Abstract:
The present invention relates to a microencapsulated chlorpyrifos or endosulfan composition comprising a polyurea shell and one or more photostable ultraviolet and visible light absorbent compound having a log molar extinction coefficient of from about 2 to 5 with respect to radiation having wave lengths in the range of about 310 to 450 nanometers, wherein said photostable ultraviolet and visible light absorbent compound does not react with the monomer used in building the polyurea shell. The result is a microencapsulated composition having unexpected long, extended insecticidal activity with high toxicity to target species and very low toxicity to non-target animals.

Description:
BACKGROUND OF THE INVENTION 
     The present in vent ion relates to microencapsulated insecticide compositions which are stabilized against environmental degradation. The present invention more specifically relates to microencapsulated chlorpyrifos or endosulfan stabilized against degradation by visible and ultra-violet light having unexpected extended insecticidal activity while having unexpected low toxicity to non-target species. 
     Chlorpyrifos, which is the common name for O,O-diethyl-O-(3,5,6-trichloro-2-pyridyl)-phosphorathio- ate, is a well-known insecticide. Two major problems of this insecticide is on the one hand its ease of decomposition when exposed to the environment and the concomitant high toxicity to non-target animals. Thus, technical chlorpyrifos has a toxicity to rats (acute oral) of an LD 50  of 168 mg/kg and a toxicity to trout (acute) of an LC 50  of 0.007 mg/kg. 
     Endosulfan, which is the common name for 6,7,8,9,10-hexachloro-1,5-5a,9a tetryhydro-6,9-methano-2,4,3-benzodioxathipia-3-oxide, is also a well-known insecticide, with stability and toxicity problems. Its toxicity problem is most acute to non-target species such as fish and bees as the technical material has an LD 50  to non-target species such as mice of 30 mg/kg. For an EC formulation to classified as &#34;only harmful&#34; its LD 50  to mice must be at least 200 mg/kg. However, to reach such a toxicity, the concentration of endosulfan must be dropped to 3%, resulting in a non-economical mixture of very low activity. 
     The microencapsulation of pesticides and insecticides has been proposed in the prior art as a way of extending the insecticidal life of pesticides while supposedly decreasing their toxicity to non-target animals. Examples are: U.S. Pat. Nos. 2,800,458; 3,069,370 , 3,116,216, 3,137,631, 3,270,100; 3,418,250; 3,429,827; 3,577,515; 3,959,164; 4,417,916; and 4,563,212. British Patent Number 1,371,179; European Patent Publication Numbers 148,169 and 165,227; and Israel Patent Numbers 79,575 and 84,910. 
     Microencapsulated chlorpyrifos has been reported in European Patent Application No. 140,548. Microencapsulated endosulfan has been reported in U.S. Pat. No. 4,230,809. in neither case is there any report of the use of ultraviolet absorbers in these microencapsulated formulations. 
     The use of an ultraviolet absorber to protect insecticides, especially pyrethroids, has been reported in U.S. Pat. Nos. 2,168,064; 3,063,893; 3,098,000; 3,130,121; 3,264,176; 3,541,203; 3,560,613; and 3,839,561. 
     U.S. Pat. Nos. 4,056,610 and 4,497,793 describe the use of specific UV absorbers in microencapsulated pyrethrins. However, these require the case of U.S. Pat. No. 4,056,610--the use of a UV absorber both the outer casing and in the liquid fill. 
     Regardless of the disclosure in the prior art, there has not yet been offered for sale microencapsulated chlorpyrifos or endosulfan, which has both extended insecticidal activity and extremely low toxicity to non-target animals. 
     SUMMARY OF THE INVENTION 
