Best Management Practice Manual 2014 For Agronomists and Growers
Best Management Practice Manual 2014 For Agronomists and Growers Wheat Canola Barley Maize 0 Introduction Clearfield® and Clearfield® Plus crops are extremely useful tools for Australian growers to optimise production in wheat, barley, canola and maize. Herbicide-tolerant Clearfield and Clearfield Plus crops simplify control of hard-to-kill weeds with high yielding non-GMO varieties. The Clearfield and Clearfield Plus Production Systems combine: • High yielding, herbicide-tolerant varieties from Australia's leading plant breeders and seed companies. These varieties are not GMO's and are tolerant to Clearfield herbicides. • Custom-designed Clearfield herbicides for knockdown and residual weed control • Clearfield Sustainability Program. Crops with Clearfield traits are now available in a number of forms: 1. Clearfield wheat varieties: tolerant to and registered for OnDuty® Herbicide only. 2. Clearfield Plus wheat varieties: tolerant to and registered for Intervix® Herbicide. 3. Clearfield Scope barley tolerant to and registered for Intervix Herbicide. 4. Clearfield canola varieties: tolerant to and registered for OnDuty Herbicide and Intervix Herbicide. 5. Clearfield maize varieties: tolerant to and registered for Lightning® Herbicide. These registrations enable growers to control over 40 weed species including annual ryegrass, brome grass, barley grass, volunteer cereals, climbing buckwheat and wild oats, using either: OnDuty on Clearfield wheat, or Intervix on Clearfield Plus wheat varieties or Clearfield Scope Barley. Intervix or OnDuty on Clearfield canola. Lightning on Clearfield maize. 1 Clearfield Stewardship Summary Clearfield crops were introduced into Australia in 1999, with Clearfield canola the first crop. Since then, Clearfield Wheat, Clearfield Maize, Clearfield Plus Wheat and Clearfield Barley have been added to the portfolio of crops. With the growing of the Clearfield Production System crops, comes the responsibility of all parties (BASF, seed breeders, Clearfield Agencies, Clearfield Accredited Agronomists and growers) to manage the sustainability of the Clearfield Production System. With the recent introduction of other herbicide tolerant cropping systems (eg Roundup Ready® canola) greater flexibility in solutions has become available but with multiple systems comes an increasing complexity, making the Clearfield Best Management Practices document as important as ever. This document outlines the Best Management Practices that will result in sustaining the Clearfield Production System as a key tool for all. 2 Contents 1.0 Clearfield and Clearfield Plus Wheat ......................................................................................... 1 1.1 Clearfield Canola .................................................................................................................... 1 1.2 Clearfield Herbicides .............................................................................................................. 2 2.0 Herbicide resistance management in Clearfield Crops ............................................................. 3 2.1 Herbicide resistance management using an Integrated Weed Management (IWM) approach....................................................................................................................................... 3 2.2 Weed and weed seed management for resistance management ......................................... 3 2.3 Development of resistance..................................................................................................... 3 2.4 Integrated weed management strategies for Clearfield & Clearfield Plus Crops. ................. 6 2.5 General Recommendations for Group B Herbicides ............................................................ 7 3.0 Optimised Weed Control with Clearfield Herbicides.................................................................. 8 3.1 OnDuty Herbicide for Clearfield wheat varieties. ................................................................... 8 3.2 Intervix Herbicide for Clearfield Barley, Clearfield Canola and Clearfield Plus Wheat. ........ 9 4.0 Controlling Volunteers from Clearfield Crops .......................................................................... 11 4.1 Summary .............................................................................................................................. 11 4.2 Important reasons to control volunteers............................................................................... 11 4.3 Controlling volunteers........................................................................................................... 12 4.4 Management actions ............................................................................................................ 12 5.0 Managing Out-crossing ............................................................................................................ 13 5.1 What is out-crossing? ........................................................................................................... 13 5.2 Potential for out-crossing in Clearfield and Clearfield Plus wheat ....................................... 13 5.3 Description of Triticum aestivum varieties with Clearfield and Clearfield Plus Technology 13 5.4 Potential for out-crossing to non-Clearfield and Clearfield Plus wheat varieties ................. 14 5.5 Potential for out-crossing to weed species related to wheat ............................................... 14 5.6 Managing out-crossing of Clearfield and Clearfield Plus wheat to related species ............ 15 5.7 Potential for out-crossing in Clearfield Scope Barley .......................................................... 15 5.8 Description of Hordeum vulgare L. (cultivated barley) varieties with Clearfield Technology .................................................................................................................................................... 15 5.9 Potential for out-crossing to non-Clearfield barley varieties ................................................ 16 3 5.10 Weediness status in Australia and Overseas .................................................................... 16 5.11 Potential for out-crossing to weed species related to barley ............................................. 16 5.12 Managing out-crossing of Clearfield Scope barley to related species .............................. 17 5.13 Managing Clearfield Wheat and Clearfield Scope Barley in the crop rotation: ................. 17 5.14 Potential for out-crossing in Clearfield Canola................................................................... 17 5.15 Description of Brassica napus varieties with Clearfield technology .................................. 17 5.16 Potential for out-crossing to non-Clearfield canola varieties ............................................. 