TECHNICAL FIELD OF THE INVENTION:

The present invention relates to herbicidal bead compositions for aquatic weed control. The present invention provides beads comprising endothall, its salts or derivatives which is being entrapped in an alginate complex. The invention further relates to a process for preparing herbicidal alginate bead compositions and a method of controlling aquatic weeds using such compositions. A safe delivery system of herbicides for aquatic weed control is another aspect of the present invention.

BACKGROUND OF THE INVENTION:
Aquatic plants are natural and important components of the aquatic environment. A large number of weeds grow alongside in the water bodies disturbing the aquatic environment. Aquatic weeds are undesirable vegetation that reproduce and grow in water. Uncontrolled growth of these weeds may hamper the water bodies and create serious environmental issues.
Algae, duckweed, watermeal, water Hyacinth, water lettuce, submerged plants such as milfoil, hydrillia, curly-Leaf pondweed, clasping-leaf pondweed, coontail, naiad, sago pondweed, emergent plants such as cattail, water lily, watershield, phragmites, purple loosestrife and bulrush are common aquatic plants that needs to be controlled.
Algae form the base of the aquatic food chain and play an important role in wastewater stabilization in ponds through photosynthetic oxygen evolution that enhances the aerobic degradation of organic matter. However, due to the high nutrient loads in these ponds, these plants grow excessively often leading to the development of dense algal blooms causing high concentrations of total suspended solids which may have a detrimental effect on a body of water and its inhabitants. In some cases, blue-green algae can produce toxins that cause animal sickness or death.
Several herbicides have been utilized to control the densities of algal populations. Endothall is one of the widely used algicides. It is a selective contact herbicide, absorbed by the leaves and roots, with limited acropetal translocation in the xylem. Amine, ammonium and alkali-metal salts of endothall are commonly used pre- and post-emergence for control of annual grass and broad-leaved weeds in sugar beet, fodder beet, beetroot, spinach and turf. Endothall or its derivatives can be used for aquatic weed control in rice.

Aquatic herbicides generally are available in sprayable or granular formulations. However this often lead to safety issues for workers due to exposure during application. It further lead to skin burn and irritation as well as eye sensitization.
US4400391 and US4401456 disclose alginate gel bead composition of herbicides and insecticides. Though the patents disclose process for preparation of alginate gel bead compositions, the products that were prepared by the process had active ingredients in very low concentration and alginate polymer matrix in high concentration. Further, storage stability of the product as well as various essential product parameters are not well defined for effective making and use for the intended pesticide activity.
There is therefore a need to develop safer and effective herbicide products as well as safe delivery system for products particularly for aquatic weed control.
Inventors of the present invention developed novel herbicidal bead compositions comprising endothall for aquatic weed control. The novel delivery system comprises gel beads comprising a herbicide and an alginate complex.

OBJECTS OF THE INVENTION:
It is an object of the present invention to provide a bead composition of endothall being entrapped in an alginate complex.
It is another object of the present invention to provide a process for preparing a bead composition comprising endothall being entrapped in an alginate complex.
It is yet another object of the present invention to provide a method of aquatic weed control using the bead compositions according to the present invention.
It is another object of the present invention to provide a safe delivery system for delivery of herbicides for aquatic weed control.
Yet another object of the present invention is to provide a composition comprising a higher concentration of endothall entrapped in a comparatively lower concentration of polymeric alginate complex.

