On 21 November, AUSVEG in collaboration with VegNET 3.0 hosted a Pub in the Paddock event in Penguin, Tasmania at Vertigan Ag.

With a focus on the specific needs of the Tasmanian growing region, the event covered innovative trial work focussing on managing herbicide resistant ryegrass, advances in mechanisation for weed control, and innovative approaches to combat white rot disease in onions.

Phil Frost, Managing Director for Arvensis Research, provided an update on the onion levy-funded project Optimising chemical and cultural control of onion white rot.

Phil spoke about the management practices the white rot project has been trialling, including soil DNA testing to determine disease risk, germination stimulants applied pre-plant to reduce disease levels, new fungicide modes of action, best-practice fungicide rotation and schedule, and biologicals to optimise crop health.

White rot is one of the most economically significant fungal diseases of onions in Australia, and is caused by the fungal pathogen Sclerotium cepivorum. White rot only affects allium crop species, particularly onion, leek and garlic crops. Sclerotium cepivorum forms small black bodies known as sclerotia which can survive in the soil for decades.

“One sclerotium per kilogram of soil can cause measurable yield loss,” Phil stated. “Ten to 20 sclerotia per kilogram can cause essentially all plants to become infected.”

White rot is spread between paddocks through soil movement, such as infected soil carried by machinery, boots, and produce bins, highlighting the importance of good biosecurity practices on-farm.

It is important to minimise risk pathways where possible by cleaning vehicles and equipment or by leaving all visitor and staff vehicles outside of growing sites, Phil told the workshop. He flagged bins and pallets as a possible cause of contamination, as these are often re-used across state borders and between properties. Bins and pallets should be disinfected and cleaned where possible and should be kept away from production areas.

The focus of the event was an onion field trial testing a variety of herbicides for their effectiveness in managing ryegrass and overall onion crop safety.

Tim Groom of TD and SM Groom Agricultural Consulting, an agricultural consultant renowned for his extensive knowledge in onions, pioneered the field trial, in collaboration with Dr Peter Boutsalis, Managing Director of Plant Science Consulting, a company specialising in herbicide resistance.

Herbicide resistant ryegrass has been identified as a major issue across almost all onion growing states nationally.

Widespread herbicide resistance in ryegrass can be attributed to a number of factors, growers heard from Tim and Dr Boutsalis. For one, ryegrass is an obligate out-crosser, this means ryegrass requires cross-pollination for successful reproduction.

Therefore, if a neighbouring property carries resistance and their ryegrass population cross-pollinates with another ryegrass population, the next generation will also be herbicide resistant. A lack of herbicide rotations, ryegrass ‘survivors’, and target-site mutations will also contribute to increased herbicide resistance

Controlling ryegrass in onions is further complicated by several factors, the workshop heard. Firstly, the timing of herbicide application plays a critical role; for example, the main group 1 herbicide, Clethodim, exhibits very low effectiveness during cooler weather.

Sowing times differ according to region and climatic conditions, although generally onions are sown in late winter. Secondly, ryegrass possesses a long germination window, especially in irrigated paddocks, with its seeds spreading throughout the soil profile due to annual cultivation practices.

Lastly, ryegrass is a highly competitive grass which will compete strongly against onion crops, exacerbating the ryegrass control challenge, and highlighting just how important research and trials are in finding solutions to mitigate the ever-present problem of herbicide resistant ryegrass in onions.

At the Pub in the Paddock event, Taz Drone Solutions also showcased a T40 agricultural drone. Attendees were shown how drones can be used for mapping and spraying of chemicals on-farm.

Challenging sloped terrain and wet weather conditions can mean traditional sprayers aren’t able to adequately control weeds on-farm. This can lead to an increased weed burden, meaning increased competition for essential inputs such as water, nutrients, and sunlight.

Growth in the agricultural drone sector has seen improved features, including 50kg spreading payloads, and 40kg spraying payloads. The T40 drone has the ability to map 6.67ha in 10 minutes, with binocular vision offering 360-degree horizontal obstacle sensing. The detection distance is up to 50 metres, allowing for intelligent terrain scouting. The drone also has dual atomised spraying systems, including a dual atomised centrifugal sprinkler, which ensures even droplets and more efficient chemical usage, allowing for 12 litres to be sprayed per minute.

A big thank you to all collaborators who made the onions Pub in the Paddock event possible, to the speakers who provided their expertise, and the attendees who took the time out of their schedule to attend.

Check the AUSVEG communication channels for more information on future onions events.