The Insect pest survey bulletin

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Material Information

Title:
The Insect pest survey bulletin
Physical Description:
v. : maps ; 26 cm.
Language:
English
Creator:
United States -- Bureau of Entomology
United States -- Bureau of Entomology and Plant Quarantine
Publisher:
Bureau of Entomology, U.S. Dept. of Agriculture
Place of Publication:
Washington, D.C.
Publication Date:
Frequency:
monthly, mar-nov. plus annual[1926-]
monthly, apr.-nov.[ former 1922-1925]
monthly, may-nov.[ former 1921]

Subjects

Subjects / Keywords:
Insect pests -- Periodicals   ( lcsh )
Entomology -- Periodicals   ( lcsh )
Genre:
serial   ( sobekcm )
federal government publication   ( marcgt )

Notes

Dates or Sequential Designation:
Vol. 1, no. 1 (May 1, 1921)-
Numbering Peculiarities:
Vol. 14, no.9 issued only as a supplement..
Issuing Body:
Vols. for May 1, 1921-1934, issued by the U.S. Bureau of Entomology; 1935- by the U.S. Bureau of Entomology and Plant Quarantine.
General Note:
"A monthly review of entomological conditions throughout the United States" (varies slightly).
General Note:
Includes annual summary starting in 1926.
General Note:
Includes some supplements.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030368280
oclc - 08816534
lccn - sn 86033699
Classification:
lcc - QL1 .I56
System ID:
AA00023228:00097

Table of Contents
    Front Cover
        Page i
        Page ii
    Trial surveys of chinch bugs in hibernation, November 1934 to March 1935
        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
        Page 109
    Back Cover
        Page 110
Full Text






THE INSECT PEST SURVEY

BULLETIN


Volume 15 Supplement Number 3


BUREAU OF

ENTOMOLOGY AND PLANT QUARANTINE

UNITED STATES

DEPARTMENT OF AGRICULTURE

AND

THE STATE ENTOMOLOGICAL

AGENCIES COOPERATING


STATE PLANT RAfARn


1 ,
















Digitized by the Internet Archive
in 2013










http://archive.org/details/insectl1935no33








INSECT PEST SURVEY BULLETIN


Vol. 15 Supplement :o.



TRIAL SURVEYS OF CHINCH BUGS IN HIBERNATION, 0C'EsZR 1934 TO MARCHff 1935

By C. M. Packard, C. Benton, and Staff of West Lafayette, Ind., Laboratory,
Division of Cereal and Forage Insect Investigations,
Bureau of Entomology and Plant Quarantine,
U. S. Department of Agriculture


Purpose of Surveys

The studies reported herein were made during the winter of 1934-35
in the vicinity of Lafayette, Ind., to gain information on winter survey
methods and to obtain estimates of chinch bug abundance in hibernation quar-
ters for comparison with surveys of the same areas at other times of year.
The ultimate objective is to determine the comparative practicability and
dependability of fall surveys in standing corn, winter surveys in hiberna-
tion quarters, and spring surveys in small grains, as bases for forecasting
chinch bug abundance in corn the following summer.

Method of Sampling

For the purposes of this study it appeared essential that the total
number of bugs present in each s-m-ile be determined. Therefore, on account
of the large numbers of bugs and large amount of material contained in
square-foot samples, it was necessary to reduce the size of the sample ma-
terially in order to handle the number desired with the time and help
available. It also seemed essential to have the individual samples com-
pletely made up of the particular hibernation medium being sampled, a thing
very difficult to do if square feet were taken, as sTmrnles that large un-
avoidably include variable quantities of extraneous material. For these
reasons, the size of sample was set at 1/5 square foot, the area enclosed
by a wire or sheet-iron ring of 6-l/16 inches in diameter. This size was
used throughout the survey trials, except for two series of 1-square-foot
samples taken from woodland leaves and litter, and one series of 1-square-
foot samnoles taken from big bluestem grass for comparison with 1/5-square-
foot samples taken from the same locations. Thec sampling was further rr-
stricted. as far as possible to well-drained south and west exposures, the
locations where bugs were most likely to be found.


