WO2018207211A1

WO2018207211A1 - A reusable charge-transfer based agrogel

Info

Publication number: WO2018207211A1
Application number: PCT/IN2018/050292
Authority: WO
Inventors: Santanu Bhattacharya; Subham BHATTACHARJEE; Deepa BHAGAT; Dipen BISWAKARMA
Original assignee: Icar - National Bureau Of Agricultural Insect Resources (nbair); Indian Institute of Science IISC
Current assignee: Icar - National Bureau Of Agricultural Insect Resources (nbair); Indian Institute of Science IISC
Priority date: 2017-05-10
Filing date: 2018-05-10
Publication date: 2018-11-15
Anticipated expiration: 2019-11-10

Abstract

The invention provides a method of obtaining a reusable charge- transfer(CT) based agrogel. The method includes selecting a first gelator (S)-methyl 2-(4-(pyren-1-yl)butanamido)-3-(1H- imidazol-4-yl)propanoate and a second gelator 2,4,7- trinitrofluorenone. At least one semiochemical is added to the first and the second gelator to obtain a mixture. Subsequent to obtaining mixture, the mixture is subjected to at least one cycle of heating and cooling to obtain a charge transfer (CT) based agrogel. The charge transfer gel thus obtained is reusable and has ability for a sustained release of the semiochemical by retaining the active agent for an extended period of time. The invention also provides a device for controlling pests.

Description

A REUSABLE CHARGE-TRANSFER BASED AGROGEL

FIELD OF INVENTION

The invention generally relates to the field of pest management and agrogels and particularly to a device for pest management and a reusable charge-transfer (CT) based agrogel.

BACKGROUND

Semiochemicals are employed as attractants and/or repellents in pest management. Examples of semiochemicals include but are not limited to pheromones, allomones, kairomones and volatile organic compounds. One such class of semiochemicals are Aliphatic alcohol based semiochemical. Examples of aliphatic alcohol based semiochemical include but are not limited to methanol, ethanol, (R)-2-butanol, n-heptanol, n-decanol, n-hexadecanol and a combination thereof. (R)-2-butanol is known as an effective semiochemical against a serious insect pest of sugarcane, Dasylepida ishigakiensis, commonly known as White Grub beetles. Ethanol alone or a mixture of ethanol and methanol is also known to act as an attractant towards various pests affecting agriculture, for example coffee berry borer, ambrosia beetles, black stem borer and Rhizophagus ferrugineus.

There are various methods known in the art for incorporating the aliphatic alcohol based semiochemicals for pest management. One such method of incorporating the aliphatic alcohols is the gel based systems. Examples of gel based systems include but are not limited to hyrdogels, polymer based gels, charge transfer gels and supramolecular gels. One such gel system described in US2014357707 A1 discloses a slow-release formulation containing a gel composition for use on pests. One of the sustained release formulation used in this gel includes a pheromone substance. Examples of pheromone used include but not limited to linear aliphatic alcohol having from 7-20 carbon, linear aliphatic aldehyde having from 12 to 20 carbon atoms, a linear aliphatic acetate having from 12 to 20 carbon atoms which is saturated or has one or more double bonds, (R)-2-butanol for insect pest targeting and/or combinations thereof. The gelling agent used is selected from the group consisting of an amino acid derivative, a long-chain fatty acid, a polyvalent metal salt of a long-chain fatty acid, a saccharide derivative and wax. However, the gel can be used only once and cannot be recycled.

Thus, there is a need in the art to develop a gel system that is robust and has the ease of synthesis, use and is environment friendly.

BRIEF DESCRIPTION OF DRAWINGS

So that the manner in which the recited features of the invention can be understood in detail, some of the embodiments are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

FIG. 1 a depicts TEM images of the charge-transfer (CT) based agrogel when semiochemical is MeOH, according to one example of the invention.

FIG. 1 b shows a plot of melting temperature ( T_gei) against varying concentration of the gelators, when mixed with MeOH alone, according to one example of the invention.

FIG. 1 c shows oscillatory amplitude-sweep plot of the gel with MeOH, according to one example of the invention.

FIG.1 d shows frequency-sweep plot of the gel formed when semiochemical is MeOH, according to one example of the invention.

FIG. 1 e shows a plot depicting thixotropic properties of the gel formed when semiochemical is MeOH, according to one example of the invention.

FIG. 2a depicts TEM images of the charge-transfer (CT) based agrogel when semiochemical is EtOH, according to second example of the invention.

FIG. 2b shows plot of melting temperature (Tgel) against varying concentration of the gelators when mixed with EtOH alone, according to second example of the invention.

