WHEN we conduct weed control operations, whether it

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1 Tiering multiple weed management strategies OOBy Jeff Werth, Queensland Department of Agriculture and Fisheries WHEN we conduct weed control operations, whether it is part of on-farm operations or even in our research trials, we tend to focus on the control achieved with each individual operation. But our focus around weed management needs to be on the weed seed bank, and how we can drive it down as far as possible. In terms of herbicide resistance management, this becomes even more critical, as managing low weed seed banks is much easier and more cost effective. Driving down the weed seed bank does not happen in one operation and requires a longer term weed management strategy involving multiple weed control tactics tiered tactics. Rather than planning these weed control tactics in isolation, it is important to determine how the tactics we have available can complement each other to achieve our ultimate goal of driving down the seed bank. A widely known example of the benefits of tiering tactics is the double knock strategy. When used with both herbicides being effective on the weed population, this is a way of ensuring that weeds not controlled by the first herbicide/s applied are subsequently controlled by the second herbicide (or cultivation) in order to prevent seed production and additional seed entering the weed seed bank. Another example is the autumn tickle, which is a light cultivation at optimum time of weed emergence (not necessarily autumn) to stimulate weed emergence. The seedlings which emerge from this tickle operation are then sprayed, perhaps even with a double knock. This can be a very effective method for driving down the weed seed bank considerably. A systems approach In 2003 at the Australian Cotton Research Institute (ACRI) we established a systems experiment focusing on the population dynamics of barnyard grass. This experiment had a range of increasing levels of intensity that can provide some insight into the benefits of tiering tactics together. The treatments in the experiment ranged from using glyphosate alone, to adding in a grass herbicide, and then to incorporating residual herbicides at planting and mid-season, to additional residuals pre-plant. The treatments used in the experiment are listed in Table 1. These treatments had quite different effects on the numbers of barnyard grass that emerged throughout the course of the experiment (Figure 1). Barnyard grass tends to emerge in a number of flushes throughout the spring and summer, but the largest of these flushes is generally in spring with the subsequent flushes being smaller. This is evident by the large increases in the emergence numbers in the Glyphosate only and Gly + grass treatments in Figure 1 at the start of each cotton growing season. As we started to bring in residual herbicides, the number of emergences was reduced. You will notice that even when residual herbicides were added at planting, there had already been a considerable flush of barnyard grass before the herbicides were applied. It was not until herbicides were applied pre-plant before the first flush of barnyard grass that the number of plants that emerged was considerably reduced. The use of residuals pre-plant, at-planting and mid-season FIGURE 1: Cumulative emergence of barnyard grass in systems trial at ACRI from TABLE 1: Treatments and herbicides used in a systems experiment conducted at ACRI from Treatments PPI PPPE EPOST POSTDIR LAYBY LPOST Glyphosate only Glyphosate Glyphosate (x2) Glyphosate None None Glyphosate + Grass Glyphosate Glyphosate (x2) Glyphosate None Haloxyfop Gly + residual (PPPE + Layby) Gly + residual (PPI + PPPE + Layby) Trifluralin Diuron Glyphosate Fluometuron Prometryn Pendimathalin Glyphosate Fluometuron Prometryn Pendimathalin Glyphosate (x2) Glyphosate Prometryn Glyphosate (x2) Glyphosate Prometryn None PPI=Pre-plant, incorporated. PPPE=Post plant pre-emergence. EPOST=Early post emergence. POSTDIR=Post emergence, directed. LPOST=Late post emergence. 16 The Australian Cottongrower October November 2016

2 Advantage Tuning specialises in diesel engine software management or remapping/tuning electronically controlled engines in all modern diesel applications. We strive to increase performance, reduce fuel consumption, optimise torque and maximise efficiency. Our target audience is, but not limited to, heavy industry which includes agriculture, on-highway trucking, mining, construction and civil as well as marine. Essentially any industry, where diesel engines can be optimised, to increase profit margins through lowering customers input cost. EURO 3, 4, 5, 6 Tuning solutions are available for most Euro 3, 4, 5 and 6 engines as well as Tier 3, 4 and 4B engines. Alterations to the software controlling these engines can dramatically decrease machine downtime and increase overall efficiency. If you have questions regarding out running options for late model diesel engines please feel free to contact us via the webpage, facebook or phone. CASE STEIGER 435 WITH AS TESTED IN THIS CONFIGURATION The customer experienced a significant fuel saving along with a vast improvement in drivability through removing the power hop. The machine could not physicall pull the implement in a higher gear at this speed, until it was tuned for this application. Please note the first picture of the gauges is prior to tuning. This represents an overall fuel saving of 42%. Advantage Tuning

