Phenoxy Reference Guide www.nufarm.com.au 3 Contents Introduction 4 Mode of Action 4 Cereal Crop Growth Stages (including Zadok’s guide) 5 A Numerical Cereal Growth Scale – Zadok’s 6 What Phenoxy Where? 6 Common Weeds Controlled 7 Using the Growth Stage of Cereal Crops to Time Herbicide Applications 8 Damage to Cereal Crops from Incorrect Phenoxy Herbicide Applications 9 Salvage Spraying of Winter Crops 10 Cereal Tolerance Guide 11-13 Plant Back Periods for Fallow Seed Bed Preparation 14-15 Spray Grazing 16 Withholding Periods 16 Reducing Off-Target Herbicide Drift 16-19 Herbicide Resistance Management 20 4 Introduction At Nufarm, we are committed to supporting Australian growers Phenoxys were first developed in the USA in the early 1940’s with the highest quality crop protection and weed control and used commercially in 1946. Today they remain amongst products so maximum outputs can be achieved. the world’s most widely used herbicides, providing farmers and other users with broadleaf weed control in a multitude of Our commitment starts with the utilisation of world-leading agricultural and non-agricultural uses. Phenoxys work by manufacturing and environmental control technology. This is disrupting plant cell growth and form a part of the Group I reflected in research and development, container management, herbicides. and the establishment of regional service centres across Australia. Nufarm guarantees its Phenoxy products, which include Nufarm Amicide® 625, Nufarm Estercide® 800, Nufarm LV Nufarm, an Australian company, is a global leader in the Estercide® 600, Nufarm Surpass® 300, Nufarm Buttress®, manufacture, supply and marketing of 'phenoxys', with Baton®, Nufarm LVE MCPA and Nufarm MCPA 500. manufacturing plants in Australia (Melbourne), England (Belvedere), Austria (Linz) and the Netherlands (Botlek). Mode of Action Phenoxy herbicides mimic the plant growth regulator indol-3- concentrations are highly regulated in plants by synthesis, acetic acid (IAA), or auxin in plants, thus it is necessary to degradation and both reversible and non-reversible review the function of auxin in plants to properly understand conjugation. Synthesis increases the IAA content, while their mechanism of action. degradation decreases it. Conjugation, which is the linking of IAA to another molecule, frequently an amino acid, inactivates Role of Auxins in Plants – Auxin is a plant growth IAA. However, if conjugation is reversible, it may act as a slow regulator that controls cell enlargement, division and plant release mechanism for maintaining relatively constant IAA development through the plant life cycle. levels. While much remains to be unravelled about the workings of Auxin Herbicide Mode of Action – Auxinic IAA, it is known that IAA binds to auxin binding proteins (ABPs) herbicides (‘phenoxys’) presumably bind to some or all of the located in the following: same sites as naturally occurring IAA and cause similar effects. • The cell membrane However, the amount of auxinic herbicides available to the • The endoplasmic reticulum (an internal cellular membrane plant is uncontrolled and, thus, auxin-like activity is unchecked. system) Plant growth becomes deregulated. • The cell nucleus Metabolic reserves are mobilized and transported to the site of • The cytoplasm growth, usually meristematic regions. Unregulated growth leads to twisting, thickening and elongation of leaves and The control of growth that IAA exerts is multifunctional. stems. Auxinic herbicides are active primarily in growing Changes induced by IAA cause rapid changes in cell plants. Plant death is gradual, due to the unconstrained elongation and both rapid and slow changes in gene mobilisation of reserves, the breakdown of repair mechanisms expression. Auxins influence other growth regulators including and, finally, the loss of function. cytokinins, abscisic acid and ethylene (a gas that functions as a plant growth regulator). Source: "How Herbicides Work: Biology to Application", Alberta Agriculture, Food and Rural Development. The concentration of IAA in plant cells regulates cell growth. However, plant tissues differ in their sensitivity. Depending on tissue type and IAA concentration, IAA may either inhibit or stimulate a response. IAA is a component of a carefully balanced system. IAA Nufarm Phenoxy Reference Guide www.nufarm.com.au 5 Cereal Crop Growth Stages (including Zadok’s guide) Crop 2-leaf stage Start of tillering Tillering stage Fully tillered stage Start of jointing Early boot stage growth Two leaves (L) First tiller (T1) Tillers come from Usually no more tillers Jointing or node The last leaf to form – the stage have unfolded; appears from the base where form after the very formation starts at the flag leaf – appears on top third leaf present, between