     According to the present invention there is provided a microencapsulated chlorpyrifos or endosulfan composition comprising a polyurea shell and one or more photostable ultraviolet and visible light absorbent compounds having a log molar extinction coefficient of from about 2 to 5 with respect to radiation having wave lengths in the range of about 310 to 450 nanometers wherein said photostable ultraviolet and visible light absorbent compound does not react with the monomer used in building the polyurea shell. The result is a microencapsulated composition having unexpected long, extended insecticidal activity with high toxicity to target species and very low toxicity to non-target animals. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The microencapsulated insecticidal composition of the present inventions are prepared using standard processes. Details for chlorpyrifos appear in Example 1. Details for endosulfan appear in Example 10. The percentage of the envelope--excluding the water and the polyvinyl-alcohol varies from 3% to 50%, preferably up to 30%. Similarly, the fill contains from 0.5% to 5% preferably 1% to 3%, of the photostable ultraviolet and visible light absorbent compound. 
     Details of the stability of chlorpyrifos are listed in Example 2. For endosulfan, it was found that it decomposed after irradiation for 100 hours at 310±5 nanometers and 475± nanometers. 
     The photostable ultraviolet and visible light absorbent compounds are selected from the group consisting of sterically hindered amines and dyes. The sterically hindered amines are in turn selected from the Ciba-Geigy products known by the general trade name &#34;TINUVIN&#34; where the preferred ones are &#34;TINUVIN -770&#34; and &#34;TINUVIN -780&#34; having the following structures and Chemical Abstract Numbers as follows: ##STR1## 
     These ultraviolet and visible light absorbent compound were chosen among other reasons because they did not react with the monomers that build the envelope. 
     The microencapsulated compositions of the invention may also optionally contain in addition to one of the &#34;TINUVINS&#34; dyes selected from the group consisting of Thermoplast green, Blue paste, Fluorescein, Sudan blue, Macrolex blue and Sedan III. 
     The microencapsulated compositions containing chlorpyrifos are listed in Table 1. Several of these compositions were studied to determine which had the longest activity against larger species, such as beetles and cockroaches, even after exposure to sunlight, (Examples 4,5 and 8) while having the lowest toxicity to non-target species, represented by mice, fish and bees (Examples 3,6 and 9). The result was that composition Numbers 14 and 15 containing chlorpyrifos were the preferred compositions, with Number 14 most preferred. 
     Almost all of the microencapsulated compositions of the present invention containing endosulfan gave poor toxicological results on mice. That is, in order to obtain a formulation with an LD 50  of 200 for mice the formulation would have to be very diluted; making it commercially unacceptable. However, compositions numbers 59 and 61 showed appreciably lower toxicity to non-target species at a commercially viable concentration of endosulfan, with number 61 the best. Examples 11 and 12 show the toxicity of these two formulations against the non-target species represented by mice and fish, respectively. 
     Thus, the present invention affords a novel microencapsulated composition containing chlorpyrifos or endosulfan, which not only can withstand relatively long exposure to sunlight, has a low toxicity to non-target species such as mice, bees and fish, while retaining commercially acceptable toxicity levels to target species such as beetles and cockroaches. 
     While the invention will now be described in connection with certain preferred embodiments in the following examples, it will be understood that it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the scope of the invention, as defined by the appended claims. Thus, the following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purposes of illustrate discussions of preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of procedures as well as of the principles and conceptual aspects of the invention. 
     EXAMPLE 1 
     Representative Preparation of the Microencapsulation of Chlorpyrifos 
     Four separate solutions: A, B, C and D were prepared as follows: 
     
