Chemical Weed Control in Saffron (Crocus sativus) Fields

Introduction Saffron is derived from the stigmas of the saffron (Crocus sativus L). It is the world’s most expensive spice and has been widely used in many countries. It is also increasingly used for medicinal purposes. Weed control in this perennial, small and low growing crop, needs a lot of labor work. Chemical approach is one of the most effective methods for weed control in saffron. Currently, some herbicide options are available for applications in saffron. For example, satisfactory broadleaved weed control would be achieved by post-emergence application of metribuzin and ioxynil after harvesting saffron flowers. Application of glyphosate and/or 2, 4-D / 2, 4-DB are used to clean up the beds prior to the new season’s flowering and growth of saffron in New Zealand. The selective weed control of weeds in saffron has not been widely reported elsewhere but some in Iran. The choice of herbicide(s) depends on the kind of weeds present. In some literatures metribuzin showed promising results for weed control in saffron fields. It is selectively used for control of annual grasses and numerous broad-leaved weeds. The objective of this study was the evaluation of the efficacy of 15 herbicides with different mode of actions, selected on the basis of dominant weed flora and previous studies, on weeds grown in saffron fields.
Materials and Methods A field study was conducted to evaluate the efficacy of herbicides for weed control in saffron (Crocus sativus) in Agricultural and Natural Resources Research and Education Center of Khorasan Razavi Province, Mashhad, in 2014-2015 growing season. The experiment was conducted in a completely randomized block design with three replications. Treatments were consisted of metsulfuron-methyl sulfosulfuron (Total®) at dose of 40 g ha-1, sulfosulfuron (Apirus®) at dose of 26.6 g ha-1, oxadiazon (Ronestar®) at dose of 2 l ha-1, oxyflurofen (Goal®) at dose of 2 l ha-1, mesosulfuron idosulfuron diflufenican (Othello®) at dose of l.6 l ha-1, metribuzin (Sencore®) at dose of 750 g ha-1 (applied after saffron harvest in autumn as pre emergence of weeds), triasulfuron dicamba (Lintur®) at dose of 165 g ha-1, atrazine (Gesaprim®) at dose of 1000 g ha-1, Bensulfuron methyl (Londax®) at dose of 50 g ha-1, bromoxinyl MCPA (Bromicide®) at dose of l.5 l ha-1, 2, 4-D MCPA (U-46 combi fluid ®) at dose of l.5 l ha-1, nicosulfuron (Cruz®) at dose of l.5 l ha-1, haloxyfop methyl (Gallant super®) at dose of l l ha-1, bentazon (Basagran®) at dose of 3 l ha-1, tribenuron methyl (Granstar®) at dose of 20 g ha-1 plus weed free and weedy checks. Herbicides were sprayed at early stage of weed growth (2-3 leafy stage) (except for metribuzin which sprayed soon after flower harvest in autumn and pre emergence of weeds) with Matabi® rechargeable sprayer calibrated to deliver 330 l ha-1. Four weeks after spraying, density and dry matter of dominant weed species were measured. At harvest, flower number, flower fresh weight and dry matter of 50 stigmas were measured. Data were analysed by SAS (9.2) software and mean were grouped by Duncan multiple range test (alpha=0.05).
Results and Discussion Density and dry matter of dominant weed species i.e. Cirsium arvense, Acroptilon repense and Poa trivialis were significantly decreased by herbicide treatments when measured four weeks after spraying. Significant decrease in flower number and/or flower fresh weight of saffron occurred when sprayed with sulfosulfuron, nicosulfuron, 2, 4-D MCPA, metsulfuron-methyl sulfosulfuron, tribenuron methyl, mesosulfuron idosulfuron diflufenican and bromoxinyl MCPA. Furtheremore, these herbicides can not be used for weed control in saffron. Metribuzin, oxadiazon, bentazon, haloxyfop methyl, oxyflurofen, bensulfuron methyl, triasulfuron dicamba and atrazine caused no significant decrease in flower number and/or flower fresh weight of saffron and then can be recommended to use for weed control in saffron fields. In the case of the possible reverse impacts of these herbicides on saffron corms in long-term use, still more studies need to be done. Dry matter of 50-stigmas of saffron flowers were not significantly different among herbicide treatments.
Conclusions Metribuzin, oxadiazon, bentazon, haloxyfop methyl, oxyflurofen, bensulfuron methyl, triasulfuron dicamba and atrazine caused no significant decrease in flower number and/or flower fresh weight of saffron and therefore can be recommended to use for weed control in saffron fields.