Biology subjects

Umina, P. A.

Publications and source records attributed to Umina, P. A..

4 recordsLinked to original sources

bioRxiv2021

Is what you see what you get? The relationship between field observed and actual aphid parasitism rates in canola crops

BACKGROUNDEstimating parasitoid abundance in the field can be difficult, even more so when attempting to quantify parasitism rates and the ecosystem service of biological control that parasitoids can provide. To understand how observed parasitism rates (in-field mummy counts) of the green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae) translate to actual parasitism rates (laboratory-reared parasitoid counts), field work was undertaken in Australian canola fields over a growing season. Parasitoids were reared within a controlled laboratory setting. RESULTSTotal observed and actual parasitism rates of M. persicae varied considerably across regions, but less so on a field level. Overall, actual parasitism was on average 2.4 times higher than that observed in the field, with rates an average of 4-fold higher in South Australia. As crop growth stage progressed, the percentage of mummies observed increased. Percentage of parasitoids reared also increased with crop growth stage, averaging 3.4% during flowering and reaching 14.4% during podding/senescing. Although there was a greater diversity of reared parasitoid species at later crop growth stages, actual parasitism rate was unaffected by parasitoid species. Diaeretiella rapae was the most commonly reared parasitoid, increasing in abundance with crop growth stage. CONCLUSIONThese findings indicate that mummy counts alone do not provide a clear representation of parasitism within fields.

zoology↗

bioRxiv2021

The effects of insecticide seed treatments on green peach aphid Myzus persicae (Sulzer) (Homoptera: Aphididae) parasitism by Aphidius colemani Viereck (Hymenoptera: Aphidiidae) and predation by Mallada signatus (Schneider) (Neuroptera: Chrysopidae)

The green peach aphid, Myzus persicae (Sulzer) (Homoptera: Aphididae), is a major pest of Brassica L. species in Australia, where it can transmit >100 viruses. Globally, this species has evolved resistance to 74 insecticides from numerous chemical groups. Although Integrated Pest Management (IPM) strategies are being implemented, chemical treatment remains the predominant method used to control aphids. Insecticide seed treatments are viewed as a softer alternative to chemical sprays and are widely used in Australian canola fields. The effects of imidacloprid, thiamethoxam, and a mixture of thiamethoxam & lambda-cyhalothrin canola seed treatments were investigated on the parasitoid, Aphidius colemani Viereck (Hymenoptera: Aphidiidae) and the predator, the green lacewing Mallada signatus (Schneider) (Neuroptera: Chrysopidae); both important natural enemies of M. persicae. The number of mummies formed by A. colemani on the untreated plants was lower than those formed on the thiamethoxam & lambda-cyhalothrin and imidacloprid treated plants. The number of A. colemani reared from mummies on thiamethoxam & lambda-cyhalothrin plants was higher than those reared from thiamethoxam and untreated plants. Significant effects of insecticide seed treatments were only noted for mummies produced while the parent parasitoids were on the plants, not for those mummies produced after their removal. This suggests seed treatment effects were immediate but not long lasting. Based on cumulative parasitoid survival days for two generations, A. colemani exposed to thiamethoxam & lambda-cyhalothrin and imidacloprid treatments had a greater fitness than those exposed to the thiamethoxam and untreated controls, possibly due to the phenomenon of insecticide hormoligosis. Despite the treatment effects observed, we did not detect any behavioural differences in M. persicae or A. colemani. Mallada signatus were not negatively affected by feeding on M. persicae on insecticide seed treated plants, suggesting they are more tolerant of seed treatments than A. colemani. The findings from this study provide a useful platform for further experimentation on the effects of seed treatments on natural enemies of M. persicae.

zoology↗

bioRxiv2021

Taxonomy, distribution and host relationships of aphidiine wasps (Hymenoptera: Aphidiidae) parasitizing aphids (Hemiptera: Aphididae) in Australia grain production landscapes

Aphid parasitoids (Hymenoptera; Aphidiidae) were surveyed within grain production landscapes in Victoria, Australia between 2017 and 2018, as well as more sporadically nationwide between 2016 and 2019. In addition, aphidiine records were collated from insect depositories around Australia and online databases. The 5551 specimens recorded constituted a total of 23 species and seven genera. Diaeretiella rapae (MIntosh) was the most common species, representing more than 70% of all aphidiines recorded. This species also showed a greater northerly geographic range than other aphidiines. During sampling between 2017 and 2019, aphidiines were reared from mummies to ascertain host-parasitoid relationships. Diaeretiella rapae was again the most commonly reared parasitoid, although aphidiine preference varied with aphid host and between states and territories. An illustrated dichotomous key to Australian aphidiines in grain production landscapes is provided for the 11 species sampled in our field surveys. This is the first comprehensive review of aphidiines sampled within Australia in over two decades. Knowledge about the diversity and distribution of these parasitoids is important for understanding their impact on current and future invasions of aphid species. In addition, understanding the interactions between grain aphids and their associated parasitoids will further support the inclusion of parasitoid wasps into integrated pest management (IPM) strategies.

zoology↗

bioRxiv2019

Forecasting the potential distribution of the invasive vegetable leafminer using "top-down" and "bottom-up" models

The vegetable leafminer, Liriomyza sativae, is an internationally significant pest of vegetable and flower crops, that was detected for the first time on the Australian mainland in 2015. Due to the early stage of its invasion in Australia, it is unclear how climatic conditions are likely to support and potentially restrict the distribution of L. sativae as it expands into a novel range and threatens agricultural production regions. Here we predicted the future establishment potential of L. sativae in Australia, using both a novel bottom-up process-based model and a popular top-down correlative species distribution model (SDM), leveraging the unique strengths of each approach. Newly compiled global distribution data spanning 42 countries was used to validate the process-based model of establishment potential based on intrinsic population growth rates, as well as parameterise the correlative SDM. Both modelling approaches successfully captured the international distribution of L. sativae based on environmental variables and predicted the high suitability of non-occupied ranges, including northern regions of Australia. The largely unfilled climatic niche available to L. sativae in Australia demonstrates the early stage of its Australian invasion, and highlights locations where important vegetable and nursery production regions in Australia are highly vulnerable to L. sativae establishment.

ecology↗