Since 2019, the Foundation of Arable Research has participated in the A Lighter Touch programme, which supports growers to shift from reliance on agri-chemistry to more sustainable crop protection practices.

It has been acknowledged for some time that pesticide rotation and new products aren’t keeping up with pathogen and pest adaptation and resistance. This mirrors a global issue in the fight against pathogens and pests.

As consumers show more interest in food that is sustainably grown and ethically produced, with minimal chemical residue, it was decided that there was an opportunity to collaborate across horticulture, arable and viticulture sectors.

Jo Drummond, the senior researcher for cereals for the foundation (Far), explains that this approach uses the crop itself and the ecosystem the crop exists in to determine the type of pest management required.

“Our key elements are utilising plant genetics, integrating new crop protection technologies and rationalising chemical pesticide programmes.

“This allows us to integrate things like classical biological control, biodiversity, plant protection products and other cultural methods like cultivar selection,” says Jo.

Working with barley crops

Yellow dwarf virus is a seasonal pathogen that causes yield loss in cereals and is transmitted to plants by aphids. Several aphid species can vector the virus.

“Young plants are the most vulnerable to aphids that spread the virus through feeding, which impacts the plant’s ability to photosynthesise by causing the leaf discolouration, plant stunting, and ultimately shrivelled grain, which affects crop yield.”

Winged aphids fly into cereal crops from pasture grasses or other crops and start colonies of wingless aphids. When plants become unsuitable or overcrowded, winged aphids reproduce and migrate to other plants or crops. Infection often starts along the edges of paddocks, and hotspots develop as the aphids move. If the infection is severe, large areas can be affected.

Traditionally, the issue is dealt with using insecticide-treated seed, which protects the young seedling, and follow-up foliar insecticide applications until the plant can withstand the infection.

Aphid flights can occur at any time, but the risk is higher in the north, where it is warmer, which means an integrated pest management approach may look a little different to parts of the South Island.

“There is an ALT [A Lighter Touch] demo farm in Pukekohe, and spring-sown barley is included in their rotation, which offered a good opportunity to look at things at a farm level,” says Jo.

“Natural beneficial predators and parasitoids do a really good job, so when looking at interventions, it’s important to understand the activity and ratio of beneficial species to aphids.”

At the Pukekohe site last season, there were plenty of beneficial species, but no aphids, suggesting the risk of YDV was low.

Monitoring the crop

The Pukekohe demonstration is on a larger scale and not replicated, compared with a replicated small-plot trial. It provides the opportunity to demonstrate how integrated pest management (IPM) can work at a paddock level.

This includes the use of both untreated and insecticide-treated seed and using IPM to make decisions around foliar insecticide applications.

“We also monitor the beneficial species like parasitic wasps, hoverflies, brown lace wings and aphid populations using sticky traps and direct searching.

“This information feeds into Aphid Chat (aphidchat.com), our online tool for managing aphids, where you can find information on risk periods, beneficial species, how to monitor, when to take action, and what options are available.”

Brown lacewing and hoverfly larvae are particularly efficient, chomping through potentially hundreds of aphids, while parasitic wasps will lay their eggs directly into a wingless aphid, which then becomes the host for the developing larva.

Sticky traps only trap flying insects and require regular replacement, so crop walks are essential to spot eggs and wingless insects.

“Any chemical intervention only buys time,” says Jo. “An insecticide seed treatment typically lasts until the crop reaches tillering. Once the crop reaches stem elongation, the plant is more resilient to infection.

“This leaves a potential risk period between when the seed treatment runs out and when the plant is robust enough to withstand infection. Knowing how the beneficial species and aphid population dynamics work helps us determine whether an insecticide is needed.

“One of the great things about IPM is that it does allow for a grower’s level of risk, so they can decide what intervention they want to put in place.”

Jo says the benefit to everyone is a reduction in our environmental and economic footprints.