Getting weeds early is key

Tom and Charm Arnott have been growing cotton on ‘Fairfield’ at Boggabilla for 24 years. Speaking to their CottonInfo Regional Extension Officer, Tom Arnott outlined how they are managing the threat of resistant weeds.

They encounter a wide range of weeds in their farming operations, including peachvine, barnyard grass, chinese lantern, feathertop Rhodes grass, fleabane, sesbania, climbing bellvine, pigweed, milkthistle, turnip and native vetch. Tom finds climbing bellvine a particular challenge in cotton, because once it is in the crop it is difficult to control, wrapping around the cotton and causing issues at harvest.

Tony Taylor, Taylor Ag Consultancy and Tom Arnott “Fairfield” Boggabilla

Tom is working with consultant Tony Taylor to implement an integrated weeds management strategy.

“Resistance in weeds is already impacting on our business. We have seen how quick it can get away and it can be hard to get back. There’s also a cost associated with trying to get back,” Tom said.

“As a result, Tony and I are mapping out a strategy to combat resistance. It’s our first year, so it’s very much a work in progress. To date, I have relied on an over the top glyphosate application and a light cultivation for weed control. We’ve learnt that spraying when the plants are too big doesn’t work – you have to get in when they’re small.

“We are now implementing a residual program, which will involve using selective pre-emergents at planting to target hard-to-kill weeds on a field-by-field basis.

“We will then use a mix of glyphosate in a double- knock approach, and conduct a more aggressive cultivation with discs and knives to cultivate closer to the plant line.

“We’ll also apply a broadleaf ‘layby’ (a residual herbicide used to control weeds in-crop) to all fields to control late weeds coming through.

“We also chip weeds: particularly in the school holidays, with the whole family doing their bit. I always have a hoe in the ute!”

Tom found the recent CRDC, CottonInfo and ICAN weed management workshops useful in learning strategies to control glyphosate-resistant weeds.

“There was plenty of information, and a lot of experience among the growers in the group. It was good to kick around ideas and talk to the agronomists,” Tom said.

Source: CottonInfo Weed Control case studies

Further information: CottonInfo weed management page