Published online 7 November 2007
Published in Crop Sci 47:2482-2485 (2007)
© 2007 Crop Science Society of America
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CROP ECOLOGY, MANAGEMENT & QUALITY
The Effect of Clothianidin Seed Treatments on Corn Growth following Soybean
W. J. Coxa,*,
E. Shieldsb and
J. H. Cherneya
a Dep. of Crop and Soil Science, Cornell Univ., Ithaca, NY 14853
b Dep. of Entomology, Cornell Univ., Ithaca, NY 14853
* Corresponding author (wjc3{at}cornell.edu).
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ABSTRACT
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Cool soil conditions after planting frequently delay corn (Zea mays L.) emergence in the northeastern United States, which contributes to occasional early-season soil insect damage. Two corn hybrids with three seed-applied insecticide treatments, which included a control, 0.25 mg a.i. seed–1 clothianidin [(E) 1-(2-chloro-1, 3-thiazolyl-5-ymethyl)-3-methyl-2-nitroguanidine], and 1.25 mg a.i. seed–1 clothianidin were evaluated in 2004 and 2005 in New York to determine how clothianidin affects corn growth and yield in an environment with low incidence of soil insect pests. Both clothianidin treatments had greater leaf area index (LAI) values (
2.60) at the 10th to 11th leaf stage (V10–11) compared with the control (2.45). The 0.25 mg a.i. rate had a greater LAI (4.46) than the 1.25 mg a.i. rate (4.28) at the silking stage (R1) and a greater mean crop growth rate from the V10–11 to R1 stage (36.5 and 32.7 g m–2 d–1, respectively). The control had a greater harvest index (0.54) than the 1.25 mg a.i. rate (0.50), but all three treatments had similar grain yield (9.7–10.3 Mg ha–1). Results from this study indicate that clothianidin seed treatments do not have phytotoxic effects on corn growth and yield in an environment with low incidence of soil insect pests. Nevertheless, we do not recommend clothianidin seed treatment as inexpensive insurance against early-season soil insect damage when corn follows soybean [Glycine max (L.) Merr.] in the northeastern United States.
Abbreviations: CGR, mean crop growth rate • DM, dry matter • HI, harvest index • LAI, leaf area index • R1, silking stage • R5.5, 
milk line stage • Vn, nth leaf stage
The Effect of Clothianidin Seed Treatments on Corn Growth following Soybean
W. J. Coxa,*,
E. Shieldsb and
J. H. Cherneya
a Dep. of Crop and Soil Science, Cornell Univ., Ithaca, NY 14853
b Dep. of Entomology, Cornell Univ., Ithaca, NY 14853
* Corresponding author (wjc3{at}cornell.edu).
Cool soil conditions after planting frequently delay corn (Zea mays L.) emergence in the northeastern United States, which contributes to occasional early-season soil insect damage. Two corn hybrids with three seed-applied insecticide treatments, which included a control, 0.25 mg a.i. seed–1 clothianidin [(E) 1-(2-chloro-1, 3-thiazolyl-5-ymethyl)-3-methyl-2-nitroguanidine], and 1.25 mg a.i. seed–1 clothianidin were evaluated in 2004 and 2005 in New York to determine how clothianidin affects corn growth and yield in an environment with low incidence of soil insect pests. Both clothianidin treatments had greater leaf area index (LAI) values (2.60) at the 10th to 11th leaf stage (V10–11) compared with the control (2.45). The 0.25 mg a.i. rate had a greater LAI (4.46) than the 1.25 mg a.i. rate (4.28) at the silking stage (R1) and a greater mean crop growth rate from the V10–11 to R1 stage (36.5 and 32.7 g m–2 d–1, respectively). The control had a greater harvest index (0.54) than the 1.25 mg a.i. rate (0.50), but all three treatments had similar grain yield (9.7–10.3 Mg ha–1). Results from this study indicate that clothianidin seed treatments do not have phytotoxic effects on corn growth and yield in an environment with low incidence of soil insect pests. Nevertheless, we do not recommend clothianidin seed treatment as inexpensive insurance against early-season soil insect damage when corn follows soybean [Glycine max (L.) Merr.] in the northeastern United States.
