United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
INSECTICIDE DUSTS TO CONTROL THE CLOVE ROOT BORER
AND THE MEADOW SPITTLEBUGT
By B. A. App and Ray T. Everly,.- -3/
Division of Cereal and Forage Insect Investigations
The clover root borer (Hylastinus obscurus (Marsh.)) has been
recognized as an important pest of red clover for many years. During
the last three seasons considerable numbers have been observed in red
clover fields in Ohio, and a large percentage of the roots in second-year
red clover fields have been infested. The control of this root borer with
insecticides has been difficult because of the protected location of the
larvae within cavities or tunnels which they gnaw in the roots. During
the last few years, however, treatment with the new organic insecticides
has given very encouraging results. Experiments conducted by Marshall
e l. (1) in 1946, 1947, and 1948 showed that technical benzene hexa-
chloride at 1.5 pounds of the gamma isomer per acre gave excellent
control of the clover root borer.
1/ This research was conducted at the Legume Seed Research
Laboratory maintained by the Bureau of Entomology and Plant Quarantine
and the Bureau of Plant Industry, Soils, and Agricultural Engineering, in
cooperation with the Ohio State University and the Ohio Agricultural
Experiment Station. The studies were made at the Ohio Hybrid Seed Corn
Producers research farm at Croton, Ohio.
2/ Resigned June 30, 1948. Now associate in entomology, Purdue
Agricultural Experiment Station, Lafayette, Ind.
3/ The authors appreciate the cooperation of John G. Dean, Jr., of
the Bureau of Plant Industry, Soils, and Agricultural Engineering, A. W.
Woodrow, of the Bureau of Entomology and Plant Quarantine, and Ralph H.
Davidson, of the Ohio State University. Theodore Davich and Elbert L.
Sleeper, of the Bureau of Entomology and Plant Quarantine, and Russell
Secrest, of the Bureau of Plant Industry, Soils, and Agricultural Engin-
eering, assisted in the field work. Richard M. Hiatt, of the Ohio State
University, assisted in the application of insecticides and calculated the
seed yields in 1948.
Since 1947 experiments have been carried on at Croton, Ohio, with
dilute dusts of various insecticides applied to the plant crowns and surface
of the soil in plots of young clover. Applications in the fall to first-year
clover or in the spring to second-year clover have been tried.
The tests were planned primarily to control the clover root borer, but
it was noted in the spring of 1948 that some of the treatments had provided
excellent control of the meadow spittlebug (Philaenus leucopthalmus (L,)).
This insect has been very abundant in Ohio legume fields for several years.
During the 1948-49 season data were taken to determine the possibility
of controlling these two important red clover pests with the same
Red clover is usually seeded in the spring as a companion crop of
wheat or oats. The clover continues to grow after the grain crop is
harvested, but as a rule no clover hay or seed is gathered the first season.
In the second year after planting a hay crop is cut in June and either a
second hay crop or a seed crop is harvested in August. The clover root
borer infests red clover in the spring of the second year. When the in-
festation is heavy, many plants are so weakened that they do not recover
after the June hay crop is cut. The stand remaining for the seed crop or
for second-crop hay is thus much reduced. The meadow spittlebug also
attacks second-year clover. Severe infestations stunt plant growth and
cause general loss of vigor.
Tests Conducted During 1947-48
During 1947-48 DDT, benzene hexachloride, and chlordane dusts were
tested in four replications of 9- by 12-foot field plots of red clover
arranged in a randomized block. The dusts were applied with a hand
fertilizer spreader that treated a strip of clover 36 inches wide. Each
insecticide was applied seven times, and one set of plots was left un-
treated to serve as a check. DDT and chlordane were applied at the rate
of 500 pounds of a 1-percent dust per acre. In the fall treatments
technical benzene hexachioride %kais used at the rate of 100 pounds of dust
containing 1 percent of the gamma isomer and in subsequent treatments
at 500 pounds of a dust containing 0.25 percent of the gamma isomer.
Sampl,-. of roots were dug and dissected in the field during the period
August 18-24, 1948. On each digging date three roots were dug from
each of five points in each plot. If by chance more than three roots were
dug, they were also examijied and recorded. The results of these
treatments are given in table 1.
An: analysis of the data by the variance method showed that, when
compared with untreated plots, there wa.s significant reduction in the
percentage of infested roots from all treatments with technical benzene
hexachiloride' and chlordane. Applications of DDT did not cause any
marked rei(duction in the percenlige of roots infested. In this test the
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differences caused by the time or number of applications were not
signi,-cant. However, a single application of any of the materials in the
spring was slightly more effective than single applications the previous
August or September. Furthermore, plots given both a fall and a spring
treatment of technical benzene ht'xachloride or chlordane contained fewer
infested roots than those given only one treatment.
