Seed Treatment for Control of Early-Season Pests of Corn and Its Effect on Yield 1

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1 Seed Treatment for Control of Early-Season Pests of Corn and Its Effect on Yield 1 Gerald Wilde, 2 Kraig Roozeboom, 3 Mark Claassen, 3 Keith Janssen, 3 and Merle Witt 2 Department of Entomology, Kansas State University, Manhattan, Kansas 66506, USA J. Agric. Urban Entomol. 21(2): (April 2004) ABSTRACT Various seed treatments were evaluated for their effect on early-season corn pests. Imidacloprid at low and high rates (Gaucho and Prescribe, respectively) and thiamethoxam (Cruiser ) at low and high rates were effective in reducing populations and exhibited systemic insecticidal activity against chinch bugs, flea beetle, wireworm, white grub, and southern corn leaf beetle. Another systemic neonicotinoid, clothianidin, was tested and was effective against these pests at all rates tested. Tefluthrin (Proshield or Force ), a pyrethroid, was tested for control of white grub, southern corn leaf beetle, flea beetle, and chinch bug and was only effective against white grub because of a lack of systemic insecticidal activity against the latter three pests. Fipronil seed treatment also was effective in controlling white grub and southern corn leaf beetle but was not effective against flea beetles or chinch bugs. In general, systemic seed treatments were as effective in controlling soilinhabiting insects (wireworms and white grubs) as the infurrow granular treatments. Our tests suggest that seed treatments, especially those with systemic activity, show great promise for growers dealing with a variety of soilinhabiting and early-season foliar-feeding insect pests. Because of the convenience of seed treatments, they will be especially useful in areas where one or more of these early-season pests are chronic problems. These treatments also will be useful on transgenic corn used for corn rootworm control to control these secondary pests that are not affected by the transgenic corn. KEY WORDS Seed treatments, imidacloprid, thiamethoxam, clothianidin, tefluthrin, fipronil Wireworm (Melanotus cribulosus) (Coleoptera: Elateridae), white grub (Phyllophaga sp.) (Coleoptera: Scarabaeidae), flea beetle (Epitrix cucumeris Harris) (Coleoptera: Chrysomelidae), chinch bug (Blissus leucopterus leucopterus (Say)) (Hemiptera: Lygaeidae), and southern corn leaf beetle (Myochrous denticollis Say) (Coleoptera: Chrysomelidae) are early-season corn pests in Kansas that can reduce stand establishment and/or early season growth (Higgins 1994). The re- 1 Accepted for publication 8 October Corresponding author: Department of Entomology, Kansas State University, 123 Waters Hall, Manhattan, Kansas , USA. Tel: ; Fax: ; gwilde@oznet.ksu.edu 3 Department of Agronomy, Kansas State University, Manhattan, Kansas 66506, USA. 75

2 76 J. Agric. Urban Entomol. Vol. 21, No. 2 (2004) cent development of seed treatments, especially those belonging to the thianicotinyl group that possess plant systemic activity, has resulted in widespread use of these products to control insect pests on a variety of crops. Cruiser is a trade name for thiamethoxam, a second-generation neonicotinoid insecticide developed by Syngenta Crop Protection, Inc. (Greensboro, North Carolina). It provides control of several commercially important insect pests on a variety of crops including barley, cotton, sorghum, wheat, and canola. It works through contact, stomach, and systemic activity (Wilde et al. 2001). Imidacloprid (Gaucho ) is commonly used as a systemic seed treatment to protect seeds and seedlings against injury by early season insects (Pike et al. 1993, Sloderbeck et al. 1996, Wilde 1997, Tharp et al. 2000). Marketed by Gustafson, Inc. (Plano, Texas), imidacloprid is effective in controlling many insects including