ADAPTING to new 2,4-D spray requirements for this season’s summer fallow and autumn double knock weed control may not be quite as onerous as first thought.
Spraying may take longer at slower speeds and with significantly more total volume to maintain efficacy, but keeping extra water up to the spray rig in the paddock could be a more difficult problem for many WA farmers than complying with the new technical aspects.
That seemed to be the consensus of opinion from farmers who attended a 2,4-D product update and application information day at Dalwallinu last week, the second in a series of six Wheatbelt information days that concludes tomorrow at Esperance.
They were organised and run by Nufarm in conjunction with northern agriculture region agronomist and spray application specialist Bill Campbell to explain critical differences between the 2,4-D spray permit that applied last season and an interim permit applying until October 1 this season.
The Australian Pesticides and Veterinary Medicines Authority (APVMA) caught Australia’s agricultural chemicals industry by surprise when it suspended the previous permit on October 4 and introduced the interim permit ahead of release later this month or next month of findings from an extended review of 2,4-D which began in 2005.
According to the APVMA, the interim permit is aimed at reducing spray drift and applies to about 220 herbicide products containing 2,4-D.
It applies whether 2,4-D is sprayed alone or in combination with adjuvants or other herbicides or fungicides.
The interim permit places significant obligation on farmers preparing to sow this season’s crop to change how and when they spray to comply with the new requirements.
The permit specifies a compulsory minimum Very Coarse (VC) droplet size spray quality, a maximum 50 centimetres boom height above canopy or target weed and defines ‘no-spray’ buffer zone minimum distances of generally five to 20 metres to downwind ‘sensitive’ environments.
It also specifies spraying 2,4-D is to be avoided when there is risk of a temperature inversion or when winds are less than 3kmh or more than 15kmh, which basically rules out night spraying for most farmers.
A record of spraying start and finish times and dates, location, product trade name, application rate, hectares sprayed, type of crop, wind speed and direction, air temperature and relative humidity, nozzle brand, model, size, type and spray system pressure, boom height and name and contact details of the sprayer operator must be completed within 24 hours and kept for two years.
As well, a non-mandatory APVMA advisory statement covering cereal crops, fallow and pasture recommends Extremely Coarse (XC) or Ultra Coarse (UC) droplet size for 2,4-D spray quality for ‘drift sensitive’ situations through to April 15.
Malcolm Gillett from Nufarm outlined the changes for about 80 farmers and agriculture business representatives who attended the Dalwallinu information day.
He acknowledged the commercial interest Nufarm had as an agricultural chemicals company and that of its subsidiary Croplands, which manufactures a range of sprayers through three-point-linkage and trail units up to self-propelled 48-metre boom models.
“But we are here today simply as the messenger,” Mr Gillett said.
He pointed out some precautions farmers normally took when spraying, such as not spraying when it is windy and leaving buffers beside water courses and around tree lines, were now mandated with specific requirements when using 2,4-D which did not apply when spraying other chemicals.
Mr Gillett said Nufarm and Croplands had negotiated an exclusive permit with the APVMA for farmers whose spray rigs were not designed to operate with a boom height down to 50 centimetres.
He said that permit allowed those farmers to use a boom height up to 85cm above the ground, provided a UC spray quality is achieved.
However Mr Gillett said the permit only allowed Nufarm’s Amicide Advance 700, Trooper 75-D, Cobber 475, Estercide Xtra 680, Zephyr 625, Amine 625, Baton Low and Estercide 800 products to be used.
He said similarly, Nufarm and Croplands had helped negotiate another permit for farmers using WEEDit, WeedSeeker and other optical spot spraying technology that only delivers a Coarse spray quality at 75cm height.
Mr Gillett said spraying 2,4-D with this equipment was permitted provided target weeds did not comprise more than 10 per cent of the application area and Amicide Advance 700 and Trooper 75-D products were used.
He pointed out both of these permits, obtained by Nufarm, required farmers to keep even more detailed records of each spraying and meet all of the other new requirements in relation to buffer zones and weather conditions.
Mr Campbell reassured farmers there were “solutions” enabling all farmers to meet their new 2,4-D spraying obligations, even for those with older model sprayers with air induction systems not designed to run at the higher 4-6 bar optimum operating pressures of many of the VC, XC and UC nozzles.
“For most of you, it will mean moving to new nozzles you’ve never used before and for some it will mean changing from low-pressure air induction nozzles to high-pressure air induction nozzles,” Mr Campbell told farmers.
He said for farmers with pulse width modulation system sprayers there was also a range of specialist Wilger nozzles to achieve VC, XC and UC spray quality.
Mr Campbell said a change from medium to VC spray quality reduced drift from 6-20 per cent down to 3pc and a further change to XC or UC cut drift to less than 1pc.
“But bigger droplets means less coverage so your total application volume in litres per hectare – at robust label rates of course – has to go up to maintain efficacy,” Mr Campbell pointed out.
He suggested farmers would need to use a minimum of 80 litres of water a hectare in light stubbles or ground cover and increase it to 100L/ha or more in high or heavy stubbles.
Mr Campbell said the greater momentum through the air of large droplets compared to smaller droplets meant bigger droplets took longer to lose momentum and fall vertically between stubble stalks to hit ground level weeds and large droplet retention on leaf surfaces was also reduced.
He said as well as using more water, farmers may have to cut their operating speed range back too.
In the information pack provided to farmers attending the update and information days was a Grains Research and Development Corporation fact sheet which compared spray quality of 23 common nozzle types in a range of orifice sizes at various pressures.
A second chart provided litres per hectare total application volumes at a range of spraying speeds for common nozzle sizes based on 50cm nozzle spacings.
Referring to both charts will help farmers determine which nozzle type and size best suits their equipment to deliver VC, XC or UC spray quality at 80l/ha or more across the speed range suited to the application or desired by the operator, Mr Campbell said.
However, he reminded farmers they needed to factor in slower turning speed on headlands, with a subsequent pressure drop on some sprayers, for their calculations on which nozzle type and size to use at what pressures and at which total application volume and over what speed range to achieve the required droplet size and maintain efficacy.
Mr Campbell strongly recommended once farmers had their spray rigs set up for the new permit requirements they used water-sensitive paper placed on the ground in the environment where they would be spraying, to check spray coverage was satisfactory at the total application volume and speed they intended using.
Yathroo farmer Carl Moltoni said after the Dalwallinu day that while he had an “issue” with the interim permit applying “across the board”, irrespective of where spraying was taking place and what adjacent drift risk environments where, he did not see problems in complying.
“For most of us it’s not a problem,” Mr Moltoni said.
“We all know what we are doing, we all try and control spray drift because most of us plant canola next to our wheat.
Rob Nankivell, Maya, said water quality and having water available in some form of trailer or truck tanker ready to refill the sprayer in the paddock to minimise delays during a now restricted spraying window, would be important.
“We’re set up to spray Fine, Coarse and Very Coarse,” Mr Nankivell said.
“We might need to ditch the Fine and go Coarse, Very Coarse and Ultra Coarse.
“I suppose there’s going to be a bit of guess work in setting it up.
“The problem is, you can’t just check with your neighbour and do what they’re doing because everybody’s in the same boat,” he said.
Clint Wyatt, Buntine, said the interim permit required farmers to “pretty much do what we’ve been doing”.
“Setting up the machines and getting the extra water to them is going to be the important bit,” Mr Wyatt said.
p More information: see www2.nufarm.com/au, contact your Nufarm territory manager or Bill Campbell on 0427 545 553.