CLIAMS:We Claim:

1. A method of preparing a controlled-release pesticide formulation, the method comprising-
preparing beads of an active complex comprising a pesticide entrapped in an alginate complex;
drying and grinding the beads to obtain pesticide-alginate powder comprising pesticide in the range of 25-39% w/w;
preparing a mixture of said powder and bentonite; and
extruding said mixture to obtain pellets of the controlled-release pesticide formulation such that the pellets comprise pesticide in the range of 1.4 – 20% w/w.

2. A slow release pesticide formulation as claimed in claim 1, wherein the pesticide is selected from a group consisting of imidacloprid, flubendiamide, hexaconazole, kresoxim methyl, metribuzin and pendimethalin.

3. A method as claimed in claim 1, wherein the beads comprising the pesticide entrapped in the alginate complex are prepared by forming a slurry of the pesticide and sodium alginate in water, followed by dropwise addition of calcium chloride solution to said slurry.

4. A method as claimed in claim 1, wherein the mixture is in the form of a dough prepared by mixing said powder, bentonite and water.

5. A method as claimed in claim 1, wherein the ratio of pesticide, alginate and bentonite in the controlled-release pesticide formulation ranges between 1:1:0.5 and 1:1:20.

6. A method as claimed in claim 5, wherein the ratio of pesticide, alginate and bentonite in the controlled-release pesticide formulation ranges between 1:1:10 and 1:1:20.

7. A controlled-release pesticide formulation comprising:
powder of an active complex comprising a pesticide entrapped in an alginate complex, said powder being dispersed in bentonite;
wherein said controlled-release pesticide formulation is prepared by first forming the powder of the active complex followed by mixing of said powder with bentonite.

8. A controlled-release pesticide formulation as claimed in claim 7, wherein the ratio of pesticide, alginate and bentonite ranges between 1:1:0.5 and 1:1:20.

9. A controlled-release pesticide formulation as claimed in claim 7, wherein the percentage release of pesticide from the controlled-release pesticide formulation within 90 days of incorporation in soil is in the range of 45-90%.

10. A controlled-release pesticide formulation as claimed in claim 7, wherein the pesticide is selected from a group consisting of imidacloprid, flubendiamide, hexaconazole, kresoxim methyl, metribuzin and pendimethalin.

Dated this 19th day of March, 2015

Aparna Kareer
Of Obhan & Associates
Agent for the Applicant
Patent Agent No. 1359
,TagSPECI:The present disclosure relates to a controlled release pesticide formulation and a method of preparing said controlled release pesticide formulation.

BACKGROUND
Pesticides including herbicides, fungicides, and various other substances used to control pests have become significant to protect crops from various pests and ensure food security. An important aspect when using pesticides is to ensure that only a desired amount of pesticide is released over a given period of time. Thus, numerous methods have been developed depending on the nature of pesticide to ensure controlled release of pesticides. While controlled release formulations of a few pesticides have been successfully developed, effective controlled release formulations of insecticides such as imidacloprid and flubendiamide, fungicides such as hexaconazole and kresoxim methyl and herbicides such as metribuzin and pendimethalin, are yet to be developed. Typically, slow release formulations demonstrate release in water, with almost 80% being released in 3-4 days. For typical pesticides used in soils, a much slower release is preferred that needs to last one crop cycle, typically 4 months for groundnut and 1 year for sugarcane. Such slow release profiles are difficult to achieve since most fillers or encapsulating materials degrade within a few days under soil conditions.
Imidacloprid is typically used as an insecticide against soil based insects such as termites and grubs. Imidacloprid is a colorless crystalline solid with a weak characteristic odor. It is known to crystallize when formulated in liquid, due to its high solubility in water. In soil, imidacloprid readily leaches out due to its high water solubility and rapid hydrolysis. Thus, it has poor long duration control over soil insects. Typical crops to which imidacloprid is applied include groundnut and sugarcane. While groundnut is a 120 day crop, sugar cane is a 1 year crop. Hence, over the entire duration of the cropping cycle, protection is needed for these crops against cane grub, white grub, termites, ground nut borer and other soil insects which damage their root system.
Various methods have been attempted to form controlled release formulations of imidacloprid. “Use of bentonite and humic acid as modifying agents in alginate based controlled release formulations of imidacloprid”, by Gonzalez-Pradas et.al., Pesticide science May 1999. v. 55 (5); and “Mobility of imidacloprid from alginate bentonite controlled release formulations in greenhouse soil”, by E González-Pradas et. al; Pesticide Science 10/1999; 55(11):1109 – 1115 disclose a conventional method of preparing controlled release formulations of imidacloprid. Said documents disclose preparing formulations of imidacloprid by mixing imidacloprid (with or without bentonite) with alginate to form slurry, which may then be added slowly to calcium chloride solution to obtain imidacloprid- alginate complex.
The conventional formulations of imidacloprid do not offer a long term (120 days to 1 year) protection. Hence, to avoid crop damage from insects, typically, farmers use multiple applications of imidacloprid during the cropping cycle. This leads to higher use of pesticide thus deteriorating the soil quality and health and further polluting the environment.
There is therefore a requirement of ensuring crop protection from insects over the entire duration of the crop without multiple pesticide applications while reducing environmental pollution. This is possible if the pesticide is released over the entire duration of the cropping period. There is therefore a need to develop a controlled release pesticide formulation which could exhibit extended release when incorporated in soil.