FIG. 2c shows oscillatory amplitude-sweep plot of the gel with EtOH, according to second example of the invention.

FIG. 2d shows frequency-sweep plot of the gel formed when semiochemical is EtOH, according to second example of the invention. FIG. 2e shows a plot depicting thixotropic properties of the gel formed when semiochemical is EtOH, according to second example of the invention.

FIG. 3a depicts TEM images of the charge-transfer (CT) based agrogel in semiochemical MeOH/EtOH in the ratio of 1 :1 (v/v), according to the third example of the invention.

FIG. 3b shows plot of melting temperature ( T_gei) vs. concentration of the gelators when mixed with 1 :1 (v/v) of MeOH/EtOH, according to the third example of the invention. FIG. 3c shows oscillatory amplitude-sweep plot of the gel with MeOH/EtOH, according to third example of the invention.

FIG. 3d shows frequency-sweep plot of the gel formed when semiochemical is MeOH/EtOH in the ratio of 1 :1 (v/v), according to the third example of the invention.

FIG. 3e shows a plot depicting thixotropic properties of the gel formed when semiochemical is MeOH/EtOH in the ratio of 1 :1 (v/v), according to the third example of the invention.

FIG. 3f depicts plots of percent weight losses at various temperatures as a function of time-confirmed sustained 'release' pattern of the semiochemicals MeOH/EtOH at ratio of 1 :1 using release system 1 agrogel, according to the third example of the invention.

FIG. 3g depicts plots of percent weight losses at various temperatures as a function of time-confirmed sustained 'release' pattern of the semiochemicals MeOH/EtOH at ratio of 1 :1 using release system 2 agrogel, according to the third example of the invention. FIG. 4a depicts TEM images of the charge-transfer (CT) based agrogel in semiochemical R- (2)- butanol, according to the fourth example of the invention.

FIG. 4b shows plot of melting temperature ( T_gei) vs. concentration of the gelators when mixed with R- (2)- butanol, according to the fourth example of the invention.

FIG. 4c shows oscillatory amplitude-sweep plot of the gel formed when semiochemical is (R)- 2- butanol, according to the fourth example of the invention.

FIG. 4d shows frequency-sweep plot of the gel formed when semiochemical is (R)- 2- butanol, according to the fourth example of the invention.

FIG. 4e shows a plot depicting thixotropic properties of the gel formed when semiochemical is (R)- 2- butanol, according to the fourth example of the invention.

FIG. 4f depicts plots of percent weight losses at various temperatures as a function of time-confirmed sustained 'release' pattern of the semiochemicals (R)-2-Butanol using release system 1 agrogel, according to the fourth example of the invention.

FIG. 4g depicts plots of percent weight losses at various temperatures as a function of time-confirmed sustained 'release' pattern of the semiochemicals (R)-2-Butanol using release system 2 agrogel, according to the fourth example of the invention. SUMMARY OF THE INVENTION

One aspect of the invention provides a method of obtaining a reusable charge-transfer (CT) based agrogel. The method includes selecting a first gelator (S)-methyl 2-(4-(pyren-1 - yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate and a second gelator 2,4,7-trinitrofluorenone. At least one semiochemical is added to the first and the second gelator to obtain a mixture. Subsequent to obtaining mixture, the mixture is subjected to at least one cycle of heating and cooling to obtain a charge transfer (CT) based agrogel. The charge transfer gel thus obtained is reusable and has the ability for sustained release of the semiochemical by retaining the semiochemical for an extended period of time.

Another aspect of the invention provides a device for controlling of pests.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments of the invention provide a charge-transfer (CT) based agrogel, methods of obtaining the agrogel and a device thereof for management of pests. All the terms mentioned in the description herein shall be interpreted in their usual and standard meaning unless otherwise specified. The invention provides a method of obtaining a charge-transfer (CT) based agrogel. The method includes the steps of selecting a first gelator molecule, (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3- (1 H-imidazol-4-yl)propanoate and a second gelator molecule 2,4,7-trinitrofluorenone. Subsequent to the selection of the first and the second gelator, at least one semiochemical is selected. The semiochemical described herein is a lower aliphatic alcohol having 2 to 5 carbon atoms selected from the group comprising of Ethanol, Methanol, (R)-2 butanol and/or combinations thereof. The selected semiochemical is added to the first gelator molecule and the second gelator molecule to obtain a mixture. The resultant mixture thus obtained is heated to a temperature of about 75°C ^t0 about 80°C for a time period of about 1 minute. Heating the mixture yields a clear dark coloured solution. The dark coloured solution obtained is allowed to cool at a temperature of about 20°C to about 24°C for a time period of about 2 minutes to obtain a charge-transfer (CT) gel. The method described briefly herein above shall be described in detail.

