# Parsimonius use of pesticide-treated seeds: An Integrated Pest Management framework 2

Jay-Ram Lamichhane

<figure><img src="image_1.png" /></figure>

To cite this version:

Jay-Ram Lamichhane. Parsimonius use of pesticide-treated seeds: An Integrated Pest Management framework 2. Trends in Plant Science, In press, 11p. hal-02937485

HAL Id: hal-02937485

https://hal.inrae.fr/hal-02937485

Submitted on 14 Sep 2020

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
1

# Parsimonius use of pesticide-treated seeds: An Integrated Pest Management framework

2

3

Jay Ram Lamichhane¹*

4

5

¹INRAE, Université Fédérale de Toulouse, UMR AGIR, F-31326 Castanet-Tolosan Cedex, France

6

*For correspondence: [jay-ram.lamichhane@inrae.fr](mailto:jay-ram.lamichhane@inrae.fr) (J.R. Lamichhane)

7

8

## Abstract:

9

10

11

12

13

Pesticide-treated seeds are usually supplied in “default” packages that leave farmers little choice for a tailor-made management of soil-borne pests and pathogens. This has led to a socio-economic impasse thereby questioning the sustainability of planting pesticide-treated seeds. Here the author proposes an Integrated Pest Management framework to overcome the current impasse.

14

15

Keywords: Seed germination; seedling emergence; crop establishment; seed treatment; soil biodiversity; sustainable agriculture

16

## The rationale behind the pesticide seed treatment

17

18

19

20

21

22

Pesticide seed treatment (PST) is an old practice that consists of treating seeds with several synthetic pesticides including insecticides, fungicides, nematicides, rodenticides or bird repellents, alone or in combination [1]. The ultimate goal of planting pesticide-treated seeds (PTSs) is to reduce damage due to biotic stresses (mainly soil-borne pests and pathogens) that may affect germinating seeds, as well as emerging and emerged seedlings and can lead to crop establishment failure, stand and yield losses [2].

23

## Pesticide seed treatment and treatment frequency index

24

25

The frequency of chemical pesticides applied via seed treatment is lower (i.e. only once per cropping season) compared with that applied via foliar applications. In most EU
countries, pesticide use is generally measured as the treatment frequency index (TFI),
which is defined as the number of pesticide applications per hectare per calendar year,
assuming the use of a standard dose for each authorized use of pesticides [3]. In France,
as in most EU countries, PST was not considered in the calculation of TFI until a few years
ago, but now the TFI calculation takes PST into account. The data show that TFI related to
seed treatment represents an important portion of pesticides introduced into the
environment (Figure 1). Nevertheless, there is an acute lack of information on PST data
which are mainly inaccessible in several parts of the world, including Europe and North
America [2].

35 The current socio-economic impasse for farmers

A great majority of pesticide-seed treatment is performed by the seed suppliers, who market treated seeds in "default" packages. This means that farmers can not chose freely between untreated or treated seeds and do not have access to tailored pesticide use based on the specific field situations (e.g. fields with a history of post-planting problems). The marketing of pesticide-treated seeds in default packages constitutes an important problem for farmers as most often they are unaware of the specific active ingredients in these packages and the pests and pathogens that would be targeted [2]. This routine-based planting of PTSs for certain crops such as soybean has led farmers to a socio-economic impasse where farmers systematically bear seed treatment costs without important economic return [4,5]. This dilemma is further exacerbated by recent findings that the planting of PTSs does not, as thought previously, result in lower human-health and environmental impacts compared with foliar applications of pesticides, including potential non-target effects [6,7].

49 No, low or inconsistent effectiveness of pesticide treated seeds answered?
Even when targeted to the right pests and pathogens, the planting of PTSs may not be effective due to a high diversity of environmental conditions, cropping systems and the diversity of soil-borne pests and pathogens across the world. Sartori et al. [8] investigated the translocation pattern of three fungicides -- viz. pyraclostrobin, carbendazim, and metalaxyl -- with different modes of action and most often applied as a seed treatment, in interaction with soil type in soybean, the most important leguminous crop worldwide.

The authors showed that, following germination of PTSs, only a small fraction of the pesticides (i.e. 15%), compared with the quantity used for seed treatment, was translocated to plant parts that need protection (i.e. stem, roots and leaves) while a large proportion of these pesticides remained in cotyledons, independent of the fungicide type.

This study also confirmed two key findings of previous studies: i) the rate of soil organic matter of a given soil affects the mobility of certain fungicides in the soil [9], and ii) the soil texture in general and the clay content in particular of a given soil affects absorbtion rate of such fungicides [10].

