Rapid assessment of early-stage herbicide-rust compatibility to support integrated management of Cryptostegia grandiflora

Le résumé fourni par la source

Cryptostegia grandiflora (rubber vine) is an invasive weed in tropical and subtropical regions worldwide and is listed as a Weed of National Significance in Australia. The rust Maravalia cryptostegiae , deliberately introduced to Australia as a biocontrol agent, contributes to long-term suppression, but does not provide complete control, making herbicide intervention necessary in many land-use contexts. For integrated weed management (IWM) to be effective, chemical and biological controls must complement rather than conflict, yet herbicide-rust compatibility has rarely been quantified. We developed a 14-day laboratory workflow to assess compatibility by combining in vitro spore germination and detached-leaf infection assays with image-based analysis. Treatments included metsulfuron-methyl (MM), a recommended foliar herbicide for rubber vine, and a novel herbistatic analogue (COT-MM). Both the herbicide and the herbistatic analogue reduced spore germination and leaf infection relative to the blank, but neither differed from the surfactant, indicating strong adjuvant-mediated inhibition. No detectable difference between MM and COT-MM was demonstrated. This rapid workflow detected early antagonism between foliar herbicide formulations and M. cryptostegiae and identified the adjuvant as a major contributor. Integrating such assays into herbicide discovery and management planning will help ensure that chemical and biological tactics reinforce one another, supporting more sustainable IWM of invasive weeds.

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