SUMMARY
A method of preparing a controlled release pesticide formulation is disclosed. Said method comprises preparing beads of an active complex comprising a pesticide entrapped in an alginate complex; drying and grinding the beads to obtain pesticide-alginate powder comprising pesticide in the range of 25 - 39% w/w; preparing a mixture of said powder and bentonite; and extruding said mixture to obtain pellets of the controlled-release pesticide formulation such that the pellets comprise pesticide in the range of 1.4 - 20% w/w.
A controlled release pesticide formulation is also disclosed. Said formulation comprises of powder of an active complex comprising a pesticide entrapped in an alginate complex, said powder being dispersed in bentonite; wherein said controlled-release pesticide formulation is prepared by first forming the powder of the active complex followed by mixing of said powder with bentonite.

BRIEF DESCRIPTION OF DRAWINGS
The accompanying drawings illustrate the preferred embodiments and together with the following detailed description serves to explain the principles of the process.
Figure 1 shows a schematic representation of the method of the present disclosure.
Figure 2 illustrates the release of imidacloprid from different formulations when incorporated in soil.
Figure 3 illustrates the release of imidacloprid from different formulations when incorporated in aqueous environment.

DETAILED DESCRIPTION
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the disclosed process, and such further applications of the principles of the invention therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to “one embodiment” “an embodiment” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in one embodiment”, “in an embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The present disclosure relates to a method of preparing a controlled-release pesticide formulation and a controlled-release pesticide formulation. The method comprises preparing beads of an active complex comprising a pesticide entrapped in an alginate complex; drying and grinding the beads to obtain pesticide-alginate powder comprising pesticide in the range of 25 - 39% w/w; preparing a mixture of said powder and bentonite; and extruding said mixture to obtain pellets of the controlled-release pesticide formulation such that the pellets comprise pesticide in the range of 1.4 - 20% w/w.
The novel and inventive feature of the method of present disclosure resides in the order of addition of bentonite. Addition of bentonite to powder of pesticide- alginate complex as opposed to first mixing bentonite and pesticide followed by forming a complex with alginate, allows obtaining controlled release pesticide formulation which exhibits improved release profile as compared to that disclosed in the prior art.
In accordance with an embodiment, the beads comprising the pesticide entrapped in the alginate complex are prepared by forming a slurry of the pesticide and sodium alginate in water, followed by dropwise addition of calcium chloride solution to said slurry. In accordance with a preferred embodiment, the slurry is prepared by first physically mixing suitable amounts of powder of pesticide and sodium alginate using mixer/grinder, followed by addition of water and homogenization by a high speed homogenizer. By way of an example, to prepare a controlled release pesticide formulation comprising of Imidacloprid, 141.5 g of imidacloprid technical grade powder and 141.5 g of sodium alginate are mixed and dispersed in 4 L of water to obtain a slurry of imidacloprid.
In accordance with an embodiment, the dropwise addition of the slurry in calcium chloride solution is done at a rate of 10 ml/min. In accordance with an embodiment, the concentration of calcium chloride is in the range of 0.03 - 0.5 M. Preferably, the concentration of calcium chloride is 0.25 M.
In accordance with an embodiment, the beads comprising the pesticide entrapped in the alginate complex are dried prior to forming a powder thereof. Preferably, drying is carried out at a temperature in the range of 60 ºC to 90 0C. In accordance with an embodiment, the beads comprising the pesticide entrapped in the alginate complex are ground to a fine powder by grinding or milling.
In accordance with an embodiment, the powder obtained after grinding the beads is mixed with bentonite and water to form a mixture in the form of dough. Said mixture can be formed by using any standard mixing or grinding techniques. Said mixture is then extruded to form pellets of controlled release pesticide formulation. In accordance with an embodiment, cylindrical pellets are formed. In accordance with an embodiment, any standard physical extrusion methods may be used to form the cylindrical pellets. Upon formation, the pellets are dried. Preferably, drying is carried out at a temperature in the range of 60 ºC to 90 0C.
A schematic representation of the process has been provided in Figure 1.
A controlled-release pesticide formulation is also disclosed. Said controlled-release pesticide formulation comprises a powder of an active complex comprising a pesticide entrapped in an alginate complex, said powder being dispersed in bentonite; wherein said controlled-release pesticide formulation is prepared by first forming the powder of the active complex followed by mixing of said powder with bentonite.
It is believed that dispersion of the powder in bentonite provides for controlled release of the pesticide from the controlled release pesticide formulation.
In accordance with an embodiment, the controlled-release pesticide formulation comprises of 1.4 - 20% of the pesticide. In accordance with an embodiment, the ratio of the pesticide, alginate and bentonite in the controlled-release pesticide formulation ranges between 1:1:0.5 and 1:1:20. In accordance with a preferred embodiment, the ratio of the pesticide, alginate and bentonite in the controlled-release pesticide formulation ranges between1:1:10 and 1:1:20. High Performance Liquid Chromatography (HPLC) analysis was used as a standard process to estimate the amount of the pesticide in the beads and the controlled-release pesticide formulation.
In accordance with an embodiment, the pesticide is selected from a group consisting of imidacloprid, flubendiamide, hexaconazole, kresoxim methyl, metribuzin and pendimethalin.
In accordance with an embodiment, the percentage release of the pesticide from the controlled-release pesticide formulation within 90 days of incorporation in soil is in the range of 45 - 90%. In accordance with a specific embodiment, the percentage release of the pesticide from the controlled-release pesticide formulation within 90 days of incorporation in soil is in the range of 50 - 60 %.
In accordance with an embodiment, the controlled-release pesticide formulation is in the form of cylindrical pellets having a diameter of 1 to 4 mm.

