2. Maintaining Biosecurity Category
2.1 MBS 337
| Programme Title: | Investigations of alternative decontaminants for plant viruses and viroids |
| Programme Leader: | John Fletcher |
| Institution: | Crop & Food Research |
Summary
The objective was to identify a safe, non-corrosive effective antiviral chemical treatment to disinfect tools and to decontaminate surfaces and containers.
Background
A number of plant viruses and viroids that constitute a biosecurity threat to New Zealand are contagious, remaining infective on tools and surfaces for some hours or a day after contact. Potexviruses such as Pepino mosaic virus (PepMV) and viroids such as Potato spindle tuber viroid (PSTVd) have a history of transmission through mechanical means and resistance to chemical degradation.
Approach & Outcomes
A survey of information on the use of chemical decontaminants for plant viruses and viroids and a report was completed. From this information five candidate chemicals were chosen along with a hydrogen peroxide based chemical requested by MAF. These chemicals were subjected to a series of decontamination experiments using sodium hypochloride as the reference. Tobacco mosaic virus (TMV), Potato virus X (PVX) and Chrysanthemum stunt viroid (CSVd) were used to test the chemicals. Experiments involved treating scalpel blades and glass slides representing the two areas of potential contamination.
Outcomes
Three reports were prepared covering the literature survey, experiments with PVX and TMV and experiments with CSVd.
Five compounds were chosen from the literature survey: Geosil 25% (hydrogen peroxide and silver, Culticlean 9% ai benzoic acid, Chitosan, Sporekill 12% didecymethy ammonium chloride, Virkon – 50% potassium peroxomonosulfate and 15% sodium alkyl benzene and compared with sodium hypochloride using a water control. In experiments with PVX and TMV for blade decontamination NaOCl at 2.4% ai solution appears effective against both PVX and TMV viruses. NaOCl and Virkon treatments reduced PVX contamination on glass surfaces but no combination of chemicals or exposure times completely decontaminated the surfaces of glass slides for either virus.
With CSVd no combination of the tested chemicals or exposure times successfully decontaminated both cutting blades and the surfaces of glass slides. Exposure to a water rinse for 30 seconds water appears as or more effective against CSVd than any chemical tested. For glass surfaces exposure to 2.4% NaOCl for 10 minutes appeared effective against CSVd. For glass surfaces and blades water rinsing before exposure to the decontaminant may provide partial decontamination and may improve decontaminant efficacy.
Summary
The objective was to identify a safe, non corrosive effective antiviral chemical treatment to disinfect tools and to decontaminate surfaces and containers. From a survey of literature suitable chemical treatments were chosen. Six compounds at two dilutions plus a water control were used to treat scalpel blades and glass slides contaminated with PVX, TMV and CSVd.
We found that for blade decontamination NaOCl at 2.4% ai solution appears effective against both PVX and TMV viruses. NaOCl and Virkon treatments reduced PVX contamination on glass surfaces but no combination of chemicals or exposure times completely decontaminated the surfaces of glass slides for either virus.
No combination of the tested chemicals or exposure times successfully decontaminated both cutting blades and the surfaces of glass slides of CSVd. Our experiments found exposure to water for 30 seconds decontaminated blades as well was as any chemical. Glass surface decontamination appeared to be most successful after exposure to 2.4% NaOCl for 10 minutes
From our experiments it appears no chemical can successfully act as an all–round virus/viroid decontaminant although NaOCl is fairly close. In combination with thorough rinsing or washing with water before applying the chemical, efficacy of Na0Cl against virus and viroids is likely to improve further.
Publications
Fletcher, J D; Lister, R A; Butler, R C (2004) Investigations of alternative decontaminants for plant viruses and viroids – experiments on the effect of chemicals on blades and surfaces contaminated with PVX and TMV. Crop & Food Confidential report No1198.