Initially (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol- 4-yl)propanoate, having the structure as shown below, is selected as the first elator.

2,4,7-trinitrofluorenone having the structure as shown below is

is selected as the second gelator.

The charge-transfer takes place between electron donating (S)-methyl2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4- yl)propanoate and electron accepting 2,4,7-trinitrofluorenone. The semiochemical selected is a lower aliphatic alcohol. Examples of lower aliphatic alcohol used for the purpose of the present invention include Ethanol (EtOH), Methanol (MeOH), (R)-2 butanol and/or combinations thereof. The Critical Gelation Concentration (CGC) of the first gelator (S)-methyl 2-(4-(pyren- 1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate required for gelation of the semiochemical is in the range of about 7.5mM to about 12mM. The Critical Gelation Concentration (CGC) of the second gelator 2,4,7-trinitrofluorenone required for gelation of the semiochemical is the range of about 7.5mM to about 12mM. Variations and/or modifications of the invention as illustrated through examples are possible, as understood by a person skilled in the art and all such variations and/or modifications are included within the scope of the invention.

Example 1 : Methanol (MeOH) as a semiochemical in the Charqe-transfer(CT) based aqroqel.

In one example of the invention, the first gelator (S)-methyl 2-(4- (pyren-1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate and the second gelator 2,4,7-trinitrofluorenone are taken in molar ratio of 1 :1 and mixed with 1 ml of MeOH. The Critical Gelation Concentration (CGC) of the first gelator (S)-methyl 2-(4-(pyren- 1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate required for gelation of MeOH is 7.5mM. The Critical Gelation Concentration (CGC) of the second gelator 2,4,7-trinitrofluorenone required for gelation of MeOH is 7.5mM.

The mixture is then heated for about two minutes in the range of temperature of about 75°C to about 80°C. The solution thus obtained is a clear dark coloured solution. The solution formed is characterized by visual inspection. Alternatively, the solution can also be characterized by spectrographic methods known to a person skilled in the art. The dark coloured solution obtained is allowed to cool at a temperature about 20°C to about 24°C. The cooling is further achieved over a time period in the range of about 2 minutes to about 5 minutes. The agrogel thus obtained has semiochemical MeOH integrated in the agrogel. FIG. 1 a depicts TEM images of the charge-transfer (CT) based agrogel when semiochemical is MeOH, according to an example of the invention. The MeOH entrapped agrogel is then characterized to determine the physical and chemical characteristics.

FIG. 1 b shows a plot of melting temperature ( T_gei) against varying concentration of the gelators, when mixed with MeOH alone, according to one example of the invention. The gel- melting temperature increases with increasing concentration of the gelator and reaches a plateau at 71 °C at a concentration of 34mM of the gelator PyHis and TNF. The melting temperature of the agrogels, i.e. gel-to-sol transition ( T_gei) increased progressively with increasing concentration of gelator (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate, a phenomenon that is general for many low molecular mass organic gelators, LMMGs. This indicates that, with increasing concentration of the gelator, the density of the gel assembly increases ensuring participation of a larger number of gelator molecules per unit volume in the thermally induced transitions. Thus, the thermal stability of the agrogel is adequate for the agricultural field trials even in hot climates around different geographical regions of the world.

Rheological studies were carried out to determine the mechanical properties of the gel.

FIG. 1 c shows oscillatory amplitude-sweep plot of the gel with MeOH, according to one example of the invention. The oscillatory frequency response of the agrogel revealed that the storage modulus G' is much higher than the corresponding loss modulus confirming viscoelastic behavior of the gel.

FIG. 1 d shows frequency-sweep plot of the gel formed when semiochemical is MeOH, according one example of the invention. The frequency-sweep response of the agrogel revealed that G' and G" are independent to the applied angular frequency. The significantly higher storage modulus (~10⁵ Pa) at [PyHis] = [TNF] = 34 mM concentration reveal remarkable mechanical strength of the agrogel.

FIG. 1 e shows a plot depicting thixotropic properties of the gel formed when semiochemical is MeOH, according to one example of the invention. The thixotropic loop test of the agrogel reveal that the agrogels is strong enough to be transported without any damage to the gel matrix.

Example 2: Ethanol (EtOH) as a semiochemical in the Charge-transfer (CT) based agrogel.

