Seed-Applied Insecticides in Cotton After the Neonicotinoid Debate: Indian Practice and Plant Stand Economics

Executive Summary

Europe restricted neonicotinoid seed dressings because of bees. India did not, and here the seed-applied insecticide is still the first insecticide decision of the cotton season, taken before the crop is in the ground. The questions that matter to an Indian grower are narrower and harder: does the dressing hold the seedling window, what is it worth against the sprays it postpones, and how long can it keep working where the leafhopper has met the same chemistry for a decade.

The Indian record answers the first two consistently and the third uncomfortably. A seed-applied systemic protects the three-to-six week establishment period, when cotton is least able to compensate, and protected-versus-unprotected comparisons put the avoidable loss at about a third of the crop. At Indian label rates the residue behaviour was benign in the studies available. On resistance it was not: five seasons of monitoring at ICAR–Central Institute for Cotton Research, Nagpur, found critical neonicotinoid resistance in leafhopper populations from Yavatmal, Chandrapur and Amravati.

What follows is what Indian trials measured, what the avoidable-loss figures do and do not include, and how a seed dressing compares with an extra foliar round at today's cotton costs.

Why the Cotton Seedling Window Decides the Season

When D. Blaise, M. V. Venugopalan and A. R. Raju of ICAR–Central Institute for Cotton Research, Nagpur, reviewed how Bt cotton hybrids changed Indian agronomy, one of the practice shifts they recorded was unglamorous and total: seed treatment with imidacloprid became, in their word, compulsory. The Bt trait answered the bollworms. It did not answer the jassid.

The pest complex attacking the seedling — leafhopper or jassid (Amrasca biguttula biguttula), thrips (Thrips tabaci), whitefly (Bemisia tabaci) and the cotton aphid (Aphis gossypii) — does its damage in the first three to six weeks, when leaf area is small and every square centimetre is being accumulated for the boll load to come. A foliar spray must be timed and paid for into that window; a seed dressing is already inside the plant when the first nymph arrives.

The seed strengthens the argument. Cotton seed is delinted, stored and handled hard, and Preethi Mylsamy and colleagues at Tamil Nadu Agricultural University, reviewing cotton seed management in the Journal of Cotton Research in 2025, note that slow and uneven emergence is a persistent quality problem. The Indian crop is grown largely from hybrid seed bought per packet, so weak emergence is a visible cash loss.

What the Neonicotinoid Debate Did, and Did Not, Change in India

The European debate is well documented. The European Food Safety Authority concluded in 2013 that clothianidin, imidacloprid and thiamethoxam posed a risk to bees, and returned to the same three in 2018 with conclusions specific to their use as seed treatments and granules — the route by which most neonicotinoid reached European field environments. In 2018 the European Union extended its outdoor ban on the three (Science, 2018).

India took another route. The same actives remain registered here as cotton seed dressers, and Yaduka Agrotech's CIB&RC Section 9(4) certificates for Thiamethoxam 30% FS and Imidacloprid 48% FS both name cotton among their crops. A registration states what a company may sell, never how well the product works; that evidence comes from trials, set out below.

Where Indian attention landed is on resistance and residue. On residue, Krishna Rolania and colleagues at CCS Haryana Agricultural University, Hisar, coated H 1098i cotton seed with imidacloprid 600 FS at 2.4 g a.i. per kg and found residues in guttation fluid, pollen and soil below detectable levels (Journal of Agriculture and Ecology, 2023). Sahoo and Singh at Punjab Agricultural University, Ludhiana, followed the same active in soil at 3.5 and 14 g a.i. per kg: peaks of 1.59 and 3.39 mg per kg at seven days, half-lives of 23.89 and 26.65 days, and nothing detectable after 60 days.

What the Indian Seed-Treatment Trials Actually Measured

The Indian seed-dressing literature is older than the debate and tests older formulations — imidacloprid as 600 FS, 70 WS or 75 WS, thiamethoxam as 600 FS or 35 FS, all delivered at visibly higher volume or mass per kilogram than today's low-volume flowables. Read the tested rates as they were tested.

At Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola, Maharashtra, P. H. Kharode, P. B. Jadhao and M. S. Bharati compared imidacloprid 600 FS at 13.5 and 18 ml per kg with thiamethoxam 600 FS at 7.5 ml per kg in 2012–13, and reported in the Indian Journal of Entomology in 2016 that those treatments afforded protection against jassid in early cotton growth.

Sanganna M. Sajjanar's two-year study, published in 2018, measured the whole establishment package. Seed treated with imidacloprid 75% WS at 3.5 g a.i. per kg recorded the highest germination, the lowest sucking-pest population, the most bolls and the highest seed cotton yield; carbosulfan 25% DS at 30 g a.i. per kg followed — a different chemical class, and the kind of alternative a resistance-management plan needs.

At Tamil Nadu Agricultural University, N. Murugesan and A. Kavitha evaluated seed treatment at 10 ml or g per kg against the leafhopper Amrasca devastans. Their 2009 paper in the Journal of Biopesticides found imidacloprid most effective at 0.8 leafhoppers per three leaves, monocrotophos at 1.23 and Pseudomonas fluorescens at 1.42; on farm, imidacloprid cut leafhopper numbers by 72.54 per cent and monocrotophos by 59.59 per cent.

