Mark M. Stevens

Russian wheat aphid (Diuraphis noxia, Mordvilko ex Kurdjumov) (RWA) is a major pest of wheat and barley. Although rice (Oryza sativa L.) is not considered a primary host, RWA has been found on drill-sown rice in Australia prior to the application of permanent water. This study investigates the persistence of RWA on rice and evaluates plant responses to infestation, with the aim of determining whether pest management interventions are justified in Australian rice-growing systems. A series of replicated glasshouse trials was conducted using single and repeated aphid infestation pressures. Results demonstrate that rice is an unsuitable host for RWA, with aphid populations declining over time in all treatments, suggesting that rice does not support self-sustaining populations. A single infestation caused no measurable injury to rice, while repeated infestations led to only minor physiological effects, with plants recovering rapidly after aphid removal. These findings indicate that RWA does not pose a direct threat to rice production in Australia under current farming practices and that the routine application of insecticides for its control in rice is not justified.

Exotic tephritid incursions are of high concern to Australia’s biosecurity and its horticultural industries. It is vital that Australia remains ready to respond to incursions as they arise, as an incursion of tephritid fruit fly species will result in significant economic losses. In this review, we compared Australian incursion management strategies for fruit flies with global management strategies and identified possible areas where improvements could be made in an Australian context. Overall, Australia has a good understanding of the main tephritid threats, of which Bactrocera species from across the Torres Strait (northern Australia) are of most concern. Effective tools for tephritid detection and early warning surveillance at points of entry are in place at ports and in horticultural areas Australia-wide and provide the basis for initiating biosecurity responses in the event of an incursion. Area-wide control measures used in successful eradication attempts globally are available for use in Australia. However, a specific tephritid emergency response plan identifying suitable response measures and control options for species of concern is not yet available. We have identified that Australia has the policies and management tools available to respond to an exotic tephritid incursion, but the speed at which this could be accomplished would be greatly improved by the development of species-specific emergency response plans.

BACKGROUND: The common armyworm Mythimna convecta is an important pest of pastures and graminaceous crops in Australia, but materials currently registered for its control are limited to broad‐spectrum compounds incompatible with integrated pest management (IPM) systems. In this study we assessed the response of M. convecta larvae to four alternative compounds using topical and dietary bioassays. RESULTS: Emamectin benzoate [LC ₅₀ (lethal concentration for 50% of insects tested) values 2.69 μg mL ⁻¹ topical, 0.017 μg active ingredient (AI) g ⁻¹ dietary] and chlorantraniliprole (LC ₅₀ values 4.87 μg mL ⁻¹ topical, 0.080 μg AI g ⁻¹ dietary) were significantly more active than either indoxacarb or cyantraniliprole. Our results showed strong parallels with data on the more extensively studied Australian strains of Helicoverpa armigera , with the most notable differences being the higher contact toxicity of emamectin benzoate to M. convecta and the lower acute dietary activity of formulated cyantraniliprole to this species, which was linked to feeding deterrence. Cyantraniliprole at dietary concentrations of ≥0.02 μg AI g ⁻¹ significantly reduced the weight of surviving larvae and frass production (an indirect measure of food consumption) over the seven‐day exposure period. There was also some evidence of chlorantraniliprole deterring larval feeding, although to a much more limited extent. CONCLUSIONS: Both emamectin benzoate and chlorantraniliprole are suitable for use against M. convecta . The decision as to which of these compounds should be prioritized for further development should be based on their potential effects on beneficial species once their optimal field rates have been determined.

This study investigated the interactions between insecticides (acephate and indoxacarb) and fungal entomopathogens (Beauveria bassiana [Bals.‐Criv.] Vuill. strain B27, Metarhizium anisopliae [Metschn.] Sorokin strain ECS1, and a commercial B. bassiana product, Velifer^® Biological Insecticide) for controlling the macadamia seed weevil, Kuschelorhynchus macadamiae Jennings and Oberprieler, in the laboratory and glasshouse. In the laboratory, additive interactions between insecticides at their full field concentrations (776 mg AI/L of acephate and 75 mg AI/L of indoxacarb) and fungal entomopathogens at 10⁷ conidia/ml (ECS1 and B27) or at full field concentration (0.5 ml of Velifer^®/L) were seen at 6 days and 12 days post‐application. Under the same experimental conditions, synergistic interactions against K. macadamiae were observed 6 days post‐application when fungal entomopathogens at 2.5 × 10⁶ conidia/ml or at 25% of full field concentration (Velifer^®) were co‐applied with insecticides at 25% of their full field concentrations, whilst additive interactions were again observed at 12 days post‐application. In the glasshouse, additive interactions between insecticides (at full field concentrations) and fungal entomopathogens (at 10⁷ conidia/ml, or at full field concentration for Velifer^®) were obtained at 6 days and 12 days post‐application. The results from this study suggest that acephate and indoxacarb have both synergistic and additive effects against K. macadamiae when deployed together with fungal entomopathogens, depending on the initial concentrations of mixture components. Combined application of entomopathogens with compatible insecticides promises to provide more effective management of K. macadamiae than individual chemical applications.

Kuschelorhynchus macadamiae is a major pest of macadamias in Australia, causing yield losses of up to 15%. Our previous studies have shown the weevil is susceptible to Beauveria bassiana and Metarhizium anisopliae. The aim of this study was to investigate horizontal transmission of both fungal species to healthy weevils from both infected adults and weevil cadavers. In a confined environment the mortality of healthy adults caused by the transmission of conidia from live fungus-infected adults was < 50%. Under similar experimental conditions, the mortality of healthy adults reached 100% when exposed to conidiated cadavers. However, when conidiated cadavers were used in more spacious environments (insect cages), the mortality of adults was < 80%. Using scanning electron microscopy, it was observed that all healthy adults had conidia attached to all external parts of the body. This suggests that although the conidia were readily transferred to the adults, the lower mortality in the larger insect cages could be the result of an unfavourable environmental factor such as low humidity. The presence of conidia attached to all the adults indicated that they did not show any discriminatory behaviour such as avoidance of conidiated cadavers infected by these two fungal species. The results from this study show that there is potential for enhanced control of adult K. macadamiae via transmission from either fungus-infected adults or conidiated cadavers and this could strengthen sustainable pest management in macadamias.

The native freshwater gastropod Isidorella newcombi attacks the roots of developing rice plants in southern Australia and is controlled using copper sulphate. The apparent tolerance of this species to moderate levels of copper (Cu) exposure led us to investigate its potential usefulness as a biomonitor species. To assess its response to chronic Cu exposure, adult I. newcombi were exposed to 0–120 µg L⁻¹ of Cu for 28 days. Lethal and sublethal responses were investigated. The relationships between subcellular biomarkers and life history traits also were explored. At exposure concentrations of 60 µg L⁻¹ Cu and above, 100% mortality was observed during the 28-day exposure period. In these treatments, there was an exposure concentration dependent decrease in the time that the snails survived. In the surviving snails, there was an exposure concentration-dependent increase in tissue Cu concentration. In the snails exposed to Cu concentrations above 15 µg L⁻¹, no eggs were produced during the final week of copper exposure, indicating that populations would not persist at Cu concentrations above 15 µg L⁻¹. The general stress biomarker lysosomal membrane destabilisation (LD) indicated organisms exposed to 10 µg L⁻¹ Cu and above were experiencing Cu induced stress. This suggests that LD could act as an early warning system for responses at higher levels of biological organisation in I. newcombi exposed to copper.