On August 19, 1948, clover on 2 square yards from each plot was cut
and threshed to determine the seed yields. An analysis of the data showed
that none of the differences were significant, because there was so much
variation among the samples from the different plots. The yield of clover
seed was slightly higher from most of the treated plots than from the
Tests Conducted During 1948-49
In the tests conducted during 1948-49 a randomized-block arrange-
ment was used, the size of the plots was increased to 9 by 18 feet, and
the treatments were replicated five times instead of four. In addition to
the materials previously tested, parathion, toxaphene, methoxychlor, and
aldrin were used in the spring tests. All the materials were applied as
dilute dusts with a fertilizer spreader in the same way as in 1947-48.
One set of plots was treated on September 13, 1948, a second set on
May 3, 1949, and a third set on both dates. A set of untreated plots was
maintained as a check.
Samples of roots were dug and dissected during the period August 15-17,
1949, to determine the effect of the treatments on the clover root borer
population. As in the previous experiment, three roots were dug at each
of five points in each plot. On each digging date an equal number of roots
was dug from each plot.
Of the materials applied on September 13, 1948 (table 2), by far the
large ..t reductions in number of borers per root were caused by benzene
hexachloride and chlordane. Parathion and DDT were much less effective
at the di.sages used.
For the different treatments applied May 3, 1949, the descending
order of efficiency at the dosages used was chlordane, aldrin, technical
benzene hexachloride, parathion, toxaphene, methoxychlor, and DDT
(table 2) Parathion averaged 0.87 borer per root when applied as a
spring treatment, as comI J red with 3.39 borers when applied in the fall.
Two applications, in the fall and in the spring, were not more effective
than a single application in either fall or spring. Excellent control was
obtained with chlordane, benzene hexachloride, and parathion. Judging
from th, r, ults, however, it seems probable that the effectiveness of
parathion was derived mainly from the spring application. DDT was
o:t pa a tixve1y ineffective.
Table 2. --Effect of various insecticides applied to red clover in
September 1948 and May 1949 on populations of the clover root borer
in August 1949
Active Average Total Reduction
Insecticide ingredient Roots borers borers in total
per acre infested per root in sample population
Pounds Percent Number Number Percent
Applications on September 13, 1948
None --- 76 5.88 441 ---
DDT 5 83 5.17 388 12.0
gamma isomer 11/4 1 .03 2 99.5
Chlordane 5 13 .21 16 96.4
Parathion 5 69 3.39 254 42.4
Applications on May 3, 1949
None --- 76 5.88 441 ---
DDT 5 57 3.89 292 33.8
gamma isomer 11/4 16 .81 61 86.2
Chlordane 5 15 .33 25 94.3
Parathion 5 24 .87 65 85.3
Toxaphene 5 40 2.15 161 63.5
Methoxychlor 10 61 2.93 220 50.1
Aldrin 2 16 .43 32 92.7
Applications on both dates
None --- 76 5.88 441 ---
DDT 10 64 4.21 316 28.3
gamma isomer 21/2 4 .04 3 99.3
Chlordane 10 0 0 0 100.0
Parathion 10 12 .43 32 92.7
for significance 19:1 16 1.56 ---.
99:1 21 2.07 ---
There was only a fair stand of clover in any of the plots. Examination
,,.st after the hay was cut showed less than 50 percent of a stand. A good
many plants died after the first cutting, and many of the others made very
poor recovery. This mortality was believed to be due largely to clover
diseases. The field also lacked pollinators, because an adjacent field of
white sweetclover attracted the honeybees away from the red clover. There-
fore, no seed was harvested from this field by the grower, and it was impos-
sible to take samples from which reliable yields of seed per acre could be
An attempt to obtain some information on the effect of the clover root
borer or. seed production was made by harvesting all the heads from a
10-stem sample taken at random in each plot and dissecting 10 heads in
e.,ch sample to determine the average number of florets per head and the
percentage of florets producing seed. To determine the average number
of seeds per head all the heads in the 10-stem sample were threshed and
the seeds counted. None of the differences recorded proved to be signif-
icant, but some of the results were interesting. In all the treated plots
except those where DDT or methoxychlor was used there was a slight in-
crease in the number of florets per head over untreated plots. Regardless
of the date of application, the heads taken from the plots treated with benzene
hexa chloride had more florets than those taken from plots treated with other
materials. Heads from some of the treated plots showed a larger percent-
.,'e of florets producing seed than heads from untreated plots. The samples
of clover from the treated plots showed a higher average number of seeds
per head than those from untreated plots (table 3).
