfalfa fields and adjacent grasslands
are given in table 3.
One alfalfa field, field 5, had a crested wheatgrass pasture adjacent
to it on the west, and beyond this open range land (fig. 2). The grass-
hopper population in the pasture averaged 50 per square yard, mostly
P.geneotettix deorum. but this species was not found in the alfalfa. After
the gr *.-!shoppers in the crop, largely Melanoplus bivittatus and NI.
mexicanus, had been destroyed by the toxaphene spray, the alfalfa was
not reinfested with A. deorum coming from the crested wheatgrass.
The population decreased more or less normally in the pasture--from
50 -per square yard on July 23 to 20 on August 31.
There was no movement of the range species of grasshoppers from
adjacent grass and pasture lands, other than of Melanoplus mexicanus
into fields 3, 4, and 6 (table 3 and fig. 2), and none of these grass or
pasture lands were sprayed. The populations in the native grassland in
*-he respective fields were 15, 16, ar'3 10 per square yard when spray
operations were begun in the alfalfa. The species in the alfalfa fields
had rnoved in considerable numbers from 3 to 6 rods into the adjacent
Lr islands. They continued to move back into the alfalfa until they were
all killed by the residual action of the spray and only the range species
werce left in the grass.







- 15-


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- 16-


Organic Chlorine in Straw From Seed Alfalfa

To determine the residues from the chlor-lane and toxaphene sprays
in threshed straw from seed alfalfa, samples from sevei i- treated fields
and from two fields that had not been sprayed were analyzed for organic
chlorine, as shown in table 4.- Ten samples were taken from each field,
and from field 6 ten additional samples from the areas treated with both
chlordane and toxaphene. In fields 3 and 4 and in a field treated by a
farmer himself all samples were taken from a single stack, in field 5 five
samples from each of two stacks, and in field 6 two samples from three
stacks and four from a third stack.
Because field spraying included marginal and strip spraying the coverage
was uneven. The greatest difference in residues was in field 5. One of the
two stacks contained most of the straw from the south end of the field., which
hadbeen sprayed most heavily. The average amounts of organic chlorine
from all fields ranged from 4 to 11 p.p.m., the highest for any sample was
26 p. p.m.
The organic chlorine analyses were made on aliquots representing 120
grams of alfalfa. Samples from two unsprayed fields, analyzed by the same
technic, did not show a measurable quantity of organic chlorine in excess of
that found in the reagent blank.

DISCUSSION

Grasshopper infestations in alfalfa and adjacent fields, field margins,
and waste areas in a solid block of farm land can be reduced 90 to 100
percent in a single season by the use of toxaphene ).r chlordane sprays.
This reduction persists through at least 2 years. Small local infestations,
however, may materialize in bad years in spite of excellent control the
first year. Although these infestations may cause little injury to the
current crop, they are an incipient source of reinfestation and should be
destroyed.
An alfalfa field that is a source of infestation should be sprayed at
least once. The application should be made after the first cutting of hay
has been taken off the field and before the new growth is more than 6
inches high. By that time most of the grasshoppers will have hatched.
Failure to recognize the significance of an inconspicuous infestation of
10 or move first- and second-instar nymphs per square yard, or failure
to spray an alfalfa field because of inclement weather, preoccupation
with other farm work, or mere neglect before the pests have grown and
spread widely through the field, may allow a two- or three-fold increase
in the area of infestation.


2/ These determinations were made at the Vincennes, Ind., laboratory
of the Division of Insecticide Investigations.





-17-


Table 4. --Organic chlorine in straw from seed alfalfa from fields sprayed
with chlordane or toxaphene. Crawford, Nebr.



