Trichogramma wasps are active in macadamia nuts and parasitising macadamia nut borer eggs. Over the last few years they have been found in good numbers in the Lismore, Nambour and the Gympie districts. This is an important development for the macadamia industry - large trees are difficult and expensive to spray while some macadamia properties are under increasing pressure from encroaching residential areas to restrict insecticide spraying.

The wasp has been identified as Trichogrammatoidea cryptophlebiae (Dubbed MacTrix). Many crop consultants are now monitoring for parasitism. Trichogramma are tiny wasps (0.4 mm long) that lay their eggs into moth eggs. The wasp eggs hatch into larvae inside the moth egg and develop into fully formed wasps inside the moth eggs. The moth eggs go a coal black colour and typically two wasps emerge from one MNB egg leaving one or two escape holes. The egg shells remain dark after the wasps have emerged so are easily distinguished from eggs that have yielded larvae.

In the past, deciding whether to spray for nut borer has been determined, in part, by moth egg pressures. Now some crop consultants are also allowing for egg parasitism rates before making spray decisions. A parasitism rate of 75% has the effect of reducing the egg pressure to a quarter of that without the wasps.

Parasitism levels have been so high in some districts and properties that insecticide spraying has been greatly reduced and in some cases not required.

Where insecticides have been applied (mainly the synthetic pyrethroid Bulldock®) adult wasps are killed by the insecticide but those still developing inside moth eggs are able to survive in reasonable numbers.

Mimic® is now registered for use against MNB in macadamias (and lychees). This insecticide has no effect on Trichogramma wasps and is an important new tool for IPM programs.

Horticulture Australia Limited (H.A.L.) and the Macadamia Society are supporting a project to understand this process better. The project is based at the Tropical Fruit Research Station, Alstonville but includes extensive collaboration with crop consultants form Atherton to Macksville.

Trials have been conducted to determine the toxicity of existing and some new insecticides to the wasps so that a better IPM package can be developed.

A colony of macadamia nut borer was established so that the wasps could be mass reared as it is difficult to rear on other host eggs. Establishment of these cultures has enabled the release of this wasp into those areas where the wasp has not been found.

A comprehensive series of trials were conducted in the 2003-5 seasons in conjunction with crop consultants and researchers under the HAL project: Advancing IPM in Macadamias MC02048.

The Trichogramma wasps can overwinter on MNB eggs on a number of common plants including bauhinias, lychees, golden rain trees, bird of paradise trees and poincianas. This species of Trichogramma is also thought to parasitise the eggs of orange fruit borer.

Commercial mass rearing systems and release strategies have been developed for this parasitoid. During the 2005-6 season about 550 hectares of macadamias were treated and the wasps no doubt spread well beyond this area. Aiming to treat 800 ha in the 2006-7 season.

For lots more information on MacTrix go to the BioResources Web Site or contact:

Richard Llewellyn at BioResources P/L

Phone 07 3289 4919