Phase sensitivity of some broad-leaved weed species to the herbicide Flex

Abstract

The effect of herbicide Flex, AS (active ingredient fomesafen 250 g/l) on annual weed species common in soybean crops was studied. The studies were conducted under greenhouse conditions in 2019-2021. The sensitivity of ragweed Ambrosia artemisiifolia L., Asian copper leaf Acalypha australis L., common lamb's quarters Chenopodium album L., common dayflower Commelina communis L., China jute Abutilon theophrasti Medik, trailing hollyhock Hibiscus trionum L., St.-Paul’swort Sigesbeckia pubescens Makino, green amaranth Amaranthus retroflexus L., elsholtzia Elsholtzia pseudocristata Levl. et Vaniot, and Siberian cocklebur Xanthium sibiricum Patrin ex Widd was determined. Weed treatment with Flex at rates of 0.75, 1.0, 1.25 and 1.5 l/ha was carried out three times a season at different stages of plant growth and development. The level of sensitivity of weed species to herbicide was judged by the decrease in height and weight of the aboveground organs of the experimental plants compared to the control. It was found that Flex herbicide completely destroys plants of all tested species in the early stages of growth and development (1-4 true leaves). When treating weeds that have formed 3-10 leaves, ragweed, green amaranth, Asian copper leaf, trailing hollyhock and Siberian cocklebur remain highly sensitive to the drug action (reduction of the aboveground weight up to 94-100%). Application of Flex on overgrown plants leads to a significant decrease in its activity against all studied weed species. When used in the third term, the herbicide is effective only on the green amaranth, suppressing the mass of the plants by 76-86%.

Phase sensitivity of perennial dicotyledonous weed species to Flex herbicide

“…Therefore, the issue of studying the sensitivity to herbicides of individual weed species at different stages of their development is of great importance [18]. Our studies also confirm that the use of herbicides on vegetative weeds is most appropriate in the early phases of their growth and development [19].…”

“…The phases of weed development in the control plants by the time of cutting are given in Table 2. To evaluate herbicidal activity, the following gradation of efficacy levels was used: 91-100% reduction in height and weight of experimental plants -very good effect, 76-90%good, 51-75% -satisfactory and 0-50% -no effect/weak effect [19].…”