**6.2 Microemulsion system: a practical approach to solve the inefficiencies of essential oil in crop protection**

Microemulsions are the thermodynamically stable isotropic solution of nanodispersions of size 10–200 nm. These are highly stabilized solutions with surfactants and co-surfactants [14, 15]. These microemulsion systems provide effective delivery systems, give extended shelf life, easy to prepare, and can easily scalable by low input of energy [16].

In microemulsion physio-chemical parameters of essential oil changes like improvement insolubilization, better bioavailability, and enhance the rate of penetration in targeted sites without any wastage [14, 17] in addition to this essential oil bio-constituents spreading capacity in aqueous solution improves and gives uniform dispersion on targeted sites after application [18] and provide good bioefficacy [19]. Moreover, in microemulsion formulation, essential oil active ingredient degradation rate decreases and enhances their shelf life for an extended period [20]. Further, due to the smaller droplet size in microemulsion also enhances wetting, spreading, and permeability and uniformly deposited over leaf surfaces [21, 22]. Characteristic features of essential oil microemulsion have been highlighted in **Figure 5**.

#### **6.3 Available essential oil microemulsions and targeted pest**

Microemulsions can incorporate the natural oil or essential oil in a high amount in water without any destabilization of active constituents. Essential oil gives a superstability performance in microemulsion form as compared to emulsion forms [23]. The essential oil has many potential active ingredients that give very good bioefficacy in insect pests. Hence, essential oil could be a better alternative to

**S.No. Essential oil Active**

1. Cinnamon oil Cinnamaldehyde

*DOI: http://dx.doi.org/10.5772/intechopen.91788*

Camphor Oil Pinene

Peppermint Oil Menthol

3 Peppermint Oil Menthol

4. Thyme oil Borneol

7. Neem oil + lemon grass oil

**271**

5. Eucalyptus oil Eucalyptol or 1,8-

8. Natural pyrethrin Pyrethrin I

**constituents**

Camphene Limonene 1,8-Cineole p-Cymene

Menthone 1,8-Cineole Menthyl acetate Isovalerate Pinene Limonene

Menthone 1,8-Cineole Menthyl acetate Isovalerate Pinene Limonene

Carvacrol Linalool Thymol Tannin Saponins Triterpenic Acids

cineol

Myrcene Citral Citronellal Geranyl Acetate Nerol Geraniol Limonene

Pyrethrin II Cinerin I Cinerin II Jasmolin I Jasmolin II

Cinnamyl Acetate Caryophyllene Linalool Eugenol Cinnamaldehyde (3-phenyl-2 propanal)

**Mode of action**

*Microemulsion Formulation of Botanical Oils as an Efficient Tool to Provide Sustainable…*

2. Castor Oil Ricinoleicacid Herbicide *Convolvulus arvensis* [23]

Jojoba Oil Gondoic acid Herbicide *Convolvulus arvensis* [23]

6. Neem oil Azadirachtin Acaricides *Tetranychus urticae* [32]

**Insect pest References**

Fungicide Gray mold of pears [24]

Herbicide *Convolvulus arvensis* [23]

Herbicide *Convolvulus arvensis* [23]

Insecticide *Sitophilus oryzae* [29]

[30]

[31]

Fungicide *Geotrichum citri* (citrus sour rot)

Insecticide *Sitophilus oryzae* (L.) and *Tribolium castaneum*

Insecticides — [28]

Insecticides *Aphis gossypii* [33]

(Herbst)

**Figure 5.** *Characteristics of essential oil microemulsion.*

synthetic pesticides. In microemulsion systems, essential oil active constituents are protected in micelles and give a useful model of the delivery system against different pest populations.

In the microemulsion system, droplet size is very small, i.e., in the range of 10– 100 nm. So, the translocation through vascular tissues is very easy in systemic, and due to good adherence and spreadability, it gives equally good results in the non-systemic mode of action. **Table 1** shows the available microemulsions in crop protection.

Cinnamon (CM) essential has been reported as a potential alternative to chemical fungicides. In CM microemulsion formulation rate of control of gray mold was increased up to 20% with 500ug L-1 in comparison with the non-microemulsion formulation. CM microemulsion postponed the ascorbic acid loss and cause no significant influence on pear qualities such as color and taste [24].

