Key points

• Off-target impacts and concern about the environment, together with 'new blood' in a farming family, are providing some of the incentives for growers to modernise their invertebrate pest management practices
• More knowledge is required on beneficial insects to support decisions to reduce insecticide use

In the absence of practice change, the continued heavy reliance on insecticides as the key management tool will increase production – and market – risks. These risks include the development of insecticide resistance, the depletion of natural enemies and the increased reliance on insecticides to control pests, and the potential for trade implications.

But practice change doesn’t come with the flick of a switch. Growers need a clear incentive to change pest management practices and to consider novel approaches.

“Resistance is making control impossible or costly. Awareness of off-target impacts, concern for the environment, new blood in the farming family – these are the drivers for change,” says Queensland Department of Agriculture and Fisheries (QDAF) principal entomologist Dr Melina Miles.

Dr Miles is based at Toowoomba and also spent many years working as an entomologist in Victoria.

“Essentially, we need a realisation that things have to change, or a desire to do better. Growers and advisers need support. They need to regularly check their information and discuss their plans and talk through whether what they want to do is reasonable and logical,” she says.

“It may only be incremental change but it needs to be constantly upgraded until it becomes normal practice.”

Dr Melina Miles, principal entomologist, Queensland Department of Agriculture and Fisheries (DAF), using a beat sheet to look for insects in canola, supporting growers in their integrated pest management practices. Photo: DAF

Insect knowledge stocktake

In 2018, under QDAF management with GRDC investment, the Independent Consultants Australia Network (ICAN) interviewed agronomists across Australia to collate industry understanding of invertebrate pests to form the basis of discussion at subsequent regional workshops.

The workshops, which included entomologists, focused on recommended best management practices, current industry practices and constraints to best management practice adoption and associated issues.

The agronomists were asked about the key pests in their regions, how they make control decisions and what further information or research they needed.

The list of invertebrate pests considered included earth mites, weevils, lucerne fleas, slugs, snails, slaters, earwigs, millipedes, wireworms, aphids (including the Russian wheat aphid and green peach aphid), Rutherglen bugs, cotton bollworms, diamondback moths, armyworms, mirids and green vegetable bugs.

“The need for more information on identification of pests and natural enemies, pest life cycles, ecology and thresholds which could inform their pest management decision-making was consistently raised by advisers,” Dr Miles says.

Economic thresholds were identified as essential tools, and dynamic thresholds as highly desirable, and there was an appreciation that economic thresholds may change over time and need revision.

The second most important issue was information on beneficial insects (predators and parasitoids) and the effect they have on pest populations. The use of models to predict the number of natural enemies required to control pest populations was also identified as a valuable decision tool.

“We have a limited number of dynamic thresholds for pests and a good understanding of which beneficials are likely to suppress pest populations, but little – or no – work has been done to put the two together,” Dr Miles says.

“The complexity of managing pests and preserving beneficials makes decisions about when and what to spray challenging. Support for decision-making around pests and beneficial impacts would probably increase confidence in holding off on sprays, and using more-selective insecticide options.”

Support to change

Not only is knowledge level a barrier to adoption of new practices, confidence and attitude to risk were also hindrances.

“Many advisers wanted their growers more involved in the decisions around pest management and to assume the risk associated with trying different approaches, or to at least drive or demand change in current management practices,” Dr Miles says.

“Support for practice change in invertebrate pest management requires clear, practical recommendations and sustained RD&E for growers and their advisers as they develop their knowledge, skills and experience in doing pest management differently.”

More information: Beneficials – Predators, Parasitoids and Pathogens (The Back Pocket Guide); Dr Melina Miles, 0407 113 306, melina.miles@daf.qld.gov.au