         ______________________________________Solution A:     1520 ml water     15.2 g polyvinylalcohol (&#34;MOWIOL-G-4)Solution B:     720 g melted chlorpyrifos     140 g Voranate M-580     4 g &#34;TINUVIN-770&#34;Solution C:     360 ml water     20 g ethylene diamine     18.3 g diethylenetriamineSolution D:     14 g propylene glycol     58.4 Nonylphenol 6 mole ethoxylated (NP-6)     10 g xanthan gum______________________________________ 
    
     Formation of the microcapsules is carried out by interfacial polymerization as follows: 
     A good emulsion of Solution B in A was made by mixing for 5 minutes in a high sheer mixer, keeping the mixture at 40° C. To this emulsion was slowly added Solution C, keeping the temperature at 40° C. The reaction mixture was cooled to 25° C. to 35° C. and the stirring was continued for 4 additional hours. Solution D was added and the mixture stirred for 15 minutes. Representative microencapsulated compositions of chlorpyrifos are listed in Table 1. 
     
                                           TABLE 1__________________________________________________________________________REPRESENTATIVE MICROENCAPSULATED COMPOSITIONS OF CHLORPYRIFOS   isocyanates             E.D.A.                 DETA                     PDA                        Tinuvin 770                              TEPA                                  Tinuvin P                                        TiO.sub.2                                           EscalolFormulation no.   types amount             (g) (g) (g)                        (g)   (g) (g)   (g)                                           (g)  Water                                                      PV__________________________________________________________________________                                                      (g) 1.     ISONATE         35  6.2 5.7 -- 0.9   --  --    -- --   360   4   M-309 2.     ISONATE         35  6.2 5.7 -- --              1  --   360   M-302 3.     ISONATE         35  --  5.7 -- --    9.6 --    -- 1    360   M-302 4.     ISONATE         35  --  5.7 -- 0.9   9.6 --    -- --   360   4   M-302 5.     ISONATE         35  6.2 5.7 -- 0.9   --  --    -- --   380   3.8   M-302 6.     Voranate         35  --  5.7 7.7                        0.9   --  --    -- --   380   3.8   M-580 7.     Voranate         35  6.2 5.7 -- 0.9   --  --    -- --   380   3.8   m-220 8.     HMDI  2.61             6.1 5.7 -- --    --  1     -- --   360   6 9.     HMDI  2.61             6.2 5.7 -- --    --  --    -- 1    360   .610.     TDI   27  6.2 5.7 -- --    --  1     -- --   360   3.611.     TDI   27  6.2 5.7 -- 1     --  --    -- --   360   3.612.     TDI   27  --  5.7 -- --    9.6 1     -- --   360   3.613.     Voranate         35  6.2 5.7 -- --    --  1     -- --   360   3.6   M-58014.     Vorante         35  6.2 5.7 -- 0.9   --  --    -- --   400   4   M-58015.     Voranate         280 39.7                 36.8                     -- 8     --  --    -- --   3040  30.4   M-58016.     Voranate         280 39.7                 36.8                     -- 8     --  --    -- --   3040  30.4   M-58017.     Voranate         280 39.7                 36.8                     -- 8     --  --    -- --   3500  35   M-58018.     Voranate         280 34.7                 31.9                     -- 9     --  --    -- --   3040  30.4   M-58019.     Voranate         4.4 0.62                 0.58                     -- 1     --  --    -- --   380   3.8   M-58020.     Voranate         35  4.2 4   -- 1     --  --    -- --   380   3.8   M-58021.     Voranate         140 20  18.3                     -- 4     --  --    -- --   1520  15.2   M-58022.     Voranate         35  5.6 5.3 -- 1     --  --    -- --   380   3.8   M-58023.     Voranate         35  5.6 5.3 -- 1     --  --    -- --   380   3.8   M-58024.     Voranate         11.7             1.86                 1.71                     -- 1     --  --    -- --   380   3.8   M-58025.     Voranate         35  5   4.6 -- 1     --  --    -- --   380   8   M-58026.     Voranate         35  6.2 5.7 -- --    --  1     -- --   360   3.6   M-580__________________________________________________________________________ EDA  Ethylene diamine DETA  Diethylene triamine PDA  Propylene diamine TEPA  Tetra ethylene penta amine 
    
     EXAMPLE 2 
     Stability of Unprotected Chlorpyrifos to UV/Visible Light 
     Unprotected chlorpyrifos was irradiated by an ultraviolet/visible light lamp for 68 hours. The stability versus the wavelength of the light is summarized as follows: 
     
         ______________________________________Wave Lengths      Extent of Degradation______________________________________313 ± 5        Total degradation365 ± 5        Low degradation404 ± 5        Low degradation436 ± 5        Medium degradation______________________________________ .sup.a In nanometers 
    
     EXAMPLE 3 
     Metthod for Determining Acute Oral Toxicity with Mice 
     It is preferable lo use Adult males (2-2.5 months) weighing 25-30 g. A solution of the formulation was obtained by using a &#34;Vortex&#34; mixer for 5 min. The quantity of the solution depended on the weight of mouse. Thus, 1 ml. solution was administered for 20 g of mouse weight. The solution was introduced by using a syringe (2 ml) through the mouth into the stomach of mouse. The test was performed in 5 replications and mortality was checked after 0,5,24,72,96,120,144,168 hours. Standardized mouse food was given during the experiment. The results for three composition of the present invention are listed in Table 2 together with the data for a standard Emulsifiable Concentrate formulation of chlorpyrifos after a time of 168 hours. 
     
