United States Denartment of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
TESTS OF DDT AGAINST THE INSECT PESTS OF STORED SEED, GRAIN, AND MILLED CEREAL PRODUCTS
R. T. Cotton, J. C. Frankenfeld, H. H. Walkden, and R. B. Schwitzgebel,
Division of Cereal and Forage Insect Investigations
In experiments conducted at Hutchinson and Manhattan, tans., during 1944 DDT appeared to be highly effective against insects that attack stored seed, grain, and milled cereal products. In concentrated form, in admixture with carrier dusts, or as a toxicant in oil-base sprays, it may constitute a valuable addition to the insecticides which are effective for combating these pests. Miscellaneous uses for this chemical are
bTests with Seed Wheat
In the course of an investigation of inert and chemical dusts for
the protection of seed from insect attack, DDT was tested and found to be highly efficient. Inert dusts protect seed from attack because they kill the insects by desiccation. Such dusts are ineffective, however, if the moisture content of the seed is much over 12.5 percent. Chemical dusts kill by contact or by poisoning due to the ingestion of the dust particles; hence their action is independent of the moisture content of the
Experimental work was undertaken with seed wheat of 12 percent
moisture content. To 500-gram samples 0.05, 0.025, and 0.005 percent by weight of technical DDT was added. The samples were placed in glass jars, together with adults or larvae of 9 species of seed-infesting insects,
one species to a jar. The jars were examined weekly to determine the effectiveness of the treatments. At the end of the first week all three dosages gave a complete kill of adults of the rice weevil (Sitophilus 2oza (L.)), the confused flour beetle (Tribolium confusumi Dbii., theed flour beetle LT. castaneum (Hbst.)) the lesser grain borer (Rizonertha dominica (F.)) the saw-toothed grain beetle (Ory~aephilus surinamensis (L.) and the larvae of the Indian-meal moth (Plodia inter--ctella (Hbn.) A complete kill of adults of the granary weevil (Sitophilus ganarius (L.)) was obtained at the end of the first week with p percent dosage and
with all dosages at the end of 2 weeks. The larvae of the cadelle tIenebroides mauritanicus (L.)) were more resistant than larvae of the other species. At the end of 5 weeks 20, 49, end 76 percent were still alive in the Jars treatpAi with the 0.05, 0.025, and 0.005 percent dosages.
Another series of tests was conducted with a 3 percent DDT-pyrophyllite dust. The results, which are given in table 1, indicate that this dust is highly effective at 15 p.p.s. of DDT. No immature forms of the insects completed their development. The use of the DDT-pyrophyllite
mixture appeared to be more advantageous than the undiluted form used in the previous experiments, probably because the mixture provided better coverage of the seed and distribution of the DDT.
Table 1.--Efficiency of 3 percentyT-pyrophyllite in protecting
seed wheat from insect attack A
t Percent mortality after.-Concentration' s 1 t 2 : 3 4 : 5 6
of DET in wheat week weeks 8 weeks I weeks a weeks t weeks
P.p.m. Rice weevil
3 o 52
Check (untreated) 2
3 147 86 89 90 90 92
15 32 99 100
30 71 98 99 100
0/ 7 10 21 21 314 34
Check (untreated) 1 19 19 23 23 25
Confused flour beetle
3 9 31 65 90 95 97
15 54 loo
0 1 4 9 9 12 13
Check (untreated) 1 1 2 2 2 4
Lesser grain borer
3 35 S4 92 92 92 92
o02/ 13 27 28 31 31 31
Check (untreated) 11 20 30 30 38 62
Saw-toothed grain beetle
3 36 56 65 65 65 6s
15 97 100
0 10 31 44 145 147 51
Check (untreated) 10 13 15 15 19 81
3 0 10 40 50 50 so80
15 40 6o so80 90 90 90
30 60o 70 80 90 100
0/ 10 10 10 10 10 90
Check (untreated) 0 0 0 0 0 0
1/ 100 insects were used in each of these tests, except with the cadelle in which case only 25 were used.
2/ Pyrophyllite (1.000 p.p.m.) without DDT.
To determine the influence o D when ed in se whet ontaining more than 12 percent moistce, sales oa ni' d 1 erc
moisture were treated with undiluted DDT at the rates OC
0.2 percent by weight. Each sample was artficJy infested t
adults of the rice weevil, and set aside for 10 d At te e that time the mortality was complete in all sa~leo Subsequnt o nations showed no emergence of weevils from these sales, indcatg that they died without having oriposited.
