Numerous PVS have evolved since the 1990s to address food safety, food quality, environmental and social impacts and to aim for more sustainable agri-food value chains (Djama 2011, Gereffi et al. 2005, Henson and Humphrey 2010). There are diverse opinions about their impact (Dietz and Grabs 2022, Mengistie et al. 2017, Raynolds 2012, Schreinemachers et al. 2012, van der Grijp 2006). This section gives a short overview of the status of paraquat in selected PVS before outlining successes and challenges in paraquat phase-out in six crops in different PVS.
No comprehensive database exists comparing how paraquat is addressed by the plethora of different PVS or individual retailers. However, the ISEAL Integrated Pest Management (IPM) Coalition’s on-line database (https://www.ipm-coalition.org/) allows users to search and compare requirements on paraquat and hundreds of other HHPs among eleven ISEAL members. Table 3 provides a summary of current status of paraquat among six ISEAL member standards, which cover cotton, sugarcane, forestry, coffee and other tropical export crops, plus two certification schemes on soya and palm oil. Three standards, Rainforest Alliance, Fairtrade and Forest Stewardship Council (FSC) have long prohibited paraquat among their producers, while Better Cotton Initiative (BCI) has a phase-out deadline of 2024, although several BCI producer countries have already achieved phase out (Jean, G., pers. comm.). One standard (Bonsucro) has no indicated paraquat restrictions, while the extent of paraquat use restrictions are unclear for Roundtable on Sustainable Palm Oil (RSPO) and Roundtable on Responsible Soy (RTRS).
Table 3
How paraquat is currently handled by selected private voluntary standards. See Supplementary file for the list of information sources).
PVS | Status of paraquat use | |
Better Cotton Initiative (BCI) | Planned phase out by 2024a | |
Bonsucro (sugar) | Unrestricted | |
Fairtrade International (various crops) | Full prohibition since at least 2005 | |
Forest Stewardship Council (FSC) | Prohibition since at least 2005 | |
Global Coffee Platform (GCP) | Red Listed, with expected max. phase out period of 3 years from each producer’s date of joining | |
Rainforest Alliance (various crops) | Full prohibition since 1993, starting with banana | |
Roundtable on Sustainable Palm Oil (RSPO) | Status unclearb | |
Roundtable on Responsible Soy (RTRS) | Status unclearc | |
a Not currently restricted under BCI but would become prohibited if specific paraquat Severely Hazardous Pesticides Formulations become Rotterdam-listed, as recommended by Rotterdam Convention Chemical Review Committee. b RSPO standard says that ‘Pesticides that are categorised as World Health Organisation Class 1A or 1B, or that are listed by the Stockholm or Rotterdam Conventions, and paraquat, are not used, unless in exceptional circumstances, as validated by a due diligence process, or when authorised by government authorities for pest outbreaks’. c RTRS standard says that ‘There is no use of agrochemicals listed in the Stockholm and Rotterdam Conventions’ and that ‘Paraquat and Carbofuran are banned according to the Stockholm and Rotterdam Conventions’. However, this is incorrect as paraquat is not yet listed on the Rotterdam PIC List. |
5.1. Replacing paraquat use in soybean production
Herbicide use, notably paraquat and glyphosate, has been an issue of human health concern in small and large-scale soybean cultivation, especially in South America (Gross 2018, Phélinas and Choumert 2017). RTRS is one PVS aiming to improve sustainability in the conventional sector. As part of a stakeholder consultation in 2015–2016, RTRS sought feedback on whether to follow the lead of other PVS, such as Fairtrade and Rainforest Alliance, and introduce a prohibition or restrictions on paraquat use in soybean supply chains. In 2016, World Wide Fund for Nature (WWF) Germany also commissioned a report on alternatives to paraquat for use on soybean in Argentina, Brazil, India and Uruguay (Neumeister 2016). It identified 38 alternative non-HHP herbicide active ingredients (at least eight registered in each country), presenting lower human and environmental risks than paraquat. In India, there were no approved uses of paraquat in soybean, while research showed best weed control results in this crop were delivered by combining a low dose of diclosulam with one round of hand weeding (Nainwal et al. 2010).
In May 2016, on the basis of their technical assessment, WWF Germany and others, including two Swiss retailers, strongly urged RTRS to completely prohibit paraquat by 2017, advocating for an integrated approach with crop rotation, manual control, and less toxic herbicides effective at low dose. They noted that several RTRS certified producers were already producing soy without using paraquat and any continued use of paraquat would hamper the uptake of RTRS in Europe by creating reputational risks for European companies. So far, it is unclear to what extent paraquat has, or has not, been phased out in RTRS soy production although the start of Brazil’s national paraquat ban implementation in 2020 should trigger a rapid change to alternatives in soy production country-wide and strengthen arguments for RTRS to push for a definitive prohibition across all its soy producing members globally.