Table: Seed-Applied Insecticide Treatments and Measured Outcomes in Indian Cotton

Plant Stand and Early Vigour: The Effect Growers See First

Growers judge a dressing by emergence at eight days and uniformity at three weeks, and that is where the Indian data are strongest. Vijayakumar Savanur, S. B. Patil and Ganesha Halikatti, at the Agricultural Research Station of the University of Agricultural Sciences, Dharwad, in 2013–14 recorded a seedling vigour index of 1089 with imidacloprid 70 WS seed treatment against 1053 with thiamethoxam 35 FS, with relative water content of 88.87 per cent. Modest in absolute terms, a vigour index at the seedling stage carries forward into the plant's capacity to build and retain fruiting forms.

How long protection lasts is the second practical question, and here the best-documented South Asian figure is not Indian. Rabia Saeed, Muhammad Razaq and Ian C. W. Hardy, in a 2016 field study in Pest Management Science, treated transgenic cotton seed with either imidacloprid at the recommended 5 g per kg or thiamethoxam and followed Amrasca devastans against the economic threshold: imidacloprid held the pest back about 20 days, thiamethoxam about 10 to 15.

The same paper carries the caveat any honest account must repeat. Beneficial arthropods declined, more steeply above the recommended rate, though imidacloprid's effect on predators was not apparent unless the recommended dose was exceeded. A 2021 review in Frontiers in Plant Science from the University of Agricultural Sciences, Bengaluru, adds that seed-applied systemic chemistry can also affect non-target endophytes.

The Size of What Is Being Protected: Avoidable Loss Figures

Two Indian studies give the scale. At the College Farm of Junagadh Agricultural University, Gujarat, D. K. Makvana, K. A. Chudasama and T. K. Balas grew the Bt hybrid KDCHH-441 in kharif 2011–12 and compared protected plots with unprotected ones: 2038.82 kg per hectare against 1312.70, a 55.31 per cent increase and an avoidable loss of 35.61 per cent. A two-season high-density planting study across kharif 2015–16 and 2016–17, reported in AGRICULTURE UPDATE, found 18.67 quintals per hectare under protection against 12.47 — an avoidable loss of 33.02 per cent.

Both figures describe what effective pest management — seed treatment plus foliar sprays — recovers in total, not what the seed dressing recovers on its own. They are the ceiling, not the dressing's own contribution, and both are old enough that the pest complex and the chemistry have moved since. Read them as a reminder of how much of a cotton crop is decided before the first spray is even contemplated.

Resistance: The Debate That Actually Matters in Maharashtra and Karnataka

This is where the Indian evidence diverges from the European argument: the concern here is not that the seed dressing is too effective, but that the target pest has stopped being killed by it.

Central India: five seasons of monitoring at CICR Nagpur

V. Chinna Babu Naik and colleagues at ICAR–Central Institute for Cotton Research, Nagpur, with Acharya N. G. Ranga Agricultural University, monitored resistance in the cotton leafhopper across the main cotton districts of Maharashtra for five consecutive seasons, 2015–16 to 2019–20, using IRAC bioassay protocols. Their 2026 paper in Scientific Reports reports critical resistance to neonicotinoids and to other classes in populations from Yavatmal, Chandrapur and Amravati; Amravati recorded the highest LC50 values for all eight insecticides tested, among them thiamethoxam 25 WG, imidacloprid 17.8 SL and clothianidin 50 WDG.

Karnataka: resistance tracking pesticide-use intensity

B. Halappa and R. K. Patil of the University of Agricultural Sciences, Dharwad, found imidacloprid resistance ratios rising with pesticide-use intensity — 3.35-fold in a low-use area, then 8.57, 9.15 and 12.27-fold (2016, Journal of Plant Protection Research). D. Sagar and R. A. Balikai, in Research on Crops in 2015, found LC50 values against imidacloprid and thiamethoxam highest in Haveri among six Karnataka districts, with clothianidin relatively lower throughout.

What it means for the seed bag

A seed dressing is applied once, to every seed, in every field, whether or not the pest is present — close to an ideal selection regime for resistance, especially where the same active is bought every season. Where the leafhopper is already resistant, a thiamethoxam or imidacloprid dressing will not replace the first foliar spray; it pays for a molecule that no longer works. Rotate the seed-treatment active — carbosulfan, or a biological such as Pseudomonas fluorescens — and do not treat the seed bag as a substitute for scouting.

Economics: The Cheapest Insecticide Is the One You Never Spray

The economics are easy to state and hard to measure, because the benefit is a spray never applied. The clearest Indian numbers come from groundnut rather than cotton, but the shape of the result carries. At Junagadh Agricultural University, D. V. Khanpara and colleagues tested seed dressings against jassids and thrips in summer groundnut over 2009–11. Imidacloprid 600 FS at 4 ml per kg gave the highest pod yield, 1962 kg per hectare, but the best incremental cost-benefit ratio, 1:8.76, went to the lower rate of 2 ml per kg — better than the same product at double the rate (1:5.47) and better than thiamethoxam 70 WS at 1 g (1:4.13) or 2 g (1:2.60) per kg (Journal of Oilseeds Research, 2017).