The microemulsion system, along with stabilizers and surfactants, gives stable physicochemical characteristics and excellent stability. Insecticidal bioassay indicated that the acute LC50 to P. xylostella was 12.477mg/L. It will be environmentfriendly and shows potential alternative features to synthetic pesticide against P. xylostella [25].

Neem, along with Karanja oil, has been termed as a natural pesticide microemulsion system. This combination has been proven economical as well as the stabilized formulation for an extended period and gives good bioefficacy against different types of crop pest populations [26].

Essential oils give combinatory properties along with synthetic pesticides. Along with stability, it also enhances the bio-efficacy against different insect pests.

Neem oil microemulsion by using biodiesel waste as co-solvent has been developed as an effective delivery system against different pests. These microemulsions are eco-friendly, economical, and safe for non-targets. The developed microemulsions highly stabilized and efficient at a low dose [27].

Lemongrass oil has been proved a right stabilizer as well as a dispersant in the neem oil microemulsion system. The primary specialty of this formulation is that these Neem ME formulations are free from any co-solvents. In the presence of lemongrass stability of active ingredient, i.e., azadirachtin also increased, and HPLC data shows a very less degradation after 14 days of storage at 54°C [28].


*Microemulsion Formulation of Botanical Oils as an Efficient Tool to Provide Sustainable… DOI: http://dx.doi.org/10.5772/intechopen.91788*

synthetic pesticides. In microemulsion systems, essential oil active constituents are protected in micelles and give a useful model of the delivery system against

In the microemulsion system, droplet size is very small, i.e., in the range of 10– 100 nm. So, the translocation through vascular tissues is very easy in systemic, and due to good adherence and spreadability, it gives equally good results in the non-systemic mode of action. **Table 1** shows the available microemulsions in crop protection.

Cinnamon (CM) essential has been reported as a potential alternative to chemical fungicides. In CM microemulsion formulation rate of control of gray mold was increased up to 20% with 500ug L-1 in comparison with the non-microemulsion formulation. CM microemulsion postponed the ascorbic acid loss and cause no

The microemulsion system, along with stabilizers and surfactants, gives stable physicochemical characteristics and excellent stability. Insecticidal bioassay indicated that the acute LC50 to P. xylostella was 12.477mg/L. It will be environmentfriendly and shows potential alternative features to synthetic pesticide against P.

microemulsion system. This combination has been proven economical as well as the stabilized formulation for an extended period and gives good bioefficacy against

Essential oils give combinatory properties along with synthetic pesticides. Along

Neem oil microemulsion by using biodiesel waste as co-solvent has been developed as an effective delivery system against different pests. These microemulsions

Lemongrass oil has been proved a right stabilizer as well as a dispersant in the neem oil microemulsion system. The primary specialty of this formulation is that these Neem ME formulations are free from any co-solvents. In the presence of lemongrass stability of active ingredient, i.e., azadirachtin also increased, and HPLC

Neem, along with Karanja oil, has been termed as a natural pesticide

with stability, it also enhances the bio-efficacy against different insect pests.

are eco-friendly, economical, and safe for non-targets. The developed microemulsions highly stabilized and efficient at a low dose [27].

data shows a very less degradation after 14 days of storage at 54°C [28].

significant influence on pear qualities such as color and taste [24].

different types of crop pest populations [26].

different pest populations.

*Characteristics of essential oil microemulsion.*

*Nano- and Microencapsulation - Techniques and Applications*

**Figure 5.**

xylostella [25].

**270**


#### **Table 1.**

*Literature survey on essential oil microemulsion for crop protection.*

Natural oil microemulsion along with botanical synergist (*Prosopis juliflora*) have been proved the stability of active constituents in ME formulation. The HPLC data showed that botanical synergist lowers the degradation rate of active components of natural oil. Further, the bioefficacy results showed a prominent biocontrol against Spodopteralitura at 400 PPM [38].

stability as well as bioactivity against different crop pests. Therefore essential oil ME could be the safest mode of a delivery system shortly. Advanced features of essen-

*Microemulsion Formulation of Botanical Oils as an Efficient Tool to Provide Sustainable…*

*DOI: http://dx.doi.org/10.5772/intechopen.91788*

**6.4 Scope of work in promoting essential oil microemulsion in crop protection**

Essential oil based microemulsion formulation is a promising tool for the biocontrol of the pests of economic importance. However, there are still some areas of

1. **The need for combinatory botanicals or synergists**: Essential oil ME in pure form requires a higher rate of application for controlling pest species, which will increase the cost of formulation and limits its usage. So, there is an urgent need for discovering new combinatory or synergistic constituents, which will

improvement that should be focused upon in order to promote oil based

tial oil microemulsion are depicted in **Figure 6**.