18 5.17 Potential for out-crossing to weed species related to Canola ........................................... 18 5.18 Managing out-crossing of Clearfield canola to related species ......................................... 19 5.19 Potential for out-crossing in Clearfield Maize .................................................................... 19 5.20 Managing practices for Clearfield maize ............................................................................ 20 6.0 Contacts ................................................................................................................................... 21 4 1.0 Clearfield and Clearfield Plus Wheat Australian standard wheat varieties are hexaploid, in other words, they are genetically comprised of three sets of paired chromosomes known as genomes. Clearfield wheat (or one-gene) varieties have experienced a mutation in one of their three genomes enabling that genome to produce ALS enzyme that is unaffected by imidazolinone herbicides. The other two genomes lack the mutation and produce sensitive ALS enzyme. One-gene wheat varieties are therefore in effect one-third tolerant of imidazolinone herbicides (and two-thirds sensitive). Clearfield Plus (or 2-gene) wheat varieties have a separate mutation on a second genome so that two of their three genomes enabling those genomes to produce ALS enzyme that is unaffected by imidazolinone herbicides. The other single genome lacks a mutation and produces sensitive ALS enzyme. Two-gene wheat varieties are therefore in effect two-thirds tolerant of imidazolinone herbicides (and one-third sensitive). Neither Clearfield nor Clearfield Plus wheat varieties are therefore completely resistant from imidazolinone injury but Clearfield Plus wheat lines are considerably more tolerant. This is demonstrated by the fact that CL JNZ and CL STL (the only two released varieties of Clearfield wheat) do not have adequate tolerance to Intervix Herbicide. By contrast the new Clearfield Plus wheat lines are able to tolerate Intervix. Note: Intervix herbicide cannot be used on non-Clearfield wheat varieties, nor can Intervix be used on non-Clearfield barley varieties, as severe crop damage will occur. Development of new Clearfield Plus two gene wheat cultivars is ongoing in partnership with all major wheat breeding programs in Australia. Single gene Clearfield development has been discontinued. 1.1 Clearfield Canola Clearfield Canola features some of the highest yielding varieties with the highest oil content available in Australia. These varieties are tolerant to Intervix herbicide. Intervix controls almost 30 weeds including wild radish, mustard, turnip and a range of grass weeds. Note: Intervix cannot be used on non- Clearfield canola varieties as sever crop damage will occur. 1 1.2 Clearfield Herbicides All Clearfield herbicides are based on the imidazolinone group of herbicides, which are part of the Group B mode of action. Group B herbicides work by inhibiting acetolactase synthase (ALS enzyme), an enzyme critical for the production of the essential amino acids leucine, isoleucine and valine which are used for protein production in plants. Advice on all Clearfield crops is available from AgriCentre®. AgriCentre staff receive ongoing training in Clearfield crops and AgriCentre agronomists have completed a detailed Clearfield accreditation course. An important component of the Clearfield Production System is the stewardship within the Clearfield Sustainability Program, which details Best Management Practices for Clearfield Crops. This program has some obligatory practices that are aimed at ensuring the sustainability of herbicide-tolerant Clearfield crops. There are four (4) key areas addressed to help ensure the sustainability of Clearfield crops: Herbicide resistance management using an integrated approach; Optimising weed control using only Clearfield herbicides for maximising crop yield and ensuring Effective weed resistance management; Control of crop volunteer plants; and Managing out-crossing to non-Clearfield crops and related weeds 2 2.0 Herbicide resistance management in Clearfield Crops 2.1 Herbicide resistance management using an Integrated Weed Management (IWM) approach The objectives of herbicide resistance management are to achieve weed control whilst preserving the value of each herbicide and each herbicide group for the longer term. Herbicide resistance management programs must consider utilising all available tools to prevent or delay the onset of herbicide resistance. 2.2 Weed and weed seed management for resistance management In practical terms, the key to an integrated approach is to reduce the weed seed bank within each paddock via the use of all available control practices. The use of herbicides is just one of these practices. Reducing the weed burden within a paddock over time can result in the reduction of selection pressure on a weed population. 2.3 Development of resistance Herbicides impose selection pressure for resistance at any rate. Label herbicide rates are a reflection of efficacy trials that indicate best control and crop yield responses. There are several factors which determine how quickly resistance develops: Seedbank Life: Weed seeds with a long seedbank life (seeds which survive for many years in the paddock) act as a buffer to slow down the onset of herbicide resistance. If resistance starts developing, a significant proportion of susceptible seeds remain which dilute the resistance pool. Conversely, resistance can be selected rapidly in weeds with a short seedbank life (common in most small seeded species such as mustards) because resistant individuals surviving a herbicide dominate the seedbank whilst susceptible seeds present from previous seasons are more rapidly depleted. Thus, within a few seasons, resistant individuals can constitute an entire paddock population. Initial Frequency: The initial frequency of naturally occurring resistant biotypes in a weed population influences a weed population's potential to develop resistance. Also, the relative fitness or vigour of 3 resistant weed biotypes affects resistance development. Generally speaking, the greater the initial frequency of resistance and the greater the fitness of the resistance biotype, the greater the potential for resistance to develop in a species population. Time: The time required for a weed population to develop resistance will vary. Resistance to a herbicide may occur in as little as two to five years, or it may never develop. For example, resistance 1 to triasulfuron developed after being used in two consecutive years of continuous cereals . Triazineresistant weeds occurred after 10 years of continuous use of triazines. The first glyphosate-resistant field population of ryegrass was found after 15 years of multiple use of glyphosate. The time required for resistance to develop depends on many factors including: Selection pressure exerted by the herbicide; Herbicide and crop rotation patterns; Seed germination dynamics; Use of herbicide