SUMMARY OF THE INVENTION:
The present invention provides a bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising
i) at least 15% by weight of endothall, its salts or derivatives; and
ii) at least one additive
wherein said external zone is capable of releasing, said endothall, its salts or derivatives when hydrated.
The present invention further provides a bead composition suspended in a media comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives; and
ii. at least one additive
wherein said external zone is capable of releasing, said endothall, its salts or derivatives when hydrated.
The present invention provides a process for preparing a herbicidal bead composition comprising steps of :
(a) preparing a pre-gel mixture comprising at least 15% by weight of endothall, its salts or derivatives, a water soluble alginate salt and an additive;
(b) preparing a gelling bath mixture comprising an alkaline earth metal solution; and
(c) dispensing uniform droplets of the pre-gel mixture into the gelling bath mixture to form said beads entrapping said internal zone.
The present invention further provides a process for preparing a herbicidal bead composition according to the present invention, said process comprising:
(a) preparing a pre-gel mixture part A;
(b) preparing a gelling bath mixture part B;
(c) dispensing uniform droplets of part A into part B;
(d) allowing the mixture to form said beads entrapping said internal zone;
(e) separating said beads;
(f) optionally drying said beads; and
(g) optionally suspending said beads in a media.
Further, the invention provides a continuous process for preparing herbicidal bead composition according to the present invention, said process comprising:
(a) preparing a pre-gel mixture part A;
(b) preparing a gelling bath mixture part B in a container with an inlet and outlet so as to optimize a continuous flow of gelling bath mixture part B;
(c) dispensing uniform droplets of part A into part B;
(d) allowing the mixture to form said beads instantly entrapping said internal zone;
(e) separating said beads continuously;
(f) optionally drying said beads in a continuous drier; and
(g) optionally suspending said beads in a media
Further, the present invention provides a method of controlling aquatic weeds, said method comprising applying to the weeds in water bodies an agronomically effective amount of a bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives; and
ii. at least one additive.
The present invention further provides a safe delivery system for aquatic weed control, said system comprising a bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives; and
ii. at least one additive.

DETAILED DESCRIPTION:
Inventors of the present invention observed that a bead composition comprising endothall can be prepared for safe and effective use for aquatic weed control.
Accordingly, the present invention provides a novel delivery system for endothall for aquatic weed control.
It has been noted that a high concentration of endothall can be incorporated in the bead composition that can be delivered safely for the intended use of aquatic weed control.
It has been further noted that the bead composition according to the present invention can be stored effectively.
It has been observed that the bead composition comprising an additive lead to many advantages for the product. The additive acts as a conditioner for the bead composition required for delivering the herbicide in a most effective way. These and the many other aspects of the invention are described hereinafter.
Thus the present invention provides a bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives; and
ii. at least one additive;
wherein said external zone is capable of releasing, said endothall, its salts or derivatives when hydrated.
In certain embodiments of the present invention, the beads are spherical in shape.
In certain embodiments, the external zone comprises an alginate gel complex.
In some embodiments, the alginate complex is an alkali or alkaline earth metal salt of alginic acid.
In some other embodiments, the alginate complex is sodium or calcium alginate.
In some preferred embodiments, the alginate complex is calcium alginate.
In an embodiment, the internal zone is entrapped in the external zone
In another embodiment, the internal zone is entrapped in the alginate complex.
In certain embodiments, the internal zone comprises endothall.
With respect to the present invention, endothall comprises, its salts and derivatives.
Salts include alkali-metal salts, ammonium and amine salts.
Preferred salts include endothall diammonium, endothall dipotassium, endothall disodium and endothall mono(N,N-dimethylalkylammonium).
Throughout the specification, the term ‘endothall’ refers to endothall, its salts or derivatives.
In certain embodiments, the internal zone according to the present invention comprises at least 15% by weight of endothall.
In certain other embodiments, the internal zone according to the present invention comprises from about 15% to about 99% by weight of endothall.
In some other embodiments, the internal zone according to the present invention comprises from about 50% to about 99% by weight of endothall.
In an embodiment the internal zone is in the form of a solution.
In another embodiment, the internal zone is in the form of a dispersion.
In an embodiment, the internal zone according to the present invention comprises at least one additive.
In an embodiment the additive acts as a surface modifying agent for the bead composition.
In another embodiment the additive as a surface modifying agent optimizes the plasticity of the bead thereby releasing the active ingredient in an effective manner.
In another embodiment the additive as a surface modifying agent improves the permeability of the external zone of the bead thereby controlling the release of herbicidal endothall to the aquatic environment where weed control is required.
In yet another embodiment, the additive is a polymer.
In a preferred embodiment, the additive is polyvinyl alcohol.
In certain embodiments, the internal zone according to the present invention further comprises at least one agrochemical excipient.
Accordingly, the present invention provides a bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives;
ii. at least one additive; and
iii. at least one agrochemical excipient.

