Australia - Nufarm, APVMA answer call for optical spraying rates

Date:05-03-2023

Increased adoption of optical spot spraying has prompted Nufarm to include applicable rates on labels for nine of its herbicides, and seen the Australian Pesticides and Veterinary Medicines Authority issue a minor-use permit to cover herbicides manufactured by other companies.

These allow the use of more knock-down and residual modes of action, and make it possible for growers to mix and rotate fallow weed-control chemicals.

Following behind-the-scenes work with the APVMA, Nufarm has led the way in the Australian herbicide space by specifying rates for optical spot spraying as well as broadacre on labels for the following herbicides:

• Dropzone: 2,4-D with droplet optimisation technology;

• Biffo: glufosinate-ammonium;

• Crucial: Triple salt advanced technology glyphosate;

• Trooper 75-D: 2,4-D plus picloram;

• Weedmaster DST: Dual salt technology glyphosate;

• Terrad’or: Tiafenacil;

• Amicide Advance 700: 2,4-D;

• Amitrole T: Amitrole plus ammonium thiocyanate; and,

• Comet 400: Fluroxypyr.

APVMA has also issued a minor-use permit for optical spot sprayer herbicide rates for a further 15 herbicides from Corteva, Sipcam, Arysta, Nufarm, Shandong Rainbow, Syngenta, Sumitomo, Nutrien Ag Solutions and FMC Australasia.

In place until 31 December 2026, the PER90223 permit is for various herbicides applied using optical sprayers.

These include: Weedseeker; WEEDIt; John Deere See & Spray; Bilberry, and other emerging green-on-brown optical spray systems to enhance weed management in fallow.

All registered products can be applied at per-hectare broadacre rates through an optical sprayer if there is no specified optical-spraying rate on the label, and growers must follow label and permit directions carefully.

In addition to the nine Nufarm products with new rates for optical spot-sprayer application, the APVMA permit provides higher-rate options for various products for use in two scenarios:

• Application of short-duration residual herbicides butroxydim, clethodim, haloxyfop-R, fluazifop-P butyl ester, quizalofop-P-ethyl, sethoxydim, triclopyr ester and flumioxazin where grass and broadleaf weed cover is up to 30 percent of the field; and,

• Higher rates of residual herbicides aminopyralid and picloram and triclopyr as the butoxyethyl ester, picloram and triclopyr as the butoxyethyl ester, metsulfuron-methyl and fluroxypyr methyl heptyl ester and aminopyralid where weed cover is up to 10pc of the field.

  
  

Expanded options for optical sprayers

Industry sources estimate around 70pc of grain-growing businesses in Queensland and northern New South Wales either own an optical spot sprayer, or use one as operated by a contractor.

Adoption of this technology in Australia’s southern and western growing regions currently sits at around 25-30pc of farms, in line with the increasing emphasis on summer weed control in these regions.

Optical spot spraying helps growers implement the WeedSmart Big 6 tactics, such as applying the double knock to protect widely-used herbicides such as glyphosate and Group 1 herbicides.

Until recently, only 2,4-D, paraquat, glufosinate and glyphosate were registered for use through optical spot sprayers.

Optical spot spraying vastly reduces the quantity of herbicide applied to cropping land in fallows, whilst conserving moisture and nutrients.

At densities of less than one weed per 10 square metres, the area sprayed with herbicides is 70-8pc less than when a blanket spray is applied.

This reduction in area treated allows growers to reduce the volume of herbicide and water used and makes it economical to include more expensive products within a grower’s chemical program.

Allowing weeds to grow in summer fallows negates much of the crop-yield benefit from conservation farming practices.

Transpiration by summer weeds is the only mechanism that can remove soil moisture, and reduce nitrogen mineralisation, to a depth of 1.2 metres or more.

The spread of difficult-to-control weeds such as feathertop Rhodes grass, fleabane and sowthistle into the southern and western growing regions is behind the increasing adoption of optical spot spraying beyond the northern region.