combinations with different modes of action; Initial frequency of naturally occurring, resistant individuals in the weed population; and The relative vigour of resistant biotypes of weeds. Based on these factors, models have been developed to predict the development of resistance in a weed population. However, due to the many factors involved and the limited information available on weed and seed biology, it is impossible to predict exactly when, if ever, a resistant population will develop. Current models provide an indication of the development of resistance; these indications are an essential input to the development of resistance management strategies and practices. The most important factors influencing a plant's potential to develop resistance are: • History of herbicide use: continuous use of the same mode of action herbicide in consecutive years without use of another mode of action herbicide used at the full label rate to target the same target weeds species may increase the potential for resistance to develop. • Cultural practices: weed control that relies solely on herbicide use and does not combine tillage or other cultural practices with herbicide applications may increase the potential for resistant populations • to develop. • Environmental conditions: environmental conditions that are not conducive to herbicide breakdown in the soil may increase the potential for resistant populations to develop. Continuous dry weather can slow the breakdown of many herbicides (e.g. imidazolinones). High soil pH inhibits the breakdown of some herbicides like SU's. The longer a herbicide persists, the longer it exerts selection pressure on a weed population, particularly if there are multiple weed flushes in one growing season. 1 P. Boutsalis, The University of Adelaide. 4 • Composition of the weed population: weed species that are very sensitive to a herbicide, are prolific seed producers and have large genetic variation are at greater risk of developing resistance. • Weed seed bank: a high soil seed bank within an individual paddock increases the selection pressure which, in turn, increases the likelihood of resistance developing. A variety of factors may cause weed control failures. Herbicide resistance is the easiest factor to test for using a herbicide resistance test. If a weed sample is not resistant on or more other factors are responsible, such as misapplication, not adhering to herbicide label recommendations, stressed weeds ad poor environmental conditions. As with most problems, prevention is the best strategy. Development of herbicide-resistant weeds can be avoided or delayed through the adoption of good management practices. The recommendations listed below take into consideration many of the points discussed so far, and are designed to prevent or delay the onset of weed resistance: • Scout fields regularly and understand the biology of the weeds present. • Consider the source of crop seeds and their potential to introduce new weed species and biotypes. • Always read and follow herbicide label recommendations. • Use crop rotations, notably rotations from dicotyledonous crops to grass crops. Weed control • Options in these types of rotations offer the most diverse means to minimise risk of resistance development. • Use the minimum number of applications of any one herbicide or herbicide group recommended per season. • Use and follow industry recommendations for various competitive weed thresholds. • Combine timely cultivation with herbicide treatments as part of the paddock management strategy, if practical. • Use tank mixes or sequential applications of herbicides that have different modes of action but operate on the same weeds species. The manufacturers of herbicides and the regulatory authorities have grouped herbicides with similar modes of action. These modes of action are exhibited on the herbicide labels. The industry publishes strategies resulting in an effective rotation between these groups. Managing herbicide resistance is an ongoing battle. Cooperation between the scientific community, agricultural chemical companies, consultants and government extension personnel is essential to prevent or delay the onset of herbicide resistance using cost effective strategies. One such strategy is the use of herbicide tolerant cropping systems. 5 2.4 Integrated weed management strategies for Clearfield & Clearfield Plus Crops. Clearfield crops are tolerant to herbicides based on the imidazolinone group, which are grouped within the Group B herbicides. Continuous use of Group B herbicides may result in the selection of weed biotypes resistant to this group of herbicides. Testing of annual ryegrass for GRDC sponsored random weed surveys across SA and Victoria have shown that the imidazolinone herbicides control some ryegrass populations that are resistant to the sulfonylurea herbicides. This is also true for some broadleaf weed biotypes resistant to sulfonylurea herbicides. Additionally, Intervix Herbicide has shown control of all randomly 2 collected samples of Brome grass that were resistant to sulfonylurea and sulfonamide herbicides . Preservation of the effectiveness of this group of herbicides is vital for efficient and cost-effective agricultural production in Australia. Therefore, effective management of the potential for the development of resistant weeds is an important part of overall crop and farm management. A number of specific management strategies, as outlined below, should be followed when using the Clearfield Production System. Growers and agronomists should give consideration to each of the following points, in order to determine an integrated weed management plan and how this fits with their crop rotation. • Always refer to the Clearfield Production System Best Management Practice - Agronomists and Growers Guide. • Always follow product label directions. Application timing is essential for optimum weed control and hence managing resistance via minimising weed seed production. • Apply no more than two (2) Group B herbicides in any four (4) year period on the same paddock-this strategy will slow the development of resistance. Consideration should be given to less frequent use to delay the onset of resistance development. This includes the use of Group B herbicides both within the Clearfield Production System and in conventional crops. • Where it is possible, care should be taken to avoid applications of Group B herbicides in consecutive years unless at least two years' previous good weed control has been achieved with methods other than Group B herbicides. Years where no Group B herbicide is used will slow the development of resistance. • Use of Group B herbicides in either summer crops or fallow is equivalent to a pre-emergent application and further Group B applications should not be made. • Farming practices, herbicide and crop rotations should be developed, which allow for the use of alternative mode of action herbicides or methods of weed control. • When using crops with Clearfield and Clearfield Plus technology, consideration should be given to the use of pre-emergence herbicides such as a Group D herbicide (e.g. pendimethalin or trifluralin), Group C (e.g.metribuzin), Group K herbicides (Sakura® or 2 Peter Boutsalis, The University of Adelaide. 