Joint Action of Herbicides on Weeds and Their Risk Assessment on Earthworm (<em>Eisenia fetida</em> L.)

Frequent and intensive use of similar modes of action herbicides increases selection pressure resulting in nature adapt and a number of herbicide-resistant weeds. The most effective methods to prevent and delay herbicide-resistant weeds are herbicide tank mixture and adjuvant mixed herbicides. This chapter intends to explain the advantages of herbicide tank mixture and adjuvant mixed herbicides. In addition, the models of estimated herbicide mixture interaction response have been explained. Although herbicide mixtures have benefits, they may present risks leading to soil pollution and affecting soil fauna such as earthworms. Therefore, we discussed the negative effect of mixture herbicides on Eisenia fetida. On the other hand, various models to calculate mixture herbicide toxicity on earthworms will be present in this chapter

The Effect of Reduced Doses of Trifluralin on Control of ‎Common Lamsquarters (Chenopodium album L.) and Redroot ‎Pigweed (Amaranthus retroflexus L.) in Potato (Solanum ‎tuberosum L.) Fields

To evaluate the reduced concentration effect of Trifluralin (Treflan EC 33%) on common lamsquarters (Chenopodium album L.) and redroot pigweed (Amaranthus retroflexus L.) in potato (cv. Agria) a field experiment based on randomized complete design with three replications was carried out at the Agriculture and Natural Resources Research Station of Ardabil during 2013. Treatments were concentration of Trifluralin (0.125, 0.25, 0.5, 1, 2 and 4 Lit a.i/ha) without weed control and weeding out (as control). Sampling of weeds were performed before and after flowering of potato. Statistical analysis showed significant differences of reduced concentrations of Trifluralin on reduction of both lamsquarters and pigweed in the field. The highest reduction in percentages of weed densities, before and after flowering (91.94 and 90.34 percent, respectively) were achieved by using 4 Lit a.i/ha of Trifluralin. Application 4 Lit a.i/ha of Trifluralin at before and after flowering reduced common lamsquarters density by 87.13 and 86.04 percentages, respectively. Application 4 Lit a.i/ ha Trifluralin at befor and after flowering reduced pigweed density by more than 90 percent. Experimental results also showed that different concentrations of Trifluralin had significant effect on mean tuber weight per plant, and potato tuber yield. The highest mean weight of tuber per plant, yield per plant and potato tuber yield was obtained at 2 Lit a.i/ha Trifluralin concentration, while it was not significantly different from that of 4 Lit a.i/ ha. Generally, application of 2 and 4 Lit a.i/ha Trifluralin incereased tuber yield by 51.85 and 50.74 percents respectively

The Joint Action of Some Broadleaf Herbicides on Potato (Solanum tuberosum L.) Weeds and Photosynthetic Performance of Potato

Herbicide mixtures are a modern weed management practice as they reduce herbicide application. This study aimes to evaluate the effect of metribuzin, halosulfuron and flumioxazin applied individually and as mixtures (metribuzin:halosulfuron and metribuzin:flumioxazin) on Chenopodium album, Amaranthus retroflexus, and potatoes on biomass and chlorophyll-a fluorescence in 21 experiments. The individual herbicide experimental design was a randomized completely block design with seven doses and three replications. The factorial experiments were performed on the basis of randomized completely block design in three replications for binary mixture experiments. Flumioxazin was very potent in controlling C. album, A. retroflexus, and injured potatoes with a 50% effective dose (ED50) of 1.21, 0.54, and 12.23 g ai·ha−1, respectively. Both mixtures of metribuzin:halosulfuron and metribuzin:flumioxazin generally showed an antagonistic effect on both weeds and potato in 12 independent experiments. Metribuzin, halosulfuron, and flumioxazin significantly decreased photosystem II activity by decreasing the maximum quantum efficiency (Fv/Fm). The metribuzin:halosulfuron mixtures almost followed the Additive Dose Model for Fv/Fm, whilst there was an antagonistic effect for the metribuzin:flumioxazin that was closely related to biomass. The results indicated that mixtures were generally antagonistic, and the endpoint choice is pivotal when assessing the joint action of mixtures

The Survival Response of Earthworm (Eisenia fetida L.) to Individual and Binary Mixtures of Herbicides

Frequent use of herbicides may impose a risk on non-target species. The objective was to test the combined toxic effect of binary herbicide mixtures&mdash;metribuzin:halosulfuron and metribuzin:flumioxazin&mdash;on non-target earthworms in two test systems: filter paper and a soil toxicity test system. The joint action experiments were independently run twice to substantiate the findings. The most potent individual herbicide was metribuzin, with a 50% lethal concentration (LC50) of 17.17 &micro;g ai. cm&minus;2 at 48 h in the filter paper test. The toxicity of the individual herbicides on the filter paper test was ranked as metribuzin&gt;halosulfuron&gt;flumioxazin. In the soil test, metribuzin and halosulfuron had high toxicity with an LC50 of 8.48 and 10.08 mg ai. kg&minus;1, respectively, on day 14. Thus, the individual herbicide ranking did not change between the filter paper and artificial soil tests. The herbicide&rsquo;s mixed effect in both test systems showed a consistent antagonistic effect relative to a Concentration Addition reference model. It indicates that the mixtures retracted the herbicide&rsquo;s action in the earthworms