An overview of workshops presented by AMIA, Nufarm with funding assistance from the AusIndustry Innovation Access Program

IntroductionRecently, AMIA, in conjunction with Nufarm, successfully applied for AusIndustry* funding to deliver a number of spray application and adjuvant workshops in mango production regions. Spray application workshops were held in six mango production regions in Australia. Each workshop was well attended by growers and related industry representatives and provided an opportunity to gain a greater understanding of new spray application technology.

For those in industry unable to attend the workshops this booklet has been developed to provide a brief snapshot of the information delivered at the workshops.

Robyn Gaskin, a specialist on adjuvants and application was invited to speak at each workshop

Robyn GaskinRobyn is an internationally recognised scientist with more than 30 years experience in the area of crop protection. She has worked for most of that time at the Crown Research Institute ‘Forest Research’, based at Rotorua, New Zealand, in the Plant Protection Chemistry group (PPCNZ). Robyn undertook her crop protection studies at Bristol and Strathclyde Universities in the U.K., principally on the behaviour and mode of action of agrochemical adjuvants.

Her specialty is their use to enhance pesticide efficacy and her work has been instrumental in the commercial introduction of more cost-effective agrochemical spray formulations for both horticulture and forestry.

Robyn’s extensive experience with the use of adjuvants in horticultural operations has been

PEST MANAGEMENT IN MANGOES

Robyn Gaskin at the Spray Application workshop held in northern NSW.

“ This project is funded under the Commonwealth Government’s Innovation Access Program. An initiative of Backing Australia’s Ability, the Commonwealth Government’s commitment to Innovation”

gained from research projects undertaken on behalf of numerous commercial clients and grower organisations, both local and international. She has worked to improve the efficacy and environmental sustainability of pesticide programmes in crops as diverse as potatoes and onions, kiwifruit, wine grapes and pine trees. Robyn’s work has proven many times that spray adjuvants, used correctly, are powerful tools to reduce pesticide use and minimise environmental contamination, while improving returns to growers.

Currently, Robyn is contracted by both the Avocado Industry Assn (NZ) and Pipfruit NZ Inc to develop more effective pesticide spray programmes for their industries, based on using superspreader adjuvants in greatly-reduced water volumes. Robyn has also assisted the Australian horticultural sector with spray adjuvant advice in recent years; currently she is collaborating in projects to (1) improve the evenness and efficiency of drying sultana grapes, and (2) lower spray carrier volumes and improve disease control in vineyards.

Adjuvants and applicationControlling pests in mangoes is a constant challenge, ensuring the often dense canopy and underlying fruit are thoroughly wetted and covered with spray.

Traditionally many growers have used high volumes of water to deliver pesticides to their target. Higher volumes means higher costs, less hectares sprayed per load, more travel to and from water supplies, higher fuel bills, greater labour inputs and less flexibility in spraying operations.

The economic benefits of lower spray volumes are well recognised, but the challenge has been how to achieve this without jeopardising reliable pest control and crop quality.

Correct application of fungicides and insecticides is critical to the success of the product, and therefore to the successful management of the target pest or disease.

Adjuvants are assisting to revolutionise pesticide application as users can achieve more cost-effective, better-targeted, and more environmentally acceptable pest control.

The term adjuvant covers a range of actions, including wetters and spreaders, uptake activators, rainfasteners, antifoams, stickers, drift reducers and water conditioners.

Agrochemical adjuvants can:

• Improve pesticide efficacy and may lead to reduced chemical use

• Reduce off-target deposits and improve environmental sustainability

• Reduce costs and increase returns to growers

Du-Wett and Designer are two new organo-silicone based super spreaders, designed specifically for the application of crop protection products to horticultural crops.

Currently trial work is being undertaken to collect data for registration of these new tools in Tropical Tree Crops.

The addition of new horticultural super-spreader surfactants has been shown to provide better coverage and better retention of agrochemicals than conventional surfactants in a range of crops.

The principle is simple.Concentrated pesticide formulations are transported in low water volumes to the target. Here Du-Wett and Designer distribute the small volume over a large area, ensuring even coverage of the target surface.

Mango orchards in Australia are often characterised by relatively large trees with thick foliage, providing a difficult structure for spray penetration. Also leaf shape, angle and surface form mean that many spray droplets do not adhere to the leaf and either miss their target completely or bounce off their target, only leaving a smear of the droplet and therefore the insecticide or fungicide that was intended to be applied.