Another study by You et al. [11], based on multi-year trials, analyzed the effectiveness of planting PTSs in controlling seed and seedling diseases of subterranean clover across contrasted soil and environmental conditions of Australia. The authors, tested nine combinations of pesticides (i.e. thiram, metalaxyl, iprodione, phosphonic acid, propamocarb, fluquinconazole, difenoconazole + metalaxyl, ipconazole + metalaxyl, sedaxane + difenoconazole + metalaxyl), against four prevalent soil-borne pathogens -- viz. *Pythium irregulare*, *Aphanomyces trifolii*, *Phytophthora clandestina* and *Rhizoctonia solani* -- causing seed and seedling diseases worldwide on a large number of crops. This study demonstrated that planting PTSs provided effective control of a seed or seedling disease only when a single soil-borne pathogen was associated with the disease, whereas this practice was ineffective when different soil-borne pathogens were associated with
75 the disease complex that resulted by synergistic interactions of different soil-borne pathogens. Indeed, increasing evidence in the literature shows that a given plant disease 76 77 is often caused by synergistic interactions among different soil-borne pests and pathogens that co-occur in a given plant or plant-parts under field conditions [12-14]. 78

79 The studies by Sartori et al. [8] and You et al [11] provide an important insight into lack of, low or inconsistent effectiveness of PTSs in controlling soil-borne pathogens that affect 80 seeds and seedlings both pre-germination, pre- and post-emergence across various soil 81 and environmental conditions. These studies, further emphasize the need for future 82 studies on other crops, such as cereals, for which seed treatment is even more common 83 compared with leguminous crops [2]. In particular, a better focus on how pesticides used 84 for seed treatments affect soil water regime, soil properties, plant biology, and the 85 diversity of pests and pathogens of a given soil can provide important insights into the 86 potential effectiveness of PTSs across environmental gradients. 87

88 **An integrated pest management framework for a parsimonious use of PTSs in**
89 **agriculture**

90 Integrated Pest Management (IPM) is a dynamic and flexible approach that takes into 91 account the diversity and the complexity of agro-ecosystems with the aim to improve the 92 sustainability of cropping systems [15]. IPM encourages the use of non-chemical and 93 sustainable cropping practices while also allowing a parsimonious use of synthetic 94 chemicals, when indispensable. 95

95 More specifically to the sustainability issues related to the use of PTSs, an IPM framework 96 (Figure 2) that combines all best management practices can significantly increase 97 economic profitability of this practice while reducing environmental risks and health 98 hazards. Such a framework is not dogmatic and can be tailored to specific contexts giving
the highest priority to non-chemical measures while allowing the use of PTSs as the last option. Because decisions about the type of seed to be planted are made much earlier in the growing season (i.e. months before planting), a strict implementation of IPM is needed while making these decisions. This IPM framework takes into account diverse types of crops grown across very different areas of the world; multiplicity of soil types, environmental conditions, and production practices; diversity in seed- and soil-borne pests and pathogens to improve crop emergence, stand development and yield performance. This is fundamental to achieve the ultimate goal of increasing economic profitability due to planting of PTSs while reducing their negative effects to human health and the environment. However, key for an effective implementation of IPM is to provide farmers with diverse choices of treated vs. differently treated seeds and the detailed information on the type of active ingredients used for seed treatments. This will allow farmers to make better use of PTSs and help solve the current dilemma of planting PTSs as a routine-based practice even when it is not needed.

## 113 Concluding remarks

The planting of PTSs remains an important practice for farmers to ensure economic profitability across areas characterized by a high pressure of soil-borne pests and pathogens. Nevertheless, there is a need to re-evaluate the routine-based planting of PTSs that is unsustainable from economic, environmental and social points of view. Therefore, farmers need market access to a range of treated vs. untreated seeds, suitable for different crops and diverse field situations. Resolving the dilemma of marketing PTSs in "default" packages is the first step to get farmers out of the current socio-economic impasse of planting PTSs as a routine-based practice, and toward a proper adoption of IPM. I invite all stakeholders to re-think the current seed supply marketing policy, to re-assess the
123 sustainability of planting PTSs as a routine-based practice, and propose an IPM

124 framework for a judicious use of PTSs.

125
126 Acknowledgements

127 I thank the anonymous reviewer for providing very constructive feedback on the previous
128 version of this paper. I apologize for the omission of any relevant articles that have not
129 been cited due to space limit. This study was partially supported by the FAST project
130 (Faisabilité et Evaluation de Systèmes de Cultures Economies en pesticides en l'Absence
131 répétée de Semences Traitées) funded by the French Agency for Biodiversity, by credits
132 from the royalty for diffuse pollution, attributed to the funding of the Ecophyto plan. I am
133 grateful to Véronique Laudinot, Chamber of agriculture of the Vosges for her earlier
134 feedback on this topic.