6 Boxer® Gold) or Group J (triallate). Consultation with an accredited agronomist regarding this use should be undertaken, particularly in situations where moderate to heavy ryegrass populations exist or where Group B resistance is suspected. • Where Group B resistance is suspected within a weed population, testing of the relevant weeds should be carried out prior to the use of crops in the Clearfield or Clearfield Plus Production System. Visit www.plantscienceconsulting.com.au for more information. • Integrated Weed Management should be undertaken on a paddock-by-paddock basis. Specific paddock planning should take into consideration the history of the paddock as well as the future use options. • Resistance management guidelines for other herbicide mode-of-action groups should also be taken into account when developing and planning rotations. 2.5 General Recommendations for Group B Herbicides 1. Not more than one application of a Group B herbicide per season. 2. If a Group B herbicide has been applied as a pre-emergent application DO NOT apply further Group B herbicides to that crop. Ensure any further post emergent herbicides from another mode of action group. 3. Apply no more than two (2) Group B herbicides in any four (4) year period on the same paddock. 4. If a post-emergent Group B herbicide is required, it should be tank mixed with another mode of action herbicide at the label rate which controls the same target weed outright. If any further applications are required in that season, it should be with a non-ALS mode of action herbicide that controls the target weed. 5. A Group B herbicide may be used alone on flowering wild radish only if a Group B herbicide has not been previously used on that crop. 6. Where a Clearfield herbicide is to be used, refer to the relevant section of this manual. 7. If a post-emergent Group B herbicide is to be used, consider using a non-Group B preemergence herbicide targeting the same species to lower the selection pressure on the Group B herbicide. 8. Keep accurate records of all herbicide usage. The above recommendations should be incorporated into an Integrated Weed Management (IWM) program. In all cases, ensure surviving weeds from any treatment do not set and shed seed. Adopt the integrated strategies mentioned in this document, including the rotation of mode of action groups. Make sure you rotate between products from different mode of action groups. Utlise strategies such as crop-topping, windrow burning, chaff carts and The Harrington Seed Destructor. 7 3.0 Optimised Weed Control with Clearfield Herbicides 3.1 OnDuty Herbicide for Clearfield wheat varieties. NOTE: CL JNZ and CL STL have adequate but limited tolerance of OnDuty Herbicide. These crops do not tolerate Intervix Herbicide. Objective: achieve optimum weed control and maintain weed resistance management practices. 1. Monitor the crop for crop growth, insect attack and weed growth regularly after sowing. Ensure the crop is free of all avoidable stress at the time of application. 2. Apply under appropriate environmental conditions when the crop has reached at least the 4 leaf stage. If the crop shows staggered growth, delay applications until 80% of plants have reached the 4 leaf stage. 3. Use caution to avoid the potential for drift to susceptible crops. Adopt good application practices that minimise spray drift. 4. Decontaminate the boom sprayer and associated equipment before spraying the crop with OnDuty Herbicide. 5. Watch out for residues of sulfonyl urea herbicides. 6. Fit the appropriate nozzles for the recommended water volume of no less than 70L/ha (medium/coarse to coarse droplet recommended). 7. Recalibrate the sprayer for the higher water volumes recommended for OnDuty. 8. Decontaminate the boom sprayer and associated equipment after applying OnDuty Herbicide. 9. Monitor weed growth: • Weeds will stop growing and competing with the crop almost immediately after OnDuty is taken up. Complete death of weeds may take from 4-6 weeks after spraying. • During this time, weeds do not compete with the crop. Weeds change colour progressively from green to either yellow or purple/red. • OnDuty may have a short-term, transient check on crop growth while plants detoxify the herbicide within their tissues. Under adverse growing conditions this check can be more pronounced and the crop may also show some transient yellowing. 8 • OnDuty may not control Group B resistant grass plants and Group B resistant broadleaf plants. 3.2 Intervix Herbicide for Clearfield Barley, Clearfield Canola and Clearfield Plus Wheat. Objective: achieve optimum weed control for crop yield, and enhance weed resistance management. 1. Monitor the crop for crop growth, insect attack and weed growth regularly after sowing. Ensure the crop is free of all avoidable stress at the time of application. 2. Timing: The ALS enzyme is more concentrated in young, rapidly growing plant material. Spray as soon as conditions allow application when the crop has reached the following growth stages: • Clearfield Barley– 3-leaf stage to 1st node stage (Z31). Application earlier than the 3leaf stage may cause unacceptable crop injury under stressful conditions. • Clearfield Canola – 2-leaf stage and no later than the 6-leaf stage. Applications earlier or later than this window are safe to the crop but may impact weed control. • Clearfield Plus Wheat – 3-leaf stage to 1st node stage (Z31). Application earlier than the 3-leaf stage may cause unacceptable crop injury under stressful conditions. Intervix Herbicide has knockdown and residual activity on weeds. It's best not to delay spraying while waiting for a “complete” germination of weeds. Best results and crop yield are obtained by spraying actively growing crops and weeds as soon as possible after the growth stages presented above for each crop type. It has been documented that plants with weak resistance can be controlled if young and actively growing and that control is reduced as plants get older. 1. Use caution to avoid the potential for drift to susceptible crops. Adopt good application practices that minimise spray drift. 2. Application: • For Clearfield Barley apply Intervix Herbicide at the recommended rate of 375 – 750ml/ha in no less than 70L of water/ha with Hasten® at 1.0% v/v or Supercharge® at 0.5% v/v. Where appropriate, add tank mix partner herbicide according to Intervix label instructions. • For Clearfield Canola apply Intervix Herbicide at the recommended rate of 300 - 500mL/ha or 600 - 750mL/ha in a no less than 70L of water/ha with Hasten® at 1.0% v/v or Supercharge® at 0.5% v/v. Where appropriate, add tank mix partner herbicide according to Intervix label instructions. • For Clearfield Plus Wheat apply Intervix Herbicide at the recommended rate of 375 – 750ml/ha in no less than 70L of water/ha with Hasten® at 1.0% 9 v/v or Supercharge® at 0.5% v/v. Where appropriate, add tank mix partner herbicide according to Intervix label instructions. 