Double-spraying with different routes significantly improved the performance of both pre- and post-emergence wheat herbicides applied by unmanned aerial spraying systems

Abstract

Unmanned aerial spraying systems (UASS) are one of the most important systems for herbicide applications. We applied pre-emergence (PRE) and post-emergence (POST) herbicides via an UASS to wheat (Triticum aestivum) fields, using different spraying volumes (22.5–60 L ha−1) and different spraying route strategies (one-time spraying or double spraying with two flight sorties routed in length and breadth). Both the spraying volume and route strategy significantly (P < 0.05) affected the control efficacy against grassy weeds and broadleaf weeds of both PRE and POST herbicides. Compared with manual spraying with a spraying volume of 450 L ha−1, the formulation of PRE herbicides (132 g·ai·ha−1 flufenacet + 132 g·ai·ha−1 diflufenican + 132 g·ai·ha−1 flurtamone) applied by the UASS with a spraying volume of 45 or 60 L ha−1 and adopting the double-spraying technique showed slightly higher or similar control efficacy against grassy and broadleaf weeds. The formulation of POST herbicides (9.75 g·ai·ha−1 florasulam + 9.75 g·ai·ha−1 halauxifen-methyl) showed control efficacies >98% against Galium spurium applied by the UASS with a spraying volume of 22.5–60 L ha−1, according to fresh weights of aboveground parts at 45 d after treatment; however, this was not the case for the control of Stellaria aquatica. The POST herbicides showed the highest control efficacy against S. aquatica when applied with UASS at a spraying volume of 60 L ha−1 and the double-spraying technique. Similarly, another formulation of POST herbicides (15.75 g·ai·ha−1 mesosulfuron-methyl + 60 g·ai·ha−1 pinoxaden) showed similar control efficacies with manual spraying against Beckmannia syzigachne, applied by the UASS with a spraying volume of 45 or 60 L ha−1, using the double-spraying strategy. Conclusion: Applying PRE or POST wheat herbicides with an UASS, double-spraying routed in length and breadth with a spraying volume of 45–60 L ha−1 should be recommended.