                       TABLE 2______________________________________ID.sub.50 ON MICE OF SEVERALFORMULATIONS OF CHLORPYRIFOS      LD.sub.50Formulation.sup.a          Formulation ofNumber       Techincal Material.sup.b                      250 g/l______________________________________ 6           2250          9,00013           2250          9,00014           &gt;2700         &gt;10,800E.C. formulation        120           480______________________________________ .sup.a From Table 1 .sup.b mg/kg 
    
     EXAMPLE 4 
     Method for Determining the Susceptibility of Beetles (Tribolium castaneum and Maladera matrida to Insecticides) 
     This method was used to measure the levels of susceptibility of population of beetles to a given insecticide. The method was carried out in a room free from insecticide contamination. The beetles were treated and held at a temperature of 30° C. for Tribolium castaneum and 25° C. for Maladera matrida and a relative humidity above 25%. Beetles were obtained, as far as possible, from the same area, and kept in a suitable container until required; and they were given adequate and standardized food before the experiment, Adult beetles of either sex were used. Tribolium castaneum were grown on flour enriched with 1% of beer yeast. Maladera matrida were obtained from the land of the farm &#34;Sufa&#34; and held in the laboratory in a suitable container on the ground which was used for food. A solution of each of the different formulations and the commercial material was obtained by using a high-shear mixer for 5 min, For each formulation Whatman paper No. 41 (d=9 cm.) was dipped into the solution during mixing and put into a petri dish (d=9 cm). The filter paper for exposure time 0 was dried in the hood, and the others were taken to the roof of the laboratory and exposed to sunlight. Approximately every 5 days, 3 petri dishes were removed from the roof and 5 beetles were placed inside each dish by using an aspirator for Trillium castaneum. The experiment was performed in 3 replications and mortality was checked each replication. The results for Maladera matrida treated with various chlorpyrifos compositions are shown in Table 3. 
     
                       TABLE 3______________________________________Maladera matridaTREATED WITH VARIOUS CHLORPYRIFOSMICROENCAPSULATED FORMULATIONS                Percent KilledExposure.sup.a    Concentration.sup.c                Formulation Type.sup.bto sun   ppm         14     13   6    EC.sub.45                                      Blank______________________________________ 0       500         100    100  100  100  0 6                   86.7   100  100  53.310                   80     93.3 93.3 53.317                   6.7    0    33.3 0______________________________________ .sup.a In days .sup.b From Table 1 .sup.c Of chlorpyrifos 
    
     EXAMPLE 5 
     Method for Determining the Efficacy of Cockroaches (Germanica blatella) to Insecticides 
     This method measured the levels of susceptibility of a population of cockroaches to Chlorpyrifos. Cockroaches were exposed to standard chlorpyrifos residues in a petri dish and mortality was determined. From the results, the times necessary for 50% and 95% knockdown (LT 50  and LT 95 ) can be determined. Adult males were used. If it was not feasible to obtain enough males, information on susceptibility can be obtained by using females. The test was carried out in a room free of insecticidal contamination. The cockroaches were exposed to the chlorpyrifos and held at a temperature between 25° C. and 30° C. and at a relative humidity above 25%. Cockroaches were given adequate and standardized food before the experiment. Cockroaches, Germanica blatella were grown in the laboratory in containers with ready-to-serve meaty dog food. 
     A solution of each of the different formulations and the commercial material was obtained by using a high-shear mixer for 5 min. A solution of different concentrations was prepared. For each formulation Whatman paper N41 (d=9) was dipped into the solution during mixing and put in a petri dish (d=9). The filter paper for exposure time was dried in a hood and the others were taken to the roof of the laboratory and exposed to sunlight. Approximately every 5 days a petri dish was removed from the roof, and 5 Germanica blatella cockroaches were placed inside. To introduce 5 cockroaches into each petri dish, the cockroaches was first anaesthetized with carbon dioxide. The test was performed in 3 replications and mortality was checked. The exposure times examined were 0,5,10,15 and 20 days, approximately. Control dishes--untreated Whatman paper with 5 cockroaches after 24 h. A cockroach was considered knocked down if it fails to move on being returned to a normal posture. The results for various microencapsulated formulations of chlorpyrifos are shown in Tables 4 and 5. 
     The tests were carried out according to the World Health Organization Technical Report Series No. 443 Geneva 1970, pp 130-133. 
     
