Alternative second knock herbicides for broadleaf weeds in fallow are there other options?

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1 Key words Alternative seond knok herbiides for broadleaf weeds in fallow are there other options? Rihard Daniel, Anthony Mithell, Linda Bailey, Denielle Kilby and Branko Duri, Northern Grower Alliane Common sowthistle, flaxleaf fleabane, double knok GRDC ode NGA00004: GRDC Grower Solutions for Northern NSW and Southern Qld Call to ation/take home messages A series of 8 trials has shown that saflufenail (Sharpen ) may have a useful role as a 2 nd knok treatment for key broadleaf weeds. Level of ontrol was at least equivalent to paraquat at L/ha of the 250 g ai/l formulation in these trials. However poor ontrol was ahieved from both paraquat and saflufenail when used as 2 nd knok treatments on flaxleaf fleabane, following glyphosate only. No option provided effetive management when applied as a 2 nd knok on tall fleabane (Conyza sumatrensis). Paraquat did not provide aeptable levels of suppression of Canadian fleabane (Conyza anadensis) when applied as a 2 nd knok at L/ha. Mixtures of saflufenail and paraquat require further evaluation as they may provide more robust ontrol of key fallow weeds. Bakground The sequential appliation of two separate herbiide treatments has beome the most ommon double knok approah used in weed management. Unfortunately these approahes have added ost, omplexity and sheduling issues to weed management programs but have been required for two main reasons: 1. To ontrol herbiide resistant weed populations, that may have been seleted by prolonged use of similar mode of ation hemistry; and 2. Control of weed speies or stages that are unsuessfully ontrolled with single herbiide appliations. Paraquat has been the key ative ingredient used in the seond knok situation and an provide effetive management of a wide range of grass and broadleaf weeds. However, it is lear we require other options to use in this management window to: 1. Avoid the more rapid seletion of paraquat resistane; and 2. Provide options that may improve weed ontrol in situations where paraquat effiay is not adequate. Sine winter 2016, NGA have been sreening a range of herbiides, to identify options that have potential for this use pattern. The two key broadleaf weeds being targeted are ommon sowthistle (Sonhus oleraeus) and flaxleaf fleabane (Conyza bonariensis).

2 Trials onduted Table 1 shows the key details of trials onduted during the last months. Table 1. Trial details Main Weed Loation Date of 1 st knok appliation Days to 2 nd knok appliation Common sowthistle Tambar Springs 9/10/ Flaxleaf fleabane Mt Tyson 17/10/ Flaxleaf fleabane Dalby 6/12/ Common sowthistle Moree 16/6/ Common sowthistle Mullaley 20/9/ Tall fleabane St Ruth 27/11/ Canadian fleabane Ceil Plains 27/11/ Common sowthistle Somerton 19/12/ NB Tall fleabane - Conyza sumatrensis, Canadian fleabane - Conyza anadensis Approah 1 st knok treatments were applied uniformly aross the entire trial area. The most ommon treatment was a mixture of glyphosate and 2,4D amine, with the rates varying with the weed stage, environmental onditions and the grower/adviser reommendations. 2 nd knok appliations were applied between 7 and 19 days after the 1 st knok treatments. All trials inluded a range of rates of paraquat for benhmarking purposes. Initial trials inluded a range of group G herbiides (all registered in fallow alone or in mixture with glyphosate or paraquat) and the group N herbiide glufosinate (Basta ). The most promising group G option was evaluated in all trials. The untreated plots in all trials had the 1 st knok herbiide treatment applied but did not reeive a 2 nd knok appliation. Results to date Trials in 2016 on both ommon sowthistle and flaxleaf fleabane showed improved effiay from saflufenail (Sharpen) as a 2 nd knok treatment ompared to flumioxazin (Valor ) or arfentrazone (eg Nail ). No further evaluation has been onduted on flumioxazin or arfentrazone. Interestingly, the performane of saflufenail has appeared more onsistent when used in a 2 nd knok appliation, partiularly on ommon sowthistle. Glufosinate was evaluated in the initial series of trials but did not provide any onsistent benefit over paraquat or saflufenail. Performane of glufosinate has appeared similar whether used in a 1 st or 2 nd knok situation (data not presented).