Abbreviations: CGR, mean crop growth rate • DM, dry matter • HI, harvest index • LAI, leaf area index • R1, silking stage • R5.5, milk line stage • Vn, nth leaf stage
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INTRODUCTION
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COOL SOIL CONDITIONS frequently occur in early-planted corn in northern latitudes, resulting in a delay in corn emergence (Gesch and Archer, 2005). In a 3-yr study in New York, corn emerged 16 to 17 d after planting following plowing and 18 to 19 d under no-till conditions when planted in late April (Cox et al., 1990). Such an extended emergence time increases the potential for reduced emergence caused by seed corn maggot (Delia platura L.) and wireworm (Melanotus spp.) damage (Hoeft et al., 2000). Modern corn hybrids yield best at higher plant densities than older hybrids (Tollenaar and Lee, 2002). Consequently, some corn growers, especially those who plant early, have begun to use seed-applied insecticides as inexpensive insurance to protect against losses in final plant densities from occasional early-season soil insect damage.
Seed-applied insecticides have recently been commercialized in the United States for the control of early-season soil insects (Andersch and Schwarz, 2003). A 0.25 mg a.i. seed–1 clothianidin rate controls seed corn maggot, wireworm, black cutworm (Agrostis ypsilon [Agrostis ipsilon]), and white grubs (Lachnosterna implicate [Phyllophaga implicate]), which are occasional early-season soil insect pests in New York (Cornell Cooperative Extension, 2006). A 1.25 mg a.i. seed–1 clothianidin rate controls the same insect pests as well as corn rootworm species (Diabrotica spp.) (Andersch and Schwarz, 2003).
Jonitz and Leist (2003) reported that clothianidin seed treatments had no phytotoxic effect on corn emergence in the absence of insect pests; however, a survey of seed lots of 63 high-performing hybrids in the U.S. Midwest found that four of seven hybrids that did not pass cold or saturated cold germination tests had been treated with seed-applied insecticides (Finck, 2006). Furthermore, the hybrids that performed poorly in the lab tests also had reduced emergence and early-season growth under field conditions. This implies that the use of seed-applied insecticides as inexpensive insurance against early-season soil insects may have negative agronomic consequences in the absence of soil insect pests, especially under cool or cool and wet spring conditions.
The objective of this study was to determine whether the seed-applied insecticide clothianidin has phytotoxic effects on corn in an environment with a low probability of early-season soil insect damage. To accomplish this, we evaluated crop development (days to emergence and silking), crop growth (LAI and mean crop growth rate), and yield (silage and grain) of corn treated with and without clothianidin seed treatment when following soybean in the rotation. To the best of our knowledge, the effect of clothianidin seed treatment on LAI, mean crop growth rate (CGR), N uptake, and harvest index (HI) has not been reported in the literature.
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MATERIALS AND METHODS
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Field experiments were conducted in 2004 and 2005 on a tile-drained Honeoye silt loam soil (fine-loamy, mixed, mesic Glossoboric Hapludalfs) at a Cornell University research farm near Aurora, NY (42°44'N, 76°40'W). The two fields used in the study have been in a corn–soybean rotation since 1990. Soil tests indicated a pH of 7.8 and high concentrations of P and K (Mehlich test) in the spring of both years.
The experimental design was a randomized complete block design in a split-plot arrangement, replicated four times, with two hybrids as main plots and three seed-applied insecticide treatments as subplots. Main plots measured 15 by 9 m and subplots measured 15 by 3 m. The northern half of the 15-m length of each subplot was harvested for silage at the milk line stage (R5.5). The southern half of the 15-m length of each subplot was harvested for grain about 6 wk later. The silage results were reported previously (Cox et al., 2007).