3. Decontaminate the boomsprayer and associated equipment before spraying the crop with Intervix Herbicide. Watch out for residues of sulfonylurea herbicides. 4. Fit the appropriate nozzles for the recommended water volume of no less than 70L/ha. 5. Recalibrate the sprayer for the higher water volumes recommended for Intervix. 6. Decontaminate the boom sprayer and associated equipment after applying Intervix Herbicide. 7. Do not apply Intervix if rainfall is expected within the following two (2) hours. Ensure label instructions for rainfastness of tank mix herbicide partner are followed if a registered tank mix used. 8. Monitor weed growth: • Weeds will stop growing and competing with the crop almost immediately after Intervix is taken up. Complete death of weeds may take from 4-6 weeks after spraying. • During this time, weeds do not compete with the crop. Weeds change colour progressively from green to yellow or purple/red. 9. Under adverse growing conditions crop growth may be suppressed and some transient yellowing may be seen as crops detoxify the herbicide within their tissues, especially if crops are treated around the 3-leaf stage. 10. Intervix will suppress some species to the extent that they may present little or no competition to the crop. The developing crop canopy will provide further limitation to their growth and competitive status. The use of Lontrel will significantly improve control on species such as capeweed and thistles. 11. Intervix is a broad-spectrum herbicide with contact knockdown activity on weeds and nontolerant crops alike. Exercise caution when applying Intervix Herbicide, and maintain good spray application techniques. In particular, avoid spray drift of Intervix Herbicide onto neighbouring crops and pastures of all kinds (medium/coarse to coarse droplet recommended). 12. Where ryegrass populations are moderate to high or if Group B resistant ryegrass is present or suspected to be present it is recommended to use a pre-emergence herbicide from an alternative Group eg Group D, J or K as appropriate. 13. Always refer to the latest labels of OnDuty and Intervix herbicides for specific directions for use before application. 10 4.0 Controlling Volunteers from Clearfield Crops Objective: control of all volunteers from Clearfield crops before flowering. 4.1 Summary • Best Management Practice is to control volunteer plants in the year following when a Clearfield or Clearfield Plus Production System crop has been grown. • DO NOT rely on Group B herbicides to control volunteers. • Volunteers from Clearfield and Clearfield Plus crops will be controlled by all herbicides currently • registered for control of conventional crops, except for Group B herbicides. For example volunteer Clearfield canola will be controlled by herbicides from Group C (eg atrazine), Group I (eg MCPA, 2,4-D), Group F (eg Paragon® Xtra), Group H (eg Velocity®), Group G (eg Sharpen®) and knockdown herbicides such as glyphosate and paraquat. • Clearfield Plus Wheat and Clearfield Barley volunteers will be controlled by glyphosate, paraquat, Group A herbicides (eg clethodim) and simazine. NOTE: Clearfield and Clearfield Plus wheat plants, and Clearfield barley plants, cannot be controlled in-crop in conventional cereals, they must be controlled pre-sowing. Clearfield canola plants cannot be controlled in-crop in conventional canola- they must be controlled pre-sowing. Atrazine and Roundup Ready Herbicide will provide in-crop control in TT and RR crops respectively. • Clean-up and farm hygiene during all stages of sowing, harvesting, storage and transport are important in the effective control of volunteers. • To facilitate volunteer control monitor paddocks during the growing year and the year after growing Clearfield and Clearfield Plus crops. • Best Management Practice is to make volunteer control part of weed, pest and disease management strategies for the farm. 4.2 Important reasons to control volunteers • Volunteer plants act as competitive weeds in following crops or pastures. • Volunteer plants may result in contamination of grain. • Volunteers may be important in the build-up and spread of major diseases. 11 • Volunteers increase the risk of herbicide tolerance spreading from cross-pollination of volunteer plants and neighbouring paddocks containing the same crop species. 4.3 Controlling volunteers A combination of hygiene, cultural and herbicide options are available to control volunteers including: • Minimise seed losses through close attention to timeliness of harvesting. • Correct setup of harvest equipment. • Seal all holes and cracks in harvest equipment which allow spillage, even of small quantities of seed (especially in the table, front elevator and grain tank). • To avoid the inadvertent spread of Clearfield and Clearfield Plus varieties between paddocks, along farm tracks, public roads and roadsides at harvest, thoroughly clean out harvest equipment using high pressure air blowers/suckers. • Practice good hygiene at harvest and during transport of grain to on-farm storages; practice good stubble management after harvest. • Spray any seed that germinates with summer rains with a knockdown herbicide at robust rates. • Control ALL volunteers in following crops or pastures with pre-sowing knockdown or with in-crop herbicides. 4.4 Management actions • Record and clean up all accidental seed spillage on and off the farm-check later for germination of volunteers and control with robust rates of knockdown herbicides. • Keep good field records of herbicides used in previous crops and herbicide-tolerant varieties in neighbouring paddocks to develop effective plans for controlling volunteers. • A crop of the same species should not follow a Clearfield or Clearfield Plus crop, as controlling volunteers within the same crop species is difficult. If successive wheat or barley crops are grown, seed should not be saved from the second crop due to the fact that volunteer seed from the previous crop may be present. 12 5.0 Managing Out-crossing 5.1 What is out-crossing? Out-crossing (or cross-pollination) can be defined as the ability of a plant species or variety to pollinate a plant of a different, related species or variety. A wide range of factors influence the ability of a given plant to out-cross with others, such as timing of flowering, pollen dispersal, pollen viability and environmental conditions. The likelihood of out-crossing varies greatly from species to species and variety to variety. Successful out-crossing may result in the offspring displaying characteristics of both parent plants. The risk of out-crossing can vary significantly between crop and weed species. The focus for management must therefore be on the control of volunteers and managing herbicide-tolerant crops and related species. Each Clearfield crop is covered individually due to the difference in potential for out-crossing. 