Fletcher, J D; Lister, R A; Butler, R C (2005) Investigations of alternative decontaminants for plant viruses and viroids – contract MBS377 project summary. Crop & Food Confidential report No 1433.
Lister, R A (2004) Liturature survey of .plant virus/viroid decontaminating agents. Crop & Food Confidential report No 1023.
2.2 MBS 347
| Programme Title: | Pest risk assessment in peat products |
| Programme Leader: | Dr Lian-Heng Cheah |
| Institution: | Crop & Food Research |
Summary
There were three objectives in this project:
- a list of unwanted pests recorded on peat and sphagnum moss;
- a protocol for preventing contamination with soil and pests in peat production;
- risk assessment of the pests present in peat.
Background
This project was in part an extension of ‘Treatment for peat and sphagnum moss (MBS 330)’. In 2004, on MAF Biosecurity’s commission, we evaluated three disinfestation treatments (dry hot air, steam and Envirosol fumigation) for their effect on micro-organisms and pests on four peat products. We found that dry hot air treatment at 85oC for 12 h and steam for 6 h gave significantly better kill of bacteria than the untreated control. Steam treatment for 6 h gave significantly better kill of fungi than the untreated control. However, these treatments did not give complete kill of fungi or bacteria although they gave complete kill of mites and nematodes. It was for this reason that MAF Biosecurity decided to investigate the above three objectives.
Approach & Outcomes
To determine the biosecurity risk of imported peat, we need to know the organisms that are likely to be associated with peat in its natural habitat prior to harvest, and match these with lists of unwanted organisms.
Unwanted organisms register
The Biosecurity New Zealand website (http://www.biosecurity.govt.nz) was searched for lists of unwanted organisms. The unwanted organisms register (http://www.biosecurity.govt.nz/pests-diseases/registers-lists/unwanted-organisms/) was searched using the following strategy:
- Category – regulated
- CTO responsibility – plant biosecurity
- Government department – MAF
-
An Excel spreadsheet of the 14 272 regulated pests returned was then created.
Literature search for biota associated with natural peat
CAB Abstracts records from 1973 to the present were searched using a broad strategy of: Topic Search = ((peat or peat bog) and (insect or insects)).
The services of Nerac (a USA-based commercial search company) were used to provide a base-line search based on the following request: “We would like to find references to the occurrence of organisms (insects, nematodes, snails, fungi, bacteria etc) in peat or sphagnum moss, preferably in the native state (i.e. in peat bogs, peat soils). Our goal is to match these species with lists of unwanted species for biosecurity purposes, so we need to cover as wide a range of organisms as possible. An example of such a record would be Ellis & Wood (1974) Canadian Entomologist 106(2): 221–222.”
Matching with the unwanted organisms register
Genus and species of organisms found were cross checked manually with those on the MAF Biosecurity unwanted organism list.
Protocols for harvesting peat and sphagnum moss
We also approached Nerac to search for protocols for harvesting peat and sphagnum moss and see that if we can find “A protocol for preventing contamination with soil and unwanted pests when harvesting peat”. In spite of extensive literature search we found no protocol for preventing contamination with soil and pests. However we found three protocols describing the methods of harvesting peat and sphagnum moss from Canada, Ireland and New Zealand. With these documents we then constructed an improved protocol for minimising contamination of peat.
Outcomes
Based on the results of our search we conclude that the pests (five species of fungi) reported in the literature are of low risk to New Zealand Biosecurity.
Summary
A total of 158 entries (organisms) were identified from the literature as being present in peat or peat bogs. Of these, five species of fungi (Mortierella alpina, M. isabellina, M. ramanniana, Ophiostoma stenoceras, Torulomyces lagena) matched at the species level with the unwanted organism register (NZ Biosecurity list). A further 24 matched at the genus level but may not match at the species level on the unwanted list. These five species of fungi were not recorded on the ‘Plant Diseases Recorded in New Zealand’ by S. R. Pennycook. M. alpina is non pathogenic to plants. Three protocols for harvesting peats were described. New Zealand methods are the best for preventing contamination with soil and pests in peat production but some improvements are suggested. Based on the results of our search we conclude that the pests (five species of fungi) that are reported in the literature are of low risk to New Zealand Biosecurity.
