Herbicide efficacy and crop safety of new tank-mix combinations in transplanted chilli

Abstract:

Weed interference during the first 45 days after transplanting can slash chilli pepper yields by more than half, yet growers in the central United States have limited herbicide options registered for this crop. This research evaluated four tank-mix combinations of pre- and post-emergence herbicides alongside hand weeding and an untreated weedy check in transplanted chilli (Capsicum annuum L. cv. Cayenne Long) at the Prairie State Agricultural University research farm, Lincoln, Nebraska, from May to October 2023. Treatments were arranged in a randomized complete block design with four replications. Weed control efficiency, crop phytotoxicity (0-25 visual scale), plant height, fruit number, and marketable yield were assessed. Imazethapyr + propaquizafop gave the best weed control (86.1%) with the lowest phytotoxicity score (6.9), producing a marketable yield of 14.8 t ha⁻¹ that was statistically on par with hand weeding (15.3 t ha⁻¹). Pendimethalin + quizalofop controlled 83.7% of weeds with moderate crop safety. Metribuzin + clethodim caused visible leaf chlorosis (phytotoxicity 22.1) and reduced yield by 18.4% relative to hand weeding. The weedy check yielded only 6.7 t ha⁻¹. These findings show that imazethapyr + propaquizafop is a viable tank-mix option for weed management in transplanted chilli where manual labour is scarce or costly.