Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N57/00—Biocides, pest repellants or attractants, or plant growth regulators containing organic phosphorus compounds
  • A01N57/18—Biocides, pest repellants or attractants, or plant growth regulators containing organic phosphorus compounds having phosphorus-to-carbon bonds
  • A01N57/20—Biocides, pest repellants or attractants, or plant growth regulators containing organic phosphorus compounds having phosphorus-to-carbon bonds containing acyclic or cycloaliphatic radicals
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N25/00—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests
  • A01N25/26—Biocides, pest repellants or attractants, or plant growth regulators, characterised by their forms, or by their non-active ingredients or by their methods of application, e.g. seed treatment or sequential application; Substances for reducing the noxious effect of the active ingredients to organisms other than pests in coated particulate form
  • A01N25/28—Microcapsules or nanocapsules
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01N—PRESERVATION OF BODIES OF HUMANS OR ANIMALS OR PLANTS OR PARTS THEREOF; BIOCIDES, e.g. AS DISINFECTANTS, AS PESTICIDES OR AS HERBICIDES; PEST REPELLANTS OR ATTRACTANTS; PLANT GROWTH REGULATORS
  • A01N43/00—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds
  • A01N43/34—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with one nitrogen atom as the only ring hetero atom
  • A01N43/40—Biocides, pest repellants or attractants, or plant growth regulators containing heterocyclic compounds having rings with one nitrogen atom as the only ring hetero atom six-membered rings