In certain other embodiments, the agrochemical excipient is selected from the group comprising agrochemical adjuvants such as surfactants, solvents, solubilizing agents, biocides, viscosity modifiers, gums and stabilizers.
In certain preferred embodiments, the agrochemical excipient is selected from surfactants, biocides and stabilizers.
In certain embodiments, the internal zone comprises a solution comprising endothall, an additive and at least one agrochemical excipient.
In certain other embodiments, the internal zone comprises a dispersion comprising endothall, an additive and at least one agrochemical excipient.
The present invention further provides a bead composition, suspended in a media, said bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives; and
ii. at least one additive;
wherein said external zone is capable of releasing, said endothall, its salts or derivatives when hydrated.
In certain embodiments, the bead composition according to the present invention is suspended in a media.
In an embodiment, the internal zone is non-permeable to the suspending media.
In certain embodiments, the suspending media is selected from the group comprising saturated polysaccharide solution, saturated xanthan gum solution or a saturated solution of alginate salts.
In certain other embodiments, the suspending media is selected from the group comprising saturated sugar solution, saturated starch solution or saturated calcium alginate solution.
Therefore, in an aspect, the present invention further provides a process for preparing a herbicidal bead composition comprising steps of:
(a) preparing a pre-gel mixture comprising at least 15% by weight of endothall, its salts or derivatives, a water soluble alginate salt and an additive;
(b) preparing a gelling bath mixture comprising an alkaline earth metal solution; and
(c) dispensing uniform droplets of the pre-gel mixture into the gelling bath mixture to form beads entrapping said internal zone.
In another aspect, the invention provides a continuous process for preparing herbicidal bead composition comprising steps of:
(a) preparing a pre-gel mixture comprising at least 15% by weight of endothall, its salts or derivatives, a water soluble alginate salt and an additive;
(b) preparing a gelling bath mixture comprising an alkaline earth metal solution in a container with an inlet and outlet so as to optimize a continuous flow of gelling bath mixture;
(c) dispensing uniform droplets of pre-gel mixture into the gelling bath mixture to form said beads entrapping said internal zone; and
(d) separating said beads continuously;
These process aspects may have more preferred embodiments comprising additional preferred steps.
Thus, in an embodiment, the present invention further provides a process for preparing a herbicidal bead composition, said process comprising:
(a) preparing a pre-gel mixture comprising at least 15% by weight of endothall, its salts or derivatives, a water soluble alginate salt and an additive;
(b) preparing a gelling bath mixture comprising an alkaline earth metal solution;
(c) dispensing uniform droplets of the pre-gel mixture into the gelling bath mixture;
(d) allowing the mixture to form said beads entrapping said internal zone;
(e) separating said beads;
(f) optionally drying said beads; and
(g) optionally suspending said beads in a media.
Further, the invention provides a continuous process for preparing herbicidal bead composition, said process comprising:
(a) preparing a pre-gel mixture part A;
(b) preparing a gelling bath mixture part B in a container with continuous flow system of gelling bath mixture part B;
(c) dispensing uniform droplets of part A into part B;
(d) allowing the mixture to form said beads instantly entrapping said internal zone;
(e) separating said beads continuously;
(f) optionally drying said beads in a continuous drier; and
(g) optionally suspending said beads in a media.
In an embodiment, the invention provides a continuous process for preparing bead compositions according to the present invention.
In another embodiment the pre- gel mixture part A comprises endothall, its salts or derivatives, a water soluble alginate salt and an additive.
In another embodiment, the pre- gel mixture part A comprises at least 15% by weight of endothall, its salts or derivatives, a water soluble alginate salt and an additive.
In some embodiments, the water soluble alginate salt is sodium alginate.
In some other embodiments, the additive is a polymer.
In some preferred embodiments, the polymer is polyvinyl alcohol.
In certain embodiments, the gelling bath mixture part B comprises an alkaline earth metal salt solution.
In certain other embodiments, the gelling bath mixture part B comprises an alkaline earth metal salt solution and at least one agrochemical excipient.
In certain preferred embodiments, the gelling bath mixture part B comprises calcium chloride solution and at least one agrochemical excipient.
In some other embodiments, the gelling bath mixture part B comprises calcium chloride solution and a biocide.
The process of making uniform droplets of pre- gel mixture part A is not particularly limiting.
The temperature of pre- gel mixture part A is kept at a range from about 0°C to about 60°C.
In an embodiment the temperature of pre- gel mixture part A is kept at a range from about 5°C to about 35°C.
The viscosity of the of pre- gel mixture part A is regulated depending on the requirement of size and shape of the bead composition.
The process of dispensing uniform droplets of pre-gel mixture part A into gelling bath mixture part B is not particularly limiting.
In an embodiment, pre-gel mixture part A is passed through an appropriate nozzle to form uniform droplets.
In an embodiment, the delivery of uniform droplets of pre-gel mixture part A into gelling bath mixture part B is accomplished by pressure actuated system, gravity feed through stationary nozzle or by appropriate encapsulation system.
In another embodiment, the delivery of uniform droplets of pre-gel mixture part A into gelling bath mixture part B is accomplished by a suitable sprayer system.
