GEN citrus tree in the sun

New Zealand researchers are fighting bugs with bugs.

The two-year project, part of the A Lighter Touch programme, is exploring a biological method of dealing with insects on citrus orchards.

The method uses understorey plantings to attract beneficial insects.

“Leaving bare earth under citrus trees and intensively mowing the grass strips between orchard rows may become a thing of the past as we revolutionise our approach through strategic planting,' said A Lighter Touch project manager Jeff Smith.

'We’ve undertaken trials planting under and beside the trees – ranging from flowering perennials such as clovers and alyssum to annuals like buckwheat and phacelia. These plants and others may hold the key to helping us enhance the agroecosystem and provide resources for beneficial insects to thrive, which would reduce the need for applications of agrichemicals.'

A Lighter Touch is a seven-year programme backed by the New Zealand horticultural industry and the federal government through the Ministry for Primary Industries’ (MPI) Sustainable Food and Fibre Futures fund.

The programme aims to reduce growers' relience on 'traditional crop protection' by carrying out research, understanding crop protection products, and integrating biological and ecological processes into food production in New Zealand.

The citrus project has brought in researchers from Lincoln University and Plant & Food Research, who have extensively reviewed literature on how to plant to attract the natural enemies of persistent pests. The researchers are now translating theory into practice.

'We’re testing to see what works under New Zealand conditions,' said Smith.

'Seeds were planted late last year on two trial sites alongside two control sites – one in a valley and one on the plains.

'So far, we’ve found that plants on the plains struggled to establish, but the valley planting was more successful. This was because there was more rainfall in the valley. The landowner also had sheep on the land, which trampled seed into the soil. In future we may look at autumn sowing to see if we can achieve a more consistent establishment.'

Smith said the programme was collecting data regularly on the trial and control sites, including fortnightly monitoring for insect presence and species.

'By spring (in New Zealand) we’ll be able to evaluate how effective the planting has been in the first year.”