Comparison of fumigation efficacy of methyl bromide alone and phosphine applied either alone or simultaneously or sequentially against Bactrocera correcta in Selenicereus undatus (red pitaya) fruit.

BACKGROUND: Bactrocera correcta (Bezzi) is a significant pest of the red pitaya fruit (Selenicereus undatus). This study investigated the insecticidal effects of methyl bromide (MB) alone, phosphine (PH3 ) alone, both applied simultaneously (PH3 + MB), and PH3 application followed sequentially by MB (PH3 → MB) against B. correcta in red pitaya fruits. RESULTS: The 3rd instar larvae of B. correcta were the most tolerant to MB alone and the combined treatments, whereas eggs were the most susceptible stage. Both the PH3 + MB and PH3 → MB treatments resulted in higher mortality at all stages than MB alone, demonstrating a synergistic effect between MB and PH3 . The toxicity of the combined treatments increased with increasing PH3 concentrations, with the optimal concentration recorded being 1.42 to 2.84 g m-3 . Further probit analysis revealed that compared to the MB treatment alone, the median lethal dose values of MB in PH3 + MB and PH3 → MB treatment, were reduced to 63.73% and 66.82%, respectively. Fruit quality was not adversely affected by either of the combined treatments. CONCLUSION: This work provides robust evidence that combining MB and PH3 to control B. correcta is highly effective, especially the PH3 → MB treatment. This combination decreased the amount of MB required for effective control at all life stages, while protecting fruit quality against MB phytotoxicity to a greater extent than conventional MB fumigation alone. © 2023 Society of Chemical Industry.

Info-gap theory to determine cost-effective eradication of invasive species.

Invasive species eradication campaigns often fail due to stochastic arrival events, unpredictable detectability and incorrect resource allocation. Severe uncertainty in model parameter estimates may skew the eradication policy results. Using info-gap decision theory, this research aims to provide managers with a method to quantify their confidence in realizing successful eradication of particular invasive species within their specified eradication budgets (i.e. allowed eradication cost) in face of information-gaps. The potential introduction of the Asian house gecko Hemidactylus frenatus to Barrow Island, Australia is used as a case study to illustrate the model. Results of this research demonstrate that, more robustness to uncertainty in the model parameters can be earnt by (1) increasing the allowed eradication cost (2) investment in pre-border quarantine and border inspection (i.e. prevention) or (3) investment in post-border detection surveillance. The combination of a post-border spatial dispersal model and info-gap decision theory demonstrates a novel and spatially efficient method for managers to evaluate the robustness of eradication policies for incursion of invasive species with unexpected behaviour. These methods can be used to provide insight into the success of management goals, in particular the eradication of invasive species on islands or in broader mainland areas. These insights will assist in avoiding eradication failure and wasteful budget allocation and labour investment.

Metabolite Variation between Nematode and Bacterial Seed Galls in Comparison to Healthy Seeds of Ryegrass Using Direct Immersion Solid-Phase Microextraction (DI-SPME) Coupled with GC-MS.