                       TABLE 4______________________________________Germanicia blatellaTREATED WITH VARIOUS CHLORPYRIFOSMICROENCAPSULATED FORMULATIONS             Percent KilledExposure  Formulation             Concentration (ppm)to Sun.sup.a  Type.sup.b 100    200  300  400  500  Blank______________________________________0      14         100    100  100  100  100  00      13         26.7   80   100  100  1000       6         0      93.3 93.3 93.3 1000      EMPIRE.sup.c             73.3   100  100  100  1000      EW-20.sup.d             100    100  100  100  1000      EC-45.sup.e             93.3   100  100  100  100______________________________________ .sup.a Hours .sup.b From Table 1 .sup.c Dow Chemical Company microencapsulated chlorpyrifos, 200 g/l .sup.d Water based formulation of Makhteshim Chemical Works. .sup.e Standardized Emulsified Concentrate (nonmicroencapsulated) formulation of chlorpyrifos. 
    
     
                       TABLE 5______________________________________Germanicia blatellaTREATED WITH VARIOUS CHLORPYRIFOSMICROENCAPSULATED FORMULATIONS             Percent KilledExposure  Formulation             Concentration (ppm)to sun.sup.a  Type.sup.b 25     50   100  150  200  Blank______________________________________0      14         100    100  100  100  100  00      EMPIRE.sup.c             26.7   33.3 53.3 80   1000      EC-45.sup.d             60     60   73.3 100  100______________________________________ .sup.a Hours .sup.b From Table 1 .sup.c Dow Chemicals Company microencapsulated chlorpyrifos, 200 g/l .sup.d Standardized Emulsified Concentrate (nonmicroencapsulated) formulation of chlorpyrifos. 
    
     EXAMPLE 6 
     Methhod for Determining Toxicity of Fish (Guppies) 
     All guppies require about the same basic care: water quality as close as possible to pH=7.0 (neutral); water temperature about 24°-25° C., and good strong light for least 12 hours a day (more light makes them grow faster). The test method was carried out in a room free of insecticidal contamination. Adult fish of either sex were used. 
     Guppies were obtained from a fish shop and kept in a suitable 16-liter aquariums (water temperature 23°-25° C.), 10 fish/aquarium, The guppies were given adequate and standardized food (Europet Basic Food) before and after the experiment. Food was withheld for 2 days before the experiment. 
     Solutions of formulation and commercial material were obtained by using a high-shear mixer for 5 min. Solutions 250,500,100,2000,4000,5000, μg/liter of the formulations were prepared. Mortality was checked after 3,6,24,48,72 and 96 hour. From the results, the times necessary for 50% and 95% mortality (LT 50  and LT 95 ) can be determined for each formulation. Test were carried out also on with golden orfe fish. The results are listed for golden orfe fish in Table 6. 
     
                       TABLE 6______________________________________TOXICITY OF A CHLORPYRIFOSMICROENCAPSULATED FORMULATIONTO GOLDEN ORFE FISHConcentration (μg/l)of Formulation 14Percent Killed           EC (μg/l).sup.b5000      2000     1000    250   50  250Time.sup.a  Percent Killed______________________________________ 0      0      0        0    0      0   0 3     100     0        0    0      0   0 6     100     0        0    0      0  1024     100    30       10    0      0  1048     100    40       20    0     10  3072     100    40       20   10     10  3096     100    40       20   10     20  30______________________________________ .sup.a Hours .sup.b Standardized Emulsified Concentrate (nonmicroencapsulated) formulation of chlorpyrifos. 
    
     EXAMPLE 1 
     Microencapsulated Chlorpyrifos using Variations of Formulation 14 and Containing Various Concentrations of Dyes 
     Following the method of Example 1, one of the preferred microencapsulated formulation, Type 14 was prepared containing various different dyes. The microencapsulated formulations prepared are shown in Table 7. 
     
                                           TABLE 7__________________________________________________________________________VARIATIONS OF FORMULATION TYPE 14 CONTAINING VARIOUS DYES                    TinuvinFormulation  Isocyanate            EDA DETA                    770  ColourNumber Type Amount            (g) (g) (g)  type   amount (g)__________________________________________________________________________14-G   Voranate       35   5.0 4.6 1    Thermoplast                                1  M-580                  green14-H   Voranate       35   5.0 4.6 1    Blue paste                                1  M-58014-I   Voranate       35   5.0 4.6 1    Fluorescein                                1  M-58014-J   Voranate       35   5.0 4.6 1    Sudan Blue                                1  M-58014-K   Voranate       35   5.0 4.6 1    Macrolex                                0.25  M-580                  Blue14-L   Voranate       35   5.0 4.6 1    Sudan III                                1  M-58014-M   Voranate       35   5.0 4.6 1    Sudan III                                1  M-58014-N   Voranate       157.5            22.3                20.7                    4.5  Macrolex                                1.5  M-580                  Blue14-O   Voranate       259  36.7                34  7.7  Macrolex                                3.0  M-580                  Blue14-P   Voranate       140  19.8                18.4                    4    Macrolex                                1.6  M-580                  Blue14-Q   Voranate       385  54.5                50.6                    11   Sudan Blue                                4.4  M-58014-R   Voranate       420  59.5                55.2                    12   --     --  M-58014-S   Voranate       385  54.5                50.6                    11   Sudan Blue                                4.4  M-58014-T   Voranate       525  74.4                69  15   Sudan Blue                                6__________________________________________________________________________ 
    
