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Corn

Clothianidin Seed Treatments Inconsistently Affect Corn Forage Yield When following Soybean

^a Dep. of Crop and Soil Sciences, Cornell Univ., Ithaca, NY 14853
^b Dep. of Entomology, Cornell Univ., Ithaca, NY 14853

^* Corresponding author (wjc3{at}cornell.edu)

Received for publication June 7, 2006.

	ABSTRACT

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Cool conditions after corn (Zea mays L.) planting frequently delay emergence in the northeastern USA, which is conducive to damage by the soil insect pest, seed corn maggot (Delia platura). Two 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-thiazol-5-ymethyl)-3-methyl-2-nitroguanidine], and 1.25 mg a.i. seed^–1 clothianidin, were evaluated in 2004 and 2005 in New York. The objective of the study was to determine if clothianidin affects final plant densities, total dry matter (DM) accumulation during vegetative growth, DM yield, and forage quality in an environment with occasional soil insect pests. Corn emerged in 7 d in 2004 so clothianidin did not affect final plant densities, but the 1.25 mg a.i. treatment vs. the control of one hybrid had 1.3 Mg ha^–1 greater DM yield. Corn emerged in 17 d in 2005, and the 0.25 mg a.i. treatment averaged 3296 more plants ha^–1 while both clothianidin treatments vs. the control of one hybrid had 1.4 to 1.7 Mg ha^–1 greater DM yields. Lack of negative responses of final plant densities, vegetative growth, and DM yield indicates that clothianidin seed treatments have no phytotoxic effect on corn. Nevertheless, seed treatments did not affect forage quality or calculated milk yields so our study indicates that clothianidin seed treatment is not justified when corn follows soybeans [Glycine max L. (Merr.)] in the northeastern USA.

Abbreviations: CP, crude protein • DM, dry matter • GDD, growing degree days • GLM, General Linear Model • IVTD, in vitro true digestibility • milk Mg^–1, kg milk Mg^–1 corn forage • milk yield, kg milk ha^–1 corn forage • NDF, neutral detergent fiber • NDFd, in vitro fiber digestibility • R1, silking stage • RM, relative maturity • Vn, nth leaf stage

	INTRODUCTION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
COOL SOIL CONDITIONS frequently occur after corn planting in northern latitudes, which delay corn emergence (Gesch and Archer, 2005). In a 3-yr study in New York, corn emergence averaged 16 to 17 d under plowed 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 seed corn maggot damage (Hoeft et al., 2000) with reported losses in final plant densities, associated with seed corn maggot damage, of 1200 to 3250 plants ha^–1 in New York (Cornell Cooperative Extension, 2006).

Seed-applied insecticides have recently been commercialized in the USA for early season soil insect control in corn (Andersch and Schwarz, 2003). Clothianidin, applied at a 0.25 mg a.i. seed^–1 rate, controls major early season soil insects (Andersch and Schwarz, 2003), including seed corn maggot, wireworm (Melanotus spp.), black cutworm [Agrostis ypsilon (Agrostis ipsilon)], and white grubs [Lachnosterna implicata (Phyllophaga implicata)]. Clothianidin, applied at a 1.25 mg a.i. seed^–1 rate, controls the same insect pests as well as corn rootworm species (Diabrotica spp.) (Andersch and Schwarz, 2003). In a Kansas study, both clothianidin rates gave complete control of white grubs, which resulted in 30 plants/9 m of row and 8.1 to 8.5 Mg ha^–1 grain yield compared with 8 plants/9 m of row and 1.8 Mg ha^–1 grain yield in the control treatment (Wilde et al., 2004). In a study in northeastern Spain (Pons and Albajes, 2002), corn treated with imidacloprid [1-(6-chloro-3-pyridin-3-ylmethyl)-N-nitroimidazolidin-2-ylideamine], another seed-applied insecticide, controlled early season soil insects, including wireworm and cutworm species, but did not consistently increase corn yield when compared with the control treatment.

Early season corn insects are occasional pests in the northeastern USA, especially when corn follows soybeans (Cornell Cooperative Extension, 2006) so seed-applied insecticides may not be necessary each year. Nevertheless, Pioneer Hi-Bred, which has 40% of the corn seed market share in New York, treated 15% of its corn seed with clothianidin at a 0.25 mg a.i. rate and 20% at a 1.25 mg a.i. rate for sales in New York in 2006 (Joe Meyer, personal communication, 2006). Apparently, some corn growers in New York may use clothianidin seed treatment as inexpensive insurance for protection against potential damage from occasional early season insects.