Organic chlorine
Total from 10 samples
Field Number of Area insecticide per field
applications treated per acre
Range Average


Acres


Pounds


P. p.m.


P. p.m.


Chlordane


1.5
3
1
2.5
1


8-23

3-10
1-9


Toxaphene


Sprayed by
farmer


Toxaphene and Chlordane


1 (toxaphene)10
1 (chlordane)


1
2.5
4.5

1.6
2.9


1-26



5-9


2-7





- 18 -


After the initial treatment of an alfalfa field it is usually necessary.
to spray the margins and parts of the field one or more times to protect
it from reinfestation, which comes chiefly from small-grain fields adjacent
to alfalfa. Infestations in these fields are often unnoticed and of no con-
sequence to the crop itself, but when the grain is cut and the grasshoppers
move into a much smaller acreage of alfalfa their numbers become
serious. Barriers against reinfestation from the outside may be made
by spraying weedy fence rows or border strips 4 to 10 rods wide within
the field.
The range-land species that were numerous in the grasslands near
Crawford, Nebr.--mostly Ageneotettix deorum, Amphitornus coloradus,
and Mermeria maculipennis Bruner--did not leave the grass for the
alfalfa even after the grass had dried up. However, some Melanoplus
mexicanus grasshoppers did move from adjacent range land into the
alfalfa, where they were destroyed by the residual action of the sprays.
Controlling such species as M. mexicanus, M. bivittatus, and M.
differentialis, which normally infest cultivated crops, v.-as the main
problem in protecting alfalfa from grasshoppers.
In both the Buffalo Gap and Crawford areas it was demonstrated that
weedy places close to a crop which harbor severe infestations nearly
every year can be sprayed so effectively that alfalfa fields are not re-
infested from them for at least 2 years.
The best results against grasshopper nymphs early in the season were
obtained when 1 pound of chlordane or 1.5 pounds of toxaphene per acre
was used. When the grasshoppers were adults, the best results were
obtained when the dosage was increased to 1.5 pounds of chlordane or 2
pounds of toxaphene per acre. Although these were not the minimum
effective dosages, they were found to be the best, because they had a
longer residual action and would give practical control under most
conditions. Lighter dosages made it necessary to increase the number
of applications to a point where the total quantity of spray used to protect
a field was equal to or greater than that used when heavier dosages are
applied in the first treatment.
Heavy rains seemed to have little effect on the residual action of
either spray, unless they fell within an hour after the spraying. Winds
up to 15 miles an hour during spray applications did not seem to affect
the results in tall vegetation and even helped to distribute the spray,
but in sparse or short vegetation best results were obtained when the
air was quiet.
The results were not so good in vegetation that had dried up or lost
its leaves so that only bare stems were present to catch the spray.
Succulent vegetation seemed necessary for best results.
Two main difficulties were observed in the farmer use of the sprays:
(1) Many farmers were unable to calibrate spray equipment so as to
obtain the proper dosage because of the lack of information concerning









the quantity of chlordane or toxaphene contained in 1 gallon of the different
commercial spray concentrates; and (2), most farmers seemed unable or
unwilling to recognize, appraise, and control any type of grasshopper
infestation before crop damage became apparent.
Organic-chlorine analyses showed that residues were present in the
straw from seed alfalfa that had been sprayed with either chlordane or
toxaphene. The greater the total amount of insecticide used on a field the
more organic chlorine was found in the straw.

Caution. --Straw from fields treated with chlordane or toxaphene should
not be fed to dairy animals, to meat animals being finished for slaughter,
or to poultry.



LITERATURE CITED

(1) Shotwell, R. L.
1949. The comparative effectiveness of poisoned bait and sprays
for grasshopper control in Lyman County, S. Dak., 1947.
U. S. Bur. Ent. and Plant Quar. E-771, 22 pp.










*


















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- 19-








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1P'i&:, 1. --Seed-alfalfa areas in various sections near Buffalo Gap, S. Dak.,
spircayed with chlordane or toxaphene for the control of grasshoppers, 1943.


























P6tuLre A lfalfa

I-------- --
Sweet Pafute




Paf.ure


Fo l low

Ii




Gr.....'




Gross
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H o g - J i - - .
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Section Lines or Tes+ Area Limits
<;sCreeks --- Field Margins E3OArea Sprayed
(9) Field Numbers


Figure 2. --Fields of seed alfalfa near Crawford, Nebr., sprayed with chlordane
or toxaphene for the control of grasshoppers, 1949.


~f~ree





'Corn
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I.
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,-,


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