Annual Grasses Control With Topramezone in Mixture With Als-Inhibiting Herbicides

Abstract

Panicoid grasses are major weeds of maize and sugarcane as well as of several other important grains, including sorghum, pearl millet, and foxtail millet. Pot trials were conducted to study the activity and potential interactions of topramezone in mixture with recommended rates of rimsulfuron or nicosulfuron on three annual panicoid grasses (i.e. Echinochloa oryzoides,E.phyllopogon, and Panicum miliaceum). Target weeds were treated at the four- to five-leaf growth stage. On the basis of fresh weight reduction, topramezone alone provided 78% control of E.oryzoides, 68% control of E.phyllopogon, and 99% control of P.miliaceum. Topramezone plus rimsulfuron or nicosulfuron provided decreased control of both Echinochloa spp. compared with topramezone alone. The decreased control of E.oryzoidesand E.phyllopogon was more pronounced with rimsulfuron as a companion herbicide in the mixtures. Slightly decreased control of P.milaceum was observed with topramezone plus rimsulfuron compared with topramezone alone, but this was not the case for topramezone plus nicosulfuron. Increased topramezone rates mixed with rimsulfuron or nicosulfuron did not improve control of E.oryzoides and E.phyllopogon compared with the lowest topramezone rate. Also, increased topramezone rates mixed with rimsulfuron or nicosulfuron showed decreased control of both Echinochloa spp. when compared with either rimsulfuron or nicosulfuron alone, suggesting a two-way interaction between topramezone and the ALS-inhibiting herbicides. The above-mentioned interaction was not observed in P.miliaceum, probably related with species sensitivity to the herbicides tested. Newly introduced or naturalized panicoid grasses in maize fields may complicate selection of companion herbicides and rates for effective weed control.

New Insights into the Interactions between Herbicides: Trends from Recent Studies

“…49 Similar outcomes have been observed in various studies. 46,53,54 This observation is in accordance with the finding of Zhang et al(1995). 22 On the other hand, several mixtures resulted in synergistic interactions in dicots.…”

“…For example, when applied on Echinochloa crus-gall , mixtures of fenoxaprop and bensulfuron, carfentrazone, halosulfuron, triclopyr, or bentazon have resulted in additivity, the most dominant interaction in monocots, and antagonistic interaction . Similar outcomes have been observed in various studies. ,, This observation is in accordance with the finding of Zhang et al(1995) . On the other hand, several mixtures resulted in synergistic interactions in dicots. ,, However, unwanted interactions were observed in dicots.…”

“…This tendency has been previously reported by Zhang et al (1995) . Except for some rare data, several studies have supported the previous trend. ,− Besides the occurrence of an additive, the significant decrease in the frequency of synergistic interactions observed in perennial weeds may be presumably due to a reduced movement of herbicides. Indeed, if the herbicide has moved weakly, top growth is removed whereas roots are unaffected, therefore limiting the control of perennial weeds…”

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“…In addition to this non-chemical strategy of crop rotation, for johnsongrass control, ALS inhibiting herbicides such as rimsulfuron at 10 g ha -1 have been found very effective (Damalas and Eleftherohorinos, 2001). However, contrary to HPPD herbicides and atrazine synergistic combination responses, many researchers (Damalas and Eleftherohorinos, 2001;Kaastra et al 2008;Damalas et al 2015) have reported two way antagonistic interactions between HPPD and ALS inhibiting herbicides, which are weed species specific. While, Schuster et al (2008) showed the decreased efficacy of sulfonylurea herbicides (nicosulfuron and foramsulfuron) on Harlan} with the addition of mesotrione to sulfonylurea herbicides.…”

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“…These factors make it difficult to predict herbicide persistence. Agro-chemical companies sometimes make combinations of herbicides, especially the selective ones so that they more effectively deal with a wide range of weed problems faced by farmers (Damalas et al, 2015). Stellar Star, active ingredients Topramezone (pyrazolone) and Dicamba (benzoic acid compound) is one such herbicide which is recommended for weed control under smallholder farming conditions.…”