In the second example of the invention, the first gelator (S)- methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4- yl)propanoate and the second gelator 2,4,7-trinitrofluorenone are taken in molar ratio of 1 :1 and mixed with 1 ml of EtOH. The Critical Gelation Concentration (CGC) of the first gelator (S)- methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4- yl)propanoate required for gelation of EtOH is 1 1 .4mM. The Critical Gelation Concentration (CGC) of the second gelator 2,4,7-trinitrofluorenone required for gelation of EtOH is 1 1 .4mM. The mixture is then heated for about two minutes in the range of temperature of about 75°C to about 80°C. The solution thus obtained is a clear dark coloured solution. The solution formed is characterized by visual inspection. Alternatively, the solution can also be characterized by spectrographic methods known to a person skilled in the art. The dark coloured solution obtained is allowed to cool at a temperature of about 20°C to about 24°C. The cooling is further achieved over a time period in the range of about 2 minutes to about 5minutes. The agrogel thus obtained has semiochemical EtOH integrated in the agrogel.

FIG. 2a depicts TEM images of the charge-transfer (CT) based agrogel when semiochemical is EtOH, according to second example of the invention. The EtOH entrapped agrogel is then characterized to determine the physical and chemical characteristics.

FIG.2b shows plot of melting temperature ( T_gei) against varying concentration of the gelators when mixed with EtOH alone, according to second example of the invention. The gel-melting temperature increases with increasing concentration of the gelator and reaches a plateau at 75°C at a concentration of 34mM of the gelator PyHis and TNF. The melting temperature of the agrogels, i.e. gel-to-sol transition ( T_gei) increased progressively with increasing concentration of gelator (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate, a phenomenon that is general for many low molecular mass organic gelators, LMMGs. This indicates that, with increasing concentration of the gelator, the density of the gel assembly increases ensuring participation of a larger number of gelator molecules per unit volume in the thermally induced transitions. Thus, the thermal stability of the agrogel is adequate for the agricultural field trials even in hot climates around different geographical regions of the world.

FIG. 2c shows oscillatory amplitude-sweep plot of the gel with EtOH, according to second example of the invention. The oscillatory frequency response of the agrogel revealed that the storage modulus G' is much higher than the corresponding loss modulus confirming viscoelastic behavior of the gel. FIG. 2d shows frequency-sweep plot of the gel formed when semiochemical is EtOH, according to second example of the invention. The frequency-sweep response of the agrogel revealed that G' and G" are independent of the applied angular frequency. The significantly higher storage modulus (~10⁵ Pa) at [PyHis] = [TNF] = 34 mM concentration reveal remarkable mechanical strength of the agrogel.

FIG. 2e shows a plot depicting thixotropic properties of the gel formed when semiochemical is EtOH, according to second example of the invention. The thixotropic loop test of the agrogel reveal that the agrogel is strong enough to be transported without any damage to the gel matrix.

Example 3: MeOH/EtOH in the ratio of 1 :1 (v/v) as a semiochemical in the Charge-transfer (CT) based agrogel.

In the third example of the invention, the first gelator (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate and the second gelator 2,4,7-trinitrofluorenone are taken in molar ratio of 1 :1 and mixed with 1 ml of MeOH/EtOH in the ratio of 1 :1 (v/v). The Critical Gelation Concentration (CGC) of the first gelator (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol- 4-yl)propanoate required for gelation of MeOH/EtOH is 9.4mM. The Critical Gelation Concentration (CGC) of the second gelator 2,4,7-trinitrofluorenone required for gelation of MeOH/EtOH is 9.4mM.

The mixture is then heated for about two minutes in the range of temperature of about 75°C to about 80°C. The solution thus obtained is a clear dark coloured solution. The solution formed is characterized by visual inspection. Alternatively, the solution can also be characterized by spectrographic methods known to a person skilled in the art. The dark coloured solution obtained is allowed to cool at a temperature about 20°C to about 24°C. The cooling is further achieved over a time period in the range of about 2 minutes to about 5minutes. The agrogel thus obtained has semiochemical 1 :1 (v/v) of MeOH/EtOH integrated in the agrogel.

FIG. 3a depicts TEM images of the charge-transfer (CT) based agrogel in semiochemical MeOH/EtOH in the ratio of 1 :1 (v/v), according to the third example of the invention. The MeOH/EtOH entrapped agrogel is then characterized to determine the physical and chemical characteristics.