The two hybrids in 2004 included DeKalb brand DKC58–33 and Pioneer brand 34D71, both 108-d relative maturity hybrids. Unfortunately, Monsanto could not provide the same DeKalb hybrid in 2005, and substituted DeKalb brand DKC61–43, which is a 111-d hybrid. Seed-applied insecticide treatments included a control, 0.25 mg a.i. seed–1 clothianidin, and 1.25 mg a.i. seed–1 clothianidin. All three treatments including the control were treated with the seed-applied fungicides Apron XL [metalaxyl-M, methyl N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-D-alaninate] and Maxim XL [fludioxonil, 4-(2,2-difluoro-1,3-benzodioxol-4-yl)-1H-pyrrole-3-carbonitrile]. Gustafson (Plano, TX) treated both hybrids with the seed-applied insecticides.
The experimental site was plowed and harrow-cultipacked a couple of days before planting in both years. The hybrids were planted on 6 May 2004 and 30 Apr. 2005 at 81,500 plants ha–1 with 277 kg ha–1 of starter fertilizer, 10–8.75–16.6 (N–P–K), with a four-row planter at 0.76-m row spacing. Preemergence herbicides provided excellent weed control in 2004 but dry conditions reduced efficacy in 2005 so all plots were hand weeded twice for further weed control. Corn emergence was determined by counting the number of emerged plants in the two center rows of each subplot starting at 50°C growing degree days (30–10°C system, Cross and Zuber, 1972) after planting. The number of days from planting to 50% emergence was determined when the counted plants divided by the expected number of plants, based on the planting rate, exceeded 50%. In random areas where seeds did not emerge, seeds were dug out but there was no evidence of seed corn maggot or wireworm damage in this study. Final plant densities for each subplot were estimated at the V4 stage (Ritchie et al., 1993) by counting all the plants along the entire length of the two center rows. Immediately after final plant densities were determined, all subplots were injected with 140 kg N ha–1 as a 32% (w/v) solution of urea [(NH2)2CO] and NH4NO3.
Five corn plants were harvested at the soil line from the two center rows of each subplot at the V10 (27 June 2004) or V11 stage (7 July 2005), the R1 stage (27 July 2004 and 22 July 2005), and the R5.5 stage (7 Sept. 2004 and 26 Aug. 2005). Plants were selected from the northern and southern edge of the grain experiment, excluding border plants or plants contiguous to previously harvested plants. At the V10–11 and R1 growth stages, green leaves from each subplot were measured with a leaf area meter (LI-3100, LI-COR, Lincoln, NE). All plants at the V10–11, R1, and R5.5 growth stages were placed in a forced-air dryer and dried at 60°C to constant moisture. The LAI and total dry matter (DM) accumulation were calculated on a land-area basis determined from final plant densities in each subplot. From the DM accumulation data, CGR, the gain in DM per unit area per unit time, was calculated from the V10–11 to R1 stages and from the R1 to R5.5 stages. Also, N uptake at the R5.5 stage was calculated as the DM accumulation data times the total N concentration, which was determined from the five-plant sample using a LECO N analyzer (LECO Corp., St. Joseph, MI) with Dumas combustion (Tate, 1994; Wiles et al., 1998).
The inner 6 m of the two center rows in the southern half of each subplot was harvested for grain with a two-row Almaco (Nevada, IA) plot combine when grain moisture was estimated to be around 250 g kg–1 water (27 Oct. 2004 and 20 Oct. 2005). Yields were adjusted to 155 g kg–1 water. Also, the HI, expressed as kilograms of grain per kilogram of total DM accumulation, was calculated from the grain yield and silage yield of each subplot.
Seed treatments were considered fixed and years, replications, and hybrids were considered random effects in the analysis of variance using PROC MIXED (SAS Institute, 1998). Hybrids were considered random because of the unintentional change in the DeKalb hybrid across years. Least square means of the seed treatment effect were computed, and the PDIFF option of the LSMEANS statement was used to determine differences among least square means at 
= 0.10.
