Effect of novel botanical synergist on the effectiveness and residue behavior of prothioconazole in wheat field

Abstract

Abstract Fusarium head blight (FHB) is an important fungal disease which can lead to serious yield losses and mycotoxin contaminations, the Fusarium strains have been found obvious resistance to many fungicides. Development of novel synergist is an important approach for addressing these challenges of postponing the development of pesticide resistance. In this study, the synergistic effect of Taxodium 'zhongshansha' essential oil (TZEO) was determined via the evaluation of synergistic ratio (SR) with three replicators under standard procedures. The best SR of 3.96 in laboratory which was observed when the weight ratio of TZEO and prothioconazole was 1 : 1 with the corresponding EC50 (half maximal effective concentration) value of Fusarium graminearum was 0.280 mg L− 1. Subsequently, an increase of 6.31% on the control effect to FHB index in field test was observed when compared to the treatment with prothioconazole alone, and the mycotoxin contamination was less than the limits of quantifications (LOQs) value satisfied to the detection of these mycotoxins which was 5 µg kg− 1 (DON, ZEN, 3-DON, and 15-DON) and 1 µg kg− 1 (OTA), respectively. It was also shown that the application of 20% TZEO EW led to a 20% reduction at least in the use of prothioconazole, which was calculated based on the control effect values of 86.41% and 90.20% between the treatments of 30% prothioconazole OD (225 g a.i ha− 1, recommend dosage) and 30% prothioconazole OD (180 g a.i ha− 1) + 20% TZEO EW (225 mL ha− 1), significantly. The initial residue of prothioconazole and prothioconazole-desthio was found to in-crease upon treatment with TZEO, which may play an important role in the synergistic effect on FHB. Moreover, none of the treatments posed a prothioconazole residue risk in the wheat grain and the environment. Finally, the essential oil was not found to have any negative influence on wheat growth, which was revealed by a study of the chlorophyll content. These results provide an important botanical synergist for use with prothioconazole to control Fusarium head blight, which will play a creative role to reduce the application of prothioconazole and postpone the development of resistance. Furthermore, in-depth study to the synergistic mechanism of this oil is necessary in our future research.