Alternative Options to Glyphosate for Control of Large Echinochloa colona and Chloris virgata Plants in Cropping Fallows

Abstract

The over-reliance on the herbicide glyphosate for knockdown weed control in fallows under minimum and zero-till cropping systems has led to an increase in populations of glyphosate-resistant weeds. Echinochloa colona and Chloris virgata are two major grass weeds in the cropping regions of northern New South Wales and southern Queensland, Australia, that have become harder to kill due to a steady rise in the occurrence of glyphosate-resistant weed populations. Therefore, to help growers contain these hard to kill fallow weeds, an alternate approach to glyphosate application is needed. With this purpose in mind, a pot study was carried out during the summer seasons of 2015 and 2016 at the Tamworth Agricultural Institute, Tamworth, NSW, Australia, to evaluate the efficacy of tank mixtures and sequential applications of Group H (4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor), Group C (inhibitors of photosynthesis at photosystem II), Group A (ACCase inhibitors) and Group L (photosystem I inhibitor) herbicides on late tillering E. colona and C. virgata plants. These herbicide groups are a global classification by the Herbicide Resistance Action Committee. Highly effective results were achieved in this study using combinations of Groups H, C, A and L herbicides applied as tank mixtures for controlling large E. colona plants. Additionally, sequential applications of Group H, C and A herbicides followed by (fb) paraquat were shown to be very effective on large E. colona plants. Late tillering C. virgata plants were generally well controlled by tank mixtures, and sequential applications proved to be highly effective on this grass weed as well. Haloxyfop in combination with paraquat as a tank mixture, via sequential application or as a stand-alone treatment, was highly effective for C. virgata control; however, using combinations of herbicide groups is the preferred choice when combating herbicide resistant weed populations. There was a clear synergy shown using Group H, Group C and Group A herbicides in combination with the Group L herbicide paraquat in this study for controlling advanced E. colona and C. virgata plants. These combinations were shown to be successful on plants grown under glasshouse conditions; however; these treatments would need to be tested on plants grown in a field situation to show whether they will be a useful solution for farmers who are trying to control these weeds in fallow.

New Case of False-Star-Grass (Chloris distichophylla) Population Evolving Glyphosate Resistance

“…Additionally, studies on other grasses such as Lolium multiflorum [48] have shown that the use of clethodim and diuron in conjunction with glyphosate is a potential control tool. Recent studies on glyphosate-resistant weeds such as Echinochloa colona and Chloris virgata [49] have shown that HPPD inhibitor herbicides, ACCase inhibitors, and photosystem I and II inhibitors have been highly effective for control when used together. Our work shows that, for now, herbicides are good alternatives for the control of C. distichophylla.…”

A systematic approach for finding herbicide synergies

“…The glufosinate-2,4-D synergy which we did not see in A. thaliana, was synergistic in Commelina communis and Echinochloa colona, but additive in Ambrosia trifida (Craigmyle et al, 2013, Ganie andJhala, 2017). The paraquat-atrazine synergy (Davidson et al, 2019) was only reported for monocot weed species Echinochloa colona and Chloris virgata. Other factors that could complicate synergies are that many studies use formulated herbicides, not pure actives.…”

“…We confirmed that the method is sensitive enough to reliably find synergies by comparing our results with recent synergy claims in peer-reviewed literature. Analysis of the synergy literature published in the last two decades showed that the 24 herbicides chosen for screening can potentially form five synergistic combinations: mesotrione-atrazine, 10, 11, 16–20 clomazone-atrazine, 15 paraquat-atrazine, 31 norflurazon-atrazine 10 and glufosinate-2,4 D. 32 Two combinations (mesotrione-atrazine, clomazone-atrazine) were rediscovered in our screen, but three were not.…”

Efficacy of Different Herbicides on Echinochloa colona (L.) Link Control and the First Case of Its Glyphosate Resistance in Greece

“…All glyphosate-resistant E. colona plants were unaffected when treated with either the recommended or the double rate in the study of Mutti et al [55]. The development of glyphosate-resistant populations of E. colona has also been mentioned by other scientists [23][24][25][26]. Model analysis of Bagavathiannan et al [56] revealed that the risk of Echinochloa spp.…”

“…Glyphosate is one of the most widespread and efficient non-selective herbicides globally, whose application is a common control practice for E. colona [20][21][22]. However, due to the continuous use of glyphosate, several E. colona accessions have been confirmed as resistant to glyphosate [23][24][25][26]. This is true either in genetically modified (GM) annual crops or in perennial crops, whereas the use of glyphosate is very often and extended.…”