Journal of Plant Diseases and Protection Zeitschrift für Pflanzenkrankheiten und Pflanzenschutz Sonderheft XX,781-786 (2006), ISSN 1861-4051 © Eugen Ulmer KG, Stuttgart

Postemergence herbicide treatments in maize against difficult to control weeds in Hungary M. TORMA1*, G. KAZINCZI2, L. HÓDI3 1 Szeged University, College of Agriculture, 15. Andrassy, H-6800 Hódmezővásárhely, e-mail: [email protected] 2 University Veszprém, Georgikon Faculty of Agricultural Sciences, P.O. Box 71, H-8361 Keszthely, e-mail: [email protected] 3 Plant and Soil Protection Service of Csongrád Country, 110. Rárosi, H-6800 Hódmezővásárhely, e-mail: [email protected] * Corresponding author

Summary In South-East Hungary the weather conditions generally are dry in spring so efficacy of preemergence weed control methods is not sufficient. Experiments were conducted in Hódmezővásárhely, southern part of the Great Hungarian Plain in 2003 and 2004 to study different postemergence weed control methods in small plots in maize. The characteristic weeds on the experimental plots were the Sorghum halepense, Datura stramonium, Chenopodium album, C. hybridum, Amaranthus retroflexus, Stachys annua. The results of the two years were very similar. The efficacy of the herbicide combinations was a bit quicker in 2004. It can be explained by the rainy and hot weather conditions. The nicosulfuron + dicamba + bentazone combined with different adjuvants controlled the S. halepense and dicot weeds with a very good result. Foramsulfuron + isoxadifen-ethyl, foramsulfuron + 2,4 D, foramsulfuron + isoxadifen + iodosulfuron-methyl-Na and rimsulfuron + mesotrione also provided a good herbicide effect. Mesotrione + atrazine killed only the dicot annual weeds excellently so the cover of Johnsongrass was high at the time of harvesting. Significant yield loss of maize was observed caused by the high weed infestation on this plot and on the untreated one. Keywords:

Maize, postemergence weed control, adjuvant, Sorghum halepense, dicot weeds

Zusammenfassung Nachauflaufherbizidbehandlungen gegen Problemunkräuter in Mais in Ungarn Im Frühjahr ist das Wetter in Südost-Ungarn meistens trocken, so dass Vorauflaufbehandlungen nur unzureichend gegen Unkräuter wirken. Aus diesem Grund haben wir in den Jahren 2003 und 2004 in Hódmezővásárhely, in südlichem Teil der Grossen Ungarischen Ebene, die Wirkung verschiedener Nachauflaufbekämpfungsstrategien auf kleinen Parzellen im Mais miteinander verglichen. Die für das Versuchsgebiet charakteristischen Unkrautpflanzen waren Sorghum halepense, Datura stramonium, Chenopodium album, C. hybridum, Amaranthus retroflexus und Stachys annua. Die in den zwei Jahren erhobenen Ergebnisse waren annähernd gleich. Im Jahr 2004 wurde eine schnellere Wirkung der Herbizidkombinationen beobachtet, was durch die feuchte und warme Witterung erklärt werden kann. Die Nicosulfuron + Dicamba + Bentazone Varianten kombiniert mit verschiedenen Adjuvantien haben mit gutem Resultat S. halpense sowie die zweikeimblättrigen Unkrautarten vernichtet. Foramsulfuron + Isoxadifen-ethyl, Foramsulfuron + 2,4 D, Foramsulfuron + Isoxadifen + Iodosulfuron-methyl-Na und Rimsulfuron + Mesotrione haben ebenfalls ausreichende Wirkungen gezeigt. Mesotrione + Atrazine konnte nur einjährige zweikeimblättrige Unkräuter in ausreichender Form bekämpfen, Daher war die Johnsongras-

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bedeckung in der Erntezeit hoch. Wegen der hohen Unkrautverbreitung auf den Versuchs- und den unbehandelten Kontrollparzellen haben wir einen signifikanten Ertragsrückgang beim Mais festgestellt. Stichwörter: Mais, Nachauflaufbehandlung, Adjuvant, Sorghum halepense, zweikeimblättrige Unkrautarten

