US2377798A - Insecticide - Google Patents

Description

Patented June 5, 1945 INSECTICIDE Simon Mareovitch, Knoxville,

The University of Tennessee Knoxville, 'lenn.,

ration, Tennessee Tenn., asslgnor to Research Corpoa corporation of No Drawing. Application May 5, 1944, Serial No. 534,356

9 Claims.

This invention relates to insecticides and fungicides, and core particularly to preparations of this kind which are used in the form of powder or dust. This application is a continuation inpart of my prior application Serial No. 439,765 filed April 20, 1942.

Insecticides of the above type usually comprise one or more toxic agents mixed with a suitable inert carrier. For example, the common ingredients used at present in roach powders consist .of sodium fluoride, sodium fluosilicate, pyrethrum, and borax. It is desirable to reduce the proportion of toxicagent in the interest or economy and saving of material, but on the other hand the effectiveness of the insecticide must not be lowered. Moreover, many of these toxic agents are poisonous to men and animals. For example, sodium fluoride is generally considered the best single insecticide for roach control, considering price and effectiveness, but a relatively large proportion of it is required in an insecticide powder to be effective and some operators use straight sodium fluoride. Such powders are poisonous and numerous instances are known where fatalities have resulted from swallowing them by mistake. Moreover, the use of large amounts of sodium fluoride is not, only expensive but also involves serious disadvantages where the supply is limited or the material is in demand for other purposes. Similar drawbacks accompany the use of various other toxic agents in insecticide powders or dusts. r

One of the objects of the present invention is to make possible the use of toxic agents such as sodium fluozide in insecticide powders in such small proportions that the powders are not poisonous.

Another object is to increase the effectiveness of the toxic agent or agents, or conversely to permit of reducing the proportion of toxic agent required in such powders while maintaining their effectiveness, with the concomitant advantages of reduced cost and saving of material.

Other objects will appear hereina ter. as the description of the invention proceeds. It has been observed that some insects, such as roaches, will clean themselves of powders and irritants. When a roach is dusted with sodium fluoride, the insect maybe observed to clean itself of the'ofiendin powder by passing its feet and antennae through its mouth. The general impression has prevailed that the roach accidentally swallows the fluoride and thus dies. Hence it hasbeen generally accepted that such insecticides should contain a relatively large proportion of the toxic agent.

when only 50 milligrams of each were used in combination a good kill resulted.

I also found that the synergistic effect is most apparent when small dosages are employed. In ordinary practice, all the advantages of this synergistic effect are not realized because more material is dusted out than is necessary. Moreover,

when small proportions of these toxics are employed, their effect may be nullified because the carriers or diluents used are incompatible and appear to destroy toxicity. Thus with most carriers heretofore employed, the proportion of toxic agent cannot be substantially reduced without destroying the effectiveness of the insecticide. Carriers such as clays, tales, earths and lime, instead of being mere diluents, actually decrease the toxicity of agents such as sodium fluoride, due to the presence of calcium and other divalent and trivalent ions.

I have further found that dry, powdered dextrin is not only entirely compatible with the toxic agents mentioned above but also preserves the synergism oi combinations thereof and itself acts synergistically and catalytically with each of them. Accordingly when dextrin is used as a carrier, the'proportion of toxic agent in the powder can be sharply reduced, while at the same time the effectiveness of the insecticide is maintained and in many cases substantially increased.

Thus, sodium fluoride can be used effectively in amounts as small as 510%in combination with approximately the sameamount oi pyrethrum. since the dextrin which comprises most or all of the remainder of the powder not only preserves but also enhances the synergistic effect. As illustrated hereinafter, I have found that excellent results are obtained with such compositions although the total amount of toxic agent is only 20% or less of the powder, the remainder being dextrin. At the same time, the amount of poisonous material is so small that the powder is relatively safe and non-poisonous.

Sodium fluosilicate may be substituted for sodium-fluoride in such a composition, although the fluoride is preferred. Also while any dextrin can be employed with good results, broadly speaking, the more acid dextrins give somewhat better results and those having a pH of 3 to 4 in a 1% solution are preferred. The dextrin should be employed as a fine powder; for example, one which will pass a 200 mesh sieve. It will be understood that, if desired, other suitable materials may be used in combination with dextrin as a diluent, although preferably the amount of dextrin should not be less than about 60%. Clay and the like which contain alkaline materials such as calcium and magnesium should be avoided because of the adverse effect of alkalinity on toxicity. Acid material such as sodium acid fluoride and sodium bisulfate, on the other hand, tend to increase toxicity.

Another advantage of dextrin is its attractiveness as a bait which continues to act for as long as several months where the powder is used in cracks and the like. Part of the dextrin can also be replaced by other bait materials. For example, I have found peanut flour to be very attractive to roaches and a small amount of this attractant, say can be substituted for an equivalent amount of dextrin to provide not only a contact insecticide, but also a foodlike substance that the roaches will eat.