Definitions

• the present application relates to an encapsulated pesticide and a method for producing the same. More particularly in relates to a pesticide which is a herbicide.
• Herbicides are commonly used in agriculture to improve the productivity and quality of the grown product.
• the global market for herbicides is estimated to reach $31.5 billion by 2020.
• Asia-Pacific is the dominant market accounting for two fifth of herbicide use, whereas North America region equates to one-third of global revenue generated by the herbicide market.
• EP 1 499 183 B2 discloses a method for preventing or reducing resistance to a pesticide of a substrate pest, which method comprises administering to the substrate or the pest a metabolic enzyme inhibitor (such as piperonyl butoxide - PBO) and (substantially simultaneously) a pesticide (such as a pyrethroid insecticide) encapsulated in a degradable capsule.
• a metabolic enzyme inhibitor such as piperonyl butoxide - PBO
• a pesticide such as a pyrethroid insecticide
• the capsule prevents an effective dose of the pesticide from coming into contact with the substrate or the pest until the inhibitor has had time to begin its inhibiting effect on the substrate.
• the formulation used in this case is Karate Zeon® which is a PVA-encapsulated insecticide (lambda-cyhalothrin) produced by Syngenta.
• EP 0427991 Al discloses an insecticidal and/or acaricidal and/or nematicidal composition which is a mixture of an encapsulated part which is formed of water-insoluble microcapsules and a flowable part which is emulsified or suspended in water.
• CN 104 904 710 A (Huazhong Agricultural University)
• a method for producing an encapsulated pesticide including the steps of
• step (b) combining the mixture of step (a) with water in the case of (i) or an oil in the case of (ii) and stirring to create an emulsion of said mixture,
• step (d) stirring the product of step (c) in order to produce particles of pesticide encapsulated in said water-insoluble reactant.
• the pesticide is water soluble. It has been discovered that a capsule coating prepared in this manner has at least some of the following advantages: The formulation process is simple and inexpensive
• the coating material is readily available, cheap and environmental friendly i.e. nontoxic and biodegradable.
• Microcapsules of less than- 100 ⁇ in diameter can be produced which can be sprayed using existing equipment on farms without clogging the spray nozzle
• the concentration of glyphosate in the encapsulated solution can be similar to existing commercial glyphosate solutions (range 330-470 g ⁇ 1 )
• the encapsulation efficiency of glyphosate can be as high as possible (more than
• the formulation process is relatively unhazardous and avoids use of highly flammable organic solvents
• the glyphosate diffuses out of the microcapsules when deployed, the microcapsules staying intact. This is in contrast to prior art formulations (for example in which glyphosate is encapsulated in PVA capsules) in which the capsules need to rupture in order to deliver the glyphosate to the locus of the substrate. This requires an external force or a chemical degradation of the capsule wall, which is difficult to control and predict.
• the at least one polysaccharide includes (or consists of or consists essentially of) alginate, chitosan or any combination thereof, and more preferably additionally includes pectin.
• the polysaccharide component is a combination of alginate and pectin, with preferred ratios being 25% alginate, 75% pectin; 50% alginate, 50% pectin; and most preferably 75% alginate, 25% pectin.
• pectin makes the walls of the capsules more compact and affects the diffusion rate of pesticide therethrough.
• the cation which combines with the polysaccharide to produce the capsule walls is preferably calcium or barium, most preferably calcium. This is preferably provided in the form of the chloride salt. It has been discovered that the provision of the salt in the form of a powder is necessary in order to create the microcapsules, otherwise a gel is formed.
• the average diameter of the particles is less than 100
• the particle size is from 2-100 micrometres as it has been discovered that the smaller the particle size, the faster the pesticide release and that size range gives the best range of release times.
• the rate of stirring of step (d) is greater than 800rpm, more preferably greater than or equal to lOOOrpm.
• the method may include the additional step of including in the water or oil of step (b) a substance which is an inhibitor of a factor causing or contributing to the resistance of the pest to the pesticide (such as piperonyl butoxide).
• a substance which is an inhibitor of a factor causing or contributing to the resistance of the pest to the pesticide such as piperonyl butoxide.
• the product significantly improves the speed of weed kill, compared to standard offering. This feature will provide significant value to growers where there is a tight window to kill weeds between crops. This product will provide growers with more flexibility in their growing rotation.
• Figure 1 is a graph showing the effect of agitation speed on the microcapsule size
• Figure 2 shows micrographs of glyphosate encapsulated with various different coating compounds
• Figure 3 is a graph showing the cumulative glyphosate release profiles for different coated capsules in 100 % humidity at 25 °C;
• Figure 4 shows a series of cumulative glyphosate release profiles for the different coated capsules in 100 % humidity in different pHs and at 25 °C;
• Figure 5 is a graph showing the effect of humidity on the release of glyphosate from capsules coated with alginate: pectin (75:25);
• Figure 6 is a graph showing the effect of temperature on the release of glyphosate from capsules coated with alginate: pectin (75:25);
• Figure 7 is a graph showing the effect of UV/visible light exposure on the release of glyphosate from capsules coated with alginate: pectin (75:25);
• Figure 8 is a graph showing the glyphosate release profiles for capsules formed of different ratios of active and coating material
• Figure 9 is a graph showing the glyphosate release profiles for capsules formed in different continuous phases.
• Figure 10 is a graph showing the glyphosate release profiles for capsules formed in
• Glacial acetic acid (Fisher Scientific; A/0360/PB17). • Phosphoric acid (Aldrich; product number 79617).
• the mixed coating solutions were prepared by stirring the required w/w ratios of the individual coating solutions for 5 min prior to the addition of glyphosate salt to ensure homogeneous mixture.
• the resultant solution was added dropwise to a stirred 250 ml breaker containing sunflower oil (100 ml) to form an emulsion using a homogeniser (IKA) at 1000 rpm with blade diameter 27 mm.
• IKA homogeniser
