Status of herbicide resistance in Phalaris minor Retz. in wheat (Triticum aestivum L.) and its management options
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Date
2019
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CCSHAU
Abstract
Herbicide resistance in Phalaris minor in wheat is the major sustainability issue, which puts the rice-wheat cropping system (RWCS) in IGP under serious threat. Therefore, the investigation entitled “Status of herbicide resistance in Phalaris minor Retz. in wheat (Triticum aestivum L.) and its management options” comprised a well structured survey and a two year experiment was undertaken. The survey was carried out during rabi season of 2017-18 (end of January to February) in five districts (Yamuna Nagar, Kaithal, Karnal, Fatehabad and Rohtak) of Haryana. Two blocks were selected from each district and three villages from each block and a total number of 300 farmers were covered from 30 villages involving 10 farmers from each village. The field experiment (18 treatments of herbicides alone and in combination with pre and post application) was carried out during rabi seasons of 2016-17 and 2017-18 at CCSHAU, Regional Research Station, Uchani, Karnal
The study revealed that at present farmers of Haryana are closely back to square one similar to the situation of herbicides resistance in P. minor in wheat in 1990’s and currently no herbicide is satisfactorily effective against resistant P. minor. Farmers are using every possible combination of herbicides in a hit and trial way and overall applying about three times recommended dose (X) of herbicides and still getting only 70-80% control. Farmers in Karnal applied more than four times and in Kaithal three and half times the recommended dose of different herbicides. Farmers accepted that clodinafop was not showing any results but still it is contributing about half of the total herbicide use. Sulfosulfuron and pinoxaden contributed one-fifth and mesosulfuron + iodosulfuron (ready-mix) contributed <5% to total herbicide use in wheat. Mesosulfuron + iodosulfuron provided good control, but farmers are sceptic due to its phyto-toxicity in wet conditions or overlapped/repeat spraying. Recently, farmers have started using pendimethalin (750-1000 g ha-1) as pre-emergence and metribuzin (50-140 g ha-1) as post-emergence tank-mix with already recommended herbicides to get desirable results. Few farmers reported that they applied metribuzin (175-350 g ha-1) at first irrigation by mixing with urea and found satisfactory control. Farmers also reported that zero-tillage reduced P. minor infestation to the extent of 15-20% than CT. More than 90% of farmers using 225-300 L water ha-1 instead of 500 L ha-1 and are using flood jet/cut or hollow cone nozzle instead of flat-fan nozzle. Most of farmers applied herbicides later than 40 DAS. All these factors further reduced herbicide efficacy. About half of farmers blamed that herbicides were poor in quality and rest believed that resistance has evolved due to mono-cropping, higher use of nitrogenous fertilizer (urea) and under/over-dose of herbicides. Overall, farmers are in terrible situation and spending lot of money and efforts to combat this dreaded weed in wheat in RWCS of Haryana.
Contrary to farmers’ fields, recommended herbicides are still providing good control of P. minor at Research Farm, however there efficacy is also getting down. Yield loss could be restored by using already recommended herbicides in combination with pre-emergence herbicide pendimethalin or metribuzin. Overall, metribuzin (PRE) followed by sulfosulfuron (POE) (175 fb 25 g ha-1) was found to be the best treatment in terms of weed control efficiency (WCE), grain yield, gross return, net return and B-C ratio. Mesosulfuron + iodosulfuron (ready-mix) alone and in combination with pre-emergence herbicides (pendimethalin or metribuzin) also performed well against weeds (P. minor as well as broadleaf) but its consistency was poor. Pyroxasulfone was best herbicide against P. minor with complete control, but was not found that effective against broadleaf weeds mainly Melilotus spp. and also caused crop phyto-toxicity at 128 g ha-1. Concerted efforts are required to educate the farmers on improved herbicide spraying techniques.
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