aphids, thrips, mites, and wireworms. It is registered and commonly used on several crops including cotton, wheat, barley, sorghum, canola, and sugar beet. Poncho (clothianidin) seed-applied insecticide, also produced by Gustafson, Inc., is a second-generation chloronicotinyl insecticide (CNI) that also has systemic activity plus crop and seed safety characteristics. No known cases of crossresistance to insecticides of other chemical groups have been documented. Few data are available on the effects of these and other seed treatments on early-season corn insect pests or yield. Seed treatments would be particularly useful in situations where one or more of these early-season pests cause chronic problems. Therefore, the objectives of this study were to evaluate several registered and experimental seed-treatment insecticides for their effects on earlyseason pests and to determine their impact on yield of two corn hybrids commonly grown in the midwestern United States. Materials and Methods Comparison of imidacloprid and thiamethoxam. Twelve tests were conducted during at four locations associated with Kansas State University (KSU) representing various soil types and agronomic practices within the state. Locations were the East Central Experiment Field, Ottawa; the Agronomy North Farm, Manhattan; the Harvey County Experiment Field, Hesston; and the Southwest Research-Extension Center, Garden City. Uniform seed lots of two corn hybrids, Asgrow 799Bt and Midland 798, were subdivided, with one portion retained as untreated and a portion sent to Syngenta Crop Protection, Inc. (Greensboro, North Carolina) and Gustafson, Inc. (Plano, Texas), respectively, for application of seed treatments. In 2000, each hybrid was treated with one (low) rate of imidacloprid (0.16 mg (AI)/kernel) and thiamethoxam (5 Flowable Seed (FS) 0.83 ml/kg of seed). In 2001 and 2002, each hybrid was treated with the low and a high (imidacloprid 1.34 mg AI/kernel, thiamethoxam ml/kg) rate of each of the two compounds. Hybrids and seed treatments were arranged in a factorial treatment structure that was replicated eight times in a randomized complete block design. Each hybrid seed treatment combination was evaluated in plots consisting of two rows spaced 76 cm apart and 6.2 m long. Reduced tillage in combination with herbicides was used to control weeds. Fertilization practices were carried out in

3 WILDE et al.: Seed treatment for corn insects 77 accordance with recommendations from KSU Research and Extension. Soil moisture at planting was adequate for seed germination and emergence. Relevant planting date and agronomic information are given in Table 1. Various parameters were measured to evaluate corn response to the insecticide treatments. Days to half silk were determined as the number of days from planting until half the ears in a plot were fully silked. Plots were harvested with a modified Gleaner K2 combine (AGCO Corp., Duluth, Georgia), equipped with a Grain Gage (Harvest Master, Inc., Logan, Utah) data collection system to determine yield, test weight, and grain moisture. Plots were examined at 2-week intervals for the presence of insects. When infestations occurred, insect numbers per plant or a damage rating were determined by examining four plants in each plot. Wireworm control. The effect of various seed treatments and a number of infurrow applied insecticides were evaluated in a field heavily infested with wireworms (Melanotus cribulosus) near Copeland, Kansas, in Republic County. Corn (MF-786) was planted and treatments applied with a v-belt seeder on 12 May Plots were one row, 9.1 m in length with three replications. Treatments were evaluated by counting the number of live plants on 5 June. Yield data were not taken because of a severe drought. White grub control. The effect of various seed treatments and a number of