The evaluation of water quality under different spray carriers and surfactant on bentazone and paraquat efficacy on control of ground cherry (Physalis divaricata L.)

Introduction: Ground cherry with the scientific name of Physalis divaricata L. is a member of the solanaceae family and is a one-year summer weed and an invasive and troublesome species that has been reported in various fields of beans, sugar beet and corn. This weed can decrease in peas and beans yield's due to competition for water, food and light during the growing season with sensitive crops (Sabeti et al., 2021). Bentazon is a selective herbicide from the benzothiadiazinone group and is used to control annual and perennial broadleaf weeds in fields of soybeans and legums. Paraquat, a foliar-applied contact herbicide belonging to the chemical family of bipyridylium, is the second most widely used pesticide throughout the world. Although it is a non-selective herbicide, its use is very wide-ranging in both agricultural and non-agricultural ecosystems (Cobb and Reade, 2010). Water is a universal solvent and it is used as a primary carrier for crop protection product applications. The properties of water used as a carrier in spray solutions can greatly influence the performance of herbicides, including glyphosate, paraquat and bentazone. Quality of water used in spray tanks can affect herbicides efficacy. Water hardness is primarily dependent on the concentration of cations such as calcium (Ca2+) and magnesium (Mg2+) in water. Many studies showed a reduction in weak acid herbicide performance into the leaf when are used by water hardness. The addition of adjuvants such as ammonium (AMS) to weak acid herbicide solution reduces the antagonistic effect of cations and enhances the control of certain weed species (Pratt et al., 2003; Nurse et al., 2008). Zollinger et al. (2010) reported that the activity of the four weak acid herbicides, such as, dicamba plus diflufenzopyr, and glufosinate increased with addition of ammonium sulphate to the spray solution; they were all antagonized by calcium and magnesium, and ammonium sulfate overcame this antagonism.
Materials and Methods: Two experiments were conducted at the research greenhouse of the Agricultural Faculty, Lorestan University, Lorestan, Iran (Lat 32° 3' N, Long 48° 21' E; 1117 m altitude) from May to September 2021. Ground cherry seeds were collected from a legums field near the research greenhouse at Lorestan University, Lorestan, Iran. The seeds were germinated by adding 1250 ppm GA3 in glass Petri dishes. Ten germinated seedlings were planted at 1 cm depth in each 2 L plastic pot filled with a mixture of sand, clay loam soil, and peat (1:1:1; v/v/v). The experiment was in factorial based on completely randomized design with four carrier water treatments included distilled water (DW), Na2CO3 (Na+), MgCO3 (Mg2+) and Al2(CO3)3 (Al3+) (in dose-response arrangements) and three replications for each treatment. 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 Discussion: The results showed that the fresh weight weed of Physalis divaricata L. were significant by different water carrier and doses application of bentazone and paraquat herbicides (P<0.01). According to EC10، EC50 and EC90 values related to different carrier bentazone and paraquat spray solution, the highest and the lowest antagonistic effect in herbicides efficacy related to Al2(CO3)3 (Al3+) and Na2CO3. The intensity of the antagonistic effects depended on the cation’s valence and ranked as and Al2(CO3)3 (Al3+) > MgCO3 (Mg2+) > Na2CO3 (Na+) > distilled water (DW). All the EDs values of different hard water carrier have been reduced using by PC Gate surfactant. The highest damage of P. divaricate was observed at 21 days after spraying using the dose of 300 and 480 gr of paraquat and bentazon.
Conclusion: In conclusion, it is necessary to use an adjuvant to prevent the reduction of herbicide efficiency, if there is a cation in the water carrying the spray. Also, the applied dose of 480 and 300 g a.i ha-1 of bentazone and paraquat spray solution with PC Gate is also recommended as the best herbicide treatment to control weed of Physalis divaricata L.