The process of forming the bead composition by mixing uniform droplets of pre-gel mixture part A with gelling bath mixture part B is not particularly limiting.
In an embodiment, the process of forming the bead composition by mixing uniform droplets of pre-gel mixture part A with gelling bath mixture part B is performed in a continuous manner.
In another embodiment, the gelling bath mixture part B is positioned with a continuous flow system in a container with an inlet and an outlet to maintain uniform concentration of the gelling bath mixture.
In some embodiments, the beads are formed instantly while dropping pre-gel mixture part A into gelling bath mixture part B.
In some another embodiments, the beads with uniform wall thickness are formed while dropping pre-gel mixture part A into gelling bath mixture part B.
In certain embodiments, the wall thickness of beads are optimized for controlled release of endothall during application.
In certain other embodiments, the wall thickness of beads are optimized by controlling the concentration of gelling bath mixture part B.
In some embodiments, the concentration of gelling bath mixture part B is controlled by the continuous flow system.
The contact time of droplets of pre-gel mixture part A with gelling bath mixture part B is kept for period less than that permits osmotic loss of endothall to the gelling bath mixture part B.
In an embodiment, the contact time of droplets of pre-gel mixture part A with gelling bath mixture part B is less than 25 seconds.
In an embodiment, the temperature of gelling bath mixture part B is kept at a range from about 0°C to about 50°C.
In another embodiment, the temperature of gelling bath mixture part B is kept at a range from about 5°C to about 35°C.
In a preferred embodiment, the temperature of gelling bath mixture part B is kept at a range from about 5°C to about 20°C.
In an embodiment, the beads are spherical in shape.
In another embodiment, the size of the beads ranges from about 0.1 mm to about 3 mm in diameter.
In a preferred embodiment, the size of the beads ranges from about 0.5 mm to about 2 mm in diameter.
In some embodiments, the beads are separated continuously.
In an embodiment, the beads are separated by a strainer or by a moving mesh belt system.
In some embodiments, beads are dried passively at room temperature by natural evaporation of water.
In some embodiments, the beads are dried by suitable drier.
In some other embodiments, the beads are dried by air flow dryer or fluid bed drier.
In an embodiment the beads are dried using a continuous dryer.
In another embodiment, the continuous dryer can be a custom made dryer with optimized temperature and pressure conditions.
In yet another embodiment, the continuous dryer can be selected from rotary vapour dryer, rotary drum dryer, spin flash dryer.
In an embodiment the process of drying the beads is industrially viable.
In certain embodiments, the beads are dried up to contain 50% by weight of water.
In some embodiments, the beads are suspended in a suitable media.
In certain embodiments, the suspending media is selected from the group comprising saturated polysaccharide solution, saturated xanthan gum solution or a saturated solution of alginate salts.
In certain other embodiments, the suspending media is selected from the group comprising saturated sugar solution, saturated starch solution or saturated calcium alginate solution.
In some embodiments, the beads are packed in water soluble bags.
In some other embodiments, the beads are packed in a suspending media that is ready to be dispersed for the intended use as a herbicide.
In some embodiments the invention provides an advantageous continuous process to prepare bead compositions of endothall.
The advantageous of the continuous process are:
a. A high yielding process (above 95%),
b. Beads with optimized wall thickness, capable of releasing endothall in a controlled manner,
c. Beads with high concentration of endothall,
d. Minimum effluent, and
e. Minimum loss of endothall in effluent.
Further, the present invention provides a method of controlling aquatic weeds, said method comprising applying to the weeds in water bodies an agronomically effective amount of a bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives; and
ii. at least one additive.
In an embodiment, the bead composition according to the present invention is used for controlling aquatic plants selected from Algae, duckweed, watermeal, water Hyacinth, water lettuce, submerged plants such as milfoil, hydrillia, curly-Leaf pondweed, clasping-leaf pondweed, coontail, naiad, sago pondweed, emergent plants such as cattail, water lily, watershield, phragmites, purple loosestrife and bulrush.
In another embodiment algae includes sensitive species such as Spirogyra and Pithophora and difficult to control species such as Nostoc and Oedogonium.
The present invention further provides a safe delivery system for aquatic weed control, said system comprising a bead compositing comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives; and
ii. at least one additive.
In an embodiment, the present invention provides a safe delivery system for aquatic weed control, said system comprising an endothall composition in the form of beads that can be delivered to water bodies safely.
In another embodiment, the safe delivery system according to the present invention avoids direct exposure and skin irritation due to endothall.
The instant invention is more specifically explained by below examples. However, it should be understood that the scope of the present invention is not limited by the examples in any manner. It will be appreciated by any person skilled in this art that the present invention includes below examples and further can be modified and altered within the technical scope of the present invention.
Examples:
Example 1: A bead composition according to the present invention is prepared as follows:
Composition of pre-gel mixture part A:
Ingredients Quantity (%w/w)
Endothall amine salt 98.75
Sodium alginate 0.75
Polyvinyl alcohol q.s