-103-
S.BR A RY
SA'AT!F ,.. :r




- o14-


Several methods were used for extracting the bugs from the eamroles.
(1) Direct dissection over a large sheet of oilcloth or paper, removin- and
ccuntinr. the bugs as they emerged or were uncovered. (2) Direct dissection
and sifting, first with a fine sieve to remove soil, then with a coarse sieve
to remove the coarse litter, and finally counting and rez:vini bu-s as they
emerged or were uncovered from the remainder. (3) Use of Berlese funnels
under ste-ir pipes to drive bugs by means of hest into collecting jars con-
taining alcohol. (4) Submergence and dissection of sample in a t-b of wrter
to float out the bugs. For lightly infested samples methods 1 .?nd 2 were
best, but for heavily infested samples methods 5 an! 4 were preferable,

Variation among Individual Samples

The numbers of bugs in individual samples were extremely variable,
even when taken from the same kind of grass and as nearly as possible from
the sare location. For instance) six 1/5-square-foct -ni six 1-ius-,-m-fot
snmnles, all taken from big bluestem grass within 100 yards along a well-
drained south}'wrd sloping- ronlside, varied as follows:


Size of sample : Bugs er sample
I..i n imu rr :-. i -- vcc. r. r-
: ".urr,6 b r: I.u-.ab,^__ : '.-.'.: r
1/5 sqi!re foot: l4 : 236 : 107
1 square foot--: 282 :3,169 : 916


Further evidence of the extreme variability in numbers of bugs in
individual samples is given in the following corn'rison between 1/-square-
foot and 1-square-foot scmnles. Twenty-five noairs were taken from the most
favorably located clumps of big bluestem in a fairly uniform area about 2
miles square, each pair consisting of adjacent 1/5-square-foot r..i a 1-square-
foot srr.-ples from the s.rme clump of grass, with the following results:


Bugs per sample
Size of sample i.....t-sitp -.- i ----l
n.: 5.i nri.m m : .. 1_ .-- : .K.E-r .t-.
: :u.ber N: m-m'rr : "2'r,.r
1/5 square foot--: 1 : 2,) 30
1 square foot----: 49 : 3,169 : 67T

Notwithstanding efforts to take the above samples from as uniform an
environment as possible the variation between th-'se of either size .;s very
great. Th- data were analyzed by the usual statistical methods but the re-
sults are not given here because the method' of analysis corm.nr.l' u;E7c were
apparently not applicable to this experiment. The distribution of chinch
blus in hibernation is so uneven that a great -.nr more and also much larger
s=rrffoles, perhaps entirely on an arr.a basis, irrespective of host plants,
would probably be necessary before the data would anroach anyt>An:- like a






-105-


ncrmal distribution susceptible of the usual statistical treatment. Such an
experiment would be time-consuming and of little, if .*n.y, practical value.

AlthouTh the 1-square-foot s-nles varied less among themselves in this
experiment and hence were possibly more reliable indicators of nonulation
than the 1/5-square-foot s-1mnles, there is probablyr not enough difference in
variation to justify the increase in work involved in their examination.
Furthermore, reducing the size of the sample makes it possible to handle a
larger number of them per given area in the time available, probably afford-
ing better chances of finding bugs if present.

The 1/5-square-foot samples also indicated a much higher infestation
than did the 1-square-foot samples. Probably this would be generally true
because the smaller sc-anles would naturally be taken from the best .-.rts of
the grass clumps, while the larger samples would necessarily include a '.*.ry-
ing amount of the sparse vegetation less likely to harbor bugs. This very
limited experiment would indicate that the number of bugs per 1/5 square foot
should be multiplied by two instead of five, to give the infestation to be
expected in 1-square-foot samples ccrr.-ocsed entirely, of grass. This relation-
shi-n would undoubtedly be variable, depending on k1:ind of grass, method of
sampling, and other factors.

Replicated Survey of Tipnecanoe County

Between November 22 and December l14, 1934, 10 1/5-square-foot samples
were taken in Tippecanoe County, 20 being taken from each of the G areas
sampled during the previous fall survey in standing corn, the entire county
being roughly divided into three rows of 3 areas each. The sr-mplir.- was re-
stricted to well-drained south and west exposures and to the bunch or tuft-
forming grasses, exclusive of timothy. The most favored grasses erer not
present throughout all the areas, hence it '-:s necessa.r" to take the samPles
from the best ones available. Twelve species were involved, the number of
samnoles being as follows: Anironogon furcatus, Fl; Andropogon sconarius, 2;
El.ym?.s canadensis, 19; E'.T.us virginicus, 15; 31,-,, striatus, 24-; S.-robolus
asper, 15; Tridens flavus, 4; Panicum vir(:turn, 13; Atheropogon curtinend-lus,
2; Hystrix .ystrixl; Sor,'o ...strum nutans, 3; Snartina mic.-:1uxisna. 1.

The number of chinch bugs in each s:,mnlje was determined and the data
wvre made un into 20 sets, each set includi..- 1 spmple from each of the 9
areas so as to be representative of the entire count:, no san-ole being used
in more than 1 set. Thus each representative county sample o--s a completely
independent set of 9 1/5-square-foot snrles. Thc results are ze: riz7d as
follows: Number of 1/5-square-foot samples in county sample, 9; nrumtbr of
county s.mnoles, 20; aver-.- number of bugs per 1/5 square foot in county
samples, minimum, 57; maximum, 35g; mean, l4o.