5.2 Potential for out-crossing in Clearfield and Clearfield Plus wheat Specific information is provided here in relation to possible out-crossing of resistant traits to other wheat varieties and related species. 5.3 Description of Triticum aestivum varieties with Clearfield and Clearfield Plus Technology Clearfield wheat varieties (CL JNZ and CL STL) have tolerance to OnDuty Herbicide and Clearfield Plus wheat varieties have tolerance to Intervix Herbicide. Current Clearfield and Clearfield Plus varieties were derived from inbreeding and chemically-induced modification. They were not derived from recombinant DNA technology, i.e. they are not GMOs. These varieties were developed via conventional back-crossing methods. The majority of wheat varieties grown in Australia are pure lines, derived from inbreeding. The tolerance has been introduced only into white spring wheat varieties to date. 13 5.4 Potential for out-crossing to non-Clearfield and Clearfield Plus wheat varieties Although wheat cultivars are classified as self-pollinators, out-crossing in wheat has been documented in both winter and spring wheat cultivars, albeit at very low incidences. Out-crossing rates of 0.1 - 5.6% among winter wheat have been reported. Increased out-crossing rate was not associated with semi-dwarf stature. A range of 0.3 - 6.05% out-crossing among Canadian spring wheat cultivars has also been reported. Studies show that out-crossing tended to be highest among cultivars with low pollen staining, spikes that tapered at the extremities and with greater spikelet opening at anthesis. There have been no reports showing that Triticum aestivum exhibits characteristics of a pest or that it is a weed in Australia. Centuries of breeding of wheat varieties has selected for a number of traits resulting in the modern wheat, which has a poor ability to survive in the wild. Traits such as heads that did not shatter were favoured due to easier harvest but this trait placed the wheat plants at a disadvantage to plants of other species, which could more efficiently distribute seed. In addition, hull-less type plants were easier to thresh but exposed the developing seed to undesirable environmental extremes. Despite these disadvantages, plants of modern wheat cultivars are occasionally found in uncultivated fields and roadsides. These occurrences are usually associated with grain dropped during harvest or transport. Plants growing in these environments do not persist, and are usually eliminated by mowing, cultivation and/or herbicide application. Wheat plants may also grow as volunteers in a cultivated field following a wheat crop. Volunteers that germinate in a crop or fallow following the use of Clearfield or Clearfield Plus crops should be controlled before flowering, as outlined in the Controlling Volunteers section of this Obligatory Practice. After almost 200 years of cultivation in Australia and throughout the world, there have been no reports of wheat becoming an invasive pest. In short, out-crossing to other wheat varieties is possible. However, the likelihood of this occurring is greatly diminished when the Clearfield Best Management Practices are followed (ie good hygiene and appropriate rotation practices, and control of volunteers prior to flowering). As wheat pollen is relatively heavy and unlikely to travel greater than 3m, the likelihood of out-crossing is considered remote. 5.5 Potential for out-crossing to weed species related to wheat There are only a few reports concerning natural cross hybridisation with related species and genera. Hybridisation within the genus Triticum has been shown to be generally less than 6%. While hybridisation between cultivated wheat and related species can occur, no known wild Triticum species exist in Australia. 14 When out-crossing does occur, it is generally due to close contact between flowers of different varieties (within 3m). A well-known inter-generic combination involving wheat is triticale, derived from crossing wheat and rye (Secale cereale). There have been no reports of triticale serving as a bridge for hybridisation with other wild grass species. Complex hybrids have been made between wheat and several species of Agropyron including A. curvifolium, A. distichum and A. juceum. There are no known reports of hybridisation between wheat and the weed species A. repens, and all reports of wheat-Agropyron hybrids involved deliberate cross-pollinations in greenhouse settings. There are no known relatives of T. aestivum in Australia. While it is possible to produce hybrids between wheat and Agropyron species, no known naturally occurring hybrids or derived species have been reported. Therefore, out-crossing to related weed species is considered highly unlikely. 5.6 Managing out-crossing of Clearfield and Clearfield Plus wheat to related species As stated, the likelihood of out-crossing to related species is low for wheat. However, the following practices should be followed to help minimise the potential for out-crosses occurring: • Control all volunteers in the season after growing Clearfield or Clearfield Plus Wheat. • If consecutive wheat crops are grown (of which one is Clearfield or Clearfield Plus Wheat), do not save seed from the second crop. Saved seed may contain both varieties, which may increase the likelihood of outcrossing when next planted. • Maintain hygiene along fence-lines where different wheat varieties may germinate. • Cover loads during harvest and transport to avoid dispersing seed. 5.7 Potential for out-crossing in Clearfield Scope Barley Specific information is provided here in relation to possible out-crossing of resistant traits to other barley varieties and related species. 5.8 Description of Hordeum vulgare L. (cultivated barley) varieties with Clearfield Technology The majority of barley varieties grown in Australia are pure lines, derived from inbreeding. Clearfield Scope Barley is derived from in-breeding and chemically-induced modification. It is not derived from recombinant DNA technology, i.e. Clearfield Scope Barley is not a GMO. Clearfield Scope barley has tolerance to Intervix Herbicide. The tolerance has only been introduced into spring barley varieties to date. 15 5.9 Potential for out-crossing to non-Clearfield barley varieties Although cultivated barley and its wild progenitor both reproduce almost entirely by selffertilisation/pollination, some isolated cases of out-crossing have been reported, albeit at extremely low incidences. In experiments designed to measure outcrossing rates in barley plants in physical contact with each other, the average rate of outcrossing was about 0.8%. The rate of out-crossing fell to 0.2% when physical contact was virtually eliminated by spacing plants 30cm apart, and when plants were 60cm or 90cm