Jonitz and Leist (2003) in a Bayer Corporation publication reported that clothianidin had no phytotoxic effect on corn emergence in the absence of soil insect pests. Four of seven hybrids, however, that did not pass cold and saturated cold germination tests were treated with a seed-applied insecticide from the 63 samples selected by farmers in a 2005 Farm Journal report (Finck, 2006). Furthermore, the hybrids that ranked last in the cold and saturated cold germination tests also had lower corn emergence and slower early season growth in the field when compared with the higher-ranking hybrids. Consequently, the use of seed-applied insecticides as inexpensive insurance for protection against occasional early season insects may have negative agronomic consequences in the absence of these pests.

Corn silage compared with grain corn requires 7.5% higher plant densities for maximum economic yield (Cox, 1997), and corn silage yields have a strong correlation with DM accumulation during vegetative development (Muchow and Davis, 1988). Corn seed that has lower emergence or slower early season growth could thus affect corn forage more than corn for grain. The objective of this study was to determine if the seed-applied insecticide, clothianidin, affects final plant densities, DM accumulation during vegetative growth, forage yield, and forage quality of corn in an environment with occasional soil insect pests such as when corn follows soybeans in the rotation. We included two hybrids in the study to determine if some hybrids are more susceptible to phytotoxic effects from insecticidal seed treatment as some hybrids are to herbicides (Pioneer Hi-Bred International, 2006). To the best of our knowledge, the effect of clothianidin seed treatments on corn growth during vegetative development and corn forage quality has not been reported in the literature.

	MATERIALS AND METHODS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
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 lat, 76°40' W long.). The two fields used in the study have been in a corn–soybean rotation since 1990 so soybean was the previous crop in both years of the experiment. 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 7.5 by 9 m and subplots measured 7.5 by 3 m. The two hybrids, which are recommended for corn silage production in New York (Cornell Cooperative Extension, 2006), included: DeKalb brand, ‘DKC 58-33’; and Pioneer brand, ‘34D71’; 108-d relative maturity (RM) hybrids, in 2004. Unfortunately, Monsanto could not provide the same DeKalb hybrid in 2005, and substituted the similar-performing DeKalb brand, ‘DKC 61-43’, a 111-d RM. Seed-applied insecticide treatments included a control treatment, 0.25 mg a.i. seed^–1 of clothianidin, and a 1.25 mg a.i. seed^–1 clothianidin treatment. All three treatments, including the control, also were treated with the seed-applied fungicides Apron XL {methyl-N [methoxyacetyl-N (2, 6-xylyl-D-alaninate)]} and Maxim XL {[fludioxinil (R)-2-(2, 6-dimethylphenyl)-methoxyacetylamino]-propionic acid methyl ester}. 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 with a four-row planter (0.76-m row spacing) at 81 500 plants ha^–1, the recommended rate for corn silage production in New York (Cornell Cooperative Extension, 2006). A banded starter fertilizer, 10–20–20 (N–P–K), was applied at a rate of 277 kg ha^–1. Pre-emergence herbicides, atrazine [6-chloro-N ethyl N'-(1-methylethyl) 1,3,5-triazine-2-4 diamine], applied at a 1.12 kg a.i. ha^–1 rate, and s-metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N- (2-methoxy-1-methylethyl) acetamide], applied at a 1.4 kg a.i. ha^–1 rate, provided excellent weed control in 2004. Dry conditions reduced herbicide efficacies 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 air growing degree days (GDD, 30–10° cut-off system as described by Cross and Zuber, 1972) after planting. 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, equaled 50%. Final plant densities of each subplot were determined at the fourth leaf stage (V4, 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 (0.1 m deep between the center of each row) with 140 kg N ha^–1 as a 32% weight volume^–1 solution of urea [(NH₂) Co] and ammonium nitrate (NH₄ NO₃).