FIG. 3b shows plot of melting temperature (Tgel) vs. concentration of the gelators when mixed with 1 :1 (v/v) of MeOH/EtOH, according to the third example of the invention. The gel-melting temperature increases with increasing concentration of the gelator and reaches a plateau at 68°C at a concentration of 34mM of the gelator PyHis and TNF. The melting temperature of the agrogels, i.e. gel-to-sol transition (Γ_9θι) increased progressively with increasing concentration of gelator (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol- 4-yl)propanoate, a phenomenon that is general for many Low Molecular Mass Organic Gelators, LMOGs. This indicates that, with increasing concentration of the gelator, the density of the gel assembly increases ensuring participation of a larger number of gelator molecules per unit volume in the thermally induced transitions. Thus, the thermal stability of the agrogel is adequate for the agricultural field trials even in hot climates around different geographical regions of the world.

FIG. 3c shows oscillatory amplitude-sweep plot of the gel with MeOH/EtOH, according to the third example of the invention. The oscillatory frequency response of the agrogel revealed that the storage modulus G' is much higher than the corresponding loss modulus confirming viscoelastic behavior of the gel.

FIG. 3d shows frequency-sweep plot of the gel formed when semiochemical is MeOH/EtOH in the ratio of 1 :1 (v/v), according to the third example of the invention. The frequency-sweep response of the agrogel revealed that G' and G" are independent to the applied angular frequency. The significantly higher storage modulus (~10⁵ Pa) at [PyHis] = [TNF] = 34 mM concentration reveal remarkable mechanical strength of the agrogel.

FIG. 3e shows a plot depicting thixotropic properties of the gel formed when semiochemical is MeOH/EtOH in the ratio of 1 :1 (v/v), according to the third example of the invention. The thixotropic loop test of the agrogel reveal that the agrogels is strong enough to be transported without any damage to the gel matrix.

FIG. 3f depicts plots of percent weight losses at various temperatures as a function of time-confirmed sustained 'release' pattern of the semiochemicals MeOH/EtOH at ratio of 1 :1 using release system 1 agrogel, according to the third example of the invention. The release pattern of the 1 :1 (v/v) MeOH/EtOH semiochemical in terms of its relative rates of evaporation at a particular temperature is determined both for the liquid MeOH/EtOH alone and MeOH/EtOH integrated in the agrogel under identical conditions. The extent of sustained release is investigated by monitoring the weight loss of the agrogel containing semiochemical kept at four different temperatures (22°C, 27°C, 35°C and 45°C) in a temperature gradient chamber. Plots of %-weight losses vs. the number of weeks show that the rates of evaporation are always greater from the MeOH/EtOH alone compared to the MeOH/EtOH integrated in agrogel. The calculated slopes from the linear fit of the data at various temperatures showed that the evaporation rate of MeOH/EtOH increased significantly with increasing temperatures. MeOH/EtOH in agrogel afforded only about 8% to about 10% weight loss after 3-4 weeks at 22°C, although it showed about 20% to about 40% weight loss at 45°C indicating that the weight loss occurred is slower at 22°C compared to that at 45°C. On the other hand, at 45°C, MeOH/EtOH alone evaporated entirely within 1 week and in contrast it took, more than 7 weeks for the near complete evaporation of MeOH/EtOH from the agrogel. Thus, the sustainable nature of the semiochemical in the agrogel for a significant period of time makes the agrogel particularly useful for the agricultural pest management applications. FIG. 3g depicts plots of percent weight losses at various temperatures as a function of time-confirmed sustained 'release' pattern of the semiochemicals MeOH/EtOH at ratio of 1 :1 using release system 2 agrogel, according to the third example of the invention. The release pattern of the 1 :1 (v/v) MeOH/EtOH semiochemical in terms of its relative rates of evaporation at a particular temperature is determined both for the liquid MeOH/EtOH alone and MeOH/EtOH integrated in the agrogel under identical conditions. The extent of sustained release is investigated by monitoring the weight loss of the agrogel containing semiochemical kept at four different temperatures (22°C, 27°C, 35°C and 45°C) in a temperature gradient chamber. Plots of %-weight losses vs. the number of weeks show that the rates of evaporation are always greater from the MeOH/EtOH alone compared to the MeOH/EtOH integrated in agrogel. The calculated slopes from the linear fit of the data at various temperatures showed that the evaporation rate of MeOH/EtOH increased significantly with increasing temperatures. MeOH/EtOH in agrogel afforded about 20% weight loss after 1 week at 22 °C although it showed more than 20% weight loss at 45°C indicating that the weight loss occurred is slower at 22°C compared to that at 45°C. On the other hand, at 45°C, MeOH/EtOH alone evaporated entirely within 1 week and in contrast it took, more than 7 weeks for the near complete evaporation of MeOH/EtOH from the agrogel.