To determine whether DDT would have a ff i
of seed wheat, the viability of the treate sos s
a month for 4 months. As indicated in table 2 o
percent by weight of DDT showed no injurious effect
Table 2.--Zffect of technical DDT on viability of see wheat otin 12 percent moisture
Concentration of Z Sermination of seed wheat afterEDT, by .teight. I month : 2 months : 3 months
Percent Percent Percent Percent Perce
0.05 91 95 93
.1 91 90 90
.2 90 90 9
Check (untreated) S7 86 87
Tests with Packaged and Balt Seeds
The success obtained with experiments on seed wheat led to more
extensive tests with DT for the prevention of insect damage to both bulk and packaged seeds of different kinds. Infestation in packed seed, par'ticularly by the Indian-meal moth, is always a problem when unused stocks must be held over the summer. Toung larvae hatch from eggs laid by the moths on or near the packages of seed, and enter envelopes at the top corners where they are not completely sealed. After feeding on the seed until they attain their full growth, they cut their way out through the packets. Other troublesome insects are the flour beetles (~ribolium spp) the saw-toothed grain beetle, and dermestids of the genera o erm n Attaaenu.
The seeds used in these tests were watermelon, corn, tomato, n lettuce in paper envelopes ranging from 1 ounce to 1 pound in sie, and sunflower in bulk in cotton bags. All the seeds were treated th 0.05 percent of technical DDT, repackaged, and placed with untreated lots in a special screened metal cabinet. A supply of wheat heavily infeted with the Indian-meal moth, the confused flour beetle, and the saw-toothed grain beetle had. been placed in the bottom of the cabinet and covered with a screened false floor on which the various lots of seed were set Insects from the infested wheat thus had an opportunity to enter the nckae of seed. The cabinet was held in a constant-temperature chamber at g0 T. and a relative humidity of from 75 to SO percent. At the end of 2 months the various lots of seed were removed and examined. The results are recorded in table 3.
Table 3.--Condition of seed containing 0.05 percent by weight of
technical DDT after exposure to insect infestation for 2 months
: Insect damage to : Type of packa ge kge ctnin:. Insect damaL to see&
and seed :Treated 'OUntreated :
I seed : seed : Treated a Untreated
In paper envelopes:
Watermelon None None A few dead Heavily infested
insects, with Indian-meal
No damage. moth and confused flour beetle.
Corn 1 hole None A few dead Heavily infested
in insects, with Indian-meal
envelope No damage. moth, confused
flour beetleand saw-toothed grain beetle.
Tomato None 1 hole No damage. Infested with
in I ndian-meal moth.
Lettuce None None 1 Qderma No damag.
In cotton baqg (bvlk)
Sunflower None None A few dead Heavily infested
insects, with Indian-meal
No damage. moth, confused
flour beetle, and saw-toothed grain beetle. Deage
to oned considerable.
Compareble result$ were obtained with a similar series of
packaged seed exposed to possible infestation In the warehouse of a commercial seed dealer during the si~mmer.
It is evident from table 3 that treatment of packa~ged and bulk seed with DDT at the rate of 0.05 percent by weight will give adequate protection from damage by most insects that infest seed. Dermestid larvae appear to be considerably more resistant to DDT than other insects. Possibly the dense coat of hairs covering the larvae prevents the dust from coming in contact with their bodies.
An objectionable feature of DDT as a seed treatment is its inability to repel the insects, but for the most part they are killed before any damage is done. Although no large-scale tests have.been conducted with the 3 percent DDT-pyropbyllite mixture
In packaged and bulk seeds, it seems probably that equally good results could be obtained by using the same dosage of the mixture as of the undiluted DDT.
Tests with DDT Sprays for Controlling Stored-product Insects
The elimination of infestations in the woodwork of grain bins, warehouses, storerooms, flour mills, and railway box cars has long been a serious problem. The cadelle causes a tremendous amount of damage by its habit of burrowing into such woodwork. It is extremely common in farm granaries, in railway box cars and in warehouses. This species and others survive f or months in these burrows. When fresh grain is placed in farm bins it often becomes infested by great numbers of these insects emerging from the woodwork. Flour and other cereals in transit in infested box cars or in storage in warehouses are similarly invaded, and heavy losses have resulted from the spread of infestation from~ woodwork to grain and milled cereal products in storage or in transit. The cadelle will cut through almost any type of bag or container to reach the milled cereal products. The use of fumigants and ordinary contact sprays, although of some value, has never been entirely satisfactory in such cases. Experiments conducted during the past season indicate that the use of a DDT-oil spray may be the best means yet discovered for destroying infestations of these insects persisting in woodwork.
