gue hPa aia . errata 2 ahead A pe 4 “* rghe9 ares PAA ce lens eh net atte fon eel Leaders eee LIBRARY OF THE UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN no.6G - 99 ILLINOIS NATURAL HISTORY SURVEY BIOLOGICAL NOTES NO. 96 Urbana, Illinois, February 1976 STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION NATURAL HISTORY SURVEY DIVISION APPARATUS AND PROCEDURE FOR EXTRACTING CORN ROOTWORM EGGS FROM SOIL JOHN T. SHAW ROBERT O. ELLIS W.H. LUCKMANN The northern and western corn rootworms complete one life cycle each year. They oviposit eggs in soil in August and September. The eggs develop slightly, go into a resting stage during the winter, and hatch in the following spring. The po- tential for damage by the larvae of these insects in the next growing season can be determined by counting the number of eggs per unit of soil. However, it is physically impossible to count these eggs without some means of extracting them from the soil, since rootworm eggs are slightly smaller than the period at the end of this sentence. Researchers at the University of Missouri (Chandler et al. 1966) developed a machine for separating rootworm eggs from soil. A sample of soil containing eggs is saturated with sodium hy- pochlorite and water, and the sample is agitated for 15-20 minutes on a ball mill. The sample is then passed in small amounts through a slowly revolving screen cylinder and washed with sprays of water from fixed nozzles and a hand sprayer. The eggs are collected in a fine-mesh screen trap for final processing. Using the basic design of the Missouri separator, we engineered a larger, enclosed machine that extracts rootworm eggs from a pint of soil in 3-4 minutes. The final stages of separating eggs from debris require another 5 minutes after which the eggs can be counted under a microscope. The Illinois machine and the final separation of eggs, using magnesium sulphate, are highly efficient, and we have repeatedly recovered 97 percent of root- CREDITS: John T. Shaw is a Junior Professional Scientist and Robert O. Ellis is Assistant for Operations, Illinois Natural History _ Survey. William H. Luckmann is Head, Section of Economic Ento- ' mology, Illinois Natural History Survey, and Head, Agricultural ; Entomology, Illinois Agricultural Experiment Station. Thanks are i given to Mr. Loyd LeMere and Mr. Larry Farlow for photographic | illustrations and to Mr. Robert M. Zewadski for editing. Supported | in part by USDA Soil Arthropod Agreement 316-15-97 and USEPA | Grant SC 802547-5. worm eggs manually placed in samples of soil. Weed scientists in the Department of Agronomy, University of Illinois, also have used the machine to extract weed seeds from soil samples in their weed pest-management program. The Illinois machine is constructed of stain- less steel, and all seams are welded watertight. The table top and cabinetry are made of stainless steel sheeting, and the supporting framework is 1/8-inch stainless steel angle frame. The plumbing is connected directly to a domestic water source. An external view of the machine, with dimensions, is shown in Fig. 1. A soil sample is placed in the sieve insert in the 9-inch diameter funnel beneath the shower head, and the sample is sprayed with full water pressure. The funnel-shaped sieve insert con- structed of 30-mesh T-304 stainless steel screen fits inside the funnel with 1-inch clearance be- tween the mesh sieve and the funnel. The wire for the sieve insert has a diameter of 0.01 inch, a mesh opening of 0.023 inch, and a weight of 20 pounds per 100 square feet. Fifty percent of the sieve’s surface is open area, allowing an easy, rapid flow of eggs and soil in suspension. The fun- nel with the sieve in place is shown in Fig. 2. The shower head is controlled by a foot pedal. The plastic garbage can under the machine collects waste water and soil. Residues of soil that cling to the sides of the sieve, the receiving funnel, and the funnel immediately below are flushed down with water sprayed from a common kitchen sink sprayer. The internal design is illustrated in Fig. 3. A 1/10-horsepower 60-RPM gearmotor, using drive-pulley reduction to 50 RPM, slowly rotates a 50-mesh T-304 stainless steel screen cylinder. The wire for the screen cylinder has a diameter of 0.009 inch and a mesh opening of 0.011 inch, nnn *Tlos yo aydues e woay sie WHOM}OOA ULOD JORAVXe OF Pasn eUlyo u RU JO ‘SUOISUOLUTP YIM “Mola [BUPXG—' | ay ‘pkey 1aMoys ay} WOdy . aAvis ay} ul paoeid 4ajem yy paderds pue st ajdwies [10s Y “}Aasul aAaIs [ves sseyureys YA jouUNy JajeWeIp YOUL-eUIN—Z “Sl ‘saaisap QT pedojs are (q) qyeys syt pue aapurjAo uvasos ayy, “suo, sayour QE pue Jajyaweip ul sayout g st (Ww) aapurljAo Uaasos [aeqs ssayureyg ‘auryo “BUI SUIJORI}XO Bsa WIIOMJOOI JO UsISAap [eUIaJUT—‘E ‘“SIy *Aeay Suljoa[[oo ay} Our ATJOea1p sAeads 9[zzou VY “Av1} BUIYDa[[O9 Use.0s [994s Sse[UIe{s pue YsNoIy Suoa][OO—'p “SIq Fig. 5.