     EXAMPLE 8 
     Following the method of Example 4, several microencapsulated formulations of chlorpyrifos were compared as to their effect against Tribolium castaneum in petri dishes after exposure to sunlight. Results are shown in Table 8. 
     
                                           TABLE 8__________________________________________________________________________COMPARISON OF SEVERAL ENCAPSULATED FORMULATIONS ONTRIBOLIUM CASATANEUM AFTER EXPOSURE TO SUNLIGHTCONCENTRATION 500 P.P.M.Exposureto sunFormulation typelightEC 14A      14 13 21 19 2  3  4  5  6  8  9  Penn phos.days Percent Killed                         Penn wall__________________________________________________________________________ 0   100   100      100         100            100               100                  100                     100                        100                           100                              100                                 100                                    100                                       100 5    6 100      100         100            100               100                  100                     100                        100                           100                              100                                 100                                    100                                       10010    6 100      100         100            100               100                   76                      20                         33                            26                               80                                 100                                    100                                        2515    0  0  60          10             36                56                   13                      0  0  23                               0  50                                     40                                        25__________________________________________________________________________ .sup.a EC 
    
     EXPERIMENT 9 
     Toxicity (Acute Contact and Oral LD 50 ) of Microencapsulated Chlorpyrifos to Honey Bees (Apir mellifera L.) 
     A. General 
     The study was performed with worker honey bees of about the same age, bred in a normal beekeeper&#39;s manner. For the tests, the bees were caught from the entrance hole of the hives in groups of ten with glass capture tubes, without anesthetics. During the tests, the bees were provided ad libritum with commercial ready to use syrup for honey bees as food. Stainless steel chambers (width 10 cm, height 8.5 cm, and depth 5.5 cm) served as test cages. The inner sides of the cages (except the front side) were covered with filter paper. The test cages were exposed in incubators at about 28° C., at 40 to 60% relative humidity in darkness, while being ventilated to avoid possible accumulations of pesticides vapor. The tests were performed in five dosages of microencapsulated chlorpyrifos and one solvent control with three replicates per dosage or control. 
     B. Contact Toxicity Test 
     First the test cages with the bees in it were exposed to CO 2  in an incubator to anaesthetize the test animals with CO 2  dosage chosen so that the anaesthetization was shorter that five minutes. The test substance was then applied to the anaesthetized bees; and the treated bees were then returned to the test cages and kept under test conditions for 48 hours. Five dosages of the test substances were tested in order to provide a rational base for a proper assessment of the control LD 50  of microencapsulated chlorpyrifos to honey bees. The anaesthetized bees are laid, ventral surface up, on filter paper in petri dishes. One μl drop per bee of microencapsulated chlorpyrifos in solvent was placed in the ventral thorax using a GC-syringe. 
     The result was an LD 50  contact of 22.1 μ/bee compared to a toxicity of 0.059 μ/bee for technical chlorpyrifos, 
     C. Oral Toxicity Test 
     Five dosages of microencapsulated chlorpyrifos in acetone were tested in order to provide a rational base for a proper assessment of the oral LD 50  to honey bees. Ten cages containing 10 bees each were prepared without food, letting the bees starve for 1 to 2 hours. Following this, 250 μl of the prepared solutions in type of Eppendorf-pipettes were hung in each cage through one of the top openings. The bees were observed as long as uptake of the solution takes place. Each bee that vomited the solution was excluded from the test. The bees were provided with normal food after the uptake of the tested solution, but at the latest after 3 hours. 
     The result was an LD 50  oral of 118.5 μ/bee compared to a toxicity of 0.25 μg/bee for technical chlorpyrifos. 
     EXAMPLE 10 
     Representative Preparation of the Microencapsulation of Endosulfan 
     Following the general method of Example 1 four solutions, A-D were prepared. 
     