Publications
Cheah, L-H; Page, B B C; Zheng, Z; Marsh, A; O’Neil, E; van Epenhuijsen, K (2005) Treatments for peat, peat products and sphagnum moss. Crop & Food Research Confidential Report No.1178. 28 pp.
2.3 MBS 351
| Programme Title: | Imported seed lot heterogeneity: implications for biosecurity sampling protocols |
| Programme Leader: | John Hampton |
| Institution: | Lincoln University |
Summary
To determine heterogeneity in imported seed lots for sowing of selected species in conjunction with evaluating the quality and effectiveness of the current MAF Plants Biosecurity Authority seed lot sampling protocols.
Background
The current border inspection requirement for regulated weed pests in seed lots imported for sowing is the drawing of a 5 kilogram sample and the laboratory inspection of that sample. This project was designed to determine the uniformity of seed lots of selected species, and to evaluate the effectiveness of the currently sampling protocols for imported seed lots.
Approach & Outcomes
Seed lot uniformity was to be determined by heterogeneity testing, as prescribed by the International Seed Testing Association (ISTA). This was to be conducted on up to five imported seed lots for each of nine species (Brassica, Pisum, Trifolium, Vicia, Zea, Festuca, Lolium, Loctuca and Lycopersicon) representing a range of seed types and sizes. Imported seed lots were to be sampled firstly using the method prescribed by ISTA for the species, and secondly drawing a 5kg sample, and an ‘other seed determination test’ as prescribed in the ISTA Rules for Seed Testing carried out on each sample.
Outcome
The goals for this research were to determine the uniformity of imported seed lots for sowing, and to evaluate the effectiveness of current Biosecurity New Zealand imported seed lot sampling protocols. It was not possible to carry out the proposed research for determining imported seed lot uniformity by heterogeneity testing, and by agreement, the topic was reviewed. It is practically impossible to produce a perfectly uniform seed lot, and some degree of heterogeneity will always occur. The extent of this heterogeneity in imported seed lots will depend on the species and the sophistication of the seed industry in the exporting country.
Protocols for sampling seed lots must take the fact that seed lots are not uniform into account, and the system used by the International Seed Testing Association (ISTA) has been designed for this purpose.
The present requirement for a 5kg sample to be drawn from a seed lot has a valid basis for the detection of regulated weed seeds, even though it is five times the size of the sample required by ISTA for seed analysis. However while the analysis of 5kg of a cereal seed is practical, it is impractical (time and therefore cost) for seeds which are smaller in size than cereals.
Recommendations
That seed lots being imported into New Zealand should be required to have the results of the “other seed determination” test, as well as the purity test results printed on the seed analysis certificate for the seed lot.
That Biosecurity New Zealand staff become familiar with how to interpret the information provided on an ISTA Orange International Seed Lot Certificate.
That the submitted sample size required for quarantine testing (other seed determination) be five times that of the ISTA submitted sample size for the species.
That personnel involved in sampling imported seed lots for quarantine be licensed MAF Seed Sampling Officers.
That imported seed lots be sampled using the same ISTA methods as seed lots sampled for export, and that for species where the required quarantine submitted sample size exceeds 1kg, the submitted sample be obtained by combining the required number of ISTA submitted size samples.
2.4 MBS 352
| Programme Title: | Effectiveness of treatments for mite eggs |
| Programme Leader: | Lisa Jamieson |
| Institution: | HortResearch |
Summary
A literature review of control treatments for mite eggs, and pilot trials to determine the efficacy of some selected treatments against mite eggs.