Five corn plants were harvested at the soil line from the two center rows (three consecutive plants from one center row and two consecutive plants from the other center row) of the outer 0.5 m on the south end of each subplot at the V10 (27 June 2004) or V11 stage (7 July 2005) and from the outer 0.5 m of the north end at the R1 (silking) stage (27 July 2004 and 22 July 2005) to estimate DM accumulation during vegetative development. Border plants were not selected at either growth stage. All harvested plants were placed in a forced-air drier and dried at 60°C to constant moisture. Total DM accumulation was calculated on a per hectare basis determined from the 5-plant sample weight and final plant densities in each subplot.

The two center rows of the inner 6 m of each subplot were harvested by hand to determine corn forage yield when corn was estimated to be at about 330 g kg^–1 DM content (7 Sept. 2004 and 26 Aug. 2005). Five plants were randomly selected from the hand-harvested plants to calculate DM content and to analyze for forage quality characteristics. The five-plant sample was ground through a chipper-shredder in the field and an approximate 1-kg subsample was taken from the shredded material and dried at 60°C in a forced-air drier to constant moisture. The subsample was further ground through a Wiley mill (Thomas Scientific, Sweetsboro, NJ), fitted with a 1-mm screen.

Subsamples (0.5 g each) were analyzed by wet chemistry for neutral detergent fiber (NDF), using the ANKOM system (ANKOM Technology, Fairport, NY) according to procedures by Van Soest et al. (1991), and for total N using a Leco FP528 N analyzer (LECO Corp., St. Joseph, MI) with Dumas combustion (Tate, 1994; Wiles et al., 1998). The crude protein (CP) concentration was calculated by multiplying total N by 6.25. Subsamples (0.25 g each) were also analyzed for in vitro true digestibility (IVTD) according to Stage 1 of the procedure described by Marten and Barnes (1980), using a 48-h incubation period at 39°C in 5 mL of buffered rumen fluid containing 20 mL of the Kansas State buffer supplemented with 0.5 g L^–1 urea. In vitro fiber digestibility (NDFd) was determined as described by Cherney et al. (2004), using the rumen buffer described by Marten and Barnes (1980) and using the Daisy II^200/220 in vitro incubator (ANKOM Technology, Fairport, NY) and the ANKOM^200–220 fiber analyzer. The buffer contained urea. Ruminal fluid inoculum was obtained from a nonlactating, rumen-fistulated Holstein cow, offered a medium-quality orchardgrass (Dactylis glomerata L.) hay diet for ad libitum intake. Digestibility samples (0.25 g) were incubated in duplicate for 48 h at 39°C, and undigested residues were treated with neutral detergent solution.

Subsamples (1.0 g) were also analyzed for ash content by combustion at 510°C for 4 h. Subsamples (0.1 g) were analyzed for starch by Dairy One (DHI Forage Testing Lab, Ithaca, NY). The subsamples were pre-extracted for sugars, and then a glucoamylase enzyme was used to hydrolyze starch to dextrose. The subsamples were then injected into an YSI 2700 SELECT Biochemistry Analyzer (YSI, Yellow Springs, OH) where dextrose is oxidized to hydrogen peroxide and lactose. Hydrogen peroxide is detected by an electrode, and current at the electrode is directly proportional to hydrogen peroxide concentration, which is directly related to dextrose and starch concentrations.

Potential milk yield indices were then estimated from the spreadsheet, Milk 2000 (Schwab and Shaver, 2001). Milk Mg^–1 (kg milk Mg^–1 corn forage), a forage quality index, was calculated from NDF, NDFd, CP, ash, and starch concentrations. Milk yield (kg milk ha^–1 corn forage) was calculated as the product of milk Mg^–1 and DM yields.

Years, hybrids, and seed treatments were considered fixed and replications were considered random effects in the analysis of variance. Years were considered fixed because of the hybrid change in the DeKalb brand and the different sampling times (V10 in 2004 and V11 in 2005) across years. Combined analyses across years and separate analyses within years were conducted for final plant densities, total DM accumulation at the V10 to V11 and R1 stages, DM yield, NDF, NDFd, CP, starch, milk Mg^–1, and calculated milk yield using General Linear Model (GLM) procedures of the SAS statistical package, Version 7.0 software (SAS Institute, 1998). The Bartlett test (P = 0.05) for homogeneity of variances was conducted for all variables. All variances were homogeneous except for NDF and CP, which indicate that the data sets from the 2 yr that included different DeKalb hybrids were mostly from the same population and that combined analyses can be conducted on all variables except NDF and CP. Table 1 shows the F probabilities of the combined analyses for variables with homogeneous variances. We also present the means of the hybrids and seed treatments for each year for all variables because NDF and CP had nonhomogeneous variances and five of the other eight variables had two-way or three-way interactions with years (Table 1). All main effects and interactions were considered significant at P = 0.05. Fisher's protected LSD (P = 0.05) was used to separate means when main effects or interactions tested significant.