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RESULTS AND DISCUSSION
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Weather conditions differed markedly between growing seasons (Table 1
). A warm and wet May contributed to >95% emergence of all treatments, with average plant densities of 77,940 plants ha–1 in 2004 (Cox et al., 2007). Wet and cool conditions characterized the summer of 2004, which resulted in stress-free conditions. The silage yield averaged 21.9 Mg ha–1 and grain yield averaged 11.6 Mg ha–1 in 2004.
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Table 1. Monthly precipitation and growing degree days (30–10°C system) during the 2004 and 2005 growing seasons and the 30-yr average at Aurora, NY.
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An exceptionally cool and dry May contributed to only 80% average emergence, with the 0.25 mg a.i. rate averaging 3626 more plants ha–1 than the control, in 2005 (Cox et al., 2007). The experimental site received only 15 mm of precipitation before 14 June and corn showed incipient water stress on the warm days during the first half of June. The experimental site received only 23 mm of precipitation between 8 July and 9 August, and both hybrids showed visible leaf wilting in late July and early August. The silage yield averaged 16.7 Mg ha–1 and grain yield averaged 8.6 Mg ha–1 in 2005.
Year and hybrid · seed treatment interactions did not exist for any measured variables, so only seed treatment effects are reported. Seed treatment did not affect crop development (Table 2
). All treatments emerged in 12 d and attained the R1 stage at 68 to 69 d after emergence. Likewise, all seed treatments averaged about 665 g kg–1 water content at silage harvest and about 255 g kg–1 water content at grain harvest. Apparently, clothianidin seed treatment does not affect crop development.
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Table 2. Days to emergence, days to silking, water content of the whole plant at silage harvest, and water content of the grain at harvest of corn with three seed treatments, averaged across two hybrids in 2004 and 2005 at Aurora, NY.
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Seed treatment affected LAI at the V10–11 and R1 stages (Table 3
). Both clothianidin treatments had about a 6% greater LAI at the V10–11 stage than the control. Clothianidin seed treatments did not have phytotoxic effects on early-season leaf development in this study. The 0.25 mg a.i. clothianidin rate also had a 4% greater LAI than the 1.25 mg a.i. rate at the R1 stage. Unfortunately, management practices before or during planting that increase early-season LAI do not, however, consistently increase grain yield. For example, Cox et al. (1990) reported that corn following plowing vs. no-till conditions consistently had 10% greater LAI values during vegetative development but only yielded greater in 1 of 3 yr. Likewise, Bullock et al. (1993) reported that corn with starter vs. no starter fertilizer on high-P soils had greater LAI during vegetative development but similar grain yield at harvest. Bullock et al. (1993) suggested that the early-season increase in LAI in their study was "transient" or "cosmetic."
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Table 3. Leaf area index (LAI) of corn at the 10th to 11th leaf stage (V10–11) and at the silking stage (R1) and mean crop growth rate (CGR) of corn between the V10–11 and R1 stages and between the R1 stage and silage harvest (R5.5 stage), averaged across two hybrids in 2004 and 2005 at Aurora, NY.
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Seed treatment did not increase CGR from the V10–11 to the R1 growth stage when compared with the control (Table 3). The 0.25 compared with the 1.25 mg a.i. clothianidin treatment, however, had an 11.5% greater mean CGR. It is not clear why mean CGR from the V10–11 to R1 growth stage differed between clothianidin treatments, resulting in the greater LAI for the 0.25 mg a.i. rate at the R1 stage. Regardless, both clothianidin treatments compared with the control had similar CGR from the V10–11 to R1 as well as from the R1 to R5.5 growth stages. The CGR from the V10–11 to R1 growth stages does not correlate with grain yield, whereas CGR from the R1 to R3 growth stages does (Uhart and Andrade, 1995; Cirilo and Andrade, 1994). Consequently, the greater CGR for the 0.25 compared with the 1.25 mg a.i. clothianidin treatment from the V10–11 to R1 growth stage may not result in yield differences between these treatments.