It is seen at once that the average number of -us mer county .c;.mle
varied greatly, notwithstanding the attempts to reduce variation by restric-
tion of the sampling to the most favorable host plants and exposures. Sta-
tistical anal'rsis of these county samples by the usual methods wvas found to





-i0r-


be futile for the reasons already stated with reference to individual 15-
cquare-foct samples, and the results are therefore not reported here. Ab-ut
;ll that can be said for the 20 renlicaticns in this experiment is th-t, al-
though they varied greatly amor: themselves, they. all showed infestatiors far
above the level of 15 per square foot, established by the Illinois workers
as indicative of abundant infestation. Assuming 'buss present in the l-sqc:r-
foot samples to be double the number in the 1/5-square-foot ---'les, for
reasons already explained, this cxprEriment indicates the presence o: about
290 bugs per square foot of bun*2h grass in the most favorable locations in
Tipoecanoe County.

Averaging the sets of 20 l/5-sqj3re-foot samples t:-ken fro-, each -r--'a
indicated considerable variation in abundance of hibernating bugs in different
parts of the county, as would be Fxnr'cted from the topo--:rahv, which ran:cs
from natural prairie with black soil, much corn, and bunch grass, to broken,
more or less wooded country with more uncultivated land, gravelly" or clay
soil, more varied crops, less corn, and less bunch grass. The infestations
by nr7-- wrre as follows:


Area, Type Fayord .grasses :Bugs per 1/5 so. ft.
Number
Northwest------- Prairie: Abundant : 393
-est OCr.ntral----: Mixed : Common 9h
Southwest-----: do. : do. 136
North Central--- do. do. 132
Central--------- ,o. : do. 157
South Central---: do. do. 8-
North'. st------- : Broken Scarce 6
East Central--. : do. !Ddo. : 126
Southeast-------: Mixed : Common 74

Surveys, of Other Ccunties and Comparative Abundance of 3us in Different
"'dia

In addition to the replicated hibernation survey- in Tionecanoe C'unty,
zin;le surveys were made in the three neirb-.oring counties covered last fall
while the b-ius were still in the cornfields. At least one 1/5-square-foot
sample was taken from each ninth of a county and from ea&h dium used. More
,r.erL one set of samples of certain media were t;,ken in some counties, for
one reason or another, but all samples of each medium are combir.cd in the
following averages. One-square-foct sarmnles were taken of the woodland ty,.s
of cover, the results heir.n divided by five for entry in t'h followinr.- table
of results in terms of bugs per 1/. square foot.










: Averar e bugs per 1/ c:- areo
Hibernating media :by counties____ _
:__entcn: Tippecanre: Cli n t -n: T irtcr
rle r Nu.mb1 :r :--er: umber
All grasses -- 221 -I3- 21
punch grasses, except timothy ------ 2SS l : 23
Timhthy-y-- c : 02 7- 7
3unch-tyne sedges ------- -- 1- : 17 -
Mat-type sedges---- -- -- -- 10
bluegrass -: -- 14 -- --
0olunteer wheat ---------------------- 2
Woodland leaves and litter------------ -- --
Woodland le-ves and litter, plus
small grass or sedge tufts--------- -- 10 -- --
Fall survey in corn, bugs per stalk--: 13 10 .


These figures indicate infestation to be in the "aCundant" rare of
15 or more bugs per square foot in all four counties, even in the lpss favor-
able media. The above table gives at least a rough idea cf the actual num-
bers of bugs present in the different tynes of cover in this year of Pxtreme
abundance. However, proeopr evaluation of different media would require data
for years and areas of greater scarcity. In a general way, the ccrnDar tive
abundance of bugs in the different counties is similarly indicated by the
different media, but determination of the actual infestation level evidently
requires different indices for different media. That is, abundant infes-
tation may perhaps be indicated by 15 bu. per square foot in the favored
bunch grasses, 8 per square foot in timothy, 5 ner square foot in bunchy
edges, 1 per square foot in woodland leaves, or from 10 to 15 per stalk in
corn before fall migration. The meaning of certain infestation levels in
different hibernation media is doubtless also affected by the comparative
abundance of the different tyn-s of cover in different areas. However, the
numbers of bugs present in z.all samples of any medium are so variable that
much more extensive sampling than was possible in these experiments would
be necessary to determine these points conclusively.

The time involved in taking and examining samples depends on several
factors, such as condition of country and roads, tyoe and a` jnaince of hi-
hermnting media, number and size of samnles, degree of infestation, and com-
pleteness of count. One man with an automobile could probably average two
counties or more per day in practical survey work, t--kin- 9 zae per cunty
and not stopping to make counts. Complete counts of all bugs in samornls
mnlht require several days per county, but by discarding samples as soon as
enough ugs were found to determine the infestation level the work could bp
much shortened and under favorable conditions could be done at once in the
field. Judging from these trials, a great many more than 9 l/v-sq'1are-feot
or 1-squaTe-foot s:emles would have to be taken in order to obtain more than
a rough idea of chinch bug abindanre in a county, in fact many more samples
than would be possible with the funds ordinarily available for su-h work.