granular insecticides applied infurrow was evaluated in a field heavily infested with white grubs (Phyllophaga sp.) near Powhattan, Kansas, in Brown County. Corn (MF-786) was planted on 7 May 2001, and treatments were applied with v-belt seeder in one-row plots 9.1 m in length replicated three times. Seed treatments were applied by the companies supplying the seeds. Treatments were evaluated by counting the number of live plants on 9 June and one person assessing stunting with a rating scale of 0 10 (0 no stunting, 10 severe stunting). Yield data was taken by hand-harvesting plots on 30 September, threshing the grain, and calculating the yield in kg per ha. Southern corn leaf beetle control. The effect of various seed treatments on southern corn leaf beetle was assessed in a greenhouse test planted on 14 May Treated seeds were planted in 6-inch pots (one seed per pot). After plants had germinated and reached the 1 2 leaf stage, field-collected adults were caged (two per plant) on the plants and allowed to feed for 8 days. Three pots (replications) were established per treatment. Treatments were evaluated on 29 May by counting the number of live beetles and assessing damage with a rating scale of 0 5 where 0 no feeding damage and 5 severe feeding damage. Chinch bug control. The effect of various seed treatments on chinch bugs was assessed in a greenhouse test planted 1 July Seeds were planted in 6-inch pots (one seed per pot), with four pots per treatment. After plants had germinated and reached the 1 2 leaf stage, adult chinch bugs collected from the field were caged (20 per pot) and allowed to feed for 4 days. Treatments were evaluated on 10 July by counting the number of live chinch bugs per plant. In previous studies, Archer (1994) indicated this artificial infestation technique correlated well with field studies and is an effective method for evaluating insect control. The test was repeated with another set of treatments in a greenhouse test planted on 5 May Ten chinch bugs were caged per plant on four plants (pots) per treatment at the spike, one leaf, and three-leaf stage. The number of live

4 78 J. Agric. Urban Entomol. Vol. 21, No. 2 (2004) Table 1. Agronomic information for seed-treatment evaluations on corn in Kansas Year Location Planting date Harvest date Previous crop Soil type 2000 Ottawa 14 Apr 09 Sep Soybean Woodson silty loam Manhattan 21 Apr 06 Sep Soybean Reading silty loam Garden City 27 Apr 22 Sep Soybean Keith silt loam Hesston 14 Apr 28 Aug Wheat Ladysmith silty clay loam 2001 Ottawa 24 Apr 13 Sep Soybean Woodson silty loam Manhattan 19 Apr 11 Sep Soybean Reading silty loam Garden City 01 May 10 Oct Soybean Keith silt loam Hesston 18 Apr 29 Aug Sorghum Ladysmith silty clay loam 2002 Ottawa 17 Apr 29 Aug Soybean Woodson silty loam Manhattan 12 Apr 09 Sep Soybeam Reading silt loam Garden City 02 May 17 Oct Soybean Keith silt loam Hesston 18 Apr 30 Aug Soybean Ladysmith silty clay loam chinch bugs was counted 3 days after plants were infested. Different sets of plants were used for each growth stage. Flea beetle control. The effect of seed treatments and infurrow applications of liquid and granular treatments on flea beetles was assessed in a field infested with flea beetles near Junction City (Geary County), Kansas. Corn (Midland 798) was planted and treatments applied on 14 April 2002 with a v-belt seeder in 9.1-m-long single-row plots that were replicated four times. Treatments were evaluated by assessing plant damage using a 0 5 rating scale (0 no feeding damage, 5 severe feeding damage) on four plants in each replicate on 5 May Yield data were not taken because a severe drought with high temperatures during the silking and pollination period severely reduced seed set. Statistical procedure. The data from the imidacloprid thiamethoxam comparison were subjected to