Seed treatment did not affect whole-plant N concentration and N uptake at the R5.5 stage (Table 4
). Likewise, seed treatment did not affect grain yield (Table 4) despite differences in LAI and mean CGR between seed treatments during vegetative growth. Apparently, management practices at planting, such as tillage, starter P on high-P soils, or seed-applied insecticide treatment, can have a positive transient effect on early LAI values that do not necessarily result in greater grain yield.
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Table 4. Whole-plant N concentration and N uptake at silage harvest, grain yield, and harvest index of corn under three seed treatments, averaged across two hybrids in 2004 and 2005 at Aurora, NY.
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Seed treatment did affect HI (Table 4). The control had a HI of 0.54 compared with 0.50 for the 1.25 mg a.i. rate. The silage yield of the control (18.9 Mg ha–1) vs. the 1.25 mg a.i. clothianidin treatment was numerically less (19.5 Mg ha–1, Cox et al., 2007), whereas the grain yield of the control was numerically greater (Table 4). Consequently, the difference in HI between these two treatments may be a statistical anomaly rather than differences in DM partitioning patterns.
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CONCLUSIONS
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Results from this study, including a year with cool conditions after planting, indicate that clothianidin as a seed-applied insecticide does not have phytotoxic effects on corn development or growth. In fact, clothianidin at the 0.25 and 1.25 mg a.i. seed–1 rates enhanced early-season leaf area development in this study. Soil insects, including seed corn maggot and wireworm, were not observed in this study so the enhanced leaf area development may have been a physiological response to clothianidin. The results of this study indicate that corn growers can safely use clothianidin seed treatments where soil insect damage is expected. In this study, soil insect damage did not occur and, despite early-season leaf area enhancement with clothianidin, grain yields were not increased.
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NOTES
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All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.
Received for publication December 19, 2006.
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REFERENCES
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- Andersch, W., and M. Schwarz. 2003. Clothianidin seed treatment (Poncho®): The new technology for control of corn rootworms and secondary pests in US-corn production. Pflanzenschutz Nachr. Bayer 56:147–172.
- Bullock, D.G., F.W. Simmons, I.M. Chung, and G.I. Johnson. 1993. Growth analysis of corn grown with or without starter fertilizer. Crop Sci. 33:112–117.[Abstract/Free Full Text]
- Cirilo, A.G., and F.H. Andrade. 1994. Sowing date and maize productivity: II. Kernel number determination. Crop Sci. 34:1044–1046.[Abstract/Free Full Text]
- Cornell Cooperative Extension. 2006. Cornell guide for integrated field crop management. Cornell Coop. Ext., Ithaca, NY.
- Cox, W.J., J.H. Cherney, and E. Shields. 2007. Clothianidin seed treatments inconsistently increase corn forage yield when following soybean. Agron. J. 99:543–548.[Abstract/Free Full Text]
- Cox, W.J., R.W. Zobel, H.M. van Es, and D.J. Otis. 1990. Growth, development, and yield of maize under three tillage systems in the northeastern USA. Soil Tillage Res. 18:295–310.[CrossRef]
- Cross, H.Z., and M.S. Zuber. 1972. Prediction of flowering dates in maize based on different methods of estimating thermal units. Agron. J. 64:351–355.[Abstract/Free Full Text]
- Finck, C. 2006. Seeds up close. Farm J. (Spring):8–10.
- Gesch, R.W., and D.W. Archer. 2005. Influence of sowing date on emergence characteristics of maize seed coated with a temperature-activated polymer. Agron. J. 97:1543–1550.[Abstract/Free Full Text]
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- Ritchie, S.W., J.J. Hanway, and G.O. Benson. 1993. How a corn plant develops. Coop. Ext. Serv. Spec. Rep. 48. Iowa State Univ., Ames.
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- Uhart, S.A., and F.H. Andrade. 1995. Nitrogen deficiency in maize: I. Effects on crop growth, development, dry matter partitioning, and kernel set. Crop Sci. 35:1376–1383.[Abstract/Free Full Text]
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ABSTRACT
INTRODUCTION