Comnrrative Xumbers of Chinch Bugs Hibernati.-.; in Different Grasses

The work of obtaining information on hibernation in different .-.Ssos
was ,.rcatlv facilitated by Philip Luginbill's knowvled:'- of the species :-
graso,- s encountered. We were very fortunate in having his assistance with the
field work and identification of grasses. In determining the comparative abun-
dance of buo s in different kinds of grasses Ardr ''-c:n furcatus (big bluestem)
was used as the standard, this grass bein.:: rated at 1CO. _Th r-tinC of eP-
graos was determined by comparing the average infestation in all the samples
cf that --r-ss taken from the various areas with the aver*.:;- infestation in all
the samuTles of A. furcatus from the same areas. For instance, the aver-ce
infestation in the 6 st,-.nles of T, flavus was 152, and the average infestation
in the 23 samples of A. furcatus from the s-.-ae areas w-is 141. The rntin.-- Cf
T. flavus w-is therefore l4l:152::lCO:x, or 10F. Certain grasses were more
prevalent than others in different areas and it would have been obviously in-
correct to make comparisons of the infestation in a species of grass in one
locality with the infestation in another species under the different ecclc--cal
and infestation conditions prevailing in another locality. All ?;..-rles were
taken from the most favorable exposures available. The woodland samples were
all 1 square foot and were taken at or close to south edges of such areas.
Some of the species represented by only one or a few samples m,." be far out
of place, otherwise the rating below is thought to be fairly accurate for this
year and region.


Hibernating media : i/:Samles-'Aver
:Rating- : : per


Androoogon scoparius (little bluestem)-----------
Tridens flavuas (tall redtop)---------------------
Andronogon furcatus (big bluestem)-------------
Srorobolus asper (long-leaved rush-grass)--------
Atheronogon curtipendulus (tall gr.a-crass)-----
Hystrix .'.,ctrix (bottle-brush grass)------------
Elymus c'-n.-densis (nodding wild rye)-------------
Elymus virvinicus var. submuticus----------------
Elymus virginicus (Virginia wild rye) ------------
Sorghaastrjn nutans (Indian grass)---------------
Dactylis Tlomerata (orchard-grass)---------------
Pnileum pratense (timothy)-------------------------
Sremus inermis awnlesss brome-grass)- -----------
lymurs striatus (slender wild rye)---------------
2'.'rus striatus var. arkansanus------------------
*&nicum virgatum (switch-grass)-----------------
eigoes (clump tyne)
-r-rtina michauxiana (tell marsh-grass)----------
3edples (sr,-rse or running tye)----------------
:lyrus virginicus var. jejunus (western wild ry.):
Xoodl1nd leaves )nd prass---------- -----------
.-7ro-',rmn reTens (qmack-rass-)-------------- -----
:-.a pr'itensis (Kentuc-- bl'.r.-r-.ss------------- -
Iodlnd le ves----------------------------------
"o nte r. whef t equals 1-- -- -- .- - --- - -
A. f,1rcat us equals 1CO,


223
o1)
100
95
7g
74
58
58
50
50
46
43
41
37
56
22
0
9
8
5

3
2
2
1


: Number
10
6
108
18
2
1
33
1
o
./
7
: 5
S57
1

2

I
: 15

13
:25

10
: 15

10
10
: CI
10
.
Q
: 10


:,? :e "[' -fs
i/' sq. ft.


log
198
12
58
l;g
118

146
56
119

30
47

62
16
11

7
10
io
2
4
10
2






-109-


VJinter Mortality

Samoles taken periodically from locations ner Lafayette gave the
follcwin7 results:


January 7 :February 1:February 20: !,arch 11 :Anril _-1
Hibernating media:Total:Dead :Total: Ded: Total: Dead Totl:Dad:Total:Ded
bugs: bugs bugs:bugs: bugs:bugs bugs:bugs:"bugs bu> Io.: .N No.: N o. : : To. :
lurch grasses----: 913 : 4 :228 : 10 1,735: l :1i34" 16 : l : 19
Timothy ------- 471 :trace: 2 : 8 : 12o:-21 : 12: 17 : 17 : 37

Winter mortality obviously has not greatly reduced the -nrosnect of
severe infestations in 1935 in the area covered by this survey. Even with 20
percent reduction in numbers of hibernsating bugs, a winter survival of over
200 -':us rer sq:-re foot of bunch grass would still be indicated for Tippecaroe
County. The cause of mortality is not evident. Corraratively few of the dead
bugs :: macroscopic indications of disease.




UNIVERSITY OF FLORIDA
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