Annual ryegrass toxicity (ARGT) is an often-fatal poisoning of livestock that consume annual ryegrass infected by the bacterium Rathayibacter toxicus. This bacterium is carried into the ryegrass by a nematode, Anguina funesta, and produces toxins within seed galls that develop during the flowering to seed maturity stages of the plant. The actual mechanism of biochemical transformation of healthy seeds to nematode and bacterial gall-infected seeds remains unclear and no clear-cut information is available on what type of volatile organic compounds accumulate in the respective galls. Therefore, to fill this research gap, the present study was designed to analyze the chemical differences among nematode galls (A. funesta), bacterial galls (R. toxicus) and healthy seeds of annual ryegrass (Lolium rigidum) by using direct immersion solid-phase microextraction (DI-SPME) coupled with gas chromatography−mass spectrometry (GC-MS). The method was optimized and validated by testing its linearity, sensitivity, and reproducibility. Fifty-seven compounds were identified from all three sources (nematode galls, bacterial galls and healthy seed), and 48 compounds were found to be present at significantly different (p < 0.05) levels in the three groups. Five volatile organic compounds (hexanedioic acid, bis(2-ethylhexyl) ester), (carbonic acid, but-2-yn-1-yl eicosyl ester), (fumaric acid, 2-ethylhexyl tridec-2-yn-1-yl ester), (oct-3-enoylamide, N-methyl-N-undecyl) and hexacosanoic acid are the most frequent indicators of R. toxicus bacterial infection in ryegrass, whereas the presence of 15-methylnonacosane, 13-methylheptacosane, ethyl hexacosyl ether, heptacosyl acetate and heptacosyl trifluoroacetate indicates A. funesta nematode infestation. Metabolites occurring in both bacterial and nematode galls included batilol (stearyl monoglyceride) and 9-octadecenoic acid (Z)-, tetradecyl ester. Among the chemical functional group, esters, fatty acids, and alcohols together contributed more than 70% in healthy seed, whereas this contribution was 61% and 58% in nematode and bacterial galls, respectively. This study demonstrated that DI-SPME is a valid technique to study differentially expressed metabolites in infected and healthy ryegrass seed and may help provide better understanding of the biochemical interactions between plant and pathogen to aid in management of ARGT.

Predicting potential global distribution and risk regions for potato cyst nematodes (Globodera rostochiensis and Globodera pallida).

Potato cyst nematodes (PCNs), golden (yellow) cyst nematode (Globodera rostochiensis, gPCN) and pale (white) cyst nematode (G. pallida, pPCN), are important invasive pests in many countries and regions where they can cause significant yield and economic loss for agriculture. Prediction and identification of habitats suitable for PCNs are critical for developing biosecurity strategies, both pre and post border, to maximise the potential for early elimination should an incursion occur. To date, the potential global distribution of PCNs has not been thoroughly studied. Therefore, this study conducted a species distribution model to illustrate the potential global distribution of PCNs and risk regions. In this study, the Maximum Entropy Model (Maxent) associated with the Geographic Information System (GIS) was employed to reveal the potential distribution of the gPCN and pPCN. In addition to bioclimate, soil quality was also included in the model. The global cultivated lands, whether the susceptible hosts were present or not, were used to assess the maximum potential risk regions. The limitation factors for PCNs distribution were also assessed. Results showed that 66% of the global land surface was suitable for gPCN or pPCN or both, and both species can colonise more than 75% of the global cultivated lands. The coldest quarter's mean temperature and precipitation were critical limitations in unsuitable regions. In summary, the global risk maps of PCNs contribute valuable additional information that complements previous national/regional distribution predictions. The results of this distribution research will contribute practical support for decision-makers and practitioners to implement biosecurity strategies from a global perspective, that incorporate prevention or promptly enforce control practices to limit the damage caused by future incursions.

Evaluation of the Likelihood of Establishing False Codling Moth (Thaumatotibia leucotreta) in Australia via the International Cut Flower Market.

Kenya and some other African countries are threatened by a serious pest Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), the false codling moth. The detection of T. leucotreta is quite difficult due to the cryptic nature of the larvae during transportation and is therefore a concern for Australia. This insect is a known pest of agriculturally important crops. Here, Maxent was used to assess the biosecurity threat of T. leucotreta to Australia. Habitat suitability and risk assessment of T. leucotreta in Australia were identified based on threatened areas under suitable climatic conditions and the presence of hosts in a given habitat. Modeling indicated that Australia is vulnerable to invasion and establishment by T. leucotreta in some states and territories, particularly areas of western and southern Australia. Within these locations, the risk is associated with specific cropping areas. As such, invasion and establishment by T. leucotreta may have serious implications for Australia's agricultural and horticultural industries e.g., the fruit and vegetable industries. This study will be used to inform the government and industry of the threat posed by T. leucotreta imported via the cut flower industry. Targeted preventative measures and trade policy could be introduced to protect Australia from invasion by this pest.

Cost-effective surveillance of invasive species using info-gap theory.