EXAMPLES
The following example(s) of method for preparing the controlled release pesticide formulation are exemplary and should not be understood to be in any way limiting.
Example 1: T1 - controlled release pesticide formulation of imidacloprid (9% imidacloprid loading; imidacloprid: sodium alginate: bentonite = 1: 1.54: 2.71)
To 1.5 litre of deionized water, 20 grams of imidacloprid (technical 97%) and 30.8 grams of sodium alginate were added slowly and mixed thoroughly to form a slurry. The slurry was homogenized for 1 hour before further use. This slurry was added dropwise to 1 litre of 0.25 M calcium chloride di-hydrate solution to form uniform spherical beads. These beads were separated from the solution by passing the solution through a sieve of 2mm size. The separated beads were further dried at 90 0C over a period of 12-15 hours. The loading of imidacloprid on these beads was found to be 11% by HPLC. These beads were further ground using a conventional grinder to obtain a fine powder. The total yield of this complex was 57.7 grams. To this entire powder, 43.7 grams of powder of bentonite was added and mixed thoroughly. A small amount of water was also added to this mixture to form dough thereof. The dough was extruded through a conventional basket type extruder. Pellets with 1-4 mm diameter were obtained upon extrusion. The pellets were dried at 900C for a period of 12-15 hours. The total yield of the final product is 98 grams. HPLC analysis was conducted to estimate the loading of imidacloprid in the formulation and was found to be 8.9%. The ratio of imidacloprid:alginate:bentonite in the pellets was found to be 1:1.54:2.71.
Example 2: T2 - controlled release pesticide formulation of imidacloprid (1.9% imidacloprid loading; imidacloprid: sodium alginate: bentonite = 1:1:15.5)
141.5 grams each of sodium alginate and imidacloprid (technical 97%) were thoroughly mixed in 4 litre of deionized water using a homogenizer for 1 hour to obtain uniform slurry. This slurry was added dropwise to 4 litre of 0.25 M calcium chloride di-hydrate solution to form uniform spherical beads. These beads were separated from the solution by passing the solution through a sieve of 2mm size. The separated beads were dried at 90 0C over a period of 12-15 hours. The loading of imidacloprid on these beads was found to be 25% by HPLC. These beads were further ground using a conventional grinder to a fine powder. The total yield of this powder was found to be 300 grams. 20 grams of the powder was mixed thoroughly with 70 grams of powder of bentonite. To this mixture, a small amount of deionized water was added to form dough thereof. The dough was extruded through a conventional basket type extruder. Pellets having diameter of 1-4 mm were obtained upon extrusion. The pellets were dried at 900C for a period of 12-15 hours. The total yield of the final product was found to be 50 grams. HPLC analysis was used to estimate the loading of imidacloprid in this final formulation and was found to be 1.9%. The ratio of imidacloprid:alginate:bentonite in the final form was 1:1:15.5.
Example 3: T3 - controlled release pesticide formulation of imidacloprid (1.4% imidacloprid loading; imidacloprid: sodium alginate: bentonite = 1:1:20)
141.5 grams each of sodium alginate and imidacloprid technical (97%) were thoroughly mixed in 4 litre of deionized water using a homogenizer for 1 hour to obtain uniform slurry. This slurry was added dropwise to 4 litre of 0.25 M calcium chloride di-hydrate solution to form uniform spherical beads. These beads were separated from the solution by passing the solution through a sieve of 2mm size. The separated beads were dried at 90 0C over a period of 12-15 hours. The loading of imidacloprid on these beads was found to be 25% by HPLC. These beads were further ground using a conventional grinder to a fine powder. The total yield of this powder was found to be 300 grams. 20 gram of the powder was mixed thoroughly with 100 grams of powder of bentonite. To this mixture, a small amount of deionized water was added to form a dough thereof. The dough was extruded through a conventional basket type extruder. Pellets having a diameter of 1-4 mm were obtained upon extrusion. The pellets were dried at 900C for a period of 12-15 hours. The total yield of the final product was found to be 89 grams. HPLC analysis was used to estimate the loading of imidacloprid in this final formulation and was found to be 1.4%. The ratio of imidacloprid:alginate:bentonite in the final form was 1:1:20.
HPLC analysis was conducted to compare the release profile of the three formulations obtained above vis-à-vis that of the formulations disclosed in prior art. To compare the release profile, blank sample (Blank) and a sample (PA) in accordance with “Use of bentonite and humic acid as modifying agents in alginate based controlled release formulations of imidacloprid”, by Gonzalez-Pradas et.al., Pesticide science May 1999. v. 55 (5) were prepared. Table 1 and 2 illustrate the release profile studies of various formulations in soil and aqueous environment respectively.
For preparing blank sample (Blank), 28.5 grams of imidacloprid was mixed with 28.5 Sodium Alginate and 443.4 grams bentonite. The mixture was homogenized by addition of distilled water followed by extrusion to form pellets.

