A Complex Coacervate Formulation for Delivery of Colletotrichum truncatum 00-003B1

A complex coacervate formulation was developed for Colletotrichum truncatum 00-003B1 (Ct), a bioherbicidal fungus against scentless chamomile, and tested in the greenhouse. A two-step process was developed to formulate Ct conidia: (1) invert emulsion preparation—emulsify an aqueous suspension of Ct...

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Bibliographic Details
Published in:Weed technology 2010-04, Vol.24 (2), p.185-192
Main Authors: Hynes, Russell K, Chumala, Paulos B, Hupka, Daniel, Peng, Gary
Format: Article
Language:English
Subjects:
Adjuvants, biological weed control, fungus
Canola oil
Chamomile
Colletotrichum
Colletotrichum truncatum
Conidia
Dew
Emulsions
Encapsulation
Phosphatidylcholines
Polysorbates
Surfactants
Symposium
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Summary:A complex coacervate formulation was developed for Colletotrichum truncatum 00-003B1 (Ct), a bioherbicidal fungus against scentless chamomile, and tested in the greenhouse. A two-step process was developed to formulate Ct conidia: (1) invert emulsion preparation—emulsify an aqueous suspension of Ct conidia in nonrefined vegetable oil with the aid of a surfactant, and (2) encapsulate the Ct conidia invert emulsion by complex coacervation. Formulation ingredients, including nonrefined vegetable oils, surfactants, proteins, and carbohydrates, and formulation-processing parameters, including mixing speed and the amount of oil added to invert emulsions, were examined for maximum retention of Ct conidia in the formulation. Most formulation ingredients considered and tested in this study were compatible with Ct, with no significant reduction in conidial germination and mycelial growth. The surfactant soya lecithin promoted the greatest retention of Ct conidia (88%) in the invert emulsion, followed by sorbitan monooleate (82%), glycerol monooleate (70%), and sorbitan trioleate (55%). Optimal retention of Ct conidia in the invert emulsion was observed with a water ∶ oil ratio of 1 ∶ 1.8 to 1 ∶ 3.7, and an overhead paddle stirring speed of 300 rpm when preparing the emulsion. Complex coacervate wall ingredients of 1% gelatin and 2% gum arabic were most effective for Ct conidia retention. In greenhouse studies, scentless chamomile disease rating, following a 24-h dew period, was higher on plants sprayed with the Ct conidia complex coacervate formulation than on plants with Ct conidia suspended in 0.1% Tween 80.
ISSN:0890-037X
1550-2740
DOI:10.1614/WT-D-09-00008.1