Invasive species can lead to community-level damage to the invaded ecosystem and extinction of native species. Most surveillance systems for the detection of invasive species are developed based on expert assessment, inherently coming with a level of uncertainty. In this research, info-gap decision theory (IGDT) is applied to model and manage such uncertainty. Surveillance of the Asian House Gecko, Hemidactylus frenatus Duméril and Bibron, 1836 on Barrow Island, is used as a case study. Our research provides a novel method for applying IGDT to determine the population threshold ([Formula: see text]) so that the decision can be robust to the deep uncertainty present in model parameters. We further robust-optimize surveillance costs rather than minimize surveillance costs. We demonstrate that increasing the population threshold for detection increases both robustness to the errors in the model parameter estimates, and opportuneness to lower surveillance costs than the accepted maximum budget. This paper provides guidance for decision makers to balance robustness and required surveillance expenditure. IGDT offers a novel method to model and manage the uncertainty prevalent in biodiversity conservation practices and modelling. The method outlined here can be used to design robust surveillance systems for invasive species in a wider context, and to better tackle uncertainty in protection of biodiversity and native species in a cost-effective manner.

A benefit-cost analysis of different response scenarios to COVID-19: A case study.

BACKGROUND: This paper compares the direct benefits to the State of Western Australia from employing a "suppression" policy response to the COVID-19 pandemic rather than a "herd immunity" approach. METHODS: An S-I-R (susceptible-infectious-resolved) model is used to estimate the likely benefits of a suppression COVID-19 response compared to a herd immunity alternative. Direct impacts of the virus are calculated on the basis of sick leave, hospitalizations, and fatalities, while indirect impacts related to response actions are excluded. RESULTS: Preliminary modeling indicates that approximately 1700 vulnerable person deaths are likely to have been prevented over 1 year from adopting a suppression response rather than a herd immunity response, and approximately 4500 hospitalizations. These benefits are valued at around AUD4.7 billion. If a do nothing policy had been adopted, the number of people in need of hospitalization is likely to have overwhelmed the hospital system within 50 days of the virus being introduced. Maximum hospital capacity is unlikely to be reached in either a suppression policy or a herd immunity policy. CONCLUSION: Using early international estimates to represent the negative impact each type of policy response is likely to have on gross state product, results suggest the benefit-cost ratio for the suppression policy is slightly higher than that of the herd immunity policy, but both benefit-cost ratios are less than one.

Ethyl formate + nitrogen fumigant: a new, safe, and environmentally friendly option for treating a 20 ft shipping container loaded with general freight.

The use of shipping containers for cargo transportation has the potential to transport insect pests from infested to non-infested areas. Fumigation is required as an appropriate biosecurity measure to exterminate insect pests. Fumigation trials were conducted in a 20 ft general purpose (GP) shipping container. Four species of mixed-age cultures, Lasioderma serricorne (F.), Sitophilus oryzae (L.), Trogoderma variabile (Ballion), and Rhyzopertha dominica (F.) were used for bioassays. Ninety g m-3 of ethyl formate + nitrogen formed non-flammable ethyl formate fumigant formulation was released into the container. The fumigation yielded sufficient concentration × time (Ct) products at a range of 437.54-449.19 g h m-3 in the container for exterminating all life stages. Ethyl formate left no residue in treated drinks. This study demonstrated that on site generation of a non-flammable ethyl formate and nitrogen fumigant can be achieved and this new application technology ensures that ethyl formate distributes evenly in the container within 30 min after application and with a variation of <3%. The research further demonstrated that an ethyl formate + nitrogen application can be used as a pre-shipment treatment for controlling all the stages of insect pests in a shipping container. After a fumigation holding period and ventilation of 15 min, ethyl formate was successfully removed from the container at 0.5-35ppm in different locations. The levels of ethyl formate in the workspace were <0.5 ppm during application, fumigation, and aeriation, which is about 5% of the 100 ppm level for ethyl formate.

In-transit fumigation of shipping containers with ethyl formate + nitrogen on road and continued journey on sea.