	RESULTS AND DISCUSSION

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

When averaged across years and hybrids, seed treatment did not affect plant density, but a year x hybrid interaction was observed (Table 1). All treatments of both hybrids emerged in 7 d in 2004 because of warm conditions after planting, and final plant densities averaged 77 198 plants ha^–1 for DKC58-33 and 78 681 plants ha^–1 for 34D71 (Table 3). All seed treatments averaged 95% or greater emergence, which indicates that clothianidin did not affect emergence when conditions were conducive for rapid emergence after planting. In 2005, however, the experimental site received only 5 GDD and 1 mm of precipitation during the 7 d following planting, and emergence of all treatments occurred 17 d after planting. Final plant densities averaged 68 925 plants ha^–1 for DKC61-43 but only 60 856 plants ha^–1 for 34D71. Also, the 0.25 mg a.i. clothianidin treatment averaged 3648 more plants ha^–1 when compared with the control treatment, which indicates that the 0.25 mg a.i. clothianidin treatment enhanced emergence when cool and dry conditions prevailed for an extended period after planting. Corn silage yields show a linear response to plant densities between 45 000 and 80 000 ha^–1 plants (Cox, 1997) so the 0.25 mg a.i. clothianidin seed treatment could have greater forage yields in 2005 because of greater plant densities.

Corn forage yield had a significant year x hybrid x seed treatment interaction (Table 1). In 2004, the 1.25 mg a.i. clothianidin treatment of 34D71 yielded 1.3 Mg ha^–1 more than the control treatment (Table 4), despite similar final plant densities and total DM accumulation at the V10 and R1 stages between the two treatments. The 0.25 mg a.i. clothianidin treatment and the control treatment within both hybrids yielded the same, which indicates that the 0.25 mg a.i. rate did not affect corn forage yield in a year when corn emerged rapidly.

Dairy producers consider corn forage quality to be of equal importance as corn forage yield because both factors strongly influence the amount of milk produced by their herds (Schwab and Shaver, 2001). When averaged across years and hybrids, seed treatment did not affect NDFd or starch (Table 1). Likewise, seed treatment did not affect NDF in either year of the study (Table 5). These three variables strongly influence the calculation of milk Mg^–1, a forage quality index (Schwab and Shaver, 2001), so seed treatment did not affect milk Mg^–1 (Tables 1 and 5). The results from this study indicate that clothianidin seed treatments do not affect corn forage quality in the DM content range (315–355 g kg^–1) that most dairy producers in the northeastern USA harvest corn forage (Cox and Cherney, 2005).

When averaged across years and hybrids, seed treatment did not affect calculated milk yield (Table 4). Consequently, clothianidin seed treatments did not affect the endproduct for which corn forage is grown for in the northeastern USA. A year x hybrid interaction was observed for calculated milk yield (Table 1). Hybrid, however, did not affect calculated milk yield in either year of the study, despite the year x hybrid interaction.

	CONCLUSIONS

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 
Clothianidin was evaluated as a seed treatment on corn silage following soybeans in the rotation in the northeastern USA. Clothianidin did not have negative effects on corn emergence, growth, and forage yield, which indicate no phytotoxic effects of clothianidin in the absence of pests. Clothianidin did not affect forage quality or calculated milk yield, which indicates that clothianidin cannot be readily justified as inexpensive insurance against early season insect pests. There may be other conditions and situations, however, where the application of clothianidin may be justified for use on corn silage production in the northeastern USA. Our research results did not elucidate those conditions and additional research in this area may be warranted.

	REFERENCES

TOP ABSTRACT INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION CONCLUSIONS REFERENCES

 

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This Article Abstract Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cox, W. J. Articles by Shields, E. Search for Related Content PubMed Articles by Cox, W. J. Articles by Shields, E. Agricola Articles by Cox, W. J. Articles by Shields, E. Related Collections Maize