The biology and ecology of macadamia lace bugs

Kirsten Ellis

doi:10.25918/thesis.415

Macadamia spp. are native to Australia and have significant commercial value worldwide for their edible nuts. Integrated pest management (IPM) can be challenging in Australia because macadamia is a native plant cultivated commercially in its native range alongside its native insect pests and their natural enemies. Attaining viable commercial yields of macadamia in Australia has historically relied heavily upon the use of chemical insecticides including organophosphates, and a shift away from reliance on insecticides has not yet happened. Of the 23 insecticides registered for use in macadamia in Australia, 19 face issues affecting their continued use, and 12 are presently not approved in the EU, US or Canada. Those international markets may refuse produce that doesn’t adhere to their own insecticide use standards, hence Australian produce may be excluded from market access. In this thesis I examine the biology and ecology of emerging major pests of macadamia in northern New South Wales (NNSW) and southern Queensland (QLD), macadamia lace bugs Cercotingis decoris and Proteatingis howardi, and how these relate to IPM practices carried out by the Australian macadamia industry. Amblypelta spp. have historically been the pests of greatest concern to the macadamia industry: this has not changed, but the make-up of the other major and minor pests has changed over time. Historically, macadamia lace bugs have been pests of minor importance; however, more recently they have become significant pests causing losses of up to 100%. There are currently no effective biological control options available to manage macadamia lace bugs, and registered chemical options are incompatible with IPM. This thesis explores pathways out of the current “pesticide treadmill” by asking questions regarding the biology and ecology of macadamia lace bugs: their temperature requirements for development, what their populations look like in orchards over time including periods when they are not causing damage to crops, and what potential biological control options could be examined. They are the first pest infesting orchards each season, with populations increasing from July (winter) when flowering commences and continuing until October when flowering finishes. Temperature requirements for development for both species have a minimum of approximately 8 °C, optimum development occurs at approximately 28 °C and they cease development above 33 °C. Juvenile development is well described by Briere 1 and 2 functions. Adults are found in orchards throughout the year after flowering, particularly in areas closer to rainforest areas. Further from rainforest areas, numbers of lace bugs decrease to zero outside flowering periods. In northern NNSW both species are found; however, only C. decoris are found south of the overlap area and only P. howardi are found further north. Four commercially available predatory insects have been identified in laboratory testing (‘the colosseum’) for further testing in the field. With further research, an area wide management (AWM) strategy including biological control options for controlling macadamia lace bugs with reduced reliance on broad spectrum insecticides could be developed. This will be necessary to ensure the long-term viability of the macadamia industry.

The biology and ecology of macadamia lace bugs

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The biology and ecology of macadamia lace bugs

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