Researchers from the Plant Protection Chemistry section of Forest Research New Zealand have undertaken research into the use of adjuvants to increase performance and decrease water volumes for a range of fruit and vegetable crops over a period of many years. The work they have done is applicable to the mango industry, but research has not been conducted on mangoes although it has been conducted on tree crops such as avocado.

The organo-silicone super-spreaders have been around since the early ‘80’s and are used widely as adjuvants for herbicides in forestry and agriculture. The properties which have ensured their success with

herbicides like glyphosate are their ability to greatly improve spray retention, coverage, penetration and herbicide uptake into the plants. This is achieved by reducing the surface tension of the spray solution so much that the herbicide can flood into the small openings on the leaf surface, the stomata and to greatly increase the amount and speed of herbicide uptake.

“ However, the physical properties desirable in those organo-silicones to increase the efficacy in herbicides are not beneficial in a horticultural situation”, says PPCNZ adjuvant scientist Robyn Gaskin. “Protectant and contact pesticides are not intended to penetrate through the stomata into foliage, and if adjuvants cause them to do so, they can damage crops. In addition, incorrect use of herbicidal super-spreaders can reduce pest and disease control through run off and increased wash off by rain.”

New ECL horticultural super-spreaders are unique surfactant blends which have been designed specifically for use on crops in most weather conditions

The practical, economic and environmental benefits arising from lower spray volumes are well recognised and growers would readily adopt the practice if they were convinced that pest and disease control could be guaranteed. Lower water volumes could mean spraying more area in a day. Alternatively spray application intervals could be shortened when pest pressure is high, or trees are undergoing rapid growth. Lower spray volumes would increase grower’s flexibility.

In research undertaken in New Zealand on a range of fruit and vegetable crops, growers had common needs from their pesticides and application. These included:

• better pest & disease control

• lower cost of pest & disease programmes

• spray more ha per day

• cover more area between rain

• shorter spray intervals at disease peaks

• reduce tractor size & soil compaction

• conserve water

• increase operational flexibility

Superspreaders have been shown to deliver better coverage and better retention of agrochemicals than conventional surfactants, in reduced spray volumes and throughout the entire season.

During the spray application workshops, held on mango orchards, Robyn used the product

Surround**, often used as a sunburn protectant in horticultural crops. This was used to indicate droplet application and capture on leaves. While many people have used dyes in the past, the white marker dries relatively quickly and is easy to see. There is no need for ultraviolet lights or wandering around your orchard at night.

** Surround is made from specially modified kaolin, a naturally occuring mineral that is also used as a food additive, in toothpaste and in cosmetics.

By using this method prior to and during the season if necessary, growers can observe droplet capture and application pattern for their own orchard. Spray equipment can be adjusted according to the conditions (eg tree size and canopy shape) to optimise spray coverage.

The potential of organosilicone adjuvants, the ‘superwetters’ to improve spray coverage and retention on a wide range of plants has been developed by New Zealand scientists from the Forest Research team in New Zealand.

Robyn Gaskin has recently completed 2 years of research of orchard trials to successfully cut water rates for pesticide sprays on kiwifruit by half. ‘We see many opportunities to lower growers’ costs using superwetter technology,” said Robyn. “The practical and economic consequences of reducing water rates for a wide range of sprays on different crops are very significant.”

An example of the cost comparisons of conventional spray programs and using a superspreader is illustrated below

While registration of Designer and Du Wett are expected in mangoes for the forthcoming season, no research trial work has been completed.

Cost comparisons for spray programs Speed 8km/h, tank 2000 litres, 60ha block, labour and machinery costs NZ $75/h

Application factor Protectant sprays Systemic sprays

Adjuvant np De Wett LI-700 +Du Wett

Adjuvant rate (litre & ha) 0.125 0.125 2.5 1+0.2

Spray volume (litre & ha) 500 200 500 200

Work rate (ha/h) 4.9 8.1 4.9 8.1

Application costs ($) 15.3 9.3 15.3 9.3

Adjuvant costs ($) 1.4 4.75 42.5 24.6

Total costs ($) 16.7 14.1 57.8 33.9

Cost ratio 100 84 100 59