Epidemic potential of Maravalia cryptostegiae , a classical biological control agent of rubber vine, in Northeastern Brazil

Rubber vines ( Cryptostegia madagascariensis and C. grandiflora ) are highly invasive weeds in the semi-arid landscapes of many tropical regions. The rust fungus Maravalia cryptostegiae has provided a spetatular and sustainable control of invasive C. grandiflora populations in Australia, after its scientific and quarantine-authorized release in the context of a classical biological control program. The Caatinga biome of Northeastern Brazil is under a devastating invasion by C. madagascariensis . This species is also susceptible to M. cryptostegia but its epidemic potential towards C. madagascariensis in Brazil remains unknown. We developed a weather-driven epidemiological model integrating experimentally derived relationships for infection as a function of temperature and wetness duration and temperature-dependent latent development. Three infection-response models were fitted to 20 experimental temperature × wetness combinations found in the literature and evaluated using information criteria and grouped cross-validation. The selected model incorporated wetness-dependent thermal breadth and provided the best overall fit ( R ² = 0.931), with prolonged wetness significantly broadening the thermal range favorable for infection. The infection and latent-development models were coupled with 25 years (2001–2025) of hourly meteorological data from 65 grid cells representing rubber-vine-infested locations in Northeastern Brazil. May–July accounted for >60% of annual infection potential, with the highest epidemic potential in Central Ceará and Western Paraíba, overlapping major host-infestation areas. Cross-continental evaluation at 13 historical monitoring sites in Queensland, Australia, reproduced documented wet-season epidemic patterns and differentiated high-impact coastal/riparian from drier inland environments. These results demonstrate strong seasonal and geographic structuring of epidemic potential, providing a quantitative basis for identifying locations and periods favorable for M. cryptostegiae establishment and epidemic development following its future release in Brazil.