Introduction The growing area of maize is about 1 200 000 ha in Hungary. Weeds are among the most important factor in maize production. They cause yield losses of 30-40 % in the case of no weed control (RAHMAN 1985, DOGAN et al. 2004). The weed flora is very diverse in Hungary. Sorghum halepense is one of the worst perennial weeds in maize field. It can be found all around the world and regarded as a serious problem in 53 countries (HOLM et al. 1977). The presence of S. halepense constitutes a major problem in most of the maize growing area of the USA, Argentina, the Mediterranean countries and Eastern Europe (MAURER et al. 1987). Based on the data of the 4th National Weed Survey S. halepense is on the 9th place in Hungary. The characteristic annual weeds of maize fields which cause most of the problem in Hungary are Echinochloa crus-galli, Amaranthus retroflexus, Ambrosia artemisiifolia, Chenopodium album, Datura stramonium, Amaranthus chlorostachys (TÓTH and SPILÁK 1998). The performance of preemergence herbicides is affected by many factors, but rainfall and soil moisture during the early part of the growing season have the greatest impact on weed control efficacy. Preemergence herbicides decline in effectiveness as soils dry due to increased adsorption on soil colloids. Most preemergence herbicides require 10-20 mm of precipitation within two weeks after application to increase their effectiveness (KÁDÁR 2001). In the Great Hungarian Plane the weather conditions generally are dry in spring so preemergence herbicide applications do not provide good effects against weeds. This is one of the reasons why maize fields treated only by postemergent herbicides increase year by year (REISINGER 2000). The aim of this study is to compare the efficacy of different postemergence herbicide treatments in maize.

Materials and methods In 2003 and 2004 experiments were carried out using a plot size of 20 m2 and 3 replications in Hódmezővásárhely, southern part of the Great Hungarian Plain Spraying was performed with a Fox Rotory sprayer fitted with TeeJet 100 02 nozzles at 2 bars and a spray volume of 400 l/ha. The herbicides were applied 4 weeks after sowing when maize had 5-6 leaves. The weeds of the experimental plots can be found in Table 1. Tab. 1: Characteristic weeds of experimental plots. Tab. 1: Charakteristische Unkrautpflanzen der Versuchsflächen.

Name of weeds Sorghum halepense Datura stramonium Chenopodium album Chenopodium hybridum Amaranthus retroflexus Stachys annua Total weed cover

Weed cover % 2003 2004 at treatments at harvest at treatments at harvest 10 30 8 17 8 30 8 20 2 5 10 20 2 5 2 5 10 20 3 5 2 4 25 75 40 85

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783

The dicot weeds had 4-8 leaves and S. halepense was 25-30 cm high at the time of the treatments. In 2003 the temperature at the time of spraying was 25 °C, the precipitation within the first 2 weeks after spraying was 6,5 mm and in 2004 the temperature was 24 °C, and 39 mm precipitation was measured. Meteorological data during the period of experiment can be seen in Table 2. Efficacy of weed control was expressed in percentage, as compared to the untreated control plots 1 and 5 week after treatment, and right before harvesting. The assessment of crop phytotoxicity was carried out as a description of the symptoms at same date of weed control efficiency test. At harvest the yield was recorded. Data were analysed statistically by an analysis of variance. Tab. 2: Weather conditions during the experimental period. Tab. 2: Witterungsbedingungen während der Versuchsperiode.

Months May June July August

Decad 1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2.

Precipitation mm 2003 0 17.9 6.5 0 1.5 6.0 16.0 5.5 19.3 0 11.0

2004 0 9.5 7.2 28.1 38.8 0 15.5 0 121.1 0 4.2

Average temperature °C 2003 2004 21.6 15.6 19.2 15.0 21.7 16.1 24.4 19.1 24.0 20.9 22.6 20.7 22.4 22.9 21.7 21.7 24.2 20.2 25.1 22.3 25.3 22.9

