Weed control efficacy and garlic crop selectivity under post-emergence applications of single and combined herbicides

Abstract

Garlic production is severely constrained by weed interference throughout its growth cycle. Given the scarcity of research on chemical weed control in this vegetable crop, the present study evaluated the efficacy of post-emergence herbicide applications against broadleaf weed species (Raphanus raphanistrum, Coronopus didymus, Stellaria media, and Rumex obtusifolius), as well as their selectivity to garlic plants, by assessing plant height, stand, phytotoxicity, and bulb diameter and yield. The herbicides tested were ioxynil (75 g ha⁻¹), ioxynil + pendimethalin (75 + 1,820 g ha⁻¹), ioxynil + pyroxasulfone (75 + 100 g ha⁻¹), fomesafen (37.5 and 75 g ha⁻¹), S-metolachlor + fomesafen (258.9 + 56.9 g ha⁻¹), and prometryn (250 g ha⁻¹). The experiment was conducted in garlic commercial fields in Curitibanos, Santa Catarina, Brazil, using a randomized block design with nine treatments, including two controls (hand-weeded and non-weeded), and four replications. Fomesafen (37.5 and 75 g ha⁻¹), S-metolachlor + fomesafen, and prometryn exhibited poor weed-control efficacy and low crop selectivity, resulting in high phytotoxicity, reduced bulb diameter, and significant yield losses. In contrast, ioxynil alone and mixed with pendimethalin or pyroxasulfone provided significant control of all target weed species and high selectivity to the garlic crop. These combinations, therefore, are promising and safe alternatives to the single post-emergence application of ioxynil in garlic crops.