The evaluation effect of dust on the efficiency of bentazone, imazethapyr and pyridate with and without PCGate on control of common purslane (Portulaca oleracea L.)

Introduction: The phenomenon of dust (Dust storms) is one of the growing critical events in Iran. One of the most serious environmental issues and air pollutants in Southwest and West Asia is dust caused by desertification processes (Li et al. 2020). Iran is exposed to the numerous dust centers due to its proximity to the deserts of neighboring countries such as Iraq, Syria and Saudi Arabia. Of 31 provinces in Iran, 22 of them are exposed a serious problem of air pollution (Sari Sarraf et al., 2016(. They can prevent the herbicide's spread on the surface of the leaf and stem and reduce the solubility, absorption and penetration of herbicides into the plant. Using an adjuvant is presented as the best recommended strategy to reduce the negative effects of dust on the herbicide's absorption and transfer (Rashki et al., 2014). Legumes are presented as a weak competitor versus weeds to absorb the water, nutrients and light during the growing season due to their slow growth rate, low height and lack of sufficient ground cover. Weeds are considered as the most important limiting factors on legumes performance, which not only leads to a decrease in the quantity and quality of the crop, but also impose a heavy cost to the farmers. Weeds are caused by a 50-80 percent reduction in crop yield when poor management of weeds happens. Therefore, it is necessary to pay attention to the management of leguminous weeds. Among the important and necessary inputs in the agricultural systems of developed countries, herbicides are offered, which is a significant part of the crop performance of these countries due to their consumption. Bentazone and pyridate are selective herbicides that are used as post-emergence and foliar applications to control broadleaf weeds in legume fields. Both of them are photosynthesis inhibitors that prevent electron transfer by binding to the QB position and taking electrons from QA in the chloroplast by forming reactive oxygen species (ROS) (Edenfield et al., 2001). Imazethapyr is a selective herbicide that inhibits the synthesis of the acetolactate synthase (ALS) enzyme, which is informally used to control many annual broadleaf weeds.

Materials and Methods: To evaluation effect of dust on the pure and mixed efficiency of bentazone, imazethapyr and pyridate without and with PCGate on control of common purslane (Portulaca oleracea L.), three dose-response experiments as factorial based on a randomized complete block design with three replications carried out at the greenhouse of Agricultural Faculty of Lorestan University, Iran, during 2023. The chemical treatments included the first factor; bentazone at 30, 60, 120, 240 and 480 g a.i.ha-1, imazethapyr at 3.13, 6.25, 12.5, 25 and 50 g a.i.ha-1 and pyridate at 37.5, 75, 150, 300 and 600 g a.i.ha-1 with and without PCGate adjuvant accompanied to 10 control and the second factor; the dust accumulated on the aerial parts of common purslane (under 0 and 20 Kg dust ha-1 conditions by dust chamber). Treatments were sprayed at four-to-five-leafy stage by using an overhead trolley sprayer that was equipped with a flat-fannozzle. Four weeks after spraying, the fresh and dry weights of the experimental units control and treated plants shoots were harvested and oven-dried at 75°C for 48 h, then weighed. The statistical analysis of data were done by RStudio with drc package and the PROC GLM procedure of SAS.

Results: The results showed that the fresh weight of common purslane were significant by dust, adjuvant and three herbicides application such as bentazone, imazethapyr and pyridate (P<0.01). The effect of dust was varied according to the herbicide efficacy on weed control. As the highest and the lowest percent of common purslane control was related to pyridate and imazethapyr, respectively. In the presence or absence of dust, the addition of PCGate were significant effect on bentazone, imazethapyr and pyridate efficacy.

Conclusions: Based on the findings, a conclusion can be drawn that the different efficacy of herbicides were affected by various factors, such as the weed species and the physicochemical incompatibilities of the herbicide formulation. The use of bentazone and pyridite is recommended in the western regions due to their favorable effectiveness in the common purslane control with PCGate when the conditions of dust occur.