Background
The current treatments such as methyl bromide or miticides for mites intercepted at the border are not completely effective against mite eggs. It has been proposed that mite treatments should be repeated after 10–14 days to kill mites that hatch from eggs. This is not feasible for all products, e.g. highly perishable crops would be rendered unsaleable if held for this period. Whole plants can be transferred into post-entry quarantine after treatment and a second treatment can then be applied to kill any hatching mites. Emerging mites, however, have the potential to infest surrounding plants and may also vector plant viruses. Therefore there is a need to identify alternative treatments that are effective against mite eggs on plants and plant products, which can be used at the border and on plants going into post-entry quarantine.
Approach & Outcomes
Extensive literature searches on alternatives to methyl bromide fumigation and miticides have been carried out using library and internet resources. Where information pertaining specifically to mite eggs was not available, information about mites in general was collected. Also, where information about treatment effect on mites was not available, the effect on other arthropods was collected.
Laboratory bioassays were undertaken to determine the viability of six-spotted mite eggs after application of the ovicide ‘Elliott clofentezine’. Other laboratory bioassays were carried out to assess the efficacy of ethyl acetatate (at 25 and 38oC) , phosphine (at 15oC) or ethyl formate (at 20oC) fumigation as potential disinfestation treatments against mite eggs using two-spotted mite eggs as the model mite species.
Outcomes
Literature review:
It was identified that further investigation is warranted for:
- fumigation with carbonyl sulphide, sulphuryl fluoride, phosphine, ethyl formate;
- heat treatment;
- contact mite ovicides: clofentezine, hexythiozox, dichlorovos, Silwetâ L-77.
Technologies that may be long-term options, when the technology is more advanced or available in New Zealand, are:
- fumigation with ethanedinitrile, methyl iodide;
- contact mite ovicide etoxazole;
- electron beam irradiation;
- ozone treatment;
- microwaves or radio frequency treatment.
‘Elliott clofentezine’ spray bioassays
It was found that ‘Elliott clofentezine’ has a direct and a residual toxic activity against six-spotted mite eggs. More than 99% of eggs were killed after being sprayed with ‘Elliot clofentezine’ at a rate of 40 ml/100L.
Ethyl acetate fumigation bioassays
Complete kill of two-spotted mite eggs was not achieved using ethyl acetate and elevated temperatures. About 70–95% of two-spotted mite eggs were killed when exposed for 8 hours to 3 500 ppm ethyl acetate at 38˚C.
Phosphine fumigation bioassays
Two-spotted mite eggs were no longer viable after exposure phosphine at 1.5 g/m3 for 8 h at 15oC.
Ethyl formate fumigation bioassays
Exposure to ethyl formate for 6 h at a concentration of 30 g/m3 at 20oC was sufficient to cause 100% mortality of two-spotted mite eggs.
Summary
To undertake a literature review of control treatments for mite eggs, and to carry out pilot trials to determine the efficacy of some selected treatments against mite eggs.
Extensive literature searches on alternatives to methyl bromide fumigation and miticides have been carried out using library and internet resources.
It was identified that further investigation is warranted for fumigation with carbonyl sulphide, sulphuryl fluoride, phosphine, ethyl formate; heat treatments; contact mite ovicides (clofentezine, hexythiozox, dichlorovos, Silwetâ L-77). Also, technologies that may be long-term options, when the technology is more advanced or available in New Zealand, are fumigation with ethanedinitrile, methyl iodide; contact mite ovicide etoxazole; electron beam irradiation; ozone treatment; microwaves or radio frequency treatment.
It was found that ‘Elliott clofentezine’ has a direct and a residual toxic activity against six-spotted mite eggs. More than 99% of six-spotted mite eggs were killed after being sprayed with ‘Elliot clofentezine’ at a rate of 40 ml/100L. About 70–95% of two-spotted mite eggs were killed when exposed for 8 hours to 3 500 ppm ethyl acetate at 38˚C. Exposure to ethyl formate for 6 h at a concentration of 30 g/m3 at 20oC or exposure to phosphine at 1.5 g/m3 for 8 h at 15oC was sufficient to cause 100% mortality of two-spotted mite eggs.