a mixed model analysis using PROC MIXED (Littell et al. 1996). Replications were considered random and hybrids and seed treatments were considered fixed. Means were separated using pairwise t-tests with a probability level of Analysis of variance was performed on all insecticide efficacy data collected. Mean separation was based on Fisher s protected LSD test at a probability level of 0.05 (SAS Institute 1988). Results Comparison of imidacloprid and thiamethoxam. Significant seed treatment by hybrid interactions occurred only in 2000 at Hesston for yield (F 30.38, df 2, P < and days to 50% silk (F 15.8, df 2, P < ). Therefore, seed-treatment main effect means across two hybrids are presented except as noted (Table 2). If the seed treatment by hybrid interaction was significant, means for each seed treatment by hybrid combination are presented. Test weight

5 WILDE et al.: Seed treatment for corn insects 79 Table 2. Corn seed treatment comparisons Hes. Treatment Rate a Man. Ott. G.C. Treatment Hybrid b Hes. Yield (kg/ha) Control M a Control a 6123 a a Control A799Bt 6052 c Imidacloprid a 7490 b a Imidacloprid M c Imidacloprid A799Bt 6785 d Thiamethoxam a 6804 a a Thiamethoxam M bc Thiamethoxam A799Bt 6366 cd Days to half silk Control M a Control 75.4 a 76.6 a Control A799Bt 78.5 c Imidacloprid b 77.1 a Imidacloprid M b Imidacloprid A799Bt 77.3 d Thiamethoxam b 76.6 a Thiamethoxam M b Thiamethoxam A799Bt 77.8 d Grain moisture (%) Control 17.4 a 10.5 a 17.1 a 16.2 a Imidacloprid ab 10.1 b 17.1 a 15.7 a Thiamethoxam b 10.1 b 17.0 a 15.6 a Man. Manhattan, Ott. Ottawa, Hes. Hesston, G.C. Garden City. Means are across two hybrids except for yield and days to silk at Hesston in Means followed by the same letter in a column are not significantly different (P < 0.05). a Imidacloprid: mg/seed, Thiamethoxam: ml/kg seed. b M798 Midland 798, A799Bt Asgrow 799Bt. and percent lodging results showed no significant seed treatment or interaction effects in any test and are not presented. Significant treatment effects and differences in yield occurred at two (Ottawa, Hesston) of the four locations (Table 2) in Yield increases due to seed treatment were particularly noted at Hesston, where a seedling infestation of chinch bugs and flea beetles occurred. Both imidacloprid and thiamethoxam significantly reduced insect populations at both Hesston and Manhattan (Table 3). Significant yield responses occurred at Ottawa, although no measurable insect populations were observed. At Hesston, yield of one hybrid (Midland 798) was reduced significantly more than that of the other (Asgrow 799 Bt). We suspect these differences were due to chinch bug susceptibility differences between the two hybrids based on chinch bug counts and vigor ratings (Table 3). No noticeable insect infestations were observed at any location in There were no significant seed treatment effects on yield at any location (Table 2). At Hesston, both rates of thiamethoxam reached half silk about a half day earlier than either rate of imidacloprid. Neither seed treatment was significantly different from the untreated check in days to half silk. At Ottawa, the higher rate of imidacloprid and both rates of thiamethoxam lowered grain moisture compared to

6 80 J. Agric. Urban Entomol. Vol. 21, No. 2 (2004) Table 2. Continued Treatment Rate Man. Ott. Hes. G.C. Man. Ott. Hes. G.C. Yield (kg/ha) Control 5709 a 6448 a 1797 a a 3347 a 1831 a 2995 a a Imidacloprid a 6135 a 1875 a a 3609 a 1954 a 3168 ab a Imidacloprid a 6433 a 1847 a a 3885 a 2084 a 3118 a a Thiamethoxam a 6157 a 1879 a a 3511 a 1897 a 3177 ab a Thiamethoxam a 6552 a 1880 a a 3918 a 2018 a 3384 b a Days to half silk Control 78.4 a 70.6 a 76.6 ab 77.1 a 87.1 a 79.3 a 76.8 a 75.7 a Imidacloprid a 70.3 a 76.9 a 77.4 a 86.5 ab 78.9 a 76.4 bc 75.6 a Imidacloprid a 70.4 a 76.9 a 77.3 a 86.1 b 79.1 a 