Effect on the Meadow Spittlebug of Insecticide Treatments for
Control of the Clover Root Borer
In the .-pring of 1948 it was observed that certain of the treatments
for the root borer had given good control of meadow spittlebug nymphs.
Benzene hexachloride applied in August and September 1947 at the rate
of 1I4 ,pounds of the gamma isomer per acre reduced the nymphal pop-
ulaio of spittlebugs the following May by 97 percent, and DDT at 5 pounds
per, are reduced it by 76 percent. Applications in May 1948 of benzene
hexachloride a!.d DDT at the same rates and of chlordane at 5 pounds per
acr e gave practica',y 1.v .O percent control of spittlebug nymphs.
During 1949 more detailed data were taken to determine the possibility
of c(ontrollinrg both the clover root borer and the meadow spittlebug with
the same treatment. On May 12, 25 stems were selected at random in
each plot. The stems were examined and the number of spittlebug nymphs
was reorded. As a result of the previous fall treatments technical benzene
htxahloride, chlordane, and DDT reduced the spring population of spittle-
bug nyi;, 99.2, 95i.5 and 83 percent, respectively. Spring treatments
with all these materials were 99 to 1,(I percent effective, as were the treat-
m enits in 1oth fall anid spring. There is therefore no advantage in treating
the same plots in ,,,th the fall and spring. Parathion, of no value as a fall
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treatment proved 87 percent eff, tive as a spring application. Methoxychlor,
aldrin, and toxaphene, tested only in the spring, furnished excellent control.
The results of these tests indicate that the same treatment will cr-ntrol
both the clover root borer and the meadow spittlebug. From the standpoint
of harmful residues in the June hay crop, fall applications would probably
be preferable, but applications late in April or early in May should be
made 4 to 6 weeks before the hay is cut, and because the plants are very
small at this time it is believed little treated foliage should be included in
that ,ut for hay. Information is needed on the insecticide residue hazard,
if any, as well as more data on the most effective and economical dosages
and methods of application. The danger of causing off flavor in vegetable
root crops subsequently grown in soils that have been treated with benzene
hexachloride must also be considered.
Replicated experiments for control of the clover root borer (Hylastinus
obscurus (Marsh.)) were conducted at Croton, Ohio, during 1947-48 and
1948-49, in which surface applications of dilute insecticide dusts were made
with a hand fertilizer spreader. DDT, benzenehexachloride, and chlordane
were tested in 1947-48. In 1948-49 the same materials and also parathion,
toxiphenv, mrnethoxvchlor, and aldrin were used.
Results obtained from the 1947-48 tests indicated that both technical
benzene i-n xachloride at 1 1/4 pounds of the gamma isomer per acre and
chlordane at 5 pounds per acre, applied in either the fall or the spring,
gave excellent control of the clover root borer. DDT at 5 pounds per acre
was not effective. Data fr.,m plots receiving both a fall and a spring
treatment showed no advantage over a single fall or spring treatment.
Similar results were obtained in 1948-49. Aldrin at 2 pounds and
parathion at 5 pounds per acre, applied early in May, also gave excellent
control, but methoxvchlor at 10 pounds, toxaphene at 5 pounds, and DDT
at 5 pounds per acre were ineffective.
(,]d samples taken in 1948 a 'id I949 showed that the treatment in-
rea sd the yields only slightly, if at all. However, the fu'.l impact of the
lss rf s +ed due to clover root borer attack would not be evident in these
>i dui to a lack of pollinators and also to poor stands .-I'ociated with
the orepealent c lover diseases,
ThI root borer treatments also t7 ave excellent control of nymphs of
the meadow spittlebug (Philaenus leucopthalmrus (L.)), which have been
very numerous in red clover fields in Ohio for several seasons. All the
atl rials that were effective against the clover root borer as either a
fall (Wa spring treatment were effective ag.iintst spittlebug nymphs. The
d(Lita Ininde; that these two important red clover p.ests may be controlled
b the sane treatment.
(1) \arsh l, I).S., NIwsome. L. D. G ri-,co, G., and Schwardt, H. H.
4'4 (5 eptr 1 of the clover r,,,,t borer. Jour. Econ. Ent. 42: 315-318.