Fumigation is required as an appropriate biosecurity measure to exterminate insect pests in shipping containers. The aim of this study was to determine if ethyl formate (EF) + nitrogen could be safely applied as an in-transit fumigant for containers transported on land and then by sea. In-transit fumigation trials were conducted in four 20 ft shipping containers during a four-day journey in December 2019 in Western Australia. Ethyl formate (90 g m-3) was released with nitrogen into the containers. Ethyl formate concentrations inside the containers and the surrounding environment on the barge were monitored at timed intervals throughout the overnight voyage. This study added new data on in-transit fumigation with ethyl formate + nitrogen via road and has successfully demonstrated safety of in-transit fumigation with ethyl formate + nitrogen via the marine sector. There was no detectable risk to the public, crew members on the barge or workers throughout the journey. In addition, all tested containers were ready to be opened and unloaded with 5-10 minutes aeration or without aeration upon arrival.

Biosecurity risks posed by a large sea-going passenger vessel: challenges of terrestrial arthropod species detection and eradication.

Large sea-going passenger vessels can pose a high biosecurity risk. The risk posed by marine species is well documented, but rarely the risk posed by terrestrial arthropods. We conducted the longest running, most extensive monitoring program of terrestrial arthropods undertaken on board a passenger vessel. Surveillance was conducted over a 19-month period on a large passenger (cruise) vessel that originated in the Baltic Sea (Estonia). The vessel was used as an accommodation facility to house workers at Barrow Island (Australia) for 15 months, during which 73,061 terrestrial arthropods (222 species - four non-indigenous (NIS) to Australia) were collected and identified on board. Detection of Tribolium destructor Uytt., a high-risk NIS to Australia, triggered an eradication effort on the vessel. This effort totalled more than 13,700 human hours and included strict biosecurity protocols to ensure that this and other non-indigenous species (NIS) were not spread from the vessel to Barrow Island or mainland Australia. Our data demonstrate that despite the difficulties of biosecurity on large vessels, stringent protocols can stop NIS spreading from vessels, even where vessel-wide eradication is not possible. We highlight the difficulties associated with detecting and eradicating NIS on large vessels and provide the first detailed list of species that inhabit a vessel of this kind.

Effects of a Potato Spindle Tuber Viroid Tomato Strain on the Symptoms, Biomass, and Yields of Classical Indicator and Currently Grown Potato and Tomato Cultivars.

The Chittering strain of potato spindle tuber viroid (PSTVd) infects solanaceous crops and wild plants in the subtropical Gascoyne Horticultural District of Western Australia. Classical PSTVd indicator hosts tomato cultivar Rutgers (R) and potato cultivar Russet Burbank (RB) and currently widely grown tomato cultivars Petula (P) and Swanson (S) and potato cultivars Nadine (N) and Atlantic (A) were inoculated with this strain to study its pathogenicity, quantify fruit or tuber yield losses, and establish whether tomato strains might threaten potato production. In potato foliage, infection caused spindly stems, an upright growth habit, leaves with ruffled margins and reduced size, and upward rolling and twisting of terminal leaflets (RB, A, and N); axillary shoot proliferation (A); severe plant stunting (N and RB); and necrotic spotting of petioles and stems (RB). Tubers from infected plants were tiny (N) or small and "spindle shaped" with (A) or without (RB) cracking. Potato foliage dry weight biomass was decreased by 30 to 44% in A and RB and 37% in N, whereas tuber yield was diminished by 50 to 89% in A, 69 to 71% in RB, and 90% in N. In tomato foliage, infection caused epinasty and rugosity in apical leaves, leaf chlorosis, and plant stunting (S, P, and N); cupped leaves (S and P); and reduced leaf size, flower abortion, and necrosis of midribs, petioles, and stems (R). Mean tomato fruit size was greatly decreased in all three cultivars. Tomato foliage dry weight biomass was diminished by 40 to 53% (P), 42% (S), and 37 to 51% (R). Tomato fruit yield was decreased by 60 to 76% (P), 52% (S), and 64 to 89% (R), respectively. Thus, the tomato strain studied was highly pathogenic to classical indicator and representative current tomato and potato cultivars, causing major losses in fruit and tuber yields. Tomato PSTVd strains, therefore, pose a threat to tomato and potato industries worldwide.