76.7 ab 75.9 a Thiamethoxam a 70.3 a 76.3 b 77.1 a 86.2 b 79.1 a 76.4 c 75.6 a Thiamethoxam a 70.4 a 76.4 b 77.2 a 85.9 b 78.9 a 76.3 c 75.8 a Grain moisture (%) Control 17.3 a 16.8 a 12.7 a 16.2 a 21.6 a 17.3 a 14.3 a 15.1 a Imidacloprid a 16.4 ab 12.6 a 16.5 a 21.2 a 17.2 a 14.4 a 15.2 a Imidacloprid a 16.3 b 12.7 a 16.0 a 21.0 a 17.3 a 14.1 a 15.4 a Thiamethoxam a 16.2 bc 12.7 a 16.5 a 21.2 a 17.3 a 14.7 a 15.1 a Thiamethoxam a 15.9 c 12.6 a 16.4 a 21.1 a 17.1 a 14.2 a 15.6 a Table 3. Cruiser and Gaucho seed insecticide effects on corn insects. Harvey County Experiment Field, Hesston, Kansas, Agronomy North Farm, Manhattan, Kansas, Manhattan Hesston Hybrid Treatment Flea beetle a,c Score Vigor b,c rating Flea beetle a,b Score Chinch bug c no/plt Plant vigor c Midland 798 None 2.15 a 2.00 a 3.3 a 13.0 a 3.2 a Midland 798 Cruiser 0.19 c 1.00 b 0.8 b 4.1 bc 1.0 c Midland 798 Gaucho 0.00 d 1.00 b 0.3 c 3.3 bc 1.0 c Asgrow RX799Bt None 1.91 b 1.98 a 3.2 a 5.8 b 2.6 b Asgrow RX799Bt Cruiser 0.00 d 1.00 b 0.4 c 4.7 b 1.1 c Asgrow RX799Bt Gaucho 0.03 d 1.00 b 0.1 c 1.7 c 1.0 c a Flea beetle score 0 5, 0 no feeding, 5 severe feeding. b Vigor rating 1 5, 1 best, 5 worst. c Means followed by the same letter in a column are not significantly different (P < 0.05).

7 WILDE et al.: Seed treatment for corn insects 81 the untreated check. Across all locations, data from 2001 suggest that no significant yield response occurred in the absence of noticeable insect attack. Yields at Hesston were extremely low because of a severe drought. Significant treatment effect on yield and days to half silk occurred at only one (Hesston) of the four locations where treatments were evaluated in The high rate of thiamethoxam was higher than the control and the high rate of imidacloprid. Again, no noticeable insect infestations occurred. Yields across all nonirrigated locations were extremely low because of a very dry growing season (Table 2). Effects on wireworm. All seed treatments significantly increased plant stands compared to the untreated check. (F 2.10, df 9, P 0.04) (Table 4). Plant stands in some of the infurrow granular treatments (Counter and Fortress) were significantly greater than the untreated check, but three (Force, Aztec, and Lorsban) were not. Extremely dry conditions and the lack of insecticide activation under these conditions may have accounted for the lack of activity of these granular treatments. Effects on white grub. All treatments significantly increased plant stand counts compared to the untreated check and significantly reduced the amount of stunting (F 10.48, df 13, P ) (Table 5). Lorsban was significantly less effective than the other treatments in reducing stunting (F 98.9, df 13, P ), but yield in Lorsban-treated plots was comparable to the other treatments, all of which were significantly greater than the untreated check (F 138.6, df 13, P 0.001). Yield in all seed treatments except fipronil were comparable to the infurrow granular insecticide treatments. Effects on southern corn leaf beetle. All seed treatments except tefluthrin (Proshield) significantly reduced beetle populations (F 24.45, df 10, P ) and feeding damage (F 12.15, df 10, P ) compared to the untreated check (Table 6). These results are not unexpected, because the beetles Table 4. Wireworm control on corn with planting time and seed treatment in Courtland, Kansas, Treatment Formulation a Rate Plant/plot b Cruiser ST 200 g AI/100 kg 27.0 a Counter 20 G 0.56 g/m 26.3 a Fortress 5 G 0.28 g/m 22.7 a Gaucho 480 ST 0.16 mg/seed 22.7 a Agrox ST 0.75 g/kg seed 22.0 a Thimet 20 G 0.56 g/m 21.7 a Force 3 G 0.37 g/m 21.3 ab Aztec 2.1 G 0.62 g/m 20.3 ab Lorsban 15 G 0.74 g/m 20.3 ab Untreated n/a n/a 14.3 b a G granular, ST seed treatment. b Means followed by the same letter in a column are not significantly different (P < 0.05).