*Advanced features of essential oil ME formulations over essential oil.*

**Figure 6.**

**273**

microemulsion system in the agriculture sector.

be very helpful in promoting essential oil ME.

Clove (CO) and lemongrass oil (LGO) ME showed potential antifungal agents against *Fusarium oxysporum* f.sp. *lycopersici* (FOL) without showing any sign of phytotoxicity in tomato plants [36].

Eukalyptus (*Eucalyptus globules*) oil ME was developed along with Karanja (Pongamiaglabra) and jatropha cakes (*Jatropha curcas*) to enhance the bioefficacy against Triboliumcastaneum, a stored grain pest. The mortality data shows that Eucalyptus oil ME with Karanja and jatropha cakes extract gives LC50 at 50 ppm, and without extract, it LC50 at 100 PPM. The GC-ms data shows that degradation % of a marker compound, i.e., 1, 8-cineole, also reduced in filtrate based ME. So, this study discovered that essential oil stability and bioefficacy could be improved in microemulsion by using these types of botanical extracts [37].

Previous studies revealed that essential oil microemulsion formulation with optimum surfactants and botanical synergists or stabilizers could improve the

*Microemulsion Formulation of Botanical Oils as an Efficient Tool to Provide Sustainable… DOI: http://dx.doi.org/10.5772/intechopen.91788*

**Figure 6.**

Natural oil microemulsion along with botanical synergist (*Prosopis juliflora*) have been proved the stability of active constituents in ME formulation. The HPLC data showed that botanical synergist lowers the degradation rate of active components of natural oil. Further, the bioefficacy results showed a prominent biocontrol against

Clove (CO) and lemongrass oil (LGO) ME showed potential antifungal agents against *Fusarium oxysporum* f.sp. *lycopersici* (FOL) without showing any sign of

Eukalyptus (*Eucalyptus globules*) oil ME was developed along with Karanja (Pongamiaglabra) and jatropha cakes (*Jatropha curcas*) to enhance the bioefficacy against Triboliumcastaneum, a stored grain pest. The mortality data shows that Eucalyptus oil ME with Karanja and jatropha cakes extract gives LC50 at 50 ppm, and without extract, it LC50 at 100 PPM. The GC-ms data shows that degradation % of a marker compound, i.e., 1, 8-cineole, also reduced in filtrate based ME. So, this study discovered that essential oil stability and bioefficacy could be improved

Previous studies revealed that essential oil microemulsion formulation with optimum surfactants and botanical synergists or stabilizers could improve the

in microemulsion by using these types of botanical extracts [37].

Spodopteralitura at 400 PPM [38].

**S.No. Essential oil Active**

9. Betel leaf (*Piper betle* L.) essential

10. Chlorpyrifos + jatropha and karanj oil

lemongrass oil

11. Clove and

**Table 1.**

**272**

oil

**constituents**

Cadinene Sesquiterpene Chavicol Geraniol Α-Thujene Terpinolene Chavibetol Phenyl Propane Trans Β-Ocimene

*Nano- and Microencapsulation - Techniques and Applications*

Safrole Caryophyllene Cineole Cadinol Eugenol Camphene Limonene Pinene Eugenyl Acetate

Karanjin Pongamol Oleic Acid

Myrcene Citral Citronellal acetyl eugenol beta-caryophyllene

vanillin crategolic acid tannins Flavinoids

cineol

*Literature survey on essential oil microemulsion for crop protection.*

12. Eucalyptus oil Eucalyptol or 1,8-

**Mode of action**

**Insect pest References**

Fungicide *Aspergillus* species [34]

Insecticides Stored Grain Pest [35]

Fungicide *Fusarium oxysporum* [36]

Insecticides *Tribolium castaneum* [37]

phytotoxicity in tomato plants [36].

*Advanced features of essential oil ME formulations over essential oil.*

stability as well as bioactivity against different crop pests. Therefore essential oil ME could be the safest mode of a delivery system shortly. Advanced features of essential oil microemulsion are depicted in **Figure 6**.