• the ee for the capsules were determined via thoroughly grinding the capsules (100 mg) periodically for 1 min after intervals of 15 min over 1 h using a mortar and pestle in an aqueous solution of potassium dihydrogen phosphite buffer (5ml).
• microcapsules 1.0 g were placed in a dialysis tube and H 2 0 (50 ml) preheated to required temperature and immediately placed in a preheated chamber (25 °C and 40 °C).
• Glyphosate release as a function of pH As a function of pH.
• Microcapsule release behaviour were studied over three pHs; 5, 7 and 8 at 25 °C under 100 % humidity.
• microcapsules 1.0 g were placed in a dialysis tube and in the required pH
• Microcapsules 1.0 g were placed in a dialysis tube and preheated H 2 0 (50 ml) at 25 °C was added.
• Table 1 shows the coating materials investigated, whether the capsules were formed, the average capsule size with coefficient of valence (CV), encapsulation efficiency (ee) and active load for each type of capsule formed.
• Figure 2 shows micrographs of glyphosate encapsulated with (a) alginate; (b) alginate: pectin (75:25); (c) 75 alginate xhitosan (75 :25) and (d) alginate xhitosan (50:50).
• alginate gelatine and 25 % (w/w) alginate composition coating formulations, the other coating formulations encapsulated glyphosate.
• Active load is relative to the encapsulated glyphosate.
• the release rate of glyphosate is the most rapid from the alginate: pectin (75:25) coated microcapsules and a release of 91 ⁇ 6 % of the encapsulated glyphosate is observed after 24 h and hence is the most efficient in releasing glyphosate among the capsules formed (figure 3).
• the release behaviour was investigated over pH range 5 -8 at 25 °C as well as pH 7 at 40 °C in 100% humidity. These conditions were specifically chosen as these are conditions that farmers are happy to work under.
• the capsule walls are formed primarily through complexation between calcium ions and functional groups such as carboxylic acid. This intermolecular interaction can be influenced by change of pH. Hence, it was purposed that changing the pH would influence the rate of glyphosate release which may lead to more efficient glyphosate release.
• the data in Figure 4 shows the average release observed for each time interval. There are number of points to note: ⁇ The release is more rapid at 40 °C in comparison to 25 °C due to rate of diffusion being directly proportional to temperature.
• alginate: pectin (75:25) coated capsules under 35 % humidity was compared to 100 % humidity at 25 °C because 35 % humidity is lowest level of humidity that the capsules are likely to be exposed in the field.
• a micropipette (1 ⁇ ) was used to replicate the droplets which are going to be formed on the surface of the crops after spraying the formulated herbicide mixture into the fields.
• the series of droplets on a petri dish were placed in a humidity chamber, where the temperature was maintained at 25 °C.
• Figure 5 shows the glyphosate release under humidity of 35 and 100 % at 25 °C. There is no significant change in the glyphosate release behaviour under humidity of 35 % and 100 % for the first 8 h. However, after 8 h there is no further release under 35 % humidity in
• glyphosate release is shown to be much slower than at 35 °C. After 24 h, 70 % of encapsulated glyphosate is released whereas at 35 °C 94 % is released.
• FIG. 7 shows the cumulative glyphosate release over 24 h at 25 °C in 100 % humidity. The plot shows no significant change between UV/vis exposed and unexposed microcapsules.
• the glyphosate release behaviour for capsules formed from formulation 2 and 3 in 100 % humidity is shown in figure 8. It can be observed that the glyphosate release from capsules formed from formulation 2 and 3 are faster in comparison to the capsules formed from formulation 1. The release after 2 h is observed as 47 ⁇ 8 % and 58 ⁇ 4 %, respectively, which is more than the 32 ⁇ 4 % observed for the capsules formed from formulation 1. It is postulated that the faster glyphosate release could be as a result of a thinner capsule wall being formed from formulations 2 and 3 in comparison to formulation 1 due to smaller quantities of coating material being used.
• PBO piperonyl butoxide
• Capsules formed in PBO and PBO-S are of similar size to the capsules formed in sunflower oil when taking into consideration the CV.
• ammonium sulfate is a known adjuvant agent for glyphosate as it binds with calcium and iron ions present in water and plant cells.
• ammonium sulfate would be employed as a scavenger to remove calcium ions present in the capsule wall, which would weaken the wall, leading to a quicker release.
• Figure 10 shows the presence of ammmonium sulfate increases the rate of glyphosate release and the release profile is similar to what was observed from the capsules prepared in sunflower oil. Hence, improving the viability of preparing the capsules in PBO.
• coatings There were a number of coatings which could have been used. However, due to the project requirements such as the coating material should be cheap to purchase, readily available, environmental friendly (biodegradable), compactable with glyphosate, easy to handle (non-hazardous) and preferably the material should already be widely used as a coating material so that future licensing is easily obtained for the product. So we decided to focus on polysaccharides as these cover all the points discussed.
• the alginate: pectin (75:25) coated capsules are stable to UV/vis and PBO-S exposure.
• Humidity does not affect the release rate form the capsules.
• the glyphosate release is temperature sensitive. In warmer climate the release is more rapid, however release remains similar when temperature is increased from 35 to 40 °C.
• Glyphosate release is also pH sensitive. For the capsules which contain alginate in its wall, the release rate was shown to be slower at pH 5 which increased with increasing pH.
• Encapsulation is also achievable using less amount of coating material than 25 g, however reducing the amount of coating material led to increase rate of glyphosate release.

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• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• General Health & Medical Sciences (AREA)
• Dentistry (AREA)
• Plant Pathology (AREA)
• Engineering & Computer Science (AREA)
• Pest Control & Pesticides (AREA)
• Agronomy & Crop Science (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Environmental Sciences (AREA)
• Toxicology (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)

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• 2017
  • 2017-07-04 GB GBGB1710736.8A patent/GB201710736D0/en not_active Ceased
• 2018
  • 2018-07-03 WO PCT/GB2018/051864 patent/WO2019008341A1/en unknown
  • 2018-07-03 CN CN201880057428.6A patent/CN111050547A/zh active Pending
  • 2018-07-03 EP EP18753450.8A patent/EP3648598A1/en not_active Withdrawn

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