1951 Weaver the seasonal behavior of meadow spittlebug and its relation to a control method

350
Table 5.-Summary
indicated.
of greenbug
field tests
showing percentage
TEsT 1
TREATMENT
Dosage1
Per Cent
Control
48 Hours
Mter
Treatment
.81
66.6
.8il
.5ft
89.8
90.4
l' Benzene
l' Benzene
Hexachloride Spray
Hexachloride Dust
Parathion Spray
Parathion Dust
Tetraethyl Pyrophosp~ate
Spray
Tetraethyl Pyrophosphate
Spray2
Pounds active ingredients per acre.
Spray applied
when temperature
was lower than
when other
"knockout." Parathion and tetraethyl
pyrophosphate probably did give sufficient control to enable predators and
parasites with favorable conditions to
restore the natural balance and prevent
another damaging increase of the pest.
One field test indicated that parathion
had greater residual toxicity than tetraethyl pyrophosphate but observations
indicated that tetraethyl pyrophosphate
was less toxic to ladybird beetles, important predators of greenbugs, than parathion. The degree of control obtained
TESTil
Dosage
Per Cent
Control
48 Hours
Mter
Treatment
.38
.44
81.6
75.6
.11
.85
86.8
97.4
applications
TEST 3
Pcr Cent Control
IIours After
Treatment
Dosage
48
168
.'l8
6't.6
77.8
.19
76.0
tl9.4
.'l7
.5't
87.6
94.4
85.8
tl8.4
.'l6
61.3
58.5
were made in same experiment.
with insecticidal applications seemed to
depend to a large extent on the loeatioIl
of the aphids on the plants when the material was applied. This was espeeially
true when there was a mat of dead leaves
at the base of the plants to shelter them.
Low temperature seemed to be the most
important factor in causing these insects
to seek shelter. Sprays were mueh more
practical than dusts for greenbug control
because they could be applied effectively
when the wind was relatively high.
LITERATURE
J.
control following treatments
CITED
C. and H. A. Dean. 1950. Effect of climatic factors on the toxicity of certain insecticides.
ECON. ENT. 43: 60il.
JOUR.
The Seasonal Behavior of Meadow Spittlebug
and Its Relation to a Control Method
C. R.
WEAVER,
Ohio Agricultural Experiment Station, Wooster
The control of nymphs of the meadow
spittlebug, Philaenus leucophthalmu8 (L.),
by springtime applications of insecticides
has some undesirable features that under
some conditions prevent the legume
grower from applying measures to reduce
the damage done by these insects. Forage
crop legumes grown for silage and for
dehydration into meal are often cut early
so that the harvest date comes too soon
after the most timely date for effective
applications of insecticides. Under any
conditions in which the application of
insecticides is unacceptable because of
the residue hazard, present control meth-
ods should not be applied.
Late April and early May are usually
busy times for the general farmer and
weather conditions often limit the use of
ground spraying or dusting equipment in
legume fields at that time. With these
facts in mind the author presents the following biological observations as being
of interest to those concerned with alternate methods of control of the meadow
spittlebug.
The spittlebug apparently does not lay
its eggs indiscriminately in fields of forage
legume crops of different ages. Observations by the writer have revealed that
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1
2
Gaines,
Vol. 4.4, No.3
JOURNAL OF ECONOMIC ENTOMOLOGY
June 1951
351
WEAVER: CONTROL OF l\IEADOW SPITTLEBUG
. Table I.-Mean
number of well formed eggs
dissected from each of 10 female spittlebugs.
NUMDEU OF EGGS
DATE
PER FEMALE
August 24
September 1
September 11
September 13
October 2
October 19
November 2
3.2
10.5
~O.6
~O.6
17.7
20.2
21.1
within a few days so that the check and
treated populations soon equalized. It
must be remembered, however that such
applications have been made t~ seed fields
and not to the newly seeded meadows
which will receive the major infestation
the following year. During June and
July, the n~w meadow is covered with a
grain crop which is not removed until
July and ~ometimes early August. Except
for tranSIent hordes of newly emerged
adults in June, migrating away from the
newly cut first year fields, the grain fields
have few adult insects present until the
ne.w legume seeding starts to produce a
faIr!y abundant foliage. Figure 1 shows
typIcal adult populations in a first year
meadow and in a new seeding. During
late July and August the adults will be
found in largest numbers in meadows
wher~ the vegetation is flourishing. The
data m the figure were taken from a field
left for a seed crop where there is a natural
decline of green succulent foliage as the
season progresses. Plants in the new seedings recover from the grain harvest sometime during August, depending upon
whether or not the grain stubble is clipped
and removed. As the foliage becomes more
luxuriant, the adult numbers gradually
increase until about the first of September, when there is a tremendous increase
suggesting that large numbers of adults
are migrating into the newly seeded fields.