Publications
Jamieson, L E; Dentener, P R; Krishna, H; Martin, N (2005) Effectiveness of treatment for mite eggs – a literature review, and preliminary experiments. HortResearch Client Report No. 15231.
Page, B B C; Zhang, Z; Krishna, H (2005) Effective treatments for the control of two-spotted mite eggs – a preliminary evaluation of phosphine and ethyl formate. Crop & Food Research Confidential Report no. 1360.
A poster has also been prepared for the 2005 Australasian Postharvest Conference in Rotorua.
2.5 MBS 353
| Programme Title: | Molecular identification for moths |
| Programme Leader: | Karen Armstrong |
| Institution: | Lincoln University |
This research programme is not completed. Further information will be included in Research Results 2005/06.
2.6 MBS 354
| Programme Title: | Lymantrids identification |
| Programme Leader: | Karen Armstrong |
| Institution: | Lincoln University |
This research programme is not completed. Further information will be included in Research Results 2005/06.
2.7 MBS 355
| Programme Title: | Taxonomic keys for wood-boring and bark beetles of forest biosecurity interest |
| Programme Leader: | Eckehard Brockerhoff |
| Institution: | Forest Research (Ensis) |
Summary
The objective of this programme was to provide taxonomic keys for beetles in the subfamilies and families of Scolytinae, Platypodinae, Cerambycidae and Buprestidae. These families include many significant pests that represent major threats to forest biosecurity, and many are regularly intercepted in packaging and other wooden materials. The keys are mostly computer-based using Lucid software. They are well illustrated and simple to use by those working in biosecurity to identify the most commonly intercepted genera and to determine when experts need to be consulted for consideration of responses.
Background
Wood-boring and bark beetles from these families are often intercepted on New Zealand’s borders, and several species have already become established here. Previously there were no keys available to easily recognise the species that are most often found and those that are of greatest concern. Native genera are also included.
Approach & Outcomes
Taxonomic keys were developed mostly for a computer-based identification programme (Lucid software). The keys are well illustrated and simple to use by those working in biosecurity to identify the most commonly intercepted genera.
Outcomes
Keys for beetles in the subfamilies and families of Scolytinae (41 genera), Platypodinae (8 genera), Cerambycidae (23 genera) and Buprestidae (4 genera) were successfully developed. These taxa include many significant pests that represent major threats to forest biosecurity, and many are regularly intercepted in packaging and other wooden materials. The software required to use the keys is included with the keys.
Publications
The Lucid identification keys are not formally published at this point. The collaboration of the authors of this report resulted in an (independent) article on interceptions of bark beetles of biosecurity interest:
Brockerhoff, E G; Bain, J; Kimberley, M; Knížek, M (in press). Interceptions of bark and ambrosia beetles, etc. Interception frequency of exotic bark and ambrosia beetles (Coleoptera: Scolytinae) and relationship with establishment in New Zealand and world-wide. Canadian Journal of Forest Research.
2.8 MBS 356
| Programme Title: | Review of ant bait efficacy |
| Programme Leader: | Margaret Stanley |
| Institution: | Landcare Research |
Summary
To identify information gaps on the efficacy of baits used to attract and kill invasive ant species.
Background
Biosecurity New Zealand is currently responding to a series of incursions of exotic invasive ant species. To date, Biosecurity New Zealand has relied heavily on a small number of baits and toxins for control of incursions. The success of responses to new incursions of invasive ants may be compromised in the absence of effective baits. As a first step to ensuring effective incursion response, Biosecurity New Zealand commissioned Landcare Research to review international information on baits and toxins used for ant control. The next step is to test the most promising of these against a selected group of high risk invasive ant species.