Composition of gelling bath mixture part B:
Ingredients Quantity (%w/w)
Calcium chloride hexahydate 15
Proxel gel 2
Water q.s.

Composition of bead:
Ingredients Quantity (%w/w)
Endothall amine salt 94.3
Polyvinyl alcohol 0.48
Sodium alginate 0.72
Proxel gel 0.1
Calcium alginate shell 4.4

Process:
Required quantity of ingredients for part A was mixed well to form the pre-gel mixture. The gelling bath mixture part B was prepared by mixing the required ingredients in a separate container having a continuous flow system. Pre-gel mixture part A as prepared above was dispensed dropwise to the gelling bath mixture part B kept at a temperature of 10-15°C. The mixture was kept under stirring. The beads were formed instantly and the contact time of part A in part B was controlled to be less than 15 seconds to obtain the beads of required size and wall thickness. The beads were continuously separated and dried using a continuous dryer.
Example 2: A comparative composition is prepared (in the absence of polyvinyl alcohol) as follows:
Composition of pre-gel mixture part A:
Ingredients Quantity (%w/w)
Endothall amine salt 99.25
Sodium alginate 0.75

Composition of gelling bath mixture part B:
Ingredients Quantity (%w/w)
Calcium chloride hexahydrate 15.0
Proxel GXL 2.0
Water QS

Composition of bead:
Ingredients Quantity (%w/w)
Endothall amine salt 94.78
Sodium alginate 0.72
Proxel GXL 0.10
Calcium alginate shell 4.40

Process for Example 1 was used to prepared the composition.

Weed control observations:
The bead compositions prepared according to the present invention was tested on various aquatic weeds for their herbicidal activity.
In the present study, algicidal activity of bead compositions were tested. Algae samples were dominated by Spirogyra, however, other species such as Zygnema and Pithophora were present. Difficult to control species Nostoc and Oedogonium were also present. The bead composition of endothall amine salt of the present invention at a concentration (0.07 mg acid equivalent/liter) were tested and observations were recorded for 1 day, 3 days and 5 days after exposure. Algae exposed to various concentrations had degraded cells 5 days post-exposure initiation. Chlorophyll concentrations for all exposures were less than half of the untreated controls. The algae in the untreated controls remained green with intact cellular structure throughout the 5 day experiment. The results are summarized in the below table.
Treatment (mg acid equivalent/liter) Chlorophyll concentration (g/g algae)
1DAT 3 DAT 5DAT
0.07 (Example 1) 30 80 20
0.07 (Example 2) 114 187 85
Control 260 300 290