Results The efficacy of the herbicide combinations and yield data are given in Table 3. The results of the two years (2003 = 03 and 2004 = 04) were very similar. The effect of the herbicide combinations against S. halepense and S. annua was a bit quicker in the second year. Nicosulfuron combined with different herbicide active ingredients and adjuvants controlled Johnsongrass (S. halepense) and dicot weeds with a very good result. Foramszulfuron also provided a good herbicide effect against the characteristic weeds of the experimental area. But in 2004 when the development stage of C. album was different those weeds which had 8 or more leaves did not die. The efficacy of foramsulfuron+isoxadifen-ethyl + iodosulfuronmethyl-Na+ester of rapeseed oil and rimsulfuron + mesotrione + etoxylated izodecil-alcohol was good. Mesotrione + atrazine + etoxylated oktilfenol killed the dicot annual weeds excellently. After spraying the development of S. halepense stopped and light lilac-white colour appeared on its leaves but no death of the weed was noticed. At the time of the harvesting the rate of the weed-cover was very high in the plots. In 2003 none of the treatments damaged the maize, but in 2004 the combinations of rimsulfuron + mesotrione + etoxylated izodecil-alcohol and foramszulfuron + isoxadifen-ethyl + iodosulfuron-methylNa + ester of rapeseed oil caused small brown spots on the leaves of the maize. The plants recovered the injury, no loss of yield was measured. The yield in the percentage of the hoeing control is shown in Figure 1. No negative herbicide side effect on the yield was measured. The high weed infestation in the untreated plot decreased the yield to 46 % and the yield losses was 30 % on the plot treated by mesotrione + atrazine + etoxylated oktilfenol due to S. halepense. On the base of the analysis of variance significant yield losses of maize was mesaured on these two parcels.

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Tab. 3: The effect of different postemergent treatments in maize. Tab. 3: Die Wirkung der Nachauflaufbehandlungen im Mais. T.

Rate

Treatments

g a.i.ha

1. nicosulfuron+dicamba+ bentazon+ ethoxylated tallow amine 2. nicosulfuron+dicamba+ bentazon+ methyloleat+methylpalmitat 3. nicosulfuron+tritosulfuron+ dicamba+ methyloleat+methylpalmitat 4. nicosulfuron+mesotrione+ etoxylated oktilfenol

-1

40+180+ 640+ 820 40+180+ 640+ 92.5+92.5 40+50+ 240+ 92.5+92.5 40+144+ 400

1. 2. 3. 1. 2. 3. 1. 2. 3. 1. 2. 3. 5. nicosulfuron+mesotrione+ 20+144+ 1. atrazine+ 500+ 2. etoxilated oktilfenol 400 3. 6. nicosulfuron+florasulam+ 40+3.75+ 1. 2,4-D ester 271.2 2. 3. 7. foramsulfuron+isoxadifen45+45+ 1. ethyl+jodosulfuron-methyl-Na+ 1.5+2000 2. ester of rapeseed oil 3. 8. foramsulfuron+ 45+ 1. isoxadifen-ethyl 45 2. 3. 9. rimsulfuron+mesotrione+ 7.5+144+ 1. etoxylated izodecil-alcohol 360 2. 3. 10. mesotrione+atrazine+ 144+500+ 1. etoxylated oktilfenol 400 2. 3. 11. hoeing control 12. untreated control

SORHA 03 04 50 80 90 95 95 93 50 80 95 95 95 93 50 80 80 98 90 95 40 80 95 95 95 95 40 80 100 100 100 100 80 98 95 75 85 95 95 90 93 80 80 95 98 95 95 60 80 85 95 85 90 0 20 0 30 0 25

DATST 03 04 100 100 100 100 100 100 100 100 100 100 98 100 90 98 100 100 100 100 95 98 100 100 100 100 100 100 100 100 100 100 98 - 100 - 100 70 90 95 95 95 90 70 85 100 98 100 95 95 100 100 100 100 100 100 100 100 100 100 100

Herbicide effect % CHEAL CHEHY AMARE STAAN 03 04 03 04 03 04 03 04 100 100 100 100 - 100 50 100 100 100 100 100 - 100 100 100 100 98 100 98 98 98 100 100 100 100 100 - 100 50 90 100 98 100 100 - 100 98 98 100 95 100 98 98 95 98 100 98 100 98 98 60 95 100 98 100 100 - 100 95 100 100 95 100 98 98 95 100 95 95 95 95 95 45 85 100 100 100 100 - 100 95 100 100 100 100 100 - 100 95 100 100 100 100 100 - 100 95 100 100 100 100 100 - 100 100 100 100 100 100 100 - 100 100 100 95 98 98 95 98 - 100 - 100 98 93 98 95 95 90 75 95 95 75 90 95 98 98 - 100 98 100 90 98 90 - 100 98 100 60 75 90 90 90 70 90 95 80 95 95 95 98 95 95 70 95 90 95 98 95 95 100 100 100 - 100 98 100 100 100 100 100 - 100 100 100 100 100 100 100 - 100 100 100 - 100 100 100 - 100 98 100 - 100 100 100 - 100 100 100 - 100 100 100 - 100 100 100

