A field study was conducted at two locations in Kansas, USA in 2011 and 2012 to test weed control efficacy and crop response to preemergence-applied pyroxasulfone alone and in combination with sulfentrazone in sunflower. Treatments included three rates of pyroxasulfone (100, 200 and 400 g ·ha -1) applied alone and tank-mixed with sulfentrazone at 70, 140 and 280 g ·ha -1. Commercial standards sulfentrazone at 140 g ·ha -1 + pendimethalin at 1390 g ·ha -1 and sulfentrazone at 140 g ·ha -1 + S-metolachlor at 1280 g ·ha -1 were also included. Pyroxasulfone at 100 g ·ha -1 controlled Palmer amaranth 87% at 3 weeks after application (WAA), but control decreased to 76% at 6 WAA. Increasing pyroxasulfone rate to ≥200 g ·ha -1 or tank mixing with sulfentazone at 140 g ·ha -1 provided ≥90% Palmer amaranth control for at least 6 WAA. Sulfentrazone alone at 70 g ·ha -1 controlled Palmer amaranth 77% at 3 WAA, but control dropped to 69% at 6 WAA. Increasing sulfentrazone rate from 70 to 140 or 280 g ·ha -1 increased control to >90% at 3 WAA, but did not maintain acceptable control at 6 WAA. Tank mixing sulfentrazone at 140 g ·ha -1 with pendimethalin at 1390 g ·ha -1 or S-metolachlor at 1280 g ·ha -1 controlled Palmer amaranth ≥90 and 84% at 3 WAA and 6 WAA, respectively. The lowest rate of pyroxasulfone (100 g ·ha -1) controlled kochia 98% and the control was complete with all other treatments. However, no treatment provided as much as 90% puncturevine control at 3 WAA and the control was commercially unacceptable (<75%) at 6 WAA. No treatment visibly injured sunflower anytime during the season or reduced sunflower plant population.
In the United States, sunflower (Helianthus annuus L.) is cultivated in the Great Plains Region for cooking oil, confectionary uses, and birdseed. In 2014, confection and oil-seed sunflower were planted on 0.63 million ha [
Weeds can cause significant sunflower yield loss. Yield loss as much as 60% has been reported when a weed population consisting of large crabgrass Digitaria sanguinalis L. Scop.), goosegrass (Eleusine indica L. Gaertn.), sicklepod (Cassia obtusifolia L.), tall morningglory (Ipomea purpturea L. Roth), ivy leaf morningglory (I. hederacea L. Jacq.), and redroot pigweed competed with sunflowers for 8 weeks after planting [
Pyroxasulfone (3-[[5-(difluoromethoxy)-1-methyl-3-(trifluoromethyl)pyrazol-4-yl]methylsulfonyl]-5,5-dimethyl-
4H-1,2-oxazole) is a relatively new herbicide in the pyrazole herbicide family. It has preemergence activity and inhibits shoot elongation of susceptible seedling plants by inhibiting the biosynthesis of very-long-chain fatty acids [
Pyroxasulfone is currently labeled in the United States for use in corn, soybean and wheat (Zidua®, BASF Corporation, 26 Davis Dr, Research Triangle Park, NC 27709, USA). The maximum labeled use rate of pyroxasulfone for corn, soybean and wheat are 235, 206 and 118 g∙ha−1, respectively. Several research reports have indicated effective annual grass and broadleaf weed control with pyroxasulfone. In non-irrigated corn in Kansas, pyroxasulfone at 250 g∙ha−1 controlled green foxtail and Palmer amaranth 86 - 100% and 87 - 99%, respectively [
Pyroxasulfone currently is not registered for use in sunflower. However, multiple coordinated field experiments from North Dakota to Kansas over a three-year period indicated preemergence (PRE)-applied pyroxasulfone controlled many annual grass and broadleaf weeds as well or better at rates three to eight-times lower than herbicides currently registered for use in sunflower with only occasional incidences of minor injury that did not reduce seed yield [
Field experiments were conducted during the 2011 and 2012 growing seasons near Hays (38.85N, 99.34W) and Colby (39.39N, 101.06W) in Kansas, USA. The Hays experimental site was rainfed and the Colby experimental site received supplemental irrigation periodically as needed to avoid moisture stress. Soil characteristics are shown in
The predominate weed species was Palmer amaranth at both locations in 2011 and 2012. Kochia was present only at Colby in 2011 and puncturevine was present at both locations in 2012. Weed control was rated visually on a scale of 0 (no effect) to 100 (complete control). Weed control ratings were determined 3 and 6 weeks after treatment across sites and years. Crop response also was rated visually at 3 weeks after treatment on a scale of 0 to 100. Unfortunately, seed yields were not determined because of late-season hail and/or substantial bird and wildlife damage (plants unrooted).