3 treatments stacked up in terms of their effect on the barnyard grass seed bank. The barnyard grass seed bank was reduced in all treatments, but there were more survivors in Glyphosate only and Gly + Grass treatments. Within the three years of the experiment, the treatments that contained residual herbicides in addition to the post-emergent herbicides almost totally depleted the seed bank. Also, note the residual program that contained a post-plant, pre-emergent residual and a layby was in the end just as effective as the treatment with the more intensive residual program. HERBICIDE RESISTANCE TESTING PROGRAM Keeping cotton weed free for eight to nine weeks can allow it to become competitive and reduce the impact of weeds. used to be quite common and is probably a more intensive approach than many are prepared to go for a number of valid reasons. But in terms of this trial, where we were also concerned with glyphosate resistance prevention, it was clear that the addition of residuals reduced the number of weeds that were subsequently sprayed with glyphosate. This significantly reduced the risk of glyphosate resistance evolving. As mentioned earlier, what we really want to focus on is the weed seed bank. Figure 2 provides more insight as to how these CataPult THIRD SEASON S RELEASE OF OPTIMISED INOCULUM FOR COTTON A combination of VAM plus Bacillus microbes to: s Increase yields s Release & capture bound phosphorous s Increase tolerance of dry spells s Increase early root growth Apply at planting or early season For orders or to receive a summary of a recent outstanding result in cotton or or info@vanadisbioscience.com.au Survey data collected from over 200 growers and consultants across cotton growing regions shows that the majority are managing herbicide resistant weeds on farm. In most cases, weeds identified are suspected resistant due to herbicide failure, with only a small number of growers using resistance testing services to confirm the status of suspect weed populations. While only a small number of growers are using resistance testing services, 40 per cent indicated that they think access to a free resistance testing program would assist them in managing resistance on their farm. Monsanto would like to assist growers and consultants to confirm the status of suspected as resistant weeds on farm and to do so, is offering a free herbicide resistance testing program for Australian cotton growers. The aim of the program is to provide access to free herbicide resistance testing for cotton growers and their consultants to assist decision making and IWM strategy development. How will it work? 1. This program is available to all farmers who have grown Roundup Ready Flex cotton in the previous three seasons. 2. Consultants/growers can test five of the major weeds present in cotton systems for resistance to three critical herbicides, Roundup Ready Herbicide with PLANTSHIELD by Monsanto, Verdict and Select. Weeds Glyphosate Verdict Select Annual Ryegrass (Lolium rigidum) Awnless Barnyard Grass (Echinochloa colonum) Liverseed Grass (Urochloa panicoides) Red Pigweed (Portulaca oleracea) Y N N Milk (sow) thistle (Sonchus oleraceus) Y N N 3. Monsanto has pre-printed testing envelopes that can be used for weed seed collection. Please or call Kate Lang (katherine.sarah.lang@monsanto.com, ) to arrange for the number of envelopes you need to be posted to you. 4. Testing will be anonymous. Monsanto will not be provided with grower identification information. 18 The Australian Cottongrower October November 2016

4 Versatile Valor for summer cropping The three distinct use patterns of Valor make it a very flexible tool in cotton production As a non-volatile spike with glyphosate and other non selective herbicides prior to sowing a range of summer and winter crops To control volunteer cotton plants (including Roundup Ready varieties) pre- or post-sowing preemergence to the crop VALOR COTTON CONSCIOUS As a lay-by treatment to control vines and other weeds in cotton Valor is a registered trademark of Sumitomo Chemical Company, Japan.

5 FIGURE 2: Numbers of barnyard grass seeds taken from soil cores in each respective treatment. Error bars represent the standard error of the mean FIGURE 3: Seed production of barnyard grass in solid (1m spacing) irrigation cotton with respect to planting time The only downside for this in terms of glyphosate resistant management was the greater number of plants that were exposed to glyphosate, as the at-plant residual missed the major barnyard grass flush. In this case, a pre-emergent residual four to six weeks prior to cotton planting may have been just as effective, with a greater benefit in terms of resistance management. Utilising crop competition We generally tend to think of cotton as an uncompetitive crop. This is true in the first stages of growth, but once the crop gets larger it can become quite competitive. This is a characteristic that we can use to our benefit. Keeping the field weed free while the cotton plants are small gives the crop the opportunity to get ahead of the weeds and out-compete them for light, water and nutrients. An example of this is shown in Figure 3, where barnyard grass planted at the same time as cotton was able to produce up to Quality where it counts Service when it matters Compatible with extended service intervals Contact Filtermax for your nearest distributor 40,000 seeds per metre. When the cotton was kept weed free for eight weeks, barnyard grass that was planted at this time was unable to compete with the cotton, and as a result produced hardly any seed. Previous research in the US also confirms that a weed free period of eight to nine weeks allows crop competition in cotton to take effect. We can keep cotton weed free by creating a clean start with a double knock prior to planting, by utilising residual herbicides around planting and early season, as well as timely applications of post-emergent herbicides while the weeds are small. Once the crop gets bigger it will complement early season weed control. This competition effect will be less in non-irrigated crops, particularly with wider rows, but some in-row competition will still occur, with the inter-row needing to be alternatively managed. HRMS and The Herbicide Resistance Management Strategy (HRMS) contains a guide as to how tiering weed management tactics can benefit not only glyphosate resistance management, but also depleting the weed seed bank. Using two nonglyphosate tactics in crop and fallow in addition to in-crop glyphosates, and preventing survivors producing seed is an important long-term strategy. Incorporating residual herbicides into the program will be beneficial for limiting the number of emerging weeds that will be exposed to glyphosate, and other post-emergent herbicides, particularly the group As. The new registrations for over-the-top and directed sprays of Bouncer 960S and Rifle 440 (see labels for proper use) should help get around some of the issues at planting if heavy rain is expected. It is worth taking the time to look through the HRMS and plan the weed management strategy that will fit your system and your weeds. Funding for this research was provided by the Cotton Research and Development Corporation, Cotton Catchment Communities Cooperative Research Centre, and Monsanto Australia. 20 The Australian Cottongrower October November 2016