<b>HRAC Group 2</b> <font size='2'> (Legacy B) </font> resistant Ageratum conyzoides from Brazil

INTERNATIONAL HERBICIDE-RESISTANT WEED DATABASE

HRAC GROUP 2 (LEGACY B) RESISTANT TROPICAL WHITEWEED
(Ageratum conyzoides)

Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)

Brazil, Matto Grosso

INTRODUCTION		TROPICAL WHITEWEED
Tropical Whiteweed (Ageratum conyzoides) is a dicot weed in the Asteraceae family. In Brazil this weed first evolved resistance to Group 2 (Legacy B) herbicides in 2013 and infests Cotton, and Soybean. Group 2 (Legacy B) herbicides are known as Inhibition of Acetolactate Synthase (Inhibition of Acetolactate Synthase ). Research has shown that these particular biotypes are resistant to pyrithiobac-sodium, and trifloxysulfuron-Na and they may be cross-resistant to other Group 2 (Legacy B) herbicides. The 'Group' letters/numbers that you see throughout this web site refer to the classification of herbicides by their site of action. To see a full list of herbicides and HRAC herbicide classifications click here.

QUIK STATS (last updated Jan 12, 2015 )
Common Name	Tropical Whiteweed
Species	Ageratum conyzoides
Group	Inhibition of Acetolactate Synthase HRAC Group 2 (Legacy B)
Herbicides	pyrithiobac-sodium, and trifloxysulfuron-Na
Location	Brazil, Matto Grosso
Year	2013
Situation(s)	Cotton, and Soybean
Contributors - (Alphabetically)	Edson Andrade Junior, Sebastião Carneiro Guimarães, and Anderson Luis Cavenaghi
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ACADEMIC ASPECTS

Confirmation Tests

Greenhouse trials comparing a known susceptible Tropical Whiteweed biotype with this Tropical Whiteweed biotype have been used to confirm resistance. For further information on the tests conducted please contact the local weed scientists that provided this information.

Genetics

Genetic studies on HRAC Group 2 resistant Tropical Whiteweed have not been reported to the site. There may be a note below or an article discussing the genetics of this biotype in the Fact Sheets and Other Literature

Mechanism of Resistance

The mechanism of resistance for this biotype is either unknown or has not been entered in the database. If you know anything about the mechanism of resistance for this biotype then please update the database.

Relative Fitness

There is no record of differences in fitness or competitiveness of these resistant biotypes when compared to that of normal susceptible biotypes. If you have any information pertaining to the fitness of Group 2 (Legacy B) resistant Tropical Whiteweed from Brazil please update the database.

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CONTRIBUTING WEED SCIENTISTS

EDSON ANDRADE JUNIOR

Research Instituto Mato-Grossense do Algodão Crop Protection Highway BR 070 KM 265 post office box 149 Primavera do Leste, 78850000, Mato Grosso Brazil Email Edson Andrade Junior Web : Web Site Link

SEBASTIÃO CARNEIRO GUIMARÃES

Associate Professor Universidade Federal de Mato Grosso Faculdade de Agronomia Av. Fernando Correa da Costa 2367 Bairro Boa Esperança Cuiabá, 78850000, Mato Grosso Brazil Email Sebastião Carneiro Guimarães Web : Web Site Link

ANDERSON LUIS CAVENAGHI

Associate Professor UNIVAG – Centro Universitário de Várzea Grande GPA CABE AGRONOMIA Av. Dom Orlando Chaves 2.655, Bairro Cristo Rei Várzea Grande, 78850000, Matto Grosso Brazil Email Anderson Luis Cavenaghi Web : Web Site Link

ACKNOWLEDGEMENTS
The Herbicide Resistance Action Committee, The Weed Science Society of America, and weed scientists in Brazil have been instrumental in providing you this information. Particular thanks is given to Edson Andrade Junior, Sebastião Carneiro Guimarães, and Anderson Luis Cavenaghi for providing detailed information.

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Herbicide Resistant Tropical Whiteweed Globally
(Ageratum conyzoides)

Country

FirstYear

Situation

Active Ingredients

Site of Action

Brazil

2013

Cotton, and Soybean

pyrithiobac-sodium, and trifloxysulfuron-Na

Inhibition of Acetolactate Synthase ( HRAC Group 2 (Legacy B)

Literature about Similar Cases

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Yew NgKwang. 2011. Chemical control of herbicide-resistant Eleusine indica in an oil palm nursery. Planter 87 : 739 - 744.