apart, the pollen migration rate fell to approximately 0.1%. Pollen migrants were only detected sporadically when pollen donor and recipient plants were separated by 3m, and no outcrossing was detected when plants were separated by 10m. Barley is not generally pollinated by insects, so any outcrossing occurs by wind pollination and distance is the most important factor that influences rates of out-crossing as a result of pollen migration in barley. In observations of pollen migration between commercial barley fields, outcrossing rates were 0.05% and 0.01% for distances of 1m and 10m, respectively. No pollen migrants were observed in these studies at distances of 20m or 50m. However, cross fertilisation with very low frequencies has been observed at distances of up to 50m and 60m (although cross pollination at such distances is rare). In short, out-crossing to other barley varieties is possible. However, the likelihood of this occurring is greatly diminished when the Clearfield Best Management Practices are followed (ie good hygiene and appropriate rotation practices, and control of volunteers prior to flowering). 5.10 Weediness status in Australia and Overseas H. vulgare occurs as an escape from cultivation and is present throughout Australia. It is listed as a naturalized non-native species present in all Australian states and territories with the exception of the Northern Territory. Barley is considered a minor weed in natural ecosystems, but is primarily a problem in agricultural or rural environments. Barley is likely to occur anywhere seed is dropped and often grows on roadsides, but seldom persists. Barley crop derived seed can develop into volunteers, but only at a very low frequency. In an environment assessment done by the USDA/APHIS in 1994, it was stated that barley occasionally escapes and becomes weedy or naturalized. However, barley is not reported as a serious or principle weed and there are no reports of barley becoming a significant weed in the US. 5.11 Potential for out-crossing to weed species related to barley The other related species present in Australia include Hordeum glaucum, H. hystrix, H. leporimum, H. marimum, H. murinium, H. secalimim, secale cereal and Triticum aestivum. Although some of these are weedy, none can cross with cultivated barley under natural conditions. In relation to interspecific crossing, with few exceptions the isolation barriers (usually hybrid sterility) are very strict between the Hordeum species and there is little or no genetic exchange in nature due to lack of chromosome 16 pairing, even where two taxa have sympatric distribution, Intergeneric hybrids can be obtained between barley cultivars and diploid, tetraploid and hexaploid wheats, but only with extensive intervention such as hormone applications, chemical treatment and embryo rescue. 5.12 Managing out-crossing of Clearfield Scope barley to related species As stated, the likelihood of out-crossing to related species is extremely low for barley. However, the following practices should be followed to help minimise the potential for out-crosses occurring: • If consecutive barley crops are grown (of which one is Clearfield Scope Barley), do not save seed • from the second crop. Saved seed may contain both varieties, which may increase the likelihood of outcrossing when next planted. • Maintain hygiene along fence-lines where different wheat or barley varieties may germinate. • Cover loads during harvest and transport to avoid dispersing seed. • Control all volunteers in the season after growing Clearfield Scope Barley. 5.13 Managing Clearfield Wheat and Clearfield Scope Barley in the crop rotation: • It is not recommended to follow Clearfield Wheat with Clearfield Scope Barley or vice-versa. If this practice is carried out it is critical to control all volunteers from the previous and subsequent Clearfield crops. Seed should not be saved from the 2nd crop. • In the event of growing two (2) Clearfield cereal crops in succession, ALWAYS ensure herbicide resistant management general recommendations for Group B Herbicides are followed in accordance with the integrated weed management strategies for Clearfield Crops. Apply no more than two (2) Group B herbicides in any four (4) year period on the same paddock. • In a situation where it is intended to grow barley following a wheat crop, Clearfield Scope Barley may prove a useful tool in managing volunteer wheat (non-Clearfield varieties) in the barley crop. 5.14 Potential for out-crossing in Clearfield Canola Specific information is provided here in relation to possible out-crossing of resistant traits to other canola varieties and related species. 5.15 Description of Brassica napus varieties with Clearfield technology Clearfield canola varieties have tolerance Intervix Herbicide and OnDuty Herbicide. Current Clearfield varieties were derived from inbreeding and chemically induced modification. They were not derived from recombinant DNA technology. These varieties were developed via conventional backcrossing methods. The majority of canola varieties grown in Australia are pure lines derived from inbreeding. A range of Clearfield Canola varieties are available with maturities to suit all canola growing regions. 17 5.16 Potential for out-crossing to non-Clearfield canola varieties Brassica napus (canola) varieties are predominantly self-pollinated, and pollinating agents such as wind and insects are responsible for only a small proportion of cross-pollination. Cross-pollination and out-crossing may vary according to variety, proximity and environmental factors, and in proximate plants may range from 3-20%. There is a chance of intra-specific crosses. Cross-pollination decreases with increasing distance from pollen source. Pollen movement decreases exponentially with distance from the source. This is because: • Pollen viability is short lived; • Honeybee behaviour (i.e. they clean their bodies of pollen before returning to a crop); and • Competition between self-fed and foreign pollen in fertile plants. • Therefore, the probability of cross-pollination and gene transfer by pollen from Clearfield crops is low. Contamination of herbicide-resistant canola varieties has been recorded following cross-pollination of paddocks in close proximity and as a result of physical admixture of seeds during harvesting. Crosspollination and transfer of herbicide-resistant canola plants is neither a new phenomenon nor a major threat, however advisors and end-users need to be aware of the risks and the consequences. Low levels of cross-pollination between neighbouring canola fields is to be expected. An assessment of the risk of out-crossing and hybridization from imidazolinone tolerant Brassica napus must consider the following factors: • The imidazolinone tolerance trait originated by conventional selection of a mutation in a native gene. • As a result, the range of genotypes and phenotypes that may be produced with this trait do not fall outside the experience of traditional genetics and plant breeding. • Transfer of imidazolinone tolerance in recipient plants requires the independent inheritance of two genes. Gene action is additive and shows incomplete dominance. This does not favour survival of heterozygous individuals for this herbicide resistance trait. Given this information, a low potential for out-crossing between Clearfield canola and other varieties does exist. For this reason, consideration should be given to avoiding the planting of Clearfield canola adjacent to other non-Clearfield canola varieties. In addition, Best Management Practice is to ensure other canola crops do not proceed or follow Clearfield canola crops. Control of volunteers in all situations is important in assisting to prevent out-crossing. 