Commercial trials evaluating the novel use of ethyl formate for in-transit fumigation of shipping containers.

The use of shipping containers for cargo transportation has the potential to transport insect pests from infested to non-infested areas. Therefore, fumigation is required as an appropriate biosecurity measure to exterminate these pests. In-transit fumigation trials were conducted in two 20 ft shipping containers during a two-day journey in both September and December 2017. Ethyl formate (90 g m-3) was purged with nitrogen (EF + N2) into the containers. Ethyl formate concentration inside containers and the surrounding environment were monitored at timed intervals throughout the journey. Fumigation achieved sufficient concentration × time (Ct) products in the containers during the journey, which can exterminate all stages of most common insect pests. The Ct products in-transit were greater than those in a shipping container being fumigated in a stationary position at a dose rate of 90 g m-³ for 24 hours exposure. Levels of EF in the environment between 1-15 m downwind from the containers and driver's cabin were less than 0.5 ppm at each of the timed intervals, 200 times below 100 ppm of EF Threshold Limit Value (TLV). Our study indicates that in-transit EF + N2 technology has the potential to deliver cost savings in the fumigation process through reduction of the Labor cost, elimination of the time a container and cargo must remain stationary in a fumigation yard and a significant decrease in total supply chain time (between container packing and receival).

Zero-tolerance biosecurity protects high-conservation-value island nature reserve.

Barrow Island, north-west coast of Australia, is one of the world's significant conservation areas, harboring marsupials that have become extinct or threatened on mainland Australia as well as a rich diversity of plants and animals, some endemic. Access to construct a Liquefied Natural Gas (LNG) plant, Australia's largest infrastructure development, on the island was conditional on no non-indigenous species (NIS) becoming established. We developed a comprehensive biosecurity system to protect the island's biodiversity. From 2009 to 2015 more than 0.5 million passengers and 12.2 million tonnes of freight were transported to the island under the biosecurity system, requiring 1.5 million hrs of inspections. No establishments of NIS were detected. We made four observations that will assist development of biosecurity systems. Firstly, the frequency of detections of organisms corresponded best to a mixture log-normal distribution including the high number of zero inspections and extreme values involving rare incursions. Secondly, comprehensive knowledge of the island's biota allowed estimation of false positive detections (62% native species). Thirdly, detections at the border did not predict incursions on the island. Fourthly, the workforce detected more than half post-border incursions (59%). Similar approaches can and should be implemented for all areas of significant conservation value.

Modeling the Risk of Entry, Establishment, Spread, Containment, and Economic Impact of Tilletia indica, the Cause of Karnal Bunt of Wheat, Using an Australian Context.

ABSTRACT Modeling techniques were developed to quantify the probability of Tilletia indica entering and establishing in Western Australia (WA), and to simulate spread, containment, and the economic impact of the pathogen. Entry of T. indica is most likely to occur through imports of bulk grain or fertilizer (0.023 +/- 0.017 entries per year and approximately 0.009 +/- 0.009 establishments per year). Entry may also occur through straw goods, new or second-hand agricultural machinery, and on personal effects of travelers who have visited regions with infected plants. The combined probability of entry and establishment of T. indica, for all pathways of entry, is about one entry every 25 years and one establishment every 67 years. Alternatively, sensitivity analysis does show that increases in quarantine funding can reduce the probability of entry to about one entry every 50 years and less than one establishment every 100 years. T. indica is spread efficiently through contaminated farm machinery, seed and soil, rain, air currents, and animals. Depending on the rate of spread of the pathogen and the amount of resources allocated for detection, the time until first detection could range from 4 to 11 years and the economic impact could range from 8 to 24% of the total value of wheat production in WA.