Data were analyzed using the general linear model procedure of the Statistical Analysis System (Statistical Analysis Systems Institute, Cary, NC, USA) and means were separated at the 5% significance level using Fisher’s protected LSD. Percent weed control data were arcsine transformed before analysis, but original values are
Hays, KS | Colby, KS | |||
---|---|---|---|---|
2011 | 2012 | 2011 | 2012 | |
Geographic location | West-central Kansas | Northwest Kansas | ||
Soil type | Roxbury silt loam | Crete silty clay loam | Keith silt loam | Keith silt loam |
Soil pH | 7.8 | 6.1 | 7.2 | 7.2 |
Organic matter (%) | 2.0 | 1.8 | 2.0 | 2.0 |
Sunflower hybrid | Mycogen 8N358CLDM | Mycogen 8N421CLDM | Mycogen 8N358CLDM | Mycogen 8N358CLDM |
Seed rate (Seeds∙ha−1) | 49,000 | 49,000 | 57,575 | 57,575 |
Planting date | 6/17/2011 | 6/11/2012 | 6/14/2011 | 6/06/2012 |
Herbicide application date | 6/20/2011 | 6/12/2012 | 6/15/2011 | 6/06/2012 |
presented in this paper. The control treatment was omitted from weed control analyses. Data were pooled over years and sites when there was no year-by-site-by-treatment interaction.
Monthly mean temperature and total rainfall data at experimental sites during 2011 and 2012 are presented in
Across sites and years, Palmer amaranth control with PRE-applied pyroxasulfone alone or in combination with sulfentrazone ranged from 87 to 99% at 3 weeks after application (WAA) and 76 to 98% at 6 WAA (
Herbicide | Rate | Palmer amaranth | Puncturevine | ||
---|---|---|---|---|---|
Pooled | Colby, 2012 | ||||
3 WAA | 6 WAA | 3 WAA | 6 WAA | ||
g∙ha−1 | -----------------------------------------------%----------------------------------------------- | ||||
Pyroxasulfone | 100 | 87 c | 76 gf | 80 a | 64 ab |
200 | 94 abc | 91 abcd | 75 a | 60 abc | |
400 | 97 ab | 97 ab | 70 abc | 54 abcde | |
Sulfentrazone | 70 | 77 d | 69 g | 45 de | 33 cdef |
140 | 92 abc | 78 efg | 40 e | 15 f | |
280 | 93 abc | 83 def | 68 abcd | 45 bcde | |
Pyroxasulfone + Sulfentrazone | 100 + 70 | 91 abc | 86 bcdef | 73 ab | 57 abcd |
100 + 140 | 95 abc | 93 abcd | 70 abc | 50 abcde | |
100 + 280 | 97 ab | 93 abcd | 67 abcd | 50 abcde | |
200 + 70 | 95 abc | 89 abcde | 80 a | 59 abc | |
200 + 140 | 97 ab | 94 abcd | 86 a | 63 ab | |
200 + 280 | 97 ab | 95 abc | 83 a | 66 ab | |
400 + 70 | 97 ab | 97 ab | 80 a | 64 ab | |
400 + 140 | 97 ab | 95 abc | 88 a | 74 a | |
400 + 280 | 99 a | 98 a | 85 a | 70 ab | |
Sulfentrazone + Pendimethalin | 140 + 1390 | 90 bc | 84 cdef | 50 bcde | 28 ef |
Sulfentrazone + S-metolachlor | 140 + 1280 | 91 abc | 84 cdef | 48 cde | 30 ef |
aData were arcsine transformed before analysis, but original values are presented in the table; bMeans followed by the same letter do not differ significantly according to LSD at 5%.