         ______________________________________Solution A: 380 ml water       3.8 g polyvinyl alcohol (MOWIOL-G4)Solution B: 180 g melted endosulfan       42 g Voranate M-580       1 g &#34;TINUVIN-770&#34;       1 g Irganox 1076Solution C: 9 g water       9.3 g tetraethylinepentamine       5.6 g Diethylene triamineSolution D: 3.5 g propylene glycol       14.6 g Nonylphenol 6 moles ethoxylated       (NP-6)       2.5 g xanthan gum______________________________________ 
    
     Solution A is heated to 80° C. and Solution B is added and an emulsion is made using a high sheer mixer for 1-2 minutes. Solution C is then added and the reaction mixture is stirred for an additional 4 hours keeping the temperature of the mixture at 50° C. The pH of the solution is then reduced to 7.6 by adding H 3  PO 4 , Solution D is added, and the reaction mixture stirred for 15 minutes. Representative microencapsulated composition of endosulfan are listed in Table 9 and 10. 
     
                                           TABLE 9__________________________________________________________________________                                          Nonyl-                                          phenol                                          6 mole                          Propyl-                               Tetra-                                     Propyl-                                          ethoxy-                                              Xan-Isocyantes     Ethylene               Diethylene                     U.V. ene- ethylene                                     ene  lated                                              than                                                 OtherSample    Quantity          diamine               triamine                     absorb-                          diamine                               pent- gly- (NP-6)                                              gum                                                 add- Conc.NumberType (g)  (g)  (g)   er: (g)                          (g)  amine: (g)                                     col: g                                          %   (g)                                                 tives                                                      a.i.__________________________________________________________________________                                                      %31   Voranate     11.7 2.0  1.9   Tinuvin                          --   --    1.2  14.6                                              2.7                                                 --   25.8M-580                77032   Voranate     11.7 --   1.9   Active C                          2.6  --    1.5  14.6                                              2.7                                                 --   --M-58033   Voranate     11.7 2.06 1.9   Active C                          --   --    1.5  14.6                                              2.7                                                 --   --M-58034   Voranate     11.7 --   1.9   Active C                          2.6  --    1.5  14.6                                              2.7                                                 --   --M-58035   Isonate     11.7 2.0  1.9   Tinuvin                          --   --    1.5  14.5                                              2.7                                                 --   --M-301                77036   Isonate     11.7 --   1.9   Tinuvin                          2.6  --    1.5  14.6                                              2.7                                                 --   --M-301                77037   Voranate     11.7 1.86 1.71  Tinuvin                          --   --    1.2  14.6                                              2.7                                                 --   24M-580                77038   Voranate     11.7 1.86 1.71  Tinuvin                          --   --    1.2  14.6                                              2.5                                                 --   25M-580                77039   Voranate     11.7 1.86 1.72  Tinuvin                          --   --    1.2  14.6                                              2.5                                                 --   25M-580                77040   Voranate     35   5.6  5.3   Tinuvin                          --   --    3.5  14.6                                              2.5                                                 Ca(No.sub.3).sub.2                                                      17M-580                77041   Voranate     35   5.6  5.2   Tinuvin                          --   --    3.5  14.6                                              2.5                                                 --   --M-580                77042   Voranate     35   5.6  5.3   Tinuvin                          --   --    3.5  14.6                                              2.5                                                 --   --M-580                77043   Voranate     35   5.6  5.3   Tinuvin                          --   --    --   2.5 -- --   --M-580                77044   Voranate     35   --   5.3   Tinuvin                          --   8.69  --   2.5 -- --   --M-580                77045   Voranate     35   --   5.3   Tinuvin                          6.9  --    --   --  2.5                                                 --   --M-580                77046   Isonate     35   5.6  5.3   Tinuvin                          --   --    3.5  --  2.5                                                 --   --M-301                77047   Voranate     35   --   --    Tinuvin                          6.9  8.64  7.0  14.6                                              2.5                                                 --   --M-580                77048   Isonate     35   --   5.3   Tinuvin                          6.9  --    3.5  --  2.5                                                 --   --M-301                77049   Voranate     18   --   5.3   Tinuvin                          --   8.64  3.5  14.6                                              2.5                                                 --   --M-580 +     17              770TDI50   HMDI 26.1 5.6  5.3   Tinuvin                          --   --    --   14.6                                              -- --   --                     77051   TDI  26.1 5.6  5.2   Tinuvin                          --   --    --   --  -- --   --                     77052   TDI  26.1 --   5.7   Tinuvin                          7.7  --    --   --  2.5                                                 --   --                     77053   HMDI 26.1 --   5.7   Tinuvin                          7.7  --    --   14.6                                              -- --   --__________________________________________________________________________ 
    
