ABSTRACT Fusarium basal rot (FBR) caused by Fusarium oxysporum f. sp. cepae is a major destructive threat to global onion production causing seedling mortality and pre‐ and post‐harvest bulb decay, often accompanied by mycotoxin concerns. Its control is notoriously difficult due to diverse transmission modes and the long‐term persistence of chlamydospores in the soil. This study was conducted to analyse the field efficacy of three novel fungicides at low dosages, and to assess their interaction with three onion cultivars exhibiting varying FBR resistance levels, namely Texas Early Grano 502 (resistant), SV7030NS (tolerant) and Yellow Sweet Spanish (susceptible). The fungicides included Lamardor 400 FS (propiconazole + tebuconazole) at 2.5 kg/ha and Priaxor Xemium Brand (fluxapyroxad + pyraclostrobin) at 1.0 or 1.5 L/ha, compared to the standard Rovral‐TS (iprodione + carbendazim) at 5.0 kg/ha (all applied via soil surface irrigation), with an additional Priaxor foliar treatment (1.0 L/ha). All treatments were applied three times at 3‐week intervals from the onset of FBR (mid‐April), and efficacy was assessed in mid‐July. The lowest FBR severity was recorded for Priaxor at 1.5 L/ha (10%), followed closely by Lamardor (10%), significantly reducing disease compared to the non‐treated controls (48% severity). Correspondingly, the highest yield was achieved with Priaxor at 1.5 L/ha (64 t/ha), followed by Lamardor (55 t/ha), both substantially exceeding the control yield (36 t/ha). Our findings suggest that these novel fungicides possess distinct efficacy profiles, which, when combined with varietal resistance, can be leveraged to develop improved, integrated management strategies against FBR.
Ramshini et al. (Sun,) studied this question.