3 Figures 1 and 2 show results from two of the trials evaluating double knok ontrol of ommon sowthistle onduted in Regrowing ommon sowthistle/m a 1st knok only Gramoxone 1.6LGramoxone 2.4L Sharpen 17g + Sharpen 26g + p<1, LSD=0.24 Figure 1. 2 nd knok ontrol of ommon sowthistle (26 days after appliation) at Mullaley Ot 2017 NB 1 st knok appliation was Glyphosate Amiide Common sowthistle/m a d bd 1st knok only Gramoxone 1.6LGramoxone 2.4L Sharpen 17g + d d Sharpen 26g + p<1, LSD: not appliable, data detransformed Figure 2. 2 nd knok ontrol of ommon sowthistle (44 days after appliation) at Croppa Creek Aug 2017 NB 1 st knok appliation was Glyphosate CT + Amiide 625 Figures 3 and 4 show results from the two sites in 2016 evaluating double knok ontrol of flaxleaf fleabane. NB Figure 4 shows the result from a site where the ommerial appliation of a 1 st knok was glyphosate alone. Previous ativity has shown that the addition of 2,4D to the first spray is generally ritial to ahieve effetive ontrol of flaxleaf fleabane, even when double knoked with paraquat.

4 0.20 Flaxleaf fleabane/m ab 0 1st knok only Nuquat 1.6L Nuquat 2.4L Sharpen 34g + p=8, LSD: not appliable as data detransformed Figure 3. 2 nd knok ontrol of flaxleaf fleabane (24 days after appliation) at Dalby Jan 2017 NB 1 st knok appliation was Glyphosate Amiide 720, signifiant differenes are only tested at the 10% level 2.5 Regrowing flaxleaf fleabane/m st knok only Nuquat 1.6L Nuquat 2.4L Sharpen 34g + p=.33, No signifiant differene Key points Figure 4. 2 nd knok ontrol of flaxleaf fleabane (17 days after appliation) at Mt Tyson Nov 2016 NB 1 st knok appliation was Glyphosate CT only Sharpen (700g/kg saflufenail) at rates of 17 and 26g/ha provided a similar level of ontrol to paraquat at 1.6 to 2.4L/ha when applied as a 2 nd knok appliation on ommon sowthistle in all 4 trials. Sharpen (700g/kg saflufenail) at rates of 34g/ha provided equivalent ontrol to paraquat at 1.6 to 2.4L/ha when applied as a 2 nd knok appliation on flaxleaf fleabane in 2 trials. Poor levels of ontrol were ahieved by all 2 nd knok options on flaxleaf fleabane when glyphosate only was used as the 1 st knok (see Figure 4).

5 No herbiide produt provided useful levels of ontrol of tall fleabane (Conyza sumatrensis) when applied following Roundup Ultra Max and Amiide 625 (data not presented). Paraquat did not provide useful levels of ontrol of Canadian fleabane (Conyza anadensis) when applied following Tordon 75D (data not presented) Conlusions The results to date indiate that the group G ative ingredient saflufenail warrants further investigation as a potential 2 nd knok option for the ontrol of a number of key broadleaf weed speies. Aross this series of trials, the level of ontrol was similar to that provided by rates of paraquat of L/ha. However in situations where paraquat failed to provide useful effiay on flaxleaf fleabane following an appliation of glyphosate only, there was no indiation of improved benefit from saflufenail. Where to next? Saflufenail learly may have a useful fit as a 2 nd knok alternative on broadleaf weeds suh as ommon sowthistle or flaxleaf fleabane. However the majority of fallow appliations have a need for both broadleaf and grass ontrol. Consequently part of the projet ativity in 2017 was to ommene an evaluation of the fit of saflufenail/paraquat mixtures to identify ost effetive but more robust options for use as 2 nd knoks. Aknowledgements The researh undertaken as part of this projet is made possible by the signifiant ontributions of growers through both trial ooperation and the support of the GRDC, the author would like to thank them for their ontinued support. NGA would partiularly like to aknowledge the assistane from our trial o-operators during this series of trials: Terry Leerentveld, Justin Commens, Warren Myring, Ben MIntyre, Aaron Goddard, Gavin Maguire, Graeme Gall and the Strang Family. Contat details Rihard Daniel Northern Grower Alliane Ph: rihard.daniel@nga.org.au Registered trademark Trademark

Fallow management of grass weeds and common sowthistle

Fallow management of grass weeds and common sowthistle Richard Daniel, Northern Grower Alliance Key words Awnless barnyard grass, feathertop Rhodes grass, liverseed grass, button grass, windmill grass,