Approach & Outcomes
Information was obtained by: searching computer databases (CAB abstracts, Current Contents, Agricola, Biological Abstracts) for relevant scientific papers, and technical reports; checking internet sites; cross-referencing; and contact with and querying of international ant researchers and biosecurity workers.
Outcomes
There is a lack of rigorous research testing toxins and baits against pest ant species. Most research has focussed on Solenopsis invicta and the development of commercial baits with lipid attractants for the management of this species. Hydramethylnon and fipronil are toxins that give effective control of ant populations for several different species. Amdro® (hydramethylnon) is very effective at controlling S. invicta and Wasmannia auropunctata. Presto® (fipronil) and Xstinguish® (fipronil) appear to be highly effective baits and the protein-based matrices of these baits make them highly attractive to species previously thought difficult to attract with baits. The Australian-manufactured insect growth regulator (IGR) baits developed for S. invicta control – Engage® (methoprene) and Distance® (pyriproxyfen) – appear to be the most effective IGR ant baits available. However, they have a lipid attractant and are unlikely to be attractive to species such as Linepithema humile, Tapinoma melanocephalum and Paratrechina longicornis. Indoxacarb is a new ‘reduced risk’ toxin that gives excellent suppression of S. invicta populations when used in the commercial ant bait Advion®. ERMA approval and registration should be sought for: Distance®; Engage®; Amdro® (high priority baits) and also Presto 01®; Advion®; Chipco Firestar® (lower priority). For S. invicta, S. richteri, Monomorium destructor, W. auropunctata and Anoplolepis gracilipes, baiting strategies exist overseas (albeit not in temperate climates), and if the recommended baits are registered, control strategies could be implemented rapidly. For S. geminata, the S invicta strategy may be applicable but this has not been tested. P. longicornis, T. melanocephalum, and A. gracilipes are likely to have highly restricted distributions in New Zealand and Lasius neglectus has a low likelihood of arrival. We recommend focusing research efforts on the species that lack effective strategies and pose some risk to New Zealand (P. longicornis, T. melanocephalum and L. neglectus) to determine which baits can be used to effectively manage them. In an incursion event now, Xstinguish® should be used, but research is required to determine the most effective baits. Given the frequency of incursions around New Zealand, highest research priority should be given to identifying effective baits with which to manage P. longicornis incursions. Field trials are required for several species to determine food preferences and the efficacy of various commercial baits (bait acceptability + toxin efficacy). Testing food preferences and bait acceptability can be achieved through choice tests reasonably quickly. Bait efficacy testing, however, is more complex and requires long-term monitoring.
Summary
The success of responses to new incursions of invasive ants may be compromised in the absence of effective baits. As a first step to ensuring effective incursion response, Biosecurity New Zealand has commissioned Landcare Research to review international information on baits and toxins used for ant control. Information was obtained by searching the databases for relevant scientific papers, and technical reports; checking internet sites; cross-referencing; and querying of international ant researchers. Hydramethylnon and fipronil are toxins that give effective control of ant populations for several different species. Amdro® (hydramethylnon) is very effective at controlling S. invicta and Wasmannia auropunctata. Presto® (fipronil) and Xstinguish® (fipronil) appear to be highly effective baits and the protein-based matrices of these baits make them highly attractive to several species. The Australian-manufactured insect growth regulator (IGR) baits developed for S. invicta control – Engage® (methoprene) and Distance® (pyriproxyfen) – appear to be the most effective IGR ant baits available. ERMA approval and registration should be sought for: Distance®; Engage®; Amdro® (high priority) and also Presto 01®; Advion®; Chipco Firestar® (lower priority). If these baits are registered, baiting strategies could be implemented rapidly for S. invicta, S. richteri, M. destructor, W. auropunctata and A. gracilipes. For S. geminata, the S invicta strategy may be applicable but this has not been tested. In an incursion event, Xstinguish® should be used on P. longicornis, T. melanocephalum, and A. gracilipes, but research is required to determine the most effective baits for incursion management.