I believe that the reasons such combinations are so eifective are that the roaches are killed by a contact action a follows:

As soon as a roach becomes dusty with this combination, the pyrethrum paralyzes the roach so that it can not use its mouth parts eifectively to remove the powder. The pyrethrum also interferes with the normal permeabilityv of the tissues and causes water droplets to appear over the body and induces salivation from the mouth.

The water thus produced serves to make a gum of the dextrin which sticks the sodium fluoride onto the roach so tightly that the roach can not remove it by the movements of its body. This gives the sodium fluoride time to dissolve in the water produced and then to enter the tissues through the pore canals of the chitin, resulting in the final knock-out. All three materials thus act in cooperation; the pyrethrum as a paralyzer and water producer, the dextrin as a sticker and the sodium fluoride as the flnal killing agent.

The synergistic effect of these three materials is illustrated by tests which show that even the residue left after 90% of the active principles (pyrethrins) have been removed will give substantially as good results as pyrethrum powder testing .9 to 1.3 pyrethrins. For example the residue left after the active ingredients in pyrethrum are removed in making fly sprays, which test only about .1 pyrethrins, can be substituted for straight Dyrethrum powder with good results when used in combination with dextrin and sodium fluoride.

Other advantages of this combination are lack of irritating effect to men using it continually, the fact that the powder adherm extremely well to walls and smooth surfaces, and the fact that the amount of sodium fluoride is so small as to make the powder relatively safe, non-poisonous and non-irritating, fatalities being practically impossible because of the large quantities that would have to be swallowed to produce toxic eflects.

The catalytic eil'ect of sodium fluoride when used with toxic agents such as pyrethrum is illustrated by the following test data. With a deposit of 0.8 mg. per sq. cm. of sodium fluoride,

about twenty-four hours were required to kill 90% of the roaches when they were allowed to remain in the test chamber for flve minutes. With pyrethrum powder at the same dosage, forty-five hours were required for a kill of only although paralysis was produced in ten minutes. When sodium fluoride and pyrethrum powder were combined in equal amounts and the mixture used in the same dosage, 100% kill was obtained in twenty hours, and excellent knock-down. With accurate technique, the same remarkable synergism is demonstrated even when these materials are employed in very small amounts. For example, with a deposit of only 0.08 mg. per sq. c'm., neither sodium fluoride nor pyrethrum powder shows toxicity against roaches within twenty-four hours, but when these materials are combined in equaLproportions and the mixture used with the same dosage, a kill of 80% is obtained.

As noted above, thissynergism is preserved and enhanced in the presence of dextrin, whereas with other materials it is destroyed and the effectiveness of the insecticide is lost unless the toxic agents are employed in large amounts. For example, with an insecticide comprising 80% dextrin, 10% sodium fluoride and 10% pmthrum, a kill of 100% may be obtained within twenty-four hours, whereas if pyrophillite or talc is substituted for the dextrin, a kill of only ill-30% is obtained. Hence for general purposes I prefer to employ 5-l0% sodium fluoride, about 10% of pyrethrum or other suitable toxic agent, and about 80% dextrin. I have found that such a composition is more eflective than pure sodium fluoride. Moreover, the amounts of the toxic agents required are greatly reduced as compared with previous insecticides in which they have been used, andbecause of the small amount of fluoride employed, this composition is relatively safe and non-poisonous.

Insecticide compositions as described above are also eifective when used as a dust against insects such as plant lice, Mexican bean beetle, cucumber beetle, potato beetle and cotton boll weevil. For use in the field, where a fungicidal effect is desired, sulfur should preferably be substituted for part of the dextrin, and in this case it may be desirable to reduce the amount of dextrin below 60% to increase the amount of sulfur, say to 40% dextrin and 40% sulfur. It will also be understood that compositions as described above can be mixed with arsenicals, other fluorides, nicotine, phenolic substances, petroleum products, Derris, clays, etc.

It will be understood that the examples set forth above are for purposes of illustration only and are not to be construed as defining the limits of the invention, since various modifications will occur to those skilled in the art without departing from the spirit of the invention. Reference is accordingly to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. An insecticide powder containing approximately 5-l0% each of pyrethrum and a fluoric ingredient of the group consisting of sodium fluoride and sodium fluosilicate, and at least 40% dextrin.

2. An insecticide powder containing approximately 540% each of pyrethrum and a fluoric ingredient of the group consisting of sodium fluoride and sodium fluosilicate, at least 40% dextrin, and sulfur.

3. An insecticide powder containing approximately 540% each of pyrethrum and a fluorie ingredient of the group consisting of sodium fluoride and sodium fluosilicate, and at least 60% dextrin.

4. An insecticide powder as defined in claim 3 in which the dextrin is of the acid type having a pH between 3 and 4.

5. An insecticide powder as deflned in claim 3 and containing also about 10% peanut flour.

6. An insecticide powder containing about 80% v powdered dextrin, 10% sodium fluoride and 10% pyrethrum.

'7. An insecticide powder comprising approxi- SIMON MARCOVITCH.