GrowNotes

Spray application manual

Module 20: Optical spot sprayers

20.1 Introduction

Published 24 January 2025 | Last updated 23 January 2025

Optical spot sprayers are designed to detect and spray only the weeds present in a paddock. Typically they have been used to apply knock-down herbicides as a fallow application, or under shielded sprayers in some cropping situations.

In any given fallow situation the actual weed cover rarely exceeds 20 to 30 per cent of the actual paddock surface, so optical spot sprayers have the potential to offer large savings in chemical use or the ability to use typically more expensive products, which can provide greater efficacy on harder-to-kill weeds. In situations where weed cover is approximately 30 per cent or more it is recommended to consider using a normal boom sprayer for blanket applications.

Before choosing a product to be applied through an optical spot sprayer, the operator needs to carefully check the intended product labels or current Australian Pesticides and Veterinary Medicines Authority (APVMA) approved permits to see if optical spot spray application is supported.

Generally, if the applied rate to be used by the optical spot sprayer is the same rate / ha as per a standard boom application, and the label does not specify or exclude the use of certain nozzle types, spray qualities or application equipment, then an application via an optical spot sprayer should be able to proceed.

However, in some cases APVMA-approved permits and labels may also permit an optical spot- spray rate, based on the tank mix concentration of product (litres of product per 100 litres of water). Often this labelled spot spray rate may be higher (on a L/ha basis applied to the spot) than the standard boom spray rate.