Example 4: R- (2)- butanol as a semiochemical in the Charqe-transfer(CT) based agrogel . In the fourth example of the invention, the first gelator (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate and the second gelator 2,4,7-trinitrofluorenone are taken in molar ratio of 1 :1 and mixed with 1 ml of R- (2)- butanol. The Critical Gelation Concentration (CGC) of the first gelator (S)- methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4- yl)propanoate required for gelation of R- (2)- butanol is 10mM. The Critical Gelation Concentration (CGC) of the second gelator 2,4,7-trinitrofluorenone required for gelation of R- (2)- butanol is 10mM.

The mixture is then heated for about two minutes at a temperature in the range of about 75°C to about 80°C. The solution thus obtained is a clear dark coloured solution. The solution formed is characterized by visual inspection. Alternatively, the solution can also be characterized by spectrograph ic methods known to a person skilled in the art. The dark coloured solution obtained is allowed to cool at a temperature of about 20°C to about 24°C. The cooling is further achieved over a time period in the range of about 2 minutes to about 5minutes. The agrogel thus obtained has semiochemical R- (2)- butanol integrated in the agrogel. FIG. 4a depicts TEM images of the charge-transfer (CT) based agrogel in semiochemical R- (2)- butanol, according to the fourth example of the invention. The R- (2)- butanol entrapped agrogel is then characterized to determine the physical and chemical characteristics. FIG. 4b shows plot of melting temperature (T_gei) vs. concentration of the gelators when mixed with R- (2)- butanol, according to the fourth example of the invention. The gel-melting temperature increases with increasing concentration of the gelator and reaches a plateau at 83°C at a concentration of 34mM of the gelator PyHis and TNF. The melting temperature of the agrogels, i.e. gel-to-sol transition ( T_gei) increased progressively with increasing concentration of gelator (S)-methyl 2-(4-(pyren-1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate, a phenomenon that is general for many Low molecular mass organic gelators, LMMGs. This indicates that, with increasing concentration of the gelator, the density of the gel assembly increases ensuring participation of a larger number of gelator molecules per unit volume in the thermally induced transitions. Thus, the thermal stability of the agrogel is adequate for the agricultural field trials even in hot climates around different geographical regions of the world.

FIG. 4c shows oscillatory amplitude-sweep plot of the gel formed when semiochemical is (R)- 2- butanol, according to the fourth example of the invention. The oscillatory frequency response of the agrogel revealed that the storage modulus G' is much higher than the corresponding loss modulus confirming viscoelastic behavior of the gel.

FIG. 4d shows frequency-sweep plot of the gel formed when semiochemical is (R)- 2- butanol, according to the fourth example of the invention. The frequency-sweep response of the agrogel revealed that G' and G" are independent of the applied angular frequency. The significantly higher storage modulus (~10⁵ Pa) at [PyHis] = [TNF] = 34 mM concentration reveal remarkable mechanical strength of the agrogels.

FIG. 4e shows a plot depicting thixotropic properties of the gel formed when semiochemical is (R)- 2- butanol, according to the fourth example of the invention. The thixotropic loop test of the agrogel reveals that the agrogel is strong enough to be transported without any damage to the gel matrix.

FIG. 4f depicts plots of percent weight losses at various temperatures as a function of time-confirmed sustained 'release' pattern of the semiochemicals (R)-2-Butanol using release system 1 agrogel, according to the fourth example of the invention. The release pattern of the (R)-2-Butanol semiochemical in terms of its relative rates of evaporation at a particular temperature is determined both for the liquid (R)-2- Butanol alone and (R)-2-Butanol integrated in the agrogel under identical conditions. The extent of sustained release is investigated by monitoring the weight loss of the agrogel containing semiochemical kept at four different temperatures (22°C, 27°C, 35°C and 45°C) in a temperature gradient chamber. Plots of %-weight losses vs. the number of weeks show that the rates of evaporation are always greater from the (R)-2-Butanol alone compared to the (R)-2-Butanol integrated in agrogel. The calculated slopes from the linear fit of the data at various temperatures showed that the evaporation rate of (R)-2- Butanol increased significantly with increasing temperatures. (R)-2-Butanol in agrogel afforded only about 20% weight loss after 6 weeks at 22°C although it showed 50% weight loss of about 45°C indicating that the weight loss occurred 2.5 times slower at 22°C compared to that at 45°C. On the other hand, at 45°C, (R)-2-Butanol alone evaporated entirely within 1 week and in contrast it took, more than 6 weeks for the near complete evaporation of (R)-2-Butanol from the agrogel.