8 82 J. Agric. Urban Entomol. Vol. 21, No. 2 (2004) Table 5. White grub control with planting time and seed treatments, Fairview, Kansas, Treatment Formulation a Rate Plants/ 9.1 m plot b Avg. damage rating c kg/ha b Proshield ST 0.7 g/100 kg 33.7 ab 0.3 de a Force 3 G 0.37 g/m 31.0 ab 1.0 c dc Aztec 2.1 G 0.62 g/m 36.3 a 0.7 dc ab Lorsban 15 G 0.74 g/m 28.7 b 1.7 b a Counter 20 G 0.56 g/m 29.0 b 0.7 dc bc Prescribe ST 1.34 mg/seed 33.0 ab 0.0 e ab Gaucho ST 0.16 mg/seed 29.3 b 0.3 de ab Clothianidin ST 0.25 mg/seed 31.0 ab 0.0 e a Clothianidin ST 1.25 mg/seed 29.3 b 0.0 e ab Clothianidin ST 1.5 mg/seed 31.3 ab 0.0 e abc Fipronil ST 50 g/kg 29.3 b 1.0 c d Fipronil ST 100 g/kg 29.0 b 1.0 c d Cruiser ST 0.78 ml/kg 30.0 b 0.0 e ab Untreated 7.7 c 8.7 a e a G granular, ST seed treatment. b Means followed by the same letter in a column are not significantly different (P < 0.05). c Damage rating scale 0 10, 0 no stunting, 10 all plants stunted. feed on the stem and above-ground portions of the plant, and tefluthrin does not have systemic activity. Effects on chinch bug. All seed treatments in 2001 except tefluthrin (Force) and fipronil significantly reduced chinch bug populations (F 77.6, df 18, P ) (Table 7). Again, as in the experiment with southern corn leaf beetle, tefluthrin (Force) failed to exhibit systemic insecticidal activity. Fipronil did not exhibit insecticidal activity against this sucking insect. In 2002, similar results were obtained in another greenhouse test (Table 7). Clothianidin, imidacloprid (Gaucho, Prescribe), and thiamethoxam (Cruiser) significantly reduced chinch bug numbers at the spike, 1-leaf, and 3-leaf stages, whereas fipronil and tefluthrin did not. Effects on flea beetle. Several seed treatments, including differing rates of clothianidin, imidacloprid (Gaucho, Prescribe), and thiamethoxam (Cruiser), significantly reduced flea beetle damage to seedling plants (F 9.092, df 31, P ) compared to the untreated checks (Table 8). Of the granular and liquid infurrow treatments, only Counter expressed significantly different control from the untreated check. Because this compound has been shown to have some systemic activity, this result is not surprising. Several seed treatments (Agrox DL Plus, Icon, and Force) did not significantly reduce damage and did not seem to affect this foliar-feeding pest.

9 WILDE et al.: Seed treatment for corn insects 83 Table 6. Southern corn leaf beetle control with seed treatments, Manhattan, Kansas, Treatment Formulation a Rate No. alive/plant b Damage rating b Proshield ST 0.7 g/100 kg 1.7 a 2.3 a Prescribe ST 1.34 mg/seed 0.0 b 0.0 b Gaucho ST 0.16 mg/seed 0.0 b 0.0 b Clothianidin ST 0.25 mg/seed 0.0 b 0.0 b Clothianidin ST 1.25 mg/seed 0.0 b 0.0 b Clothianidin ST 1.5 mg/seed 0.0 b 0.0 b Fipronil ST 50 g/kg 0.0 b 0.7 b Fipronil ST 100 g/kg 0.3 b 0.7 b Cruiser ST 0.28 ml/kg 0.0 b 0.0 b Cruiser ST 3.3 ml/kg 0.0 b 0.0 b Untreated 2.0 a 3.0 a a ST seed treatment. b Means with the same letter in a column are not significantly different (P < 0.05). Table 7. Chinch bug control on corn with seed treatments, Manhattan, Kansas, CB/plant, 2001 CB/plant, 2002 Treatment Rate Formulation a 1 Leaf b Spike b 1 Leaf b 3 Leaf b Clothianidin 1.25 mg AI/seed ST 0.0 f 0.0 c 0.3 d 