For cotton itself the recent economics come from IPM programmes, because that is how the dressing is actually deployed. In Guntur district, Andhra Pradesh, A. D. G. Grace and colleagues compared insecticide-resistance-management (IRM) plots with farmers' practice and reported in the Journal of Entomological Research in 2024 that seed cotton yield was 26.42 quintals per hectare under IRM against 24.01, with cost of cultivation of Rs 73,640 against Rs 83,802 per hectare. IRM plots needed eight sprays on average against 12.75, and the additional profit came to Rs 22,118 per hectare.

In Kurnool district, in a two-year validation sponsored by ICAR–CICR, Nagpur, M. Sivarama Krishna and colleagues recorded pink bollworm green-boll damage of 9.5 per cent under IRM against 21.8 per cent in 2021–22, and 8.2 against 20.2 per cent in 2022–23; sprays averaged 3.85 against 6.85 and the benefit-cost ratio 1.16:1 against 0.33:1 (Ecology, Environment and Conservation, 2024). Foliar chemistry is not cheap either: a three-season evaluation at Navsari Agricultural University, Gujarat, gave imidacloprid 17.8 SL an insecticidal cost-benefit ratio of 1:12.34, essentially matching flonicamid 50 WG at 1:12.44 (Plant Archives, 2025). A dressing that removes one spray is worth more than it costs.

Where Our Own Registrations Sit

Yaduka Agrotech Limited holds CIB&RC Section 9(4) registrations relevant to this discussion, and it is worth being precise. Thiamethoxam 30% FS is registered with cotton named on the certificate, for jassid, aphid and whitefly, at a label rate of 10 ml per kg of seed for cotton. Imidacloprid 48% FS is registered for cotton and a wider list of crops against aphid, whitefly, jassid and thrips; our label prints no per-kilogram seed rate for it, so none is quoted. Our Imidacloprid 18.5% + Hexaconazole 1.5% FS combination is registered for groundnut and wheat, not cotton — a reminder that a seed-dressing rate is tied to a named crop and cannot be carried across.

Seed Primer, the multilayer biopolymer coating carrying Trichoderma harzianum Th4d that ICAR–IIOR validated, sits on the biological side of the same decision, comparable to the Pseudomonas fluorescens and Trichoderma seed treatments in the Indian literature. The two are not rivals so much as two answers to the same question about the seedling window. A CIB&RC licence tells a grower what we may sell, and on which crops; it says nothing about how well the product performs.

Application Guidance for Seed Companies and Growers

For a grower buying treated seed, or treating it on the farm, the operational rules that follow from the evidence above are short.

• Treat as close to sowing as logistics allow. A dressing degrades, and a biological coating is alive; seed treated weeks in advance and stored warm is a different product from seed treated the week before sowing.
• Stay inside the labelled rate and the named crop. The trials that gave the highest yield were not always the ones that gave the highest return, and no rate transfers between crops.
• Keep the chemical and the biological apart. A neonicotinoid dressing and a biopolymer Trichoderma coating belong in sequence or as alternatives, never blended in one drum.
• Rotate the mode of action between seasons. Where CICR has documented critical neonicotinoid resistance in leafhopper, the same seed-dressing active buys protection that is no longer delivered.
• Plan the follow-up spray. A seed dressing delays the pest; it does not cancel the scouting calendar or the first foliar round in a high-pressure year.

For a seed company doing pre-packaging treatment, the extra considerations are liability and continuity: label the treatment, record active and rate batch by batch, and accept that treated seed returned from the market cannot go back into the food and feed chain. Compatibility matters too — thiram, carboxin plus thiram, tebuconazole and metalaxyl dressings are routinely applied alongside an insecticide in the same treater, and the treater's slurry volume and drying practice, not the label alone, decide whether the seed reaches the field in fit condition.

Conclusion

The neonicotinoid debate changed European agriculture and left Indian cotton largely untouched, at least in the seed bag; two of the relevant actives sit in our own CIB&RC portfolio. What the debate should have sharpened in India are the questions asked of a dressing.

On those questions the evidence is reasonably clear. A seed-applied systemic insecticide protects a short, decisive window; it improves emergence and early vigour as well as reducing pest numbers; and where the crop went unprotected, the avoidable loss ran at about a third of the crop. The residue behaviour at Indian label rates was benign in the studies available, with nothing detectable in guttation fluid, pollen or soil in Haryana and no soil residues after 60 days in Punjab. Against that, the resistance record from CICR Nagpur and from Karnataka is serious and recent, and it is the real Indian version of this debate.

The practical conclusion is not to stop dressing cotton seed but to dress it deliberately: at a labelled rate for the named crop, rotating the active between seasons, keeping chemical and biological apart, and never treating the seed bag as a substitute for the scouting calendar.

References and Sources

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