FIG. 4g depicts plots of percent weight losses at various temperatures as a function of time-confirmed sustained 'release' pattern of the semiochemicals (R)-2-Butanol using release system 2 agrogel, according to the fourth example of the invention.

The release pattern of the (R)-2-Butanol semiochemical in terms of relative rates of evaporation at a particular temperature is determined both for the liquid (R)-2-Butanol alone and (R)-2- Butanol integrated in the agrogel under identical conditions. The extent of sustained release is investigated by monitoring the weight loss of the agrogel containing semiochemical kept at four different temperatures (22°C, 27°C, 35°C and 45°C) in a temperature gradient chamber. Plots of %-weight losses vs. the number of weeks show that the rates of evaporation are always greater from the (R)-2-Butanol alone compared to the (R)-2- Butanol integrated in agrogel. The calculated slopes from the linear fit of the data at various temperatures showed that the evaporation rate of (R)-2-Butanol increased significantly with increasing temperatures. (R)-2-Butanol in agrogel afforded about 40% weight loss after 3 weeks at 22°C although the weight loss was about 60% at 45°C indicating that the weight loss occurred 1 .5 times slower at 22°C compared to that at 45 °C. On the other hand, at 45°C, (R)-2-Butanol alone evaporated entirely within 1 week and in contrast it took more than 7 weeks for the near complete evaporation of (R)-2-Butanol from the agrogel.

The agrogel thus obtained in the above examples is water insoluble and does not undergo swelling and shrinking with changes in temperature or humidity. Further, the agrogel obtained is not hygroscopic in nature and is not moisture sensitive.

INDUSTRIAL APPLICABILITY:

The charge transfer (CT) based agrogel obtained by the method described herein above and as characterized is incorporated into a device for effective pest management. The device includes but is not limited to a semiochemical integrated agrogel, an arrangement to mount the device and a collection apparatus. The semiochemical integrated agrogel can be loaded onto a retaining means. In an embodiment of the invention, the retaining means is a container. Examples of the container include but is not limited to a vial, a tube, a bottle, a flask, a cylinder, a tumbler, a beaker, a bowl, a bag, a can, a canister, a carton, a jar, a jug, a kettle, a packet, and a capsule. Alternatively the semiochemical integrated/integrated agrogel can be layered as a thin film on a suitable material. The material is selected from a group examples of which include but is not limited to glass, plastic, fiberglass and the like. The collection apparatus is at least one selected from the group including but not limiting to bottle, flask, cylinder, tumbler, beaker, bowl, bag, can, canister, carton, jar, jug, kettle, packet or a combination thereof. The collection apparatus is mounted vertically below the container having the pheromone entrapped agrogel. The collection apparatus is configured to entrap the pests attracted towards the semiochemical integrated agrogel.

The invention provides semiochemical integrated with gelators which forms agrogel. The formed agrogel is an immobile viscoelastic semi-solid mass which is easily handled and transported without refrigeration. Further, due to its slow-release properties, it allows a reduction in the frequency of semiochemical discharging in the agriculture fields. Such semiochemical integrated agrogels are insoluble in water, exhibit high residual activity and excellent efficacy in the open orchard, even during rainy seasons. Subsequent to the complete release of the semiochemical from the agrogel, the agrogel can be reused to make fresh agrogels over and over again. The semiochemical integrated agrogel can be used in any season and at any temperature due to oxidative, photochemical and thermal stability of the agrogel.

The reusability of the gel is achieved by recovering the gel after first use and reconstituting the gel by adding to the recovered gel at least one semiochemical. The semiochemical described herein is a lower aliphatic alcohol having 2 to 5 carbon atoms examples of which include Ethanol, Methanol, (R)-2 butanol and/or combinations thereof. The resultant mixture thus obtained is heated to a temperature of about 75°C to about 80°C for a time period of about 1 minute. Heating the mixture yields a clear dark coloured solution. The dark coloured solution obtained is allowed to cool at temperature about 20°C to about 24°C for a time period of about 2 minutes to obtain a charge-transfer (CT) gel.

The formulations of agrogel developed for semiochemicals such as pheromones and kairomones dramatically disrupt the lifecycle of harmful crop pests, example of which include, but is not limited to white grub beetle, Dasylepida ishigakiensis, coffee berry borer Hypothenemus hampei, ambrosia beetle, Xylosandrus crassiusculus, Xylosandrus germanus, Cnestus mutilates, Hylurgops palliates, Tomicus piniperda, Trypodendron domesticum, poultry ranches , Fannia canicularis, Muscina stabulans, Musca domestica , Rhizophagus ferrugineus , flies, pests either alone or in combination thereof.