In the course of experimental work on the treatment of wooden farm granaries to eliminate infestations and to prevent grainirfesting insects from burrowing into the woodwork, the interior walls of some bins were sprayed with a refined odorless kerosene containing 6 percent of DDT. The solution was applied with a paintspray gun at a pressure of 410 pounds per square inch.-A few days after treatment the floors of the bins were littered with large numbers of -dead adults and larvae of the cadelle. In one bin approximately 9,000 dead cadelles were swept from the floor at the base of 10 linear feet of sprayed wall. The killing action per-sisted for some time, since dying cadelles were emerging from the walls for weeks after the treatment.
The floors, walls, and partitions of storerooms and the lower floors of flour mills frequently harbor insects that invade flour,, feed, or seed temporarily stored in such places. Spraying with a refined odorless kerosene containing 5 percent of DDTi cleaned up an inl'estation. of flour beetles in a wallboard partitition of a flourstorage room, and gave excellent results against silverfish infestations in a wheat-sample room and the first floor of a flour mill.. Insects present in the sprayed areas were killed, and the residual effect caused the death of invading silverfish for many weeks after treatment.
DDT Treatment of Bags to Prevent Entrance of Stored-product Insects
In an earlier report 1/ it was stated tha-)t paper impregnated
with a 10 percent solution of DDYT in acetone offered great resistance to penetration by insects, and it was suggested that this repellent property might be used to advantage in the treatment of materials used to package milled cereal products.
In subsequent tests, bags were made of kraft paper that had been treated in three ways--Cl) by dirpinp, in a 10 percent solution of DDT in acetone, (2) by painting one side with varnish containing 10 percent of DDT, and (3) by coating one side with a standard clay coating liquor containing 10 percent of DDT. The bags were filled with flour, tightly sealed and exposed to a heavy infestation of the cadelle, the lesser grain borer, and the confused flour beetle. All the treated bags resisted penetration by these insects for many months, whereas
bags made of untreated kraft paper were usuwAly penetrated within a few days.
l/ Cotton, R. T., B~alzer, A. I., and Young, 11. D?. The possible utility of DDT for insect-proofing paper bags; (Scientific Note) Jour. Econ. Ent- 37: 1410. .1944.
Another test was conducted mith ordinary cotton flour bags and with No. 5 kraft paper bags such as used in grocery stores. One series of bags was treated by spraying the outside with a 5 percent solution of DDlT in carbon tetrachloride, and a second series was dipped in a similar solution. After aeration to allow the carbon tetrachloride to evaporate, 1 pound of uninfected flour was placed in each bag. The cloth bags were closed by tying the tops with
string. The tops of the paper bags were glued, and then further sealed with Scotch Tape. The treated bags, together with the untreated checks, were placed in a metal tank containing grain heaviA4 infested with cadelle larvae and confused flour beetle adults. After
1 month's exposure the bags were removed, the flour sifted, and a record made of any infestation. Prom the data in table )4 it is evident that considerable resistance to insect attack is Imparted to both types of bags by impregnation with MDT. The greater infestation in the cloth bags is due to the ability of the insects to penetrate fabric more easiLy than paper.
Table 1.-..Resistance of cotton and paper bags treated with 5 percent
of MDT in carbon tetrachloride to infestation by stored-product
2Insects found in bags after
Type of package I ot Number of holes
and treatment 3Flour Beetle : Cadelle 3 in bag
2Adults 2Larvae : Larvae
spray, 5 ml. 71 20 1
6 1 2)4 1
3 0 17 3
Dip 7 0 40
2 1 4
Check (untreated) 37 99 51 20
Spray, 5.1.- 19 T144 10
o 0 0 0
10 ml. 0 0 0 0
Dip 0 0 0 0
0 0 0 0
0 0 1 1
Check (untreated) 93 206 15 4
In another test two 100-pound cotton bags, one treated by
dipping in a 5 percent solution of DDTi in carbon tetrachloride and the other untreated, were filled with flour and stored next to each other in a mill basement. In a few hours the untreated bag was literally covered with silverfish, whereas not a single insect was
observed on -the treated bag.
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