PHENOXY HERBICIDES 70 YEARS OF SUCCESS

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2 70 Years of success - Still going strong Seventy years ago, a group of herbicides called phenoxies were invented in Britain and the United States. Phenoxies are now used as a general term for a group of herbicides that mimic the effect of natural plant hormones called auxins. Auxins are only found in plants and regulate growth, one of their functions is to make the plant grow towards the light. Reference: A Brief Guide to Biology. Pearson, Prentice, Hall, Inc. The Nufarm story Nufarm produce phenoxies here in the UK. Our site at Wyke (near Bradford), which was established in 1877 as a Picric Acid manufacturer, now produces Phenoxy herbicides, Glyphosate, intermediates and inhibitors. The site employs over 300 people and is the largest flexible phenoxy production unit in the world. Evolution of Phenoxy Herbicides Introduction of commercial use in the UK 1945 MCPA and 2,4-D 1954 MCPB 1957 CMPP and 2,4-DB 1980 CMPP-P and 2,4-DP-P Nufarm Key Phenoxy Herbicides 1. When sunlight is overhead, the IAA molecules (auxins) produced by the meristem are distributed evenly in the shoot. 2. Once the sunlight shines on the shoot at an angle, the IAA molecules move to the far side and induce elongation of cells on that side. 3. Cell elongation results in the bending of the shoot towards the light. The twisting effect of a phenoxy treatment on Docks. Phenoxies have the same mode of action as auxins, overdosing the plant, leading to uncontrolled growth, thickening and twisting causing the plant to grow itself to death. Phenoxies are truly systemic and travel throughout the plant. They are selective in grass and cereals but an auxin group called butyrics (2,4-DB / MCPB) are also selective in many clovers and legumes. Phenoxies are more relevant today than ever! The demise of many active ingredients including isoproturon and trifluralin in recent years has left fewer options for broad-leaved weed (BLW) control in cereals. The lack of new herbicide modes of action, combined with a heavy reliance on sulphonylureas (e.g. Ally) in winter and spring cereals has led to the development of ALS resistance in some BLWs. In the UK, confirmed cases of BLW resistance are is increasing year-on-year where weed control has relied upon the use of sulphonylureas. Product Actives Crops Agritox 500 g/lt MCPA & Grass PastureMaster 360g 2,4-D + 315g MCPA Grass Clovermax 240 g/lt 2,4-DB + 40 g/lt MCPA & Grass Depitox 500 g/lt 2,4-D & Grass Duplosan KV 600 g/lt mecoprop-p Easel 750 g/lt MCPA & Grass High Load Mircam 600 g/lt mecoprop-p + 80 g/lt dicamba Mircam Plus 43.3 g/lt mecoprop-p g/lt MCPA g/lt dicamba Tropotox 400 g/lt MCPB Peas Thrust 344 g/lt 2,4-D g/lt dicamba Grass Turfmaster 43.3 g/lt mecoprop-p g/lt MCPA g/lt dicamba Amenity Minimising the resistance risk Avoid using ALS inhibitors as the sole means of broad-leaved weed control in successive years. Always use ALS inhibitors in mixture with herbicides of a different mode of action e.g. phenoxy herbicides. Investigate cases of poor weed control and keep good spray records. Long history of ALS use and declining performance against broad-leaved weed species indicates resistance may have developed. The limited efficacy of non-chemical control methods along with the long persistence of weed seeds means that early detection of resistance is vital.

3 MCPA (2-methyl-4-chlorophenoxyacetic acid) 2,4-D (2,4-Dichlorophenoxyacetic acid) AGRITOX and EASEL DEPITOX MCPA was invented during World War II, and first sold commercially in Formulated as a salt or an ester, MCPA offers a good broad-leaved spectrum in cereals and grassland. Rate response depends on species and size but in generally you need g active in mixtures in cereals minimum. Like MCPA, 2,4-D was also developed during World War II at Rothamsted Experimental Station with the aim of increase crop yields for a nation at war. It is now one of the most widely used herbicides in the world. 2,4-D is typically formulated as an amine salt, but more potent ester formulations exist. As well as cereals and grass approvals, Depitox can be used around apple and pear trees. Depitox has an approval for use through a hand held sprayer. Agritox and Easel are the leading MCPA formulations from Nufarm. In grassland, MCPA offers good control of Thistles and Buttercups. By mixing with 2,4-D in the formulation PastureMaster, Docks and Rushes will also be controlled. In new leys, Clovermax (MCPA + 2,4-DB) can be used from 3 leaf stage of the grass and 1-2 trifoliate leaves of the clover. Phenoxies are some of the most trusted herbicides in agriculture, and MCPA is certainly one of the main stays in grassland. Agritox and Easel have an approval for use on grass that has been under-sown. Depitox is the leading 2,4-D brand in the UK. The weed spectrum is largely similar to Agritox although Depitox is slightly weaker than Agritox on Thistles and Buttercup, but stronger on Docks and Ragwort. Depitox alone is not strong enough against Ragwort. Thrust (2,4-D + dicamba) is a much stronger option and should be targeted at the rosette stage. PastureMaster (2,4-D + MCPA) should be the product of choice when Soft Rush is the problem. Agritox and Easel are also approved for use in cereals (winter wheat, winter barley, spring barley, oats and rye). For Agritox, the latest time of application is before GS33 in winter wheat, and GS31 for winter and spring barley, oats and rye. Easel (750g MCPA) has a later cut off of GS39 in winter wheat. This is particularly useful for late poppy control. Mircam Plus (MCPA + CMPP + Dicamba) offers a broader spectrum of weed control including Charlock, Fat Hen, Fumitory, Volunteer Oilseed Rape and Shepherd s Purse. Mircam Plus can be used up to before GS31 on winter and spring wheat, barley and oats. Depitox also has a cereals label (winter and spring wheat, winter and spring barley, winter oats and winter and spring rye). All these cereals have an approval for under-sown grass. 2,4-D can be more damaging to cereal ears at later growth stages, so Depitox cut off is before GS31 on all cereal crops. Like in grassland, Depitox has a similar activity to Agritox, particular strengths are Charlock, Poppy, Creeping Thistle and Speedwells.