at 280 g∙ha−1 increased Palmer amaranth control to 97% compared to 87% for the same rate of pyroxasulfone alone; however, it was similar to the same rate of sulfentrazone alone (93%). Mixing higher rates of pyroxasulfone (200 and 400 g∙ha−1) with any rate of sulfentrazone did not improve Palmer amaranth control. In a multi-location study conducted in Kansas, North Dakota and South Dakota, increased Palmer amaranth control by combining pyroxasulfone and sulfentrazone at the lowest rates tested (167 + 105 g∙ha−1) compared to the same rate of pyroxasulfone alone was also reported previously [
At 3 WAA, sulfentrazone alone at 70 g∙ha−1 provided the least Palmer amaranth control (77%) of all the treatments tested (
As the season progressed, Palmer amaranth control decreased in sunflower plots treated with lowest rate of pyroxasulfone (
At Colby in 2012, no treatment provided >88% puncturevine control at 3 WAA (
At 6 WAA, puncturevine control decreased considerably with all treatments compared to 3 WAA. No treatment provided ≥75% control (
At Colby, PRE-applied pyroxasulfone at 100 g∙ha−1 controlled kochia 98% and 200 and 400 g∙ha−1 rates provided 100% control at 3 WAA (
g∙ha−1 | Sulfentrazone | ||||
---|---|---|---|---|---|
------------------------------------------------g∙ha−1----------------------------------------------- | |||||
0 | 70 | 140 | 280 | ||
--------------------------------------------------%-------------------------------------------------- | |||||
Pyroxasulfone | 0 | - | 99 b | 100 a | 100 a |
100 | 98 b | 100 a | 100 a | 100 a | |
200 | 100 a | 100 a | 100 a | 100 a | |
400 | 100 a | 100 a | 100 a | 100 a | |
Pendimethalin | 1390 | - | - | 100 a | - |
S-metolachlor | 1280 | - | - | 100 a | - |
aData were arcsine transformed before analysis, but original values are presented in the table; bMeans followed by the same letter do not differ significantly according to LSD at 5%.
complete control at higher rates. Combinations of sulfentrazone at 140 g∙ha−1 plus S-metolachlor at 1280 g∙ha−1 or pendimethalin at 1390 g∙ha−1 also provided complete control of kochia at 3 WAA. There was little or no change in kochia control for any treatment from 3 to 6 WAA (data not shown).
No treatment visibly injured sunflower anytime during the season or reduced plant population in any site-year (data not shown). This is consistent with previous reports of excellent tolerance of sunflower to pyroxasulfone over a wide range of soils and environments [
Results from this study support previous findings and indicate pyroxasulfone has potential to be a valuable preemergence herbicide in sunflower. Combinations of pyroxasulfone at 100 g∙ha−1 and sulfentrazone at 140 g∙ha−1 or pyroxasulfone alone at 200 g∙ha−1 provided similar or greater broadleaf weed control with no crop injury compared to commercial standards sulfentrazone at 140 g∙ha−1 plus S-metolachlor at 1280 g∙ha−1 or pendimethalin at 1390 g∙ha−1. Additional studies are needed on additional weed species over wide range of soils and environmental conditions.
The authors thank BASF Corporation for their financial support of this project. Contribution number 16-142-J from the Kansas Agricultural Experiment Station.
SeshadriS. Reddy,Phillip W.Stahlman,Patrick W.Geier, (2015) Broadleaf Weed Control in Sunflower (Helianthus annuus) with Preemergence-Applied Pyroxasulfone with and without Sulfentrazone. Agricultural Sciences,06,1309-1316. doi: 10.4236/as.2015.611125