Soil-washing apparatus and methods used in counting wireworm eggs

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Title:
Soil-washing apparatus and methods used in counting wireworm eggs
Physical Description:
Mixed Material
Creator:
Shirck, F. H
United States -- Bureau of Entomology and Plant Quarantine
United States -- Dept. of Agriculture
Publisher:
U.S. Department of Agriculture, Bureau of Entomology and Plant Quarantine ( Washington, D.C )
Publication Date:

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Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030609778
oclc - 793286730
System ID:
AA00017471:00001


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ET-71 Janua:. 1 ..

U: Ited States ?D.. ',ri ,.it of A, riculture
Eu .; :c.u of Ei.tcic',lczy and Plant Q':,,..t ,.




:L-2A. ..H..: ; F. 7'F ,T,'.: A: ;.1ET-ODS UCED IN (C:Ur: ." >.' ;*-,...'; r, EI,_:

E!, F. H. Shii,:c., Divisiciin of Truck Crop and -rden
L.sc'ct Ir..vestigations j/



:.- diffi:'ities encountered in separating v-irworro ,3 from la;:.e
!ic,_l.-2 ol .l *-.-:T:',les of soil have necessitated certain ,..._es in he ap-
p -':a'. ....E mel.i ods ;. lob .: in stux ies .'aling with 1. .._' and early larval
stia^s of th's i:ict. It is believed that the soil-washing apparatus de-
scric-i herein :.; resents an improv-:rc'.it over i'.at previously used and i-j i'rted
upon. l

'Th.e *.':':?r h: a wooden f..in .'.Aork, 4 feet in hei..t, which sup] ',rts the
3 s5lv..s u. -. F..... *:1.. (fi.'. 1) attach.:Lt to this framework collect the run-
off ".h:.:: \ ''. c- U-.ro.: :. ch sieve, dischargi:,.- it onto successively finer
siv'-:.:- below" (fit. 2). ..-- vertical spacing between sieves is 15 inches. i::
arr.:^,.:. -".t of si':.-':= r::-ul:.; in a r:ap:id w.-i .'" action, with less tendency for
tr. ?..-..., to clc; than where all sieves are placed one directly beneath
-not'er. Mor,:over, tu'id water strikes the mi.--i'e i- bottom sieves at
av c.::-.,'e, t:.us r-,ici:. the tendency to splash. o, the o.-: arr,,.. i-. -nt
r:kc-s it .:"y to spray additic:,.! clear water onto sieve ch threatens to
clog, rL:- facilitates te removal of the sieves ....n the washing op:-ration is
ccmpFle ted.

I.-. using tI.; wt:.h: r the sample of soil is pl'' :.'i in the tub which rests
,c:l. ..- fr--.rc, j::-,: the r:!7 is fill-:ld rne, rly full of water. The mixture s,
.h- '.. : ..y "rr: 1 .-i, ca.e Le'., t:-k:-n to m.ash c'.: dissolve all -. cllf. When
e m lur -.. -1I stir 2 ,:.^ has the :,,...:.' it>t cf soil in i ._ -iion
it :- "lc.Ed c:.:- coarse tcp screen ; pv.,',-: the cork out of a 2-inch
_. i ".: bot'.c.c- of ".. '.1b. Stirr i is continued while the Nixture
d,---.. Addtiol.. clear water is sprayed first on one screen .::i.1 then on
.' .:r, whe-.":r '.!. n": for -i'. tio',t dilution fl is greatest.
i...-:* :^':ris r,''ai:. ir:.g .. the scr-.;' is washed vith cle. water ...- then removed
fr:r. -.: sieves a:.' exam',.-d.

1/ Acknowledgement is made of the assistance rendered F C. Abertson, of the
F I :: S, field laborato :... of the E .reau of Entcmol. an Plant Q rntine, who aidd
in the construction of the soil washer.
-/ Shirck, F. H., A D il-...: .... Device for 7 in Wireworm I vesIt tion J r.
E::n. E..t. 23: 991-9'34, ii us. 1930.









-2-


The number and size of the sieves and the nesh sizes of the screen cloth
used can be varied to suit the particular requirements of the investigator.
In the work with wireworm eggs it was found that sieves measuring 14 by 18 by
2- inches, inside dimensions, were of satisfactory size. The frames of the
sieves are made of white pine and they were treated with hot linseed oil
before being placed in use. These frames are fastened together with screws
at the corners, and the copper screen cloth is held in place by a light -..ooden
::.-.t nailed to the bottom edge of each sieve. The following screen mesh sizes
are used in the r:-p'ctive sieves: top sieve, 12 meshes to the linear inch;
middle sieve, 24 meshes to the linear inch; bottom sieve. 40 meshes to the
linear inch.

The wireworm eggs pass through the first two sieves and are recovered
from the debris left on the bottom sieve. This debris is placed in a pan having
a 40-mcsh screen bottom, and the pan is then lowered into another pan containing
a saturated solution of sodium chloride. The eggs, together with much debris
light enough to float, are then skimmed from the surface of the brine with the
skimmer shown on the stand of the binocular in figure 3. Only a thin lay,~r of
debris is collected at one time so that the layer will not be deep enough to
cover completely any wireworm eggs contained therein. Number 30 tinned. iron
wires, spaced one-half inch apart, are soldered to the top edge of the skimmer.
This divides the skimmer into fields of convenient width, making possible
the rapid and accurate examination of the debris under the binoculars.

If time does not permit the examination of all the material at the time
of washing, it may be stored in a preservative solution and examined later,
provided, of course, that the needs of the investigation do not require that
the insects or eggs contained therein be kept alive. In the work with wire-
worm eggs it was found that a 4-percent solution of carbolic acid served sat-
isfactorily as a preservative. The eggs that had been placed in this preserv-
ative were dead white, in contrast to their natural pearly color, and were
therefore easier to detect after being stored in the carbolic acid solution.









-- ft
/


Figure l.--Pattern for sheet metal funnels.
































Digitized by the Internet Archive
in 2012 with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation


http://archive.org/details/soilwash00unit















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Figure 2.--Soil washer for soil insect investigations.


Figure 3.--Method of examining washed residue.




UNIVERSITY OF FLORIDA


3 1262 08721 6429




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