Evaluation of Novel Chemical and Thermal Weed-Control Tools for Silverleaf Nightshade

Abstract Silverleaf nightshade, a highly invasive perennial weed, poses a serious threat to crops and orchards in Mediterranean regions. This weed reproduces both sexually, through seeds, and asexually, via an extensive rhizome network, contributing to its persistence and spread. Managing silverleaf nightshade is particularly challenging, requiring integrated chemical and non-chemical approaches. This study evaluated the effectiveness of preemergence and postemergence herbicides and thermal control methods at three growth stages (2-3, 4-6, and 7-10 true-leaf stages [TL]) of silverleaf nightshade. Seven preemergence herbicides were tested in a dose-response experiment at rates between 0.0625X and 2X of the recommended label rate on seedling emergence from three populations. Metribuzin, pyroxasulfone, pendimethalin, and sulfosulfuron suppressed seedling emergence by 80-90% at 28 days after treatment. Seven postemergence herbicides were tested on the same three seed populations, and on plants grown from rhizomes. Treatments were applied at three rates: the recommended label rate (1X) and two exploratory rates 0.5X and 2X. At the 1X and 2X rates, aminopyralid and glufosinate reduced biomass by more than 90% at all growth stages. Fluroxypyr and imazapic reduced biomass by more than 95% at the 2-3 TL growth stage across all application rates. At the 4-6 and 7-10 TL growth stages, biomass reduction >90% was achieved only at the 2X rate. Propane flaming at 33.3, 50 and 100 kg ha⁻¹ and electrocution with 18, 45 and 90 J (correspond to 0.5X, 1X and 2X application rates) tested across the three growth stages. Both thermal methods were highly effective at the 2-3 TL stage, reduced biomass >95%. The results highlight the importance of early intervention, as both herbicide and thermal treatments efficacy declined significantly as the weeds matured. Integrating pre and postemergence herbicides with thermal treatment could improve the long-term management of silverleaf nightshade in Mediterranean cropping systems.