The author's experience with spraying
for adult spittlebug control has paralieled
that reported by other workers. Sprays
applied in June, July, and August m~y
result in large initial reductions, but in
te!l days ~otwo weeks an almost complete
rcmfestatlOn rcsults. New secdings with
sprays applied in early August show tIle
same tendency to reinfestation as do old
I First, second, and third ~'ear designations
cate the year or harvest.
arc applied to indi-
Downloaded from http://jee.oxfordjournals.org/ by guest on June 6, 2016
in northl.'rn Ohio thl.' insect usually does
not appear in I.'conomically important
numbprs in sl.'cond and third year meadows..1 The important damage is usually
done m thl.'first year fields. This indicates
that thl.' bulk of thl.' I.'ggs must be deposited in tht' nt'w st'e-dings.
To obtain data on the comparative
populations in the first, second and third
ye-ar fidds, sWl.'epsamples ~ere taken
from such fields on June 12 when a large
perce-ntage of the adult insects had
ellll.'rge-dfrom the spittle masses and
migration frOl~l the field had not yet
startl.'d. In .thls case, the plots sampled
were a pOl'tlOnof a field rotation eJ\:periment and were locatt'd side by side in
blocks so that during the previous year
tl~(' adults would havt' had an opportuIllty to lay I.'ggsthroughout the block uniformly. The adult populations as measured by the swe-e-psshould be indicative
of thc rdativc number of eggs placed
the-re the ye-ar bdore-. Adult spittlebugs
pe-r swe-e-pof a 15 inch net for the three
type-s of ml.'admv wl.'rl.':first year, 18.1,
sl'eond ye-ar,2.9, and third year, 0.9. This
indicate-d an owrwhelming tendency for
lhe populations to occur in the first year
meadow.
l\Iundingl.'r (1946) states that on grass
Philaenllsleucophthalmus
commonly places
the I.'~gmass in the axil betwecn leaf and
st(,Ill and C('lll('nts the leaf over it. The
tl.'lllklley to lay t'~gs in crevices between
plant portions makes wheat and oat stubble an ideal egg laying medium. The
author has obse-rved that eggs are most
readily found on grain stubble and only
oeeasiollally on legume stubble and gree;"
plant parts. The eggs are inserted between the dead leaf sheath and the stem.
If the grain stubble serves as a more attractive oviposition site, then the first
y:ar meadows, seeded to grain the prenous Yl.'ar,would be most likely to recpive the majority of the eggs.
Reduction of the succeeding year's
nymphs by control of the adults has not
prt'sented a promising approach to the
eoutr?l problem bl.'causeof the rapid reinf('statIon ?f treat.ed fields. Wilson (1949)
reported httle resillual effect of DDT upon
adults four wel.'ks aIte-r treatment applied on July 12. l>ielou (1950) showed
immediate reductions of adults bv DDT
applications in .Junc and Julv 'but in
ncarly every case reinfestatiOI~'occurred
352
U)
z
..
AVGusr
1<'IG.
J '0/. 44, Xo, :1
JOURNAL OF ECONOl\IIC ENTOMOLOGY
I.-Spittlebug
SEPT£MSER
OCT()8ER
populations in two Iegullle
fields.
~
.8
:::
a.
.6
It
4
:;J...
.2
..
...
1949
TReATED 8.19
9-2
TREATED
12
.,
24
•
12
·Ie
24
,
IE
II
Z
=>
o
...•
~
...•
1.0
8
:=
.6
~
4
~
2.
1950
Q!
Ie
'I
AUGUST
FIG.
14
•
It
II
t4
SEPTEMBER
•
It
II
OCTOBER
~.-Time of treatment and recovery of
spittlebug populations.
Ratios from three sprayed populations in
1950 and two in 1949 arc shown. In 1950,
the population in the plots treated August
9 soon recovered to equal that of the
check. Populations of plots treatel[ on
September 2 and 13 never recovered. In
1949, the data from figure 2 show that
adult spittlebug populations in plots
treated on August 19 reeovcred to :some
extent but never equalled the eheek
while those treated on September 2 neVl'r
recovered.
Because of the distributional nature of
the ratios involved, ordinary statistical
tests of the recovery rates arc not applicable. Mr. Paul ::\loranda, Statistical Laboratory, Ohio State University,l suggested and applied a non parametric test
described by Mann (1945). Two uses arc
made of this test. The first is for detecting
whether or not the ratios of tl'eatell and
untreated populations associated with a
fixed interval of time after the spray date
(e.g. 1-10, 11-20 ... 61-70 days after the
spray date) decrease as the date of spraying becomes later. The second usc of the
test is for detecting whet.her or not for It
given field the ratios tend to increasl' with
time following treatment.
According to Mr. l\foranda's computation and interpretation there was evidence of a downward tn'nd in ratios associated with a fixed inten'al of time afte!'
the spray date as the date of spraying
Theassistance
ofDonald
R. Whitneytheslutiulie.llr"ulmentisgratefully
aeknowledged.
1
ill
Downloaded from http://jee.oxfordjournals.org/ by guest on June 6, 2016
and the field
will not become reinfested. The adults
apparently move over large areas during
the period prior to September. After their
migration into new seedings where the
eggs are to be laid they do not move about
enough to cause serious reinfestations of
plots from which th('y have b('('n eliminat('d.