—Laboratory arrangement for the final separa- tion of corn rootworm eggs from soil. Magnesium sulphate and water flow by gravity into the separatory funnels. The funnels can be removed from the stand. and 30.3 percent of the screen surface is open area. The wire weight is 28.4 pounds per 100 square feet. The cylinder is 5 inches in diameter and 30 inches long and has a 10-percent slope (the slope is very important). The cylinder is mounted on a 3/4-inch diameter shaft. Seven fan T-jet No. 8004 nozzles mounted both in front of and behind the cylinder spray it with water. If the wa- ter pressure is below 35 lb/in? at the installation site, special nozzles will be required to compensate for the low pressure. The water containing eggs and soil spills into a trough at the lower end of the cyl- inder. This trough is slanted toward the front of the machine, causing eggs and soil to drop into a collecting tray constructed of the 50-mesh stain- less steel screen used in the cylinder. A nozzle sprays the eggs and debris in the collecting tray. A close-up view of the collecting trough and tray is shown in Fig. 4. Cleaning the upper surface of the machine is facilitated by a large hole which funnels into the lower unit, and all water and soil is voided through one outlet into the waste container. A stainless steel partition separates the electric motor compartment from that of the screen cyl inder, and for safety a steel mesh guard is located in front of the electric motor. The screen cylinder is the most importan unit in this machine. It is geared to turn at 5@ RPM. During construction, the seams of the ma chine must be carefully soldered so that all surfaces are smooth. This is extremely important. The ma chine will not be reliable if cracks or uneven areas occur in the cylinder. Extra soldering is necesse to fill minute cracks. Careful soldering is alse needed for the collecting tray so that all corners are filled with solder and all surfaces are smooth Before using the machine, one collects soil in the field, using an acceptable sampling procedure. A sample may be a composite of sub samples or a number of individual samples taken ai various locations in a field. The sample is sifted through a 1/4-inch hardware cloth screen and mixed thoroughly. One pint of soil is measured ane placed in the sieve in the top funnel under the shower head. The sample is sprayed for 3 minutes and any remaining soil is flushed down with the hand-operated kitchen sprayer. The sample move: through the screen cylinder, and in 3-4 minute! all of the eggs and remaining debris collect in th collecting tray. The collecting tray is then sprayec thoroughly with the hand-operated spraye The collecting tray is removed from th machine, and the eggs and remaining debris a flushed into a 1,000-ml separatory funnel with stopcock opening of approximately 7mm. Se Fig. 5 for the arrangement of equipment for th final processing of corn rootworm eggs. Approxi mately 500 ml (about 1 pint) of 2 mol magnesium sulphate solution (MgSO,) are used to flush th eggs and debris into the funnel. The funnel i shaken vigorously and returned to the holding rack in about 30 seconds the heavier debris sinks to th bottom of the funnel. The stopcock is then opened and the debris and about 450 ml of the magne sium sulphate solution are drained from the funne Care should be taken not to drain off all of th magnesium sulphate solution, since the eggs wi be floating on its surface. The stopcock is closed 500 ml of water are added to the funnel, and th funnel is shaken again. The sample must settle fo no less than 1 minute (this time is critical) to pe mit the eggs to sink to the bottom of the funne Next the stopcock is opened and closed quickl to drain the eggs and about 50 ml of water into petri dish. The eggs are counted under a binocula microscope, and the number of eggs per pint o soil is recorded. The MgSO, solution can be reuset by straining it through a sieve to remove mino debris. REFERENCE CHANDLER, J. H., G. J. MUSICK, and M. FAIRCHILD, 1966. Apparatus and procedure for sep ration of corn rootworm eggs from soil. Journal ¢ Economic Entomology 59:1409-1410. i Reset Leth at eaee DINTCR tise