135
136 References

137 1 Lamichhane, J.R. et al. (2020) Revisiting sustainability of fungicide seed treatments for field crops. *Plant Dis.* 104, 610–623

139 2 Hitaj, C. et al. (2020) Sowing Uncertainty: What We Do and Don't Know about the Planting of Pesticide-Treated Seed. *Bioscience* DOI: 10.1093/biosci/biaa019

141 3 Lamichhane, J.R. et al. (2016) Toward a reduced reliance on conventional pesticides in European agriculture. *Plant Dis.* 100,

143 4 Mourtzinis, S. et al. (2019) Neonicotinoid seed treatments of soybean provide negligible benefits to US farmers. *Sci. Rep.* 9, 11207

145 5 Rossman, D.R. et al. (2018) Profitability and efficacy of soybean seed treatment in Michigan. *Crop Prot.* 114, 44–52

147 6 Nettles, R. et al. (2016) Influence of pesticide seed treatments on rhizosphere fungal and bacterial communities and leaf fungal endophyte communities in maize and soybean. *Appl. Soil Ecol.* 102, 61–69

150 7 Zaller, J.G. et al. (2016) Pesticide seed dressings can affect the activity of various soil organisms and reduce decomposition of plant material. *BMC Ecol.* 16, 37

152 8 Fadel Sartori, F. et al. (2020) Soybean seed treatment: how do fungicides translocate in plants? *Pest Manag. Sci.* DOI: 10.1002/ps.5771

154 9 Sharom, M.S. and Edgington, L. V (1982) The adsorption, mobility, and persistence of metalaxyl in soil and aqueous systems. *Can. J. Plant Pathol.* 4, 334–340

156 10 Liu, X. et al. (2018) Uptake and distribution characteristics of the novel fungicide pyraoxystrobin in cucumber plants. *RSC Adv.* 8, 27152–27156

158 11 You, M.P. et al. (2020) Understanding why Effective Fungicides against Individual Soilborne Pathogens are Ineffective with Soilborne Pathogen Complexes. *Plant Dis.* 104, 904–920

161 12 Harvey, P.R. et al. The Pythium-Fusarium root disease complex – an emerging constraint to irrigated maize in southern New South Wales. , *Australian Journal of Experimental Agriculture*, 48. (2008), 367–374

164 13 Madriz-Ordeñana, K. et al. (2019) Prevalence of Soil-borne Diseases in Kalanchoe blossfeldiana Reveals a Complex of Pathogenic and Opportunistic Fungi. *Plant Dis.* 103, 2634–2644

167 14 Lamichhane, J.R. and Venturi, V. (2015) Synergisms between microbial pathogens in plant disease complexes: A growing trend. *Front. Plant Sci.* 6,

169 15 Barzman, M. et al. (2015) Eight principles of integrated pest management. *Agron. Sustain. Dev.* 35,

171
<figure><img src="image_3.png" /><figcaption>**Figure 1.** Treatment frequency index (TFI) of major field crops in France, calculated as the number of pesticide applications per hectare per calendar year. The calculation is based on the results of a questionnaire survey in 2017 of 28 000 field crop farmers. The TFI due to seed treatment corresponds to 1 when all seeds are treated. A TFI <1 means that either the farmer planted treated seeds only in certain areas of his field or he mixed the treated seeds with the non treated ones. In these cases, the percentage of area planted or the quantity of treated seeds used over total provide the real value of TFI. Overall, TFI due to seed treatments represents a non-negligible part of chemical input for most of these crops and can reach several hundred thousand cubic meters of active ingredients per cropping season. ST: seed treatment, TFI Other: treatments performed with pesticides other than fungicides, insecticides and herbicides (e.g. rodenticides, bird repellents).</figcaption></figure>

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187
<figure><img src="image_4.png" /><figcaption>**Figure 2.** An Integrated Pest Management framework that combines all key crop management levers to improve seed germination, seedling emergence and thereby the quality of crop establishment. This framework prioritizes the non-chemical means of crop protection although the use of pesticide-treated seeds is allowed as the last option, based on a *priori* risk assessment of planting areas. The priority given to these measures decreases from left to right with the lever « inoculum management » and « chemical seed treatment » receiving the highest and lowest priority, respectively. More focus on crop diversification and, in general, on non-chemical measures, enhances soil microbial diversity that plays an important role in soil health. In this way, an increased level of beneficial soil microbial community helps to suppress soil-borne pests and pathogens and to reduce negative impact on seed and seedlings through biotic factors. Inoculation management refers both to the soil- and seed-borne inoculum and it is based on three key cropping practices: (a) crop diversification that includes crop rotation, inter- and cover-cropping; (b) tillage or no-tillage that comprise conventional, minimum or no-tillage, depending on specific situations; and (c) use of healthy seeds through using steps such as, testing seed sanitary quality before use, performing selective sorting of non-certified seeds, testing for good seed germination ability before planting, and applying biological seed treatments to manage seed-borne diseases when non-certified on-farm seeds have to be used. The horizontal arrow from left to right represents a set of IPM levers whereas the vertical arrows represent individual IPM levers. The order of the roman numerals indicate the increasing priority given to the individual IPM levers. The dotted arrows indicate that biological and chemical control should be applied for specific situations. The figure was partly created using BioRender (https://biorender.com/).</figcaption></figure>