     
                                           TABLE 10__________________________________________________________________________                        Nonyl-                        phenol                        6 mole                        ethoxy-SampleIsocyanates          Amines   Irganox                        lated                             Xanthan                                  %NumberType Quantity          Type              Quantity                   1076 gr.                        (NP-6)                             gum  a.i.__________________________________________________________________________54   Isonate     38.5 DETA              5.0  1    Solid                             --   19.4M-342     PDA 6.8       additive55   Voranate     45.5 DETA              5.93 1    Solid                             --   21.3M-580     PDA 8.06      additive56   Voranate     38.5 DETA              5.01 1    Solid                             --   23.8M-580     PDA 6.857   Voranate     42   DETA              5.7  1    Solid                             14.8 26.0%M-580     PDA 7.4       Liquid                             2.558   Voranate     42   DETA              5.57 1    Solid                             14.8 30.7%M-580     PDA 9.54      Liquid                             2.559   Isonate     42   DETA              5.57 1    Solid                             14.8 25.1%M-342     PDA 7.4       Liquid                             2.560   Isonate     42   DETA              5.57 1    Solid                             14.8 25.2%M-310     TEPA              9.3       Liquid                             2.561   Isonate     42   TEPA              9.3  1    Solid                             2.5  25.6%M-342     DETA              5.57      Liquid__________________________________________________________________________ 
    
     EXAMPLE 11 
     Following the method of Example 3, the two best microencapsulated formulations of the present invention containing endosulfan were listed for their toxicity to non-target species, represented by mice. The results are shown in Table 11. This shows the lower toxicity of formulation 61 as against formulation 59. 
     EXAMPLE 12 
     Following the method of Example 6, the two best microencapsulated formulations of the present invention containing endosulfan were tested for their toxicity to non-target species, fish, compared with the non-microencapsulated EC-35 formulation. The results are shown in Table 12. This shows the lower toxicity of formulation 61 as against both formulation 59 and against the non-microencapsulated EC-35 formulations of endosulfan. 
     
                       TABLE 11______________________________________THE TOXICITY TO MICE OF THETWO BEST MICROENCAPSULATEDFORMULATIONS OF ENDOSULFAN.sup.aExposure  Formulation No. 59                    Formulation No. 61Time in  Solution concentration - mg/kgHours  33.3   50     75   112.5  33.3 50   75   112.5______________________________________ 1      0      50     50   50     0    0    0    0 3     50      50    100  100     0    20  100  100 24    50     100    --   --      0    50  --   -- 48    50     --     --   --     50   100  --   -- 72    50     --     --   --     50   --   --   --168    50     --     --   --     50   --   --   --______________________________________ .sup.a Percent mortality. 
    
     
                                           TABLE 12__________________________________________________________________________THE TOXICITY TO FISH OF THE TWO BESTMICROENCAPSULATED FORMULATIONS OF ENDOSULFAN.sup.a   EC-35  Formulation No. 59                       Formulation No. 61Exposure Time   Solution concentration - mg/lin hours   1 5 10 2.5            5 8 16                  50                    100                       2.5                         5 8 16                               50                                 100__________________________________________________________________________ 3      0  0        30          0  0               0                 0                   0                     0 0 0  0                              0                                0                                  0 6      0  0        30          0  0               0                10                  10                     0 0 0  0                              0                                0                                  024      0 57        70          0 20              20                40                  43                    100                       0 0  0                              0                               20                                  5048      0 57       100          0 20              30                40                  71                    -- 0 0 30                             30                               30                                 10072      0 57       -- 0 20              30                40                  71                    -- 0 0 30                             30                               40                                 --96      0 57       -- 0 20              30                40                  71                    -- 0 0 30                             30                               40                                 --__________________________________________________________________________ .sup.a Percent mortality.