Yield kg (10m2)-1

2004 12.05 11.90 12.00 12.04 11.63 11.62 11.60 11.85 11.65

8.54 12.26 5.68

SD5% = 1,13; T = time of evaluation: 1. one week after treatments, 2. five weeks after treatments, 3. before harvest

120 yield kg (10m 2) -1

100 80 60 40 20 0 1

2

3

4

5

6

7

8

Tab. 2) 3) treatments (in Tab.

Fig. 1: Relative yield in relation to the hoeing control. Abb. 1: Relative Erträge in Beziehung zur gehackten Variante.

9

10

11

12

Post-emergence herbicide treatments in maize

785

Discussion The objective of weed management is to reduce weed density to an economic threshold level. The economic weed threshold is the point at which weed control action pay for themselves in term of the amount of crop saved. In the countries of EC it is a tendency to reduce herbicide use in weed management (LOTZ et al. 2002). One possibility for it is to use site-specific herbicide application based on weed map. Reductions in herbicide use achieved depend on the level of weeds in field, but can be as high as 40 % to 50 % (GERHARDS et al. 1997, 2000). In an evaluation of site-specific postemergence weed control of broadleaf and grass weeds in maize, WILLIAMS et al. (2000) showed a 51 % reduction in rimsulfuron and 11.5 % reduction in bromoxynil plus therbuthylazine use, compared with conventional herbicide spraying. In the conventional weed control in order to reduce the herbicide applications we have to apply herbicides once (preemergence or postemergence) in a vegetation period. The choosing of weed control technology depends on the weed infestation and the weather conditions in spring. Preemergent herbicides have no effect against S. halepense developing by rhizome. Nicosulfuron and rimsulfuron can be used selectively in maize for control of S. halepense (ELEFTHEROHORINOS and KOTOULA-SYKA 1995). In our experiments mixture of nicosulfuron with different dicot killer herbicide active ingredients provide an excellent weed control effect against S. halepense and dicot weeds without using preemergent herbicides. Adjuvants enhance the effectiveness of herbicide however, they often increase the potential for crop injury. In our weed infestation condition adjuvants (Frigate, Dash, Extravon) improve the efficiency of nicosulfuron in the same level, while in an experiment Dash showed a better result against Abuthilon teophrasti than other adjuvants (KOVÁCS 2004). Broad spectrum of weeds can be controlled by application of combination contained foramszulfuron. Atrazine and mezotrione having a seasonlong residual effect delay the emergence of annual dicot weeds. Mesotrione can be applied without causing phytotoxicity in crops following maize in the rotation (TORMA et al. 2004). In 2004 the penetration of the herbicides into the leaves (and rhizomes) of the weeds was a bit quicker because of the rainy and hot weather conditions after spraying. On the base of our results nicosulfuron, rimsulfuron and foramsulfuron combined one of the dicot killer herbicides can be recommended for postemergence weed control in maize fields infested with S. halepense and broadleaf weeds. Growers can make their decision which technology to choose on the base of the cost of the herbicide- combinations.

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REISINGER, P.: Kukorica (Zea mays L.) In: Hunyadi et al., (eds.): Gyomnövények, gyomirtás, gyombiológia, Mezőgazda kiadó, Budapest, 494-503, 2000. TORMA, M., B. RADVÁNY, L. HÓDI: Effect of mesotrione residues on following crops. Zeitschrift für Planzenkrankheiten und Pflanzenschutz, Sonderheft, XIX., 801-805, 2004. TÓTH, Á., K. SPILÁK: A IV. Orzságos Gyomfelvételezés tapasztalatai. Növényvédelmi Fórum, Keszthely, Abstracts, 49, 1998. RAHMAN, A.: Weed control in maize in New Zealand. In: Maize~ management to Market. Eagles, H.A. Wratt, G.S. (eds). Agronomy Society of New Zealand-Special Publication 4, 37-45, 1985. WILLIAMS, M.M., R. GERHARDS, D.A. MORTENSEN: Two-year weed seedling population responses to a post-emergent method of site-specific weed management. Precision Agriculture 2, 247-63, 2000.