5.2. Replacing paraquat use in oil palm
Oil palm plantations have long been the target of civil society campaigns in Southeast Asia and beyond to prohibit use of paraquat, due to high reported levels of risky handling practices and of occupational poisonings (Kamsia et al. 2014, Myzabella et al. 2019, PANAP 2017, Tenaganita and PANAP 2002). In 2011, CABI was commissioned to assess herbicide use in oil palm production and identify potential alternatives (Rutherford et al. 2011). Researchers surveyed weed management practices by selected producers in Malaysia, Indonesia and Papua New Guinea to collate information on herbicide and non-herbicide methods used for ground cover management, as well as their cost-effectiveness as perceived by the producers.
Fifteen synthetic chemical herbicides were used by survey respondents. Glyphosate and metsulfuron were used by almost all, and 2,4-D, triclopyr and paraquat were each used by roughly half of the respondents. All responding producers regularly monitored ground cover vegetation on their plantations and all managed growth by planting a cover crop(s) and through application of herbicide. Most applied organic mulch, while many relied on hand pulling, slashing or the use of a hoe (see Table 4).
Table 4
Weed management methods used by oil palm producers surveyed in Indonesia, Malaysia and Papua New Guinea
(Source: Adapted from Table 1 in Rutherford et al. (2011)).
Ground cover management method | % producers using in mature oil palm crop (n = 25) |
Herbicide application | 96 |
Organic mulch | 88 |
Slashing | 56 |
Uprooting plants with a hoe | 56 |
Cover crop planted | 40 |
Mechanical (mower, tractor) | 36 |
Uprooting plants by hand | 32 |
Biological control | 32 |
Grazing by livestock | 28 |
Plastic sheeting mulch | 4 |
Increased palm planting density | 4 |
The use of herbicides, cover crops and mulch by producers was reflected by their perceived cost-effectiveness in comparison with other methods. In contrast, manual approaches to weeding were considered to be much less cost-effective. Several other IWM methods, however, including mechanical weeding, increasing palm density, covering the ground with sheeting and grazing by livestock, were considered to be more cost-effective, yet used by few producers. The authors of the report commented that these non-herbicide methods might have potential for broader uptake by producers, especially if underlying reasons for the observed poor rate of adoption could be understood and addressed.
Case studies from four producers in the same focus countries showed that elimination of paraquat use was achieved partly by replacing it with less hazardous products and/or partly by adoption of non-herbicide approaches – specifically, manual and mechanical weed management, application of various mulches and cultivation of cover crops. The authors highlighted that, in many instances, IWM methods were considered to not only be safer, but more efficient and more cost-effective than using herbicides.
The CABI assessment concluded that a range of herbicide and non-herbicide measures were available for effective weed management in oil palm and that reductions in herbicide use were readily achievable through a variety of non-herbicide methods and also more rational use of herbicide products and/or paraquat substitution with less toxic substances. They emphasised how, to be successful, measures must be adopted within an integrated approach to weed control, as opposed to being used in isolation.
Data from one recent Indonesian study on effectiveness of certified standards in improving environmental performance among smallholder oil palm growers suggested that RSPO certified smallholders were much less likely to use paraquat: 0–11% reported use in two types of RSPO smallholder groups, compared with 34–95% of smallholder groups certified by the national oil palm standard and with 30% of uncertified growers (Chalil and Barus 2020).
More recent research from one Indonesian plantation confirms the economic and ecological viability of less intensive management practices and replacing herbicide use with mechanical weeding (Darras et al. 2019). Plants, above-ground arthropods, and below-ground fauna were positively affected by mechanical versus chemical weed control, while no detectable negative effects of reduced fertilizer use or mechanical weeding were found on oil palm yields, soil nutrients and functions (mineral nitrogen, bulk density, and litter decomposition). Water infiltration and base saturation also tended to be higher under mechanical weeding.