Table 1: % Release study of samples under soil conditions
Sample Description Pouch content % w/w %release in 15 Days %release in 30 Days %release in 60 Days %release in 90 Days
Blank (No complex; physical mixture of imidacloprid, sodium alginate and bentonite in the ratio of 1:1:15) 5 12.84 33.8 81.48 92.41
PA (Imidacloprid:Alginate:Bentonite = 1:1.5:2.71) 5 10.34 30.03 100 100
T2 (Imidacloprid:Alginate:Bentonite = 1:1:15) 5 1.9 7.7 46.08 53.22

Table 2: % Release study by suspending samples in deionized water
Sample Description 1 hr (%) 3hr (%) 8hr (%) 24hr (%) 48hr (%) 72 hr (%) 100 hr (%)
Blank(Imidacloprid: Alginate:Bentonite = 1:1:15.5) 5.23 12.25 24.73 44.33 79.2 93.13 99
PA (Imida:Alginate:Bentonite ratio = 1:1.5:2.71 10 15 35 62 84 90 100
T1 (Imida:Alginate:Bentonite ratio = 1:1.5:2.71) 2.37 4.045 28.2 61.5 96.793 100 100
T2: Imida:Alginate:Bentonite ratio = 1:1:15 1.82 6.25 11.76 29.5 49.9 63.7 76.5
T3: Imida:Alginate:Bentonite ratio = 1:1:20 1.72 2.08 16.36 31.17 44.49 61.68 67.14

Observations: Tables 1, 2 and Figures 2, 3 indicate that the formulation of present disclosure exhibits an improved release profile as compared to that disclosed in the prior art. This clearly indicates that the presently claimed formulation will be effective for a longer period of time. Under normal field conditions the pellet is expected to release imidacloprid for over 1.5 years. Further, as evident from Table 2, soil moisture is expected to play a major role in controlling the release of the imidacloprid.

INDUSTRIAL APPLICATION
The method of preparing the slow release formulation is easy to perform and economical. The controlled release pesticide formulation thus obtained is cost effective and highly efficient. The controlled release pesticide formulation of the present disclosure exhibits improved release profile when compared to the prior art and is effective over a longer duration of the cropping cycle. Even after 3 months of release, only 50% of pesticide is released which suggests that the formulation can work for over one year. This will be will be suitable for a wide variety of crops such as groundnut, sugarcane, soybean and other cereal crops, in case of imidacloprid. Fungicides such as hexaconazole and kresoxim methyl can be used to control fungal growth on leaves of plants such as paddy, grapes, apple and vegetables; and herbicides such as metribuzin and pendimethalin can be used for broad leaf weed control and typically used for crops such as potato, sugarcane and wheat. he controlled release pesticide formulation of the present disclosure also eliminates the requirement of repeatedly using the formulation thereby reducing the financial burden on the farmers as well as the environmental burden.