From the results as shown in the above table it is evident that the bead compositions according to the present invention can be effectively used for algae control. The compositions wherein the additive is present acts as a structure modifying agent which in turn affected the permeability of the bead wall thereby controlling the release on endothall for the intended algae control. When treating an algae complex, multiple species within the complex should be considered. With the species differentiation, comes differential tolerances and susceptibility of the various species being treated. When the most susceptible algal species dominates the complex, it is easily controlled when treated.
It has been observed that sensitive species are Spirogyra and Pithophora. Nostoc and Oedogonium were noted as species that are difficult to control. With the death of the most susceptible and most dominate species, it allows secondary, more tolerance species to proliferate. The secondary species then increase in percentage because of the lack of the competing susceptible species, and the secondary more tolerant species use the nutrient release from the susceptible species as a nutrient source to “bloom”. Yet, as time increases the secondary species tolerance was observed to be overcome by the continued exposure to the algaecide. Due to the continued exposure over a few days, the secondary more tolerant species were also succumbed to the algaecide application. This observation is supported by the data provided in the table.
,CLAIMS:1. A bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising
i) at least 15% by weight of endothall, its salts or derivatives; and
ii) at least one additive
wherein said external zone is capable of releasing, said endothall, its salts or derivatives when hydrated.
2. A bead composition according to claim 1 wherein said alginate complex is an alkali or alkaline earth metal salt of alginic acid.
3. A bead composition according to claim 1 wherein said alginate complex is sodium or calcium alginate.
4. A bead composition according to claim 1 wherein said internal zone is entrapped in said external zone
5. A bead composition according to claim 1 wherein said endothall is selected from the group comprising endothall diammonium, endothall dipotassium, endothall disodium and endothall mono(N,N-dimethylalkylammonium)
6. A bead composition according to claim 1 wherein said internal zone comprises from about 15% to about 99% by weight of endothall.
7. A bead composition according to claim 1 wherein said the additive is a polymer.
8. A bead composition according to claim 1 wherein said the additive is polyvinyl alcohol.
9. A bead composition suspended in a media comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i. at least 15% by weight of endothall, its salts or derivatives; and
ii. at least one additive
wherein said external zone is capable of releasing, said endothall, its salts or derivatives when hydrated.
10. A bead composition according to claim 9 wherein said suspending media is selected from the group comprising saturated polysaccharide solution, saturated xanthan gum solution or a saturated solution of alginate salts.
11. A process for preparing a herbicidal bead composition wherein said process comprises:
(a) preparing a pre-gel mixture of at least 15% by weight of endothall, its salts or derivatives, a water soluble alginate salt and an additive;
(b) preparing a gelling bath mixture comprising an alkaline earth metal solution; and
(c) dispensing uniform droplets of the pre-gel mixture into the gelling bath mixture to form said beads entrapping said internal zone.
12. A process according to claim 12 wherein said water soluble alginate salt is calcium alginate.
13. A process according to claim 12 wherein said gelling bath mixture comprises calcium chloride solution and a biocide
14. A continuous process for preparing herbicidal bead composition wherein said process comprises:
(a) preparing a pre-gel mixture comprising at least 15% by weight of endothall, its salts or derivatives, a water soluble alginate salt and an additive;
(b) preparing a gelling bath mixture comprising an alkaline earth metal solution in a container with an inlet and outlet so as to optimize a continuous flow of gelling bath mixture;
(c) dispensing uniform droplets of pre-gel mixture into the gelling bath mixture to form said beads entrapping said internal zone; and
(d) separating said beads continuously
15. A method of controlling aquatic weeds, said method comprising applying to the weeds in water bodies an agronomically effective amount of a bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
i) at least 15% by weight of endothall, its salts or derivatives; and
ii) at least one additive.
16. A method according to claim 15 wherein said aquatic weed is selected from the group comprising algae, duckweed, watermeal, water Hyacinth, water lettuce, submerged plants such as milfoil, hydrillia, curly-Leaf pondweed, clasping-leaf pondweed, coontail, naiad, sago pondweed, emergent plants such as cattail, water lily, watershield, phragmites, purple loosestrife and bulrush.

17. A safe delivery system for aquatic weed control, said system comprising a bead composition comprising:
a) an external zone comprising an alginate complex; and
b) an internal zone comprising:
I. at least 15% by weight of endothall, its salts or derivatives; and
II. at least one additive.