Publications
Stanley, M C (2004) Review of Efficacy of Baits Used for Ant Control and Eradication. Landcare Research Contract Report: LC0405/044.
2.9 MBS 357
| Programme Title: | Survey of Allium viruses in New Zealand |
| Programme Leader: | John Fletcher |
| Institution: | Crop & Food Research |
Summary
To complete a preliminary survey of regulated viruses, bacteria and phytoplasmas in a representative group of Allium spp. crops in Auckland and Marlborough. Results from this survey would help determine the need and scope for a larger national survey in the future.
Background
MAF requires a survey of all Allium crops to determine the baseline distribution of currently regulated bacteria, fungi, viruses and phytoplasmas in New Zealand, in particular whether any are present and if so, their distribution and whether they can be eradicated or controlled. MAF will use this information to determine the phytosanitary requirements for imports of Allium seed and nursery stock.
Approach & Outcomes
In early December 2004, a visual survey of five onion, and three garlic fields in the Auckland region was carried out. Specimens from a harvested Rakkyo (A.chinense) crop were also included in the survey. The entire field was walked and plants showing symptoms of bacterial, fungal and phytoplasma disease were collected. Following the same pattern 100 leaves were randomly collected for virus assays and to estimate virus incidence. Similarly in January 2005 a survey of nine onion and garlic crops in Marlborough was also completed.
Laboratory assays and culturing determined the presence or absence of the above pathogens in the survey specimens.
Outcomes
From this survey of Allium crops in Auckland and Marlborough we believe there is nothing to indicate that any specimens were infected with phytoplasmas or regulated bacteria.
Onion white rot (Sclerotium cepivorum) was observed in one Auckland garlic crop with a incidence of 1–3%. In Marlborough, white rot was observed in a shallot and a garlic crop along with Alternaria porri, Penicillium spp., Aspergillus spp. and Puccina allii, all at low incidence rates.
The survey has further confirmed the presence of all Allium viruses previously recorded in New Zealand, in some cases on what appear to be new hosts. In particular we appear to have detected the regulated virus Shallot Mite-borne Latent Virus (SMbLV) in A. cepa, A. ascalonicum and A.sativum, and Shallot Yellow Stripe Virus (SYSV) in A. cepa for the first time in New Zealand. We may also have detected the regulated virus Onion Mite-borne Latent Virus (OMbLV) on A. cepa and A. chinense or alternatively we may have found a wider host range for the Allexiviruses Garlic Virus B (GVB), Garlic Virus C (GVC) and Garlic Virus D (GVD). There is also some doubt regarding which carlaviruses are present in A. cepa and A. ascalonicum since one or both may be infected with the regulated virus Sint-Jan’s Onion Latent Virus (= Welsh onion latent virus) (SJOLV). Further work is needed to confirm these tentative observations, and preserved material will be analysed further using molecular determinations.
Summary
MAF required a survey of all Allium crops to determine the baseline distribution of currently regulated bacteria, fungi, viruses and phytoplasmas in New Zealand. MAF will use this information to determine the phytosanitary requirements for imports of Allium seed and nursery stock.
This report summarises a preliminary survey of regulated viruses, bacteria and phytoplasmas in a representative group of Allium spp crops in Auckland and Marlborough.
None of the Allium crops in Auckland and Marlborough were infected with phytoplasmas or regulated bacteria. The survey confirmed the presence of all Allium viruses previously recorded in New Zealand, and in some cases on what appear to be new hosts. In particular we detected the regulated virus SMbLV in A. cepa, A. ascalonicum and A. sativum, and SYSV in A. cepa for the first time in New Zealand. We may also have detected the regulated viruses OMbLV and SJOLV. Further work is needed to confirm these observations using molecular determinations.
