Citrus spray application workshops: Feb. 2018

A fruit with water sensitive paper sprayed with a kaolin clay mixture.

Matt McWilliams (Interlink) discusses the Surround® kaolin clay treated trees at the Sunraysia workshop.

Scott Mathews (Syngenta) discussing the interpretation of water sensitive paper.

Alison MacGregor (consultant) overviewing the use of flagging tape on poles to follow the air flow of a sprayer at the Sunraysia workshop.

Phillip Lintern (Agspec) discussing the technical aspects of spray adjuvants at the Griffith workshop.

Steven Falivene (NSW DPI Citrus Development Officer) conducting a nozzle output test.

UV dye results at night.

The interlink multi-head fan spray unit being tested.

Citrus spray workshops were conducted on 8 February 2018 at the NSW DPI Dareton research station and on the 28 February at the NSW DPI Griffith research station. Workshop organiser, Steven Falivene (NSW DPI Citrus Development Officer), said “the main purpose of the field days was to provide growers with the skills and knowledge to test the performance of their spray machines and to understand the options they have to improve this. The knowledge gained will also help growers that are purchasing a new spray machine be more informed and to ask the right questions. Spray application field days in the past did a great job with demonstrating the use of water sensitive paper, but there needed to be more information on how to interpret the results. Therefore, the latest workshops presented the relevant technical and practical information from leading experts in Australia.” <

Four industry experts presented at the workshop; Scott Mathews (Syngenta), Alison MacGregor (spray application and horticultural consultant), Matthew McWilliams (Interlink spray machine manufacturer) and Phillip Lintern (Agspec adjuvant specialist). The workshop was sponsored by Interlink, Agspec, Syngenta, Guidolin Engineering, Sunraysia Citrus Growers and Mildura Agricultural Supplies.

Matthew started the indoor session by describing the different attributes of various types of commonly used citrus spray machines. Of particular interest was the discussion of good air movement within the trees and the various fan configurations. Scott and Alison discussed various aspects of spray application. This included a discussion on the absorption of chemicals into the tree, the behaviour of different types of droplets moving through the air and hitting the target, the effect of temperature and humidity on droplet evaporation, droplet size distribution of nozzles and how to interpret droplet assessment methods (i.e. water sensitive paper or UV dye).

Phillip completed the theory session by explaining the different types of adjuvants and how they affect spray application. Of special interest was the discussion of a pine oil based adjuvant (e.g. Flexstend®) that can reduce the evaporation of droplets on leaves, thereby increasing the opportunity of the active ingredient to be absorbed into the leaf. These pine oil adjuvants might have potential in improving the uptake of micronutrients and systemic insecticides. However, Phillip warned participants that there are two types of pine oils available; a cheaper one which is used for killing weeds and that growers should therefore ask their reseller if the product they intend to use on their trees is made from the slightly more expensive but safer, higher grade quality pine oil.

At the outdoor session Steven demonstrated how to test nozzle outputs and to quickly calculate litres per ha volume application rates. Matt then discussed the important pre-season and pre-spray maintenance and checks. Scott and Alison discussed the options available for adjusting spray machines for optimum performance. Steven Falivene and Andrew Creek (NSW DPI citrus development officers) then led the group through some spray tests using water sensitive paper and Surround® kaolin clay. Some growers returned at night to inspect the ultraviolet (UV) dye treated trees. These trees were treated at different volumes and speeds and the UV dye clearly showed the differences in application efficiency. Steven was advised that special UV lamps (valued at $5,000) were needed, however he bought a variety of cheaper UV torches (for $15) from eBay instead and they performed extremely well. Any grower can now conduct these tests relatively inexpensively in their own orchard.

A secondary outcome of the workshops was observing the performance of the multi-head spray machine provided by Interlink. This machine had been set up with a double manifold of nozzles so it could spray with 60 or 120 nozzles. This meant medium-high volume spraying (5,500 L/ha) could be achieved using the 2 L/min nozzles. This is beneficial because the smaller nozzles produce smaller droplets and ultimately provide more effective coverage. The twin manifold also meant that switching from high to low volume spraying is easily done by turning off a manifold; no more changing of nozzles is required. The 5,500 L/ha application rate performed just as well as any other spray machine seen at previous field days (including oscillating boom), and even achieved acceptable foliar spray coverage at lower application rates (~ 1,700 L/ha).

Further workshops can be conducted upon request, simply register your interest with your local citrus development officer. However,  they will occur in late April and start at about 1:30 pm. A workshop dinner will be included which enables all participants to be able to view the UV dye treated trees as darkness falls.