0.3 bc Clothianidin 0.25 mg AI/seed ST 1.3 def 0.0 c 0.0 d 0.3 bc Prescribe 1.34 mg AI/seed ST 0.3 f 0.0 c 0.0 d 0.5 bc Poncho 1.5 mg AI/seed ST 0.0 f 0.0 c 0.0 d 1.0 bc Poncho mg AI/seed ST 0.0 c 0.3 d 0.0 c Cruiser 5 FS 50 g/100 kg seed ST 3.0 cde 0.0 c 2.0 c 3.3 b Cruiser 5 FS 100 g/100 kg seed ST 3.3 cd 0.0 c 0.0 d 1.5 bc Cruiser 5 FS 200 g/100 kg seed ST 1.0 def 0.0 c 0.8 d 0.3 bc Cruiser 5 FS 400 g/100 kg seed ST 0.0 c 0.3 d 0.3 bc Gaucho 600 FS 65 g/100 kg seed ST 1.0 bc 0.5 d 8.0 a Prescribe 600 FS 500 g/100 kg seed ST 0.5 ef 0.0 c 0.0 d 8.5 bc Force ST 2.5 FS 527 g/100 kg seed ST 17.0 b 1.3 b 8.0 b 9.5 a Cruiser 5 FS 50 g/100 kg seed ST 2.3 cdef 0.0 c 0.3 d 2.0 bc Fipronil 50 g/100 kg seed ST 20.0 a 9.8 a 9.3 a 8.8 a Gaucho 50 g/100 kg seed ST 4.3 c 0.0 c 0.8 d 2.3 bc Untreated Check 18.8 ab 9.3 a 9.3 a 9.3 a a ST seed treatment. b Means followed by the same letter in a column are not significantly different (P < 0.05).

10 84 J. Agric. Urban Entomol. Vol. 21, No. 2 (2004) Table 8. Flea beetle control with planting time and seed treatments, Junction City, Kansas, Treatment Formulation a Rate Rate unit Place b rating c,d Damage Clothianidin mg AI/seed ST 0.2 e Clothianidin mg AI/seed ST 0.1 e Prescribe ST 1.34 mg AI/seed ST 0.3 de Aztec 2.1 G 0.62 g/m IF 2.2 ab Counter 20 G 0.56 g/m IF 0.3 cde Lorsban 15 G 0.74 g/m IF 1.9 abc L0263-A1 ST 1.00 mg AI/seed ST 0.2 e L0263-A1 ST mg AI/seed ST 0.3 de Cruiser 600 FS 50 g/100 kg seed ST 0.4 cde Cruiser 600 FS 100 g/100 kg seed ST 0.2 e Cruiser 600 FS 200 g/100 kg seed ST 0.3 de Cruiser 600 FS 400 g/100 kg seed ST 0.1 e Gaucho 600 FS 65 g/100 kg seed ST 0.8 be Prescribe 600 FS g/100 kg seed ST 0.1 e Force ST 300 FS g/100 kg seed ST 2.8 a Force 3 G 0.47 g/m TB 1.8 abcd Warrior 1 EC 17.2 ml/ha IF 1.9 abc Cruiser 600 FS g/100 kg seed ST 0.4 cde ICON g/100 kg seed ST 2.7 a Regent 4 SC ml/m IF 2.5 a Regent 4 SC ml/m IF 1.9 abc Regent 4 SC ml/m IF 2.7 a Gaucho 600 FS g/100 kg seed ST 0.5 cde Capture 2 E g/100 kg seed IF 2.1 ab Leverage 2.7 EC ml/m IF 1.7 abcde Agrox DL-Plus ST 2.2 g/kg ST 1.8 abcde Untreated 2.3 ab Untreated 2.7 a Untreated check 2.2 ab a G granular, ST seed treatment, FS flowable seed treatment, SC soluable concentrate, EC emulsifiable concentrate. b Seed treatment, IF infurrow, TB T band. c Damage rating scale 0 5, 0 no damage, 5 severe feeding damage. d Means followed by the same letter in a column are not significantly different (P < 0.05). Discussion In these seed-treatment tests, imidacloprid at low and high rates (Gaucho, Prescribe, respectively) and thiamethoxam (Cruiser) at low and high rates were effective and exhibited insecticidal activity against chinch bug, flea beetle, wireworm, white grub, and southern corn leaf beetle. Another systemic neonicotinoid, clothianidin, was tested at low and high rates for control of these insects and was also effective at all rates tested. Tefluthrin (Proshield or Force), a pyrethroid, was tested for control of white grub, southern corn leaf beetle, flea beetle, and chinch bug, and was only effective against white grubs because of a lack of systemic