The pheromone entrapped agrogel as provided herein can be targeted towards various forest pests, veterinary pests and agricultural products which include but are not limited to coffee, sugarcane, fruit trees and also for ornamental trees in nurseries such as Apple, Cherry, Chestnut, Dogwood, Lilac, Magnolia, Maple, Peach, Pear, Mulberry, and Yellowwood. With the deployment of agrogel carrier systems, there is less need to use pest resistant genetically modified crops as well. Also, transportation of the pheromone entrapped agrogel is trouble- free due to the significant mechanical strength of the agrogels. The foregoing description of the invention has been set for merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.

Claims

We claim:

1 . A method of obtaining a reusable charge-transfer (CT) based agrogel, the method comprising of:

I. selecting a first gelator, (S)-methyl 2-(4-(pyren-1 - yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate;

II. selecting a second gelator, 2,4,7-trinitrofluorenone;

III. adding at least one semiochemical to the first and the second gelator to obtain a mixture; and

IV. subjecting the obtained mixture to at least one cycle of heating and cooling to obtain a charge transfer (CT) based agrogel.

2. The method of claim 1 , wherein the charge transfer is between electron donating first gelator and electron accepting second gelator.

3. The method of claim 1 , wherein the molar ratio of first gelator to the second gelator is about 1 :1 .

4. The method of claim 1 , wherein the semiochemical is a lower aliphatic alcohol having 2 to 5 carbon atoms, wherein the lower aliphatic alcohol is selected from the group comprising of Ethanol, Methanol, (R)-2 butanol and/or combinations thereof.

5. The method of claim 1 , wherein the mixture is heated to a temperature of about 75°C to about 80°C for a time period of about 1 minute.

6. The method of claim 1 , wherein the mixture is cooled to a temperature of about 20°C to about 24°C for a time period of about 2 minutes.

7. The method of claim 1 , wherein the reusability of charge transfer (CT) based agrogel is achieved by:

a. Recovering the gel after first use; and b. Reconstituting the gel by repeating steps II I and IV of claim 1 .

8. A reusable charge-transfer (CT) based agrogel, the gel comprising of:

- a first gelator molecule, (S)-methyl 2-(4-(pyren- 1 -yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate; a second gelator molecule, 2,4,7- trinitrofluorenone; and

- at least one semiochemical.

9. The agrogel of claim 8, wherein the molar ratio of the first gelator to the second gelator is about 1 :1 .

10. The agrogel of claim 8, wherein the semiochemical is a lower aliphatic alcohol having 2 to 5 carbon atoms; wherein the lower aliphatic alcohol is selected from the group comprising of Ethanol, Methanol, (R)-2 butanol and/or combinations thereof.

1 1 . The agrogel of claim 8, wherein the agrogel is a sustained release agrogel.

12. A device for management of pest, the device comprising of:

- a charge-transfer (CT) based agrogel; - a means for retaining the gel system; and

- a collecting apparatus coupled to the retaining means and configured for trapping the pests.

13. The device of claim 12, wherein the charge-transfer (CT) based agrogel comprises of:

- a first gelator molecule, (S)-methyl 2-(4-(pyren-1 - yl)butanamido)-3-(1 H-imidazol-4-yl)propanoate;

- a second gelator molecule, 2,4,7-trinitrofluorenone; and

- at least one semiochemical.

14. The charge-transfer (CT) based agrogel of claim 13, wherein the molar ratio of the first gelator to the second gelator is about 1 :1 .

15. The charge-transfer (CT) based agrogel of claim 13, wherein the semiochemical is a lower aliphatic alcohol having 2 to 5 carbon atoms; wherein the lower aliphatic alcohol is selected from the group comprising of Ethanol, Methanol, (R)-2 butanol and/or combinations thereof.

16. The device of claim 12, wherein the charge-transfer (CT) based agrogel is a sustained release gel.

17. The device of claim 12, wherein the charge-transfer (CT) based agrogel is reusable.

18. The device of claim 12, wherein the retaining means is a container, wherein the container is selected from a group comprising a thin glass plate, a glass film, a plastic film, a thin plastic plate, a vial, a tube, a bottle, a flask, a tumbler, a beaker, a bowl, a bag, a can, a canister, a carton, a jar, a jug, a kettle, a packet and a capsule.

19. The device of claim 12, wherein the collection apparatus is at least one selected from a group comprising a thin glass plate, a glass film, a plastic film, a thin plastic plate, a vial, a tube, a bottle, a flask, a tumbler, a beaker, a bowl, a bag, a can, a canister, a carton, a jar, a jug, a kettle, a packet and a capsule.