Data to support the belief that spittlebugs readily infest fields treated in August
and do not reinfest fields treated during
September were collected from three fi('lds
in each of the years 1949 and 1950. All
tests were replicated in randomized blocks
with plot sizes of 100 by 100, 200 by no,
70 by 90, 90 by 90, and 50 by 100 feet.
Treatment dates in 1949 were August 8,
19,30 and September 2 and 19. Treatment
dates in 1950 were July 27, August 10, 12,
and September 2, 3, 13, and 20. The effectiyc insecticides used were DDT and methoxychlor at concentrations varying from
1 to 2 pounds of the technical material per
acre. Both materials gave good initial reductions of the adult populations. Sweep
samples were obtained from both treated
and untreated plots at varying int('rvals
of time aft('r treatment. Most plots were
swept weekly through October, although
the time interval varied due to the
weather and other factors. At least 50
and usually 100 sweeps were made in each
treatment at ('ach sampling.
The ratio of populations in the treated
plots to those in the untreated plots ,vas
then computed and the increase in this
ratio used as a measure of reinfestation.
To conserve space, only a typical portion
of the data is pres('nted. In the graph
(Fig. 2) the ratios of treated to untreated
populations are plotted against time.
I
~
II:
o
will reduce the population
CHECK.
....
I-
lll('adows. Data collected in 1949 and
19.50 at 'Vooster, Ohio, show, however,
that an application of insecticide during
the last week in August or in September
1.0
June
1951
"rEAVER:
CONTROL OF l\fEADOW SPITTLEBUG
353
to August 24. On August 24 a total of 32
well formed eggs were found within 4 of
10 females dissected. Table 1 shows the
numbers of ('ggs found on seven different
dates.
Apparently maximum egg development
is reached during the first 10 days in
September and is maintained until cold
weather kills the insects. Probably no
oviposition occurs prior to the development of filature eggs, therefore it seems
reasonable to assume that adult female
spittlebugs do not lay substantial numbers of eggs until September under
Northern Ohio conditions.
Since the development of eggs of the
spittlebug is coincident with the lessening
nomadic activity of the insect, one insecticide application, timed to take advantage
of these events, should result in good control of the species by reducing the number
of eggs laid and the subsequent nymphal
infestation the following spring. The efficacy of such treatments will be reported
in another paper.
SUMMARY.-cndernorthern Ohio conditions, heavy populations of adult spittlebugs build up in newly seeded legume
fields during the last of August and the
first of September. The majority of eggs
are laid in the newly seeded fields which
have a residue of straw and stubble from
the grain harvest. Control measures applied to fields prior to the September
build-up are ineffectual because of reinNew York.
The author has never observed spittle- festation from surrounding untreated
bug eggs in the field prior to September. areas. Little or no reinfestation occurs if
The fact that none w{'reobserved docs not insecticides are applied after the last of
('onstitute proof that they are not present August. The development of eggs within
in the field before that time. Dissections the female is simultaneous with the adult
of adult females were made by the author migration into the new seedings. These
during th{' summrr and fall of 1950 to facts should be useful in timing the treat(lrtermine when the eggs developed within ment of fields containing egg laying adults
the female. No welI formed eggs were as a means of reducing the resulting
found within any dissected females prior nymphal populations.
LITERATURE
CITED
Mann, H. B. 19·'5. l'\on parametric tpsts against trend. Econometrica 13(8): 245-59.
Mundinger, F. G. 1946. The control of spittle insects in strawberry plantings. JOUR. EeON. ENT.
39(S): ~99-S05.
Osborn, Herbert. 1916. Studies of life histories of frog hoppers in Maine. :Maine Agr. Expt. Sta. Bul.
254.
Pielou, D. P. 1950. The effect of insecticide applications on the insect fauna and seed yield of alsike
e1oVl'r in southern Ontario. Can. Ent. 82(7): 141-60.
Wilson, M. C. 1949. Orglmic insecticides to controlllifalfa insects. JOUR. EeRN. ENT. 42~8): 496-8.
Downloaded from http://jee.oxfordjournals.org/ by guest on June 6, 2016
brcoJlles later. An exception to this occurr{'d. No downward tr{'nd was noted
in the interval of tinw 1 to 10 days following treatn1f'nt. This indicat{'d that all
the treatments probably reduced the populations to about the same level and that
this level is maintained for a short time
after treatnwnt.
The second usc of the test showed an
upward tr{'nd in the ratios, indicating
that reinfestation occurred, in the fields
sprayed August 19 or before. Fields
trcatrd August 30 or later showed no such
tr{'ud. lJolh applications of the test support the ('oujeeture that the later the
spray date thc less reinfestation of the
plols.
The fact that adult spittlebug populations can be reduced and maintained at
a low levrl by one application of insecticide in late August or early September
would b{' of no practical value if substantialnumbers of the eggs of the insect were
laid prior to that time. Osborn (1916) did
not observe any spittlebug eggs being
laid through the month of August in
Maine. lie stated that well developed eggs
\wre not found in dissected specimens before August and that by the middle of
August only occasionally are eggs with
well formed shells to be found within the
females. Mundinger (1946) reported that
oviposition began in July but was most
int{'nsivc in 5f'pt{'mber and October in