11 WILDE et al.: Seed treatment for corn insects 85 activity and/or insecticidal activity against the latter three pests. Fipronil seed treatment was effective in controlling white grub and southern corn leaf beetle but ineffective against flea beetle and chinch bug. In general, the systemic seed treatments were as effective in controlling soil-inhabiting insects (wireworms and white grubs) as the infurrow granular treatments. In the tests involving imidacloprid and thiamethoxam at four locations in Kansas over 3 years, yield increases were usually associated with noticeable insect activities (either chinch bugs or flea beetles or both). These results are similar to those obtained by Wilde et al. (1999) and Wilde et al. (2001) in a study of seed treatment effects on yield in sorghum and wheat, respectively. These studies also showed that yield responses in sorghum and wheat were usually associated with some insect pest control. Our tests suggest that seed treatments, especially those with systemic activity, show great promise for growers dealing with a variety of soil-inhabiting and early-season foliar-feeding insect pests. Because of the convenience of seed treatments, they will be especially useful in areas where one or more of these early-season pests are chronic problems. These treatments will also be useful on transgenic corn used for corn rootworm control to control these secondary pests that are not affected by the transgenic corn. Acknowledgments This is paper No J, Kansas State University Agricultural Experiment Station. References Cited Archer, T. L Economic injury levels and chemical control of the Russian wheat aphid. pp In Peairs, F., M. Kroening, & C. Simmons (Eds.), Proceedings of the Sixth Russian Wheat Aphid Workshop, Fort Collins, Colorado. Cooperative Extension Service, Colorado State University, Fort Collins, Colorado. Higgins, R. A Insect Management. pp In Corn production handbook. Extension Bulletin C-560. Cooperative Extension Service, Kansas State University, Manhattan, Kansas. Littell, R. C., G. A. Milliken, W. W. Stroup & R. D. Wolfinger SAS system for mixed models. SAS Institute, Inc., Cary, North Carolina. Pike, K. S., G. L. Reed, G. T. Graf & D. Allison Compatibility of imidacloprid with fungicides as a seed-treatment control of Russian wheat aphid (Homoptera: Aphididae) and effect on germination growth, and yield of wheat and barley. J. Econ. Entomol. 86: SAS Institute Stat user s guide ed. SAS Institute, Cary, North Carolina. Sloderbeck, P. E., M. D. Witt & L. L. Buschman Effects of imidacloprid seed treatment on greenbug (Homoptera: Aphididae) infestations on two sorghum hybrids. Southwestern Entomol. 21: Tharp, D., S. L. Blodgett & G. D. Johnson Efficacy of imidacloprid for control of cereal leaf beetle (Coleopotera: Chrysomelidae) in barley. J. Econ. Entomol. 93: Wilde, G Effect of imidacloprid seed treatment and plant time applications of insecticides on chinch bug (Heteroptera: Lygaeidae) and resulting yields of sorghum. J. Agric. Entomol. 14: Wilde, G., K. Roozeboom, M. Claassen, P. Sloderbeck, M. Witts, K. Jansen, T. Harvey, K. Kofoid, L. Broods & R. Shufran Does the systemic insecticide imidacloprid (Gaucho ) have a direct effect on yield of grain sorghum? J. Prod. Agric. 12: Wilde, G. E., R. J. Whitworth, M. Claassen & R. A. Shufran Seed treatment for control of wheat insects and its effect on yield. J. Agric. Urban Entomol. 18: 1 11.