Faba bean growers now have another option to
control rust late in the season and prevent yield losses.
Faba bean growers now have another chemical option available to control rust. Pulse Australia advises growers and agronomists that tebuconazole fungicide can now be used in faba bean and broad bean crops in all states.
Pulse Australia industry development manager (southern and central) Wayne Hawthorne says the Australian Pesticides and Veterinary Medicines Authority (APVMA) has advised that Pulse Australia’s application for a new permit for tebuconazole use in faba beans and broad beans has been approved.
“This comes as a result of residue studies and trial work conducted by the GRDC-funded ‘Registration for minor use chemicals for the grains industry’ project,” he says.
"Rust in faba and broad beans has been more prevalent in recent years, particularly in southern Australia,” Mr Hawthorne says. “Tebuconazole has previously been approved for application early in the crop cycle to control the fungal disease cercospora, but now it can also be applied later in the season to control both cercospora and rust.”
Rust has the potential to reduce seed size and, if not controlled, could cause a reduction in yield of 30 to 40 per cent. While other products are available to control rust, Mr Hawthorne says having another option means growers can choose a cheaper product and can rotate fungicide groups to avoid resistance developing to a particular chemical group.
“Protecting crops from yield loss to diseases such as rust and cercospora is generally cost-effective,” Mr Hawthorne says. “Tebuconazole can be used in combination with other products to control other fungal diseases where necessary.”
The new permit also provides bean marketers with the assurance that grain will fall within maximum residue limits for chemical residues.
The new faba bean variety PBA Rana remains popular with growers for the 2014 season after strong performances in the market in 2012 and 2013, but it is susceptible to rust infection. This variety provides growers in the high-rainfall zone with access to markets for medium-sized faba beans of good quality. Premium prices were paid last harvest.
Faba beans have rotational benefits and fit into both mixed-farming and continual-cropping systems mainly in Victoria, South Australia and New South Wales. Faba bean crops will tolerate waterlogging better than other pulses, cereals and canola and can be grown on more acidic soil types, provided correct inoculation procedures are followed to ensure nodulation. They have also found a niche in some medium to lower-rainfall areas where they are sown early into no-till stubble systems.
The new permit for tebuconazole has been issued as PER13752 and applies from 31 May 2013 until 30 June 2016. A copy is available from the APVMA website (http://permits.apvma.gov.au/PER13752.PDF). The old permit (PER12657) and the three-day withholding period are no longer current. Significant changes to observe with the new permit are:
- where it is the only active in products containing 430 grams per litre of tebuconazole;
- long withholding periods (WHPs): 21 days for harvest and 14 days for grazing (adherence to these new WHPs should not be difficult for bean growers);
- approved use for rust and cercospora; and
- a maximum of three applications at 145 millilitres of product per hectare still applies.
Rust in faba beans
The major fungal diseases affecting faba beans are chocolate
spot (Botrytis fabae), ascochyta blight (Ascochyta fabae) and
cercospora leaf spot (Cercospora zonata). However, rust (Uromyces
viciae-fabae) can also become a problem in prolonged wet seasons.
Rust can occur from mid-spring onwards and is favoured by warm
temperatures (above 20°C) and moist conditions. Rust infection can
occur following only six hours of leaf wetness and does not require
extended wet periods for infection to spread. Protection from rust is
most critical from late flowering to the end of flowering when pods are
filling (15 to 20 weeks after emergence). The impact of rust on yields will
vary according to seasonal conditions and the variety sown.
The Doza variety is moderately resistant to resistant, while PBA Rana
and PBA Kareema are moderately resistant to susceptible. A severe
outbreak of rust in some regions put varieties to the test in 2011. Late
planting is recommended for high-disease-risk areas.
Foliar sprays of mancozeb, tebuconazole or chlorothalonil provide the
added benefit of suppressing chocolate spot and ascochyta blight later
in the season. Copper sprays will also control rust and chocolate spot.
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