a lower leaves join the young head starts end of tillering. Small of the extended stem. The yet to fully leaf and the main stem and continue forming in the main tiller. swellings – joints – form developing head can be felt expand shoot. Usually 3 or forming, usually Tillering completed at the bottom of the as a swelling in the stem. 4 leaves are on the until there are 5 when first node detected main tiller. Heads main tiller. leaves on the main at base of main stem. continue developing shoot. Secondary and can be seen by roots developing. dissecting a stem. Zadok’s 2 leaves unfolded 4 leaves unfolded 5 leaves on main 6 leaves on the main Z35-Z45. decimal (Z12) (Z14). shoot or stem shoot or stem (Z16). First node formed at code Main shoot and 1 (Z15). Main shoot Main shoot and three base of main tiller (Z31). tiller (Z21). and 1 tiller (Z21). tillers (Z23). Herbicide Suitable stage for Suitable stage for Suitable for Many herbicides can Suitable for 2,4-D No herbicide should be spraying spraying many spraying at the 3-4 spraying many be sprayed up to the spraying. applied at this stage. Too stage herbicides, but too leaf stage. Too early herbicides at the end of tillering. Suitable late for 2,4-D application early for 3 leaf for the 5 leaf stage 5 leaf tillering for 2,4-D spraying. except harvest aid stage of application. of application. stage. applications. • There is no difference between spring wheat varieties sown on the same day in the rate of appearance of new leaves. • At the early boot stage, the last flowering part - the pollen - is being formed. This occurs earlier in barley than in wheat or triticale. Source: ‘Weed Control in Winter Crops 2004’, NSW Agriculture. 6 A Numerical Cereal Growth Scale – Zadok’s A decimal scale describing cereal crop growth stages is now The main stages of interest to cereal producers applying widely used. This scale, called Zadok’s decimal code, herbicides are: describes the principal growth stages: 1 Seedling Growth 2 Tillering 3 Stem Elongation 4 Booting 0 Germination 4 Booting 7 Milk Development Zadok’s scale is based on the individual plant, not the general 1 Seedling Growth 5 Ear Emergence 8 Dough Development appearance of the crop. Therefore, to use the scale, a 2 Tillering 6 Flowering 9 Ripening representative selection of plants should be examined from a 3 Stem Elongation paddock. Each primary growth stage is further subdivided into secondary Other commonly referred to growth stages: stages extending the scale from 00 to 99. 3 leaf: 3 fully unfolded leaves on the main shoot only. Zadok 13. The first number represents the growth stage and the following number indicates the number of plant parts, e.g. Z12 indicates Double ridge – when the cereal plant changes from leaf production to ear initiation, normally around 4-6 leaves on the a young plant with only two leaves fully unfolded, commonly main stem. Zadok 14-16. referred to as 2 leaf stage. See the first diagram in Cereal Crop Growth Stages (p5). 5 leaf: 5 fully unfolded leaves on the main shoot only. Zadok 15. A series of pairs of numbers can be used to further describe the Tillering: Tiller formation period. Plants past seedling stage and growth stage. For example 14/21 indicates the main tiller with before stem elongation. Zadok 21 to 29. See the diagrams in 4 fully unfolded leaves, commonly referred to as the 4 leaf Cereal Crop Growth Stages. stage, but this plant has the main stem and one more tiller. Note that additional tillers are counted separately to the main tiller. Jointing: Crop becoming erect or booting up to the stage when See the second diagram in Cereal Crop Growth Stages. the flag leaf is just visible. Zadok 31 to 39. See the fifth diagram in Cereal Crop Growth Stages. Boot: Head plainly felt in the stem before head emergence. Zadok 35 to 45. See the sixth diagram in Cereal Crop Growth Stages. What Phenoxy Where? Product Summer Tank mix Tankmix Tankmix Tankmix Post-em tank Tankmix most Spray/Graze in Early post-em Late post-em Weeds / SpraySeed®2 Roundup® diuron grass mix with SU trace pasture in cereals in cereals melons herbicides herbicides elements MCPA 500 0 0 X ✔ X ✔ X ✔ ✔ 0 LVE MCPA 0 ✔ ✔ ✔ ✔ ✔ ✔ 0 ✔ 0 Amicide® 625 ✔ ✔ X ✔ X ✔ X ✔ X ✔ LV Estercide® ✔ ✔ ✔ 0 X ✔ ✔ X X ✔ 600 Estercide® 800 ✔ ✔ ✔ 0 X 0 ✔ X X 0 Buttress® 0 0 X ✔ X 0 X ✔ X X Surpass® 300 0 0 ✔ 0 X 0 X 0 X 0 ✔ Recommended 0 Not preferred X Not recommended option Nufarm Phenoxy Reference Guide www.nufarm.com.au 7 Common Weeds Controlled Amicide® 625 Buttress® Estercide® 800 LV Estercide® 600 LVE MCPA MCPA 500 Surpass® 300 Bathurst Burr 800ml-2.2L 1.0-3.2L 700ml-2.8L 900ml-3.7L 1.6L 1.0-2.0L 1.6-2.3L Bladder Ketmia Capeweed 1.1-2.8L 2.1-3.2L 450ml-1.4L 600ml-3.7L 1.7L 2.1L 2.9-5.8L Erodium 1.4-3.2L 700ml 900ml 400-500ml (in mix)