5.3. Replacing paraquat use in coffee
Fairtrade and Rainforest Alliance certified coffee farmers have been prohibited from using paraquat for at least 15 years (Table 3). This prohibition currently applies to around 1.23 million small and medium-scale coffee farmers - almost 10% of the estimated 12.5 million coffee farms in this category (WCR 2021) - and numerous large estates in Latin America, Africa and Asia (Fairtrade 2020, Rainforest Alliance 2021). These producers are successfully growing and selling high quality coffee; several initiatives are supporting them to reduce reliance on herbicides or even eliminate them. Most focus on implementing IWM approaches, often making use of ground cover vegetation, either leaving naturally occurring non-competitive plants to thrive or sowing leguminous cover crops, with considerable co-benefits for soil conservation, moisture retention and biodiversity, particularly for, as well as avoiding economically damaging weed problems (CATIE and Rainforest Alliance 2021, PAN UK 2016b, Ramírez 2021). Many coffee farmers have learnt to combine ground cover with some level of mechanical/manual weed control, mulching with prunings from shade trees and weed cuttings, and grazing by small livestock. This has provided soil health benefits and reduced fertiliser application rates (Bellamy 2011, Gamboa and Umana 2018, Staver et al. 2020b).
From the mid-1970’s, glyphosate and several other systemic herbicides, e.g. glufosinate ammonium, became available and partially replaced paraquat use. However, these alternatives are not without their problems. Several authors have documented phytoxicity issues and highlighted the harmful effects of reliance on high dose, blanket applications of glyphosate on young coffee trees (Castanheira et al. 2019, Chaverria 2018, Nelson 2008). Phytotoxic damage from drift of glyphosate droplets in coffee seedlings is common and, in addition, there are reports of contamination by this herbicide to non-target plants via the rhizosphere (Barbosa et al. 2020). In addition, Costa Rica’s Regional Institute for Research on Toxic Substances (IRET) has documented increasing problems of glyphosate phytotoxicity and how this is triggering non-certified farmers to return to spraying paraquat (Ramírez 2021). Paraquat import volumes into Costa Rica remain high, at over 870,000kg active ingredient per annum, and the third most imported pesticide (by volume) after mancozeb and glyphosate (Elidier 2022). This is of concern to IRET and other members of the pesticides working group of the National Secretariat for Chemicals Management.
In efforts to replace both paraquat and glyphosate use in coffee within Costa Rica, there is growing interest in the introduction of botanical herbicides, which are used elsewhere in Latin America, e.g. Mexico. However, registrations for their use in Costa Rica are still at the initial stage. In general, there is increased awareness of the negative effects that herbicides can cause in coffee production systems, especially by small and medium scale farmers in hillside areas. This awareness has led to a reduction in herbicide use and increased acceptance of the concept that weeds are a necessary component of coffee agroecosystem.
5.4. Replacing paraquat use in tea
There are over 200,000 ha of tea in Sri Lanka, of which almost 60% is in smallholdings. These smallholdings are highly productive and produce 73% of Sri Lanka’s tea (compared to 20% from large plantations). Weed management has always been a major cost for Sri Lankan tea production, second only to harvesting, with an estimated 800% increase since the 1990s. The use of herbicides, including paraquat, has been the main method for managing weeds in almost all large tea plantations, although less than 10% of tea smallholdings currently use chemical herbicides (ASLM 2022). Reliance on herbicides in large plantations resulted in the rapid development of resistant weed populations, for example, of the 23 most damaging weeds in Sri Lankan tea, 20 had resistance to both paraquat and glyphosate (Peiris and Nissanka 2016).
Following a national paraquat ban in 2012 and restrictions on the use of glyphosate in Sri Lanka in 2014 (Marambe and Herath 2019), alternatives to herbicide use in tea were sought, with support from the Global Environment Facility to set up Herbicide-Free Integrated Weed Management (HFIWM) validation sites and to promote this technology among farmers. Herbicide-free techniques, already applied in India for tea with promising results, involve the manipulation of ground-cover plants through the selective removal of noxious weeds and the promotion of beneficial flora. The method involves training of tea workers to distinguish damaging (so-called ‘hard’) plants from beneficial or non-damaging (‘soft’ or ‘innocent’) ones; ‘hard’ weeds are removed before they seed and ‘soft’ weeds are allowed to seed, after which they are manually removed. Over time, the tea plantation or smallholding becomes dominated by ‘soft’ weeds. This technique has been monitored for cost-benefits and found to not only reduce fertilizer and labour costs but to also increase yields (possibly by reducing the phytotoxic effects of chemical herbicides on the tea plant). HFIWM advantages include gains from mulching and composting, as well as achieving several other sustainability indicators (Gunarathne and Peiris 2017, Peiris 2016). Facilitated through support from both the public and private sector, including the Rainforest Alliance, the uptake of herbicide-free weed management is growing in Sri Lanka, already with an estimated 15,000 farmers trained in the technology (ASLM 2022).