4 CMPP-P (methylchlorophenoxypropionic acid) DUPLOSAN KV, HIGH LOAD MIRCAM AND MIRCAM PLUS Mecoprop, commonly known as CMPP (or MCPP), was registered in This initial formulation consisted of two chemical isomers in equal proportion, only one of which is the active herbicide. New technologies in the 1980s allowed for the creation of products with higher concentrations of the optically active isomer. The new formulation was named mecoprop-p, or MCPP-P. Duplosan KV is the key brand from Nufarm, and is formulated as a potassium salt. Phenoxybutyric herbicides Butyric phenoxies are generally about half as active, but have some unique selective properties. MCPB 4-(4-chloro-o-tolyloxy) butyric acid TROPOTOX Discovered at Wye College, London University in 1955 by Professor Louis Wain, MCPB is converted to MCPA in crops which have the conversion mechanism. The crops that don t have this mechanism, will be tolerant. Some legume crops, notably Peas and Clover lack the conversion mechanism and therefore are tolerant, however others are not e.g. Lucerne, Beans. Tropotox is approved for use in Combining and Vining Peas. The weed spectrum is similar to MCPA, but less than half as active. Duplosan is no longer approved for use in agricultural grassland. Thrust and PastureMaster have taken over, with both products offering a good range of weed control, often complimented by fluroxypyr for chickweed where required. Duplosan KV still has an approval in grass (seed crops) and managed amenity turf. CMPP can also be found in Turfmaster, one of our amenity specific products. 2,4-DB 4-(2,4-dichlorophenoxy) butyric acid CLOVERMAX and CLOVERMASTER Duplosan KV works in cooler weather than other phenoxies. A very useful addition to weed control in cereals, it boosts Cleaver and Fat Hen which tends to get left behind by sulphonylureas. The addition of Duplosan KV in the spring will also act as a very useful anti-resistance strategy, especially where used in a situation with resistant Chickweed. Duplosan KV will generally strengthen the weed control of anything it is mixed with, and as a stand alone product, is very strong on leguminous volunteers, Cleavers, Charlock, Small Nettle and Shepherd s Purse. Control of Grounsel, Polygonums, Scentless Mayweed are all added to the spectrum with the addition of dicamba. High Load Mircam contains CMPP+dicamba and is a very well rounded product for use before GS31 in winter and spring wheat, barley and oats. 2,4-DB is the key active in CloverMaster, and one of the key actives within Clovermax. 2,4-DB is safe to Clover when applied before 4th trifoliate leaf stage because young Clover can t convert 2,4-DB to 2,4-D. If applied when Clover (or Lucerne) is more mature, it will damage, or kill the crop. Clovermax and CloverMaster are approved for use in cereals and grass, focussing on new leys, best control is achieved when weeds are small. Clovermax and CloverMaster can be applied to cereals crops (wheat, barley or oats) under-sown with Red or White Clover. Other legume crops, such as Peas and Beans are not tolerant of 2,4-DB as they have the ability to convert it to 2,4-D, which causes the damage.

5 Getting the most out of phenoxies Apply when weeds are actively growing. Ensure the correct spray quality to ensure good coverage on the target weed, whilst avoiding drift and observing buffer zone restrictions. Timing for the control of perennial weeds is important. Understand your target and the best time to apply. Always check the label for best application timing. Phenoxies take about 6 hours to get in the plant. If it rains then you will have reduced activity. Product Stewardship These products are soluble in water. The level of a pesticide in drinking water should not exceed 0.1 parts per billion. These minute levels are detected in water sample so it is important to adopt effective Stewardship of these products and observe Best Practice guidelines. Use approved products recommended by a BASIS qualified agronomist. Keep pesticides in a locked, bunded store. Application is made by a trained operator with current qualifications. Check and calibrate spray equipment on an annual basis. Fill in areas away from drains and water courses. Clear any spills immediately. Spray when weather and soil conditions are suitable i.e. no risk of drift and soils not too wet. Leave buffer strips between watercourses and sprayed areas. Clean and wash sprayers at the end of the day. Dispose of washings on an untreated area of grassland. Never exceed label rates. FURTHER INFORMATION Details of application rates and timings are given in Nufarm labels and product literature; both of which can be accessed from our website Alternatively, ring the Nufarm helpline on , Monday to Friday Use plant protection products safely. Always read the label and product information before use. For label and safety information, refer to the Nufarm website Nufarm UK Ltd, Wyke Lane, Wyke, Bradford, BD12 9EJ. Agritox, Clovermax, Easel, PastureMaster, Thrust, High Load Mircam, Mircam Plus, Turfmaster, Tropotox, Depitox and Duplosan KV are all Trademarks of Nufarm. Nufarm UK Ltd Wyke Lane, Wyke, Bradford, West Yorkshire