Eleusine indica has been reported to have become a dominant weed in oil palm nurseries after repeated chemical usage, especially of the same chemicals. This weed species is reported to be resistant to a number of herbicides including glyphosate. The main strategy to prevent or avoid herbicide resistance has been to apply combinations of herbicides in mixtures or in sequence. A field trial was conducted in an oil palm nursery to determine the effectiveness of clethodim, a new grass herbicide, in combination with glyphosate against E. indica that had been reported to be resistant to glyphosate. A total of ten treatment combinations were evaluated. Clethodim 26 per cent w/w EC at 0.9 litre product per hectare and 1.125 litres product per hectare with or without added adjuvant were found to be effective in controlling E. indica up to four weeks after spraying. However, weed succession by species of sedges and broadleaved weeds (Cyperus digitatus, Borreria latifolia, Ageratum conyzoides, Phyllanthus amarus and Cleome rudidosperma) occurred within the sprayed areas as early as three weeks after spraying; where glyphosate IPA 41.0 per cent w/w SL alone at 2.0 litres product per hectare was ineffective, indicating weed resistance. The lower rate of glyphosate IPA 41.0 per cent w/w SL+clethodim 26 per cent w/w EC at 2 litres+0.54 litre product per hectare only provided 85 per cent control, and is followed with regeneration of the E. indica at three weeks after spraying. However, there was no succession by other weeds in this glyphosate IPA+clethodim mixture. The treatment with glyphosate IPA 41.0 per cent w/w SL+clethodim 26 per cent w/w EC at 2 litres+0.9 litre product per hectare was most effective and gave excellent control of E. indica and at the same time there was no weed re-growth or succession up to four weeks after application. The responses observed in all glyphosate IPA+clethodim combinations suggest synergistic activity in mixture..

Adegas, F. S. ; Oliveira, M. F. ; Brighenti, A. M. ; Prete, C. E. C. ; Vieira, O. V.. 2007. Management of weeds on the sunflower crop resistant to herbicides of the imidazolinone group. Documentos - Embrapa Soja : 179 - 182.

Pot experiments were conducted to evaluate the selectivity of sunflower genotypes, which were tolerant, to imidazolinone herbicides. The genotype resistant result of the crossing among CMS 425 × RHA 427 was then used. The herbicides were chlorimuron, cloransulam, diclosulam, foramsulfuron + iodosulfuron, imazamox, imazapic, imazapic + imazapyr, imazapyr, imazaquin, imazethapyr, metsulfuron, nicosulfuron and oxasulfuron and used in the dosages commercially recommended by the manufacturer (1X), half the dosage (1/2X) and twice the dosage (2X), complemented with a control for each treatment. Through visual evaluation and by the sunflower dry matter weight, it was observed that the herbicides imazamox and imazethapyr were the most selective, followed by imazaquin, imazapyr and imazapic + imazapyr. The remaining herbicides such as chlorimuron, cloransulam, diclosulan, foramsulfuron + iodosulfuron and imazapic caused severe injuries in all dosages used or starting with the 1X dosage such as metsulfuron, nicosulfuron and oxasulfuron. Subsequently, 2 field experiments were conducted in Brazil, in the 2003 spring/summer season, and another during the 2004 autumn/winter season. The herbicides used were imazethapyr, imazamox, imazapyr, imazapic and imazapic + imazapyr. All the herbicides were applied in post-emergence at the 1X dosage and using no weeding, hand weeding and one single application of graminicide as control plots. The selectivity to the same sunflower genotype and the control of dicotyledonous weeds were evaluated. Except for imazapic, the herbicides had acceptable selectivity for the crop. All the herbicides used were efficient in controlling Euphorbia heterophylla and Ageratum conyzoides. The best control of Bidens sp. and Sida rhombifolia was obtained by the use of imazapyr and imazapic + imazapyr. Imazapic alone, however, promoted the lowest control for these 2 weed species. The analysis of the weed total dry weight did not show statistically significant differences among the herbicides. The competition of the dicotyledonous weeds with the crop and the moderate to high phytotoxicity of imazapic resulted in reductions of plant height, diameter of the flower head, weight of 1000 achenes and sunflower yield..

Evbuomwan, F. O. ; Akinyemiju, O. A.. 1995. Tolerance of Echinochloa colona (L.) Link and Cyperus rotundus L. to propanil. Plant Protection Quarterly 10 : 32 - 34.

The morphological and physiological bases of the response of Ageratum conyzoides, Oryza sativa [rice], Echinochloa colona [E. colonum] and Cyperus rotundus to a post-emergence application of propanil were studied in screenhouse trials at Ile-Ife during 1990 and 1991. Propanil retention, absorption and translocation to the roots of these species were measured using a UV-VIS [visible light] spectrophotometer. The leaf area, leaf angle and stomatal density were determined quantitatively. Stomata distribution and thickness of epicuticular wax were observed from photo-micrographs of transverse sections of the leaves. The following findings were demonstrated when A. conyzoides was compared to the other species investigated: it retained more propanil on the leaf surface; it absorbed and translocated more propanil into the plant tissues; it had the thinnest epicuticular wax, highest stomatal density, and greatest leaf area and leaf angle, as well as a wider distribution of stomates. It was suggested that these factors may be responsible for the susceptibility of A. conyzoides to propanil toxicity in the field. Rice, E. colonum and C. rotundus retained little propanil on the leaf surface, absorbed less and had limited or no translocation of propanil to the stems and roots. It was inferred that these factors may be responsible for their tolerance to propanil..

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