Authors: Raghuveer Singh and Ravindra Singh Shekhawat
system (RWCS) is one of the major cropping system and it cover more than 15 million hectare area in South East Asian countries including India, Pakistan, Bangladesh and Nepal. Decline factor productivity, depletion of ground water, mining of soil fertility, burning of crop residue in field, emergence of new pest & disease and development of herbicides resistances (HRs) in weeds (mainly P minor) are the major sustainability issue who threaten the future scope of RWCS. Herbicides resistances speed up by monocropping and use of chemical herbicides indiscriminately.
We can’t combat herbicides resistance weeds simply by using the alternative herbicides or the herbicides with more powerful toxicant in it. First time herbicide resistance reported in country by Malik and Singh in Phalaris minor against Isoproturon in Haryana in 1991 under rice wheat cropping system (RWCS). Ecology of rice wheat cropping system support the growth of Phalaris minor and continuous use of broad leaf herbicides (2-4 D) after independence put pressure and the weed flora shifting (mix weed population to field dominated by grassy weed) occur under RWCS. To control the grassy weeds farmers use continuously single herbicides (isoproturon) over the period of one and half decade along with uninterrupted rice wheat cycle cause development of resistance in P minor. During 1992-93 around 0.8 to 1.0 million hectare area affected by the resistance biotype of P minor in north Indian state and it required 8 to 11 times higher herbicides dose to get 50% growth reductions (GRs) as compare to susceptible biotype.
Keeping above fact in mind in 1997-98 four alternate herbicides (clodinafop, sulfosulfuron, fenoxaprop and traloxydim) were recommended for resistant affected area and isoproturon recommendation withdrawan. These alternate herbicides found very effective against P minor in initial stage and wheat restore its previous production level but after one decade of effective control of P minor again reports comes about the development of cross and multiple resistance against these herbicides from 2002 onwards in RWCS (Table 1). At present in country resistance level against new herbicides in general follow a pattern (clodinafop> fenoxaprop> sulfosulfuron> pinoxaden), it depends upon area to area. Now our researchers further focusing to develop the new herbicides like as pyroxasulfone (testing going on field level to check the efficacy) to combat HRs in P minor and on other side our farmers using higher dose of herbicides or applying more than one application same or different herbicide to control the weeds. But it increasing cost of cultivation and also polluting our ecosystem.
Table 1. Herbicides resistant weeds in India
| Sr No | Species | Reported first time | Site of action |
| 1 | Phalaris minor | 1991 | PSII inhibitors (Ueeas and amides) (C2/7) |
| 2 | Phalaris minor | 1994 | ACCase inhibitors (A/1) |
| 3 | Phalaris minor | 2006 | Multiple resistance ACCase inhibitors (A/1) ALS inhibitors (B/2) PSII inhibitors (Ueeas and amides) (C2/7) |
| 4 | Phalaris minor | 2013 | ALS inhibitors (B/2) |
| 5 | Rumex dentatus | 2014 | ALS inhibitors (B/2) |
One thing clear that simply use of more powerful herbicides can’t combat HRs issue we need to learn mechanism of HRs development and how tackle HRs at farmer’s field level by breaking the weed cycle first we learn about the factors which speed up the process HRs development
Factors inducing the HRs development in weeds as per (Das 2011)
- Weed PER SE
- Initial frequency of the resistant individual of weed species
- Hypersensitivity of the susceptible population of weeds towards herbicides
- Selection pressure for build-up of the resistant population
- Biological fitness
- Weed biology (seed dormancy, seed multiplication rate, mode of
- pollination) and soil seed bank
- Mode of inheritance of resistance gene
- Role of herbicides
- High efficacy or potency of herbicides
- Single target herbicides or very peculiar in mode of action
- Continuous use of single herbicides without rotation
- Method, time and dose of herbicides application
- Cropping pattern
- Monoculture
- Method of crop establishment (Zero tillage) It is clear that use of chemical herbicides injudiciously ultimately end with development of HRs we can’t suggest our farmers to stop use of chemical herbicides because it cause considerable loss in term of economic yield. Here same point given about How can farmers delay or escape the HRs development
- Diversification in the present RWCS.
- Break the crop cycle by growing fodder, pluses and oilseeds crops so weed life cycle hampered.
- Divide whole field in four parts and grow fodder crops on rotational bases.
- Follow the herbicides rotation in place of depends on single herbicide.
- Use pre and post herbicides combination and tank mix or ready mix than depends on single herbicides to get better result in the area where already HRs developed and weed not controlled effectively.
- Always use the recommended dose of herbicides (under and over dose of herbicides speed up the HRs development).
- Use certified seeds and change the variety in every 3 to four year old crop seed get affected by mixing of weed seeds.
- Adopt the Integrated farming system (IFS) approach instated of cropping system. IFS more ecological sound and resistance approach for biotic and abiotic stress.
- Use integrated weed management instead of depends only on chemical weed control.
- Don’t use the seeds of affected area in the new areas otherwise new area also get infected by HRs weed seed.
Herbicides resistance is a necessary evil of chemical use but by suitable agronomic management we can delay it occurrence at farmers field level or maintain it below threshold level
References:
1. Yadav, A. and Malik, R.K. (2005). Herbicide Resistant Phalaris minor in Wheat-A Sustainability Issue. Resource Book. Department of Agronomy and Directorate of Extension Education, CCSHAU, Hisar, India, p. 152.
2. Yadav D.B., Yadav, A., Punia, S.S. and Chauhan, B.S. (2016). Management of herbicide-resistant Phalaris minor in wheat by sequential or tank-mix applications of pre- and post-emergence herbicides in north-western Indo-Gangetic Plains. Crop Protection 89, 239-247.
3. ISHRW (2017) The International Survey of Herbicide Resistant Weeds. Online. Internet. Saturday, accessed on October 21, 2017, http://www.weedscience.org/summary/Country.aspx?CountryID=21.
4. Das TK (2011) Weed science basic and application first edition Jain brothers, New Delhi pp 910.
About Author / Additional Info:
I am working as a scientist at ICAR-IIFSR, Modipuram, Meerut, Uttar Pradesh, India.