What the research measured
Results in the cited studies divide by pest pressure. In 91 Mid-South trials over 14 years, neonicotinoid-treated seed yielded 700 kg/ha more than fungicide-only seed on average, significant in two of four states and with higher net return in 8 of 14 years. In Indiana, a meta-analysis of 15 years of trials run under deliberately high rootworm pressure found an 8.7% yield increase associated with the seed treatment, while three-location Indiana trials in 2012–14, 84 Quebec fields in 2012–16 and a 2022 Iowa on-farm trial reported no yield difference between treated and untreated or fungicide-only seed.
Four peer-reviewed analyses (an Indiana 2000–15 meta-analysis of 69 efficacy trials; Indiana field trials at three locations 2012–14; 91 Mid-South trials in four states over 14 years; 84 Quebec corn and soybean fields 2012–16) and one five-replicate Iowa on-farm strip trial (2022). All test the neonicotinoid component on conventional corn.5 independent sources.What it is. A factory-applied insecticide coating, clothianidin or thiamethoxam at 0.25 mg per kernel (the base seed-protection rate) or 1.25 mg (the corn rootworm rate), bundled with seedling fungicides on virtually all conventionally produced corn seed; by 2011 preemptive insecticide use covered 79–100% of US maize. It protects seedlings from wireworms, seedcorn maggots, white grubs and rootworm larvae for the first weeks after planting.
Study conditions and limitations
- Pest pressure decides the result: 92.6% of Quebec corn fields had under 1 wireworm per bait trap and the authors judged the treatment useful in under 5% of cases, while the Indiana meta-analysis trials mostly followed a late-planted corn trap crop to maximize rootworm egg-laying.
- Rate matters: 0.25 mg per kernel is the seed-protection rate and 1.25 mg the rootworm rate. The Indiana 2012–14 trials found no yield benefit from either rate over naked seed at any of eight location-years.
- The insecticide effect is hard to separate from the fungicide: the Indiana meta-analysis notes seed treatments were paired with fungicides in most site-years, calling that “an important confounding factor”, and the Quebec corn comparison measured stand at 5.80 vs 5.73 plants per metre.
- Regional: the Mid-South gain was significant only in Louisiana (1,093 kg/ha) and Mississippi (416 kg/ha); Arkansas (111) and Tennessee (140) were not, and the net-return advantage by state was significant only in Louisiana.
- The treatment cost is bundled into the seed price and not disclosed; published estimates in the Indiana meta-analysis ran from about $17/ha to $52.36/ha, and the Iowa on-farm insecticide package cost $3.68/ac more than fungicide-only seed.
- Off-target exposure: the Indiana study estimated that over 94% of the state’s honey bee foragers and over 42% of its land area encounter neonicotinoid planter dust during corn sowing.
Read the sources · 5
- A Meta-Analysis and Economic Evaluation of Neonicotinoid Seed Treatments and Other Prophylactic Insecticides in Indiana Maize From 2000–2015 With IPM Recommendations ↗
Fifteen years (2000–15) of Purdue insecticide efficacy trials in Indiana corn, 69 trials, only 8 of them following soybean and the rest following corn (21) or a late-planted corn trap crop (40) to build rootworm pressure: all rootworm-rate insecticides including the 1.25 mg clothianidin seed treatment raised yield over untreated checks (Hedge’s g 0.82 across 31 site-years), the seed-treatment-associated yield increase was 8.7%, and every compound had over an 80% probability of recovering its cost. Only the neonicotinoid seed treatments raised early stand. The authors suggest the treatments be optional and rotated.
- Planting of neonicotinoid-treated maize poses risks for honey bees and other non-target organisms over a wide area without consistent crop yield benefit ↗
Randomized four-replicate trials at three Indiana locations in 2012 and 2013 and two in 2014 comparing naked seed, 0.25 mg clothianidin plus fungicide and 1.25 mg clothianidin plus fungicide: no yield benefit from either treated seed in any location-year. The same study estimated over 94% of Indiana honey bee foragers are at risk of exposure to planter dust and over 42% of the state receives deposition during maize sowing.
- Impacts of neonicotinoid seed treatments on soil-dwelling pest populations and agronomic parameters in corn and soybean in Quebec (Canada) ↗
Paired treated and untreated strips in 84 corn and soybean fields across seven Quebec regions (2012–16): 92.6% of corn fields and 69.0% of soybean fields had under 1 wireworm per bait trap, corn stands were 5.80 vs 5.73 plants per metre, and no significant plant stand or yield difference was found in either crop. The authors conclude the treatments are useful in under 5% of cases and should not be used prophylactically.
- Value of Neonicotinoid Insecticide Seed Treatments in Mid-South Corn (Zea mays) Production Systems ↗
Ninety-one insecticide seed treatment trials from Arkansas, Louisiana, Mississippi and Tennessee over 14 years: neonicotinoid plus fungicide outyielded fungicide-only seed by 111, 1,093, 416 and 140 kg/ha by state (significant in Louisiana and Mississippi) and 700 kg/ha across all states. Net returns were $1,446/ha against $1,390/ha, significantly higher in 8 of 14 years and, by state, only in Louisiana.
- Are Fungicide and Insecticide Seed Treatments Necessary for Corn? ↗
Five replicated strips in Buchanan County, Iowa, planted May 9, 2022 after a cover crop: fungicide-only, fungicide plus thiamethoxam (Cruiser 5FS) and a humic-acid package without fungicide or insecticide all averaged 214 bu/ac, with no two treatments differing by more than the 14 bu/ac LSD. The insecticide package cost $3.68/ac more and the fungicide-only strips returned nearly $4/ac more.
Before you buy, ask
- What pest or disease pressure did the trials with a response actually have?
- What does the treatment cost per unit, and how many bushels would it need to add to pay?
- Can I buy the same variety untreated or with a different package?
Record
- Sources checked
- October 12, 2026. Every figure shown is printed on the linked page; unit conversions are noted on the chart.
- Company response
- None yet. Makers and suppliers of this product can send corrections, additional trials, or a statement; it is published here, labelled, and never edits the research summary. Send a correction →