5.5. Replacing paraquat in potato haulm desiccation
Paraquat and diquat have been the predominant herbicides used in haulm desiccation prior to potato harvesting to aid the harvest process (Da Silva et al. 2021, Griffin et al. 2022). Paraquat has been reported to have a low impact on potato quality (Da Silva et al. 2021); however, the risk and possible impacts of residues remaining in harvested tubers are likely affected by environmental conditions, including weather (Krupek et al. 2021). Paraquat was preferred because it is fast acting, compared to other herbicides (Da Silva et al. 2021). Together, these factors raised the risks of an overuse of paraquat during haulm desiccation, with potential consequences for human and environmental health.
The ban of both paraquat and diquat in Europe has led to increased investments into the search for suitable alternatives. Among the most popular alternatives is mechanized flailing, sometimes followed by flaming or a lower toxicity herbicide (Kardasz et al. 2019). Mechanization of haulm removal has required changing planting times in parts of northern Europe to avoid the operation of heavy machinery during times when the soil is soft due to rain (Griffin et al. 2022, Krupek et al. 2021). Despite the ban of the predominant herbicides used for potato haulm desiccation, yields per hectare have consistently increased in countries like Ireland, where soil saturation can limit the operation of heavy machinery prior to late-season potato harvests (Griffin et al. 2022). The development of lighter, more effective machinery will likely capitalize on the paraquat and diquat bans to improve the sustainability of potato production in northern Europe. For example, the Irish Government has set alternatives to herbicide use in haulm desiccation as an objective in their Targeted Agricultural Modernization Scheme (DAFM 2022).
5.6. Replacing paraquat for pineapple foliage destruction
One specific and relatively recent use of paraquat involves the need to achieve rapid rotting of pineapple foliage post-harvest in Costa Rica. Pineapple cultivation produces about 250 tons of crop waste per hectare (Lopez-Herrera et al. 2014), which needs to be treated quickly or removed from the field to prevent the spread of the stable fly Stomoxys calcitrans, a livestock pest. Rotting pineapple foliage is highly attractive to stable fly for egg-laying and if poorly managed can become a breeding ground for this economically harmful pest (PAN UK 2016a). Until 2005, it was common practice for most pineapple producers in Costa Rica to avoid this problem by desiccating foliage with very high volumes of paraquat, followed by burning. This practice, however, led to serious environmental contamination and problems of soil erosion. Numerous pineapple supply chains have been working to manage pineapple foliage waste and stable fly populations without resorting to paraquat (PAN UK 2017, UNDP 2012).
Rainforest Alliance has prohibited paraquat since 1993, with the creation of the sustainable agriculture standard, applicable first for bananas only, but opened to other crops a few years later. Stable fly is a particular challenge to the 45 Costa Rican pineapple producers growing to the Rainforest standard. In response, the standard identified a series of good agricultural practices, such as stubble management, for preventing, monitoring and sustainably controlling different pests. By 2020, 95% of Rainforest-certified pineapple producers had received relevant training and none were using paraquat (M-A Bonilla, Rainforest Alliance, pers. comm). Most producers now reincorporate pineapple organic matter into the soil (a valuable nutrient and soil structure improver) and some apply decomposer microbes to the post-harvest foliage. This greatly reduces the time that the crop waste can serve as an attractive breeding site for stable fly.
While there are sometimes constraints with availability and quality of the microbial products, uptake of this agroecological solution to pineapple waste has been rapid and widespread among most Rainforest Alliance producers. Rainforest Alliance report there is no yield penalty and the practice delivers considerable benefits for soil health in the medium term from returning 250t/ha organic matter to fields. This improves soil nutrients, structure and acidity to levels optimum for pineapple growth and produces healthier plants which are better able to resist pests and/or disease attack.
Since 2018, pineapple company Nicoverde has promoted practices to reduce reliance on pesticides and boost on-farm biodiversity, training producers and running demonstration plots. They have documented four seasons of success in dealing with post-harvest crop waste without paraquat, on their own110 ha pineapple farm and from 100 small and medium-scale pineapple growers with a mean farm size of 4.4 ha. Their field-validated protocol consists of mechanical chopping/harrowing, followed by four applications of a tailor-made selection of decomposer microbes, produced in Nicoverde’s own biolab and sold at 50% discount to Nicoverde growers. About 3–4 weeks after treatment, the decomposing material is then incorporated into the soil. This practice is effective in preventing build-up of stable fly populations and contributes to regenerating soil health and protecting groundwater from pollution. Growers expressed satisfaction with the crop waste management protocol because it avoids the health risks from paraquat spraying, while improving soil quality.
Careful planning and timing of foliage treatment or destruction and subsequent replanting is an important consideration in achieving good control of stable fly without resorting to paraquat, especially in zones with heavy rain periods when tractor-mounted machinery cannot be used.