5.17 Potential for out-crossing to weed species related to Canola In all the research literature reviewed by Scheffler and Dale (1994), the possibility of hybridisation between Brassica napus and related species, even under optimum conditions, is often low. Methods 18 of ovule culture and embryo rescue, developed over several decades, have extended the range of species that can be sexually hybridised with Brassica napus. However, such in vitro methods are not indicative of the probability of similar hybrids occurring by cross-pollination under natural conditions. Even where there is an inter-specific hybridisation between B. napus and a related species growing in proximity, poor vigour and high sterility in the hybrids will generally mean the hybrids and their progeny will not survive in either an agricultural or natural habitat. • In a post-doctoral study at the CRC for Weed Management Systems in Adelaide, 50 million seeds from imidazolinone resistant wild radish hybridisation experiments were tested for hybridisation -7 involving ALS resistance. Fewer than five (5) plants were determined as potentially resistant (10 ). -5 Although not directly comparable, this is less than the figure of 10 determined by Steve Powles and C. Preston of the CRC as the natural frequency in untreated populations for ALS resistant alleles in annual ryegrass. The closer the relationship between the parental genotypes, the greater the probability of successful hybridisation and gene transfer. This means that the likelihood of out-crossing to a related weed species is even lower than that for out-crossing to other canola varieties. Therefore, the chances of successful, long-term survival and establishment of the gene in new hybrid-derived populations of related species is even lower. 5.18 Managing out-crossing of Clearfield canola to related species Out-crossing between canola varieties and between canola and related weeds is known to occur. For this reason, management practices described here should be followed to minimise the likelihood of out-rossing with Clearfield canola: • Control all Clearfield canola volunteers in the following year. • Control all Brassica weeds both in-crop and in adjacent sites such as fence lines before flowering. • Where possible, avoid growing Clearfield canola in paddocks adjacent to other canola varieties. • Best Management Practice is to not grow consecutive canola crops, regardless of variety. • Cover loads during harvest and transport to avoid dispersing seed. 5.19 Potential for out-crossing in Clearfield Maize Maize in Australia is often grown in complex rotations of summer and winter crops in relatively confined geographic areas. These systems often utilize a wider variety of management techniques, including cultivation, knock-down and pre-emergent herbicides. Maize is not invasive, has relatively low seed dormancy, low seed shedding and is a poor competitor during early seedling stage. These factors decrease the potential for maize to become weedy. 19 The Clearfield trait does not infer any additional advantages other than tolerance to Lightning Herbicide and therefore Clearfield Maize will act in a very similar manner to non-Clearfield varieties in the environment. Maize is an open pollinated species and therefore there is potential for Clearfield varieties to crosspollinate with non-Clearfield varieties. However, given the relatively low potential for invasiveness of maize in general, Clearfield maize is considered to show a low risk as a result of any outcrossing. Maize has been shown to have the ability to produce fertile hybrids by outcrossing to other species. However, other Zea species sexually compatible with Zea mays are not found in Australia and therefore there is not potential interspecies target for outcrossing. The overall risk of outcrossing of the Clearfield gene is Australia is extremely low. 5.20 Managing practices for Clearfield maize The greatest risk in Clearfield maize is the potential for the development of resistance. This is particularly the case in situations where there is the potential for rotations between maize and Clearfield canola, Clearfield wheat/Clearfield Plus wheat and Clearfield barley are possible. In these situations, whilst typically a different weed spectrum is being targeted (ie summer weed species vs winter weed species) there is a still a higher risk which needs to be managed. Whilst the risk of genetic transfer is extremely low, Best Management Practices to minimize risk in Clearfield Maize are: • Control all Clearfield maize volunteers in the following year. • Where possible, avoid growing Clearfield maize in paddocks adjacent to other maize varieties. • Avoid growing consecutive maize crops, regardless of variety. • Cover loads during harvest and transport to avoid dispersing seed. • Avoid using Group B herbicides in fallow situations where Clearfield maize crops are planned to be grown in the following season. • Avoid growing Clearfield maize following a winter Clearfield crop. • Consideration should be given to the use of residual herbicides from alternate mode of action groups [eg atrazine (Grp C), s-metolachlor (Grp K), pendimethalin (Grp D)] in order to reduce weed populations. 20 6.0 BASF Contacts Sales Team Contact Number E-mail Trevor Gillespie - National Sales Manager Crop Protection 0418 162 705 [email protected] Chris Ryan - Regional Sales Manager Southern Region(WA, SA, VIC, TAS) 0400 090 276 [email protected] Lachlan Broad - Area Sales Manager SA, VIC, TAS 0407 880 746 [email protected] David Clegg - Area Sales Manager, WA 0408 630 641 [email protected] Lindsay McRae - Regional Sales Manager Northern Region (NSW, QLD, NT) 0438 033 887 [email protected] Andy Byard - Area Sales Manager, Northern NSW, QLD 0407 880 472 [email protected] Joel Murphy - Area Sales Manager, Southern NSW 0437 791 730 [email protected] Southern Region (WA, SA, VIC, TAS) Northern Region (NSW, QLD, NT) 21 Contact your local Agricentre© for further information: agro.basf.com.au Customer service Australia-wide: 1800 558 399 Clearfield, OnDuty, Intervix, Lightening, Paragon and Sharpen are registered trademarks of BASF. 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