Germination responses of vipergrass (Dinebra retroflexa) to environmental factors and herbicide options for its control

Abstract

Vipergrass [Dinebra retroflexa (Vahl) Panzer] is an annual weed of the Poaceae family distributed in several parts of Australia, Asia, and Europe. Very limited information is available on its germination response to different environmental conditions. Knowledge of its seed ecology and biology could help in formulating better weed management decisions. Experiments were conducted to study the effect of alternating temperatures, light conditions, salt stress, water stress, seed burial depths, and wheat residue amounts on the germination or emergence of D. retroflexa. Also, different pre- and post-emergence herbicides were evaluated to control D. retroflexa. The highest germination (98%) was recorded at 30/20 C followed by 35/25 C (95%). Light was required for the germination of D. retroflexa. Germination decreased with an increase in sodium chloride (NaCl) concentrations. Even at 80 mM NaCl, 81% of seeds were germinated, indicating its high salt tolerance. Seed germination gradually decreased with an increase in water stress and no germination was recorded at -0.8 MPa osmotic potential. The emergence of D. retroflexa decreased with an increase in seed burial depths. The highest germination (83%) was recorded for surface-sown seeds, and emergence was reduced to zero at a burial depth of 2 cm. Seedling emergence was decreased from 82% to 2% when the crop residue load was increased from 0 to 800 kg ha-1. Applications of pre-emergence herbicides (at field rates), such as diuron, isoxaflutole, pendimethalin, pyroxasulfone, S-metolachlor, terbuthylazine, and triallate; and post-emergence herbicides, such as clethodim, haloxyfop-methyl, glufosinate, glyphosate, imazamox plus imazapyr (a commercial mixture), and paraquat resulted in complete control (100%) of D. retroflexa. Knowledge gained from this study will help to understand the potential spread of D. retroflexa to other areas and to formulate integrated weed management strategies for its effective control.