Publications
Fletcher, J D; Lister, RA; Wright, P J; Viljanen-Rollinson, S L H; Andersen, M T; Wei, T (2005). Survey of Allium pests in New Zealand. Crop & Food Research Confidential Report No.1518.
2.10 MBS 358
| Programme Title: | Evaluation of irradiation as a phytosanitary treatment |
| Programme Leader: | Dr Robert Wynn-Williams |
| Institution: | Canesis Network Ltd |
Summary
An evaluation of methods of heat treatment, including irradiation, on rendering seeds including weed seeds, non-viable and on pathogens (especially fungi).
Background
MAF needed to know what the effective doses of irradiation should be with regard to the safe importation of seeds treated by irradiation.
Approach & Outcomes
The Project team reviewed the literature, including standards and systems used by other countries and combined with their existing knowledge and experience summarized this in a report suitable for MAF to compare the efficacy of irradiation treatment to heat treatment, and set scientifically-justifiable import measures for irradiated commodities.
Outcomes
Biosecurity requires that internationally traded plant material is free of pathogens (including both fungi and bacteria) and that all weed seeds are unviable (i.e. will not propagate). This report has demonstrated that irradiation – beta, gamma or X-rays all have very similar affects – with sufficient dosage, can be used to assure that imported material complies with these requirements. Literature concerning a wide range of seed-borne pathogens has been reviewed and it has been shown that typical D-values range between 0.3 and 3 kGy. Seed-borne pathogens are usually more radiation resistant than those in other food products, such as meat, probably due to the low water activity and the presence of anti-oxidants. It was also demonstrated that high or low temperatures during irradiation can increase radiation susceptibility, and that pre- and post-irradiation heat treatment can act synergistically with irradiation. Post-irradiation storage conditions are highly important in retaining low numbers of pathogens, since frequently a few individuals will survive the irradiation treatment.
The seeds themselves are typically more resistant to irradiation in that they can germinate even if subjected to high doses. The irradiation environment (particularly temperature) and post-irradiation storage conditions are important, for the same reason as for eliminating pathogens. Radiation resistance varies dramatically between species, and even between cultivar. Because of the wide range of susceptibilities, it is difficult to recommend a dose that will certainly reduce seed germination to zero percent. Nevertheless, it is worth noting that even at low doses of around 1 kGy, sprout and seedling growth rates are often significantly retarded by irradiating seeds, and there is qualitative evidence that irradiation-weakened individuals die before they can propagate.
It is important to estimate which organisms are present when recommending doses because of the large range of radiation-susceptibilities encountered among organisms. However, the literature reviewed in this report shows that a general rule-of-thumb is that a dose of 25 kGy is likely to render many seeds unable to germinate and the remainder unable to develop and propagate. The most irradiation-resistant pathogen cited is a yeast Saccharomyces cerevisiae var. ellipsoideus (Stehlik and Kaindl, 1966) which had a D-value of 3 kGy when irradiated at about 20 degC (note, at 45degC the D-value was 0.5 kGy) whilst virtually all other pathogens have D-values of 2.5 kGy or less. Thus, a dose of 25 kGy will also substantially reduce and effectively destroy pathogen populations. Careful post-irradiation storage is important.
Summary
It was required to evaluate methods of heat treatment, including irradiation, on rendering seeds including weed seeds, non-viable and on pathogens (especially fungi). MAF needed to know what the effective does of irradiation should be with regard to the safe importation seeds treated by irradiation. Literature was reviewed, in a report comparing the efficacy of irradiation treatment to heat treatment, and set scientifically-justifiable import measures for irradiated commodities. As a general rule-of-thumb a dose of 25 kGy is likely to render many seeds unable to germinate and the remainder unable to develop and propagate.
Publications
Marsh, C; Wilkins, A; Wynn-Williams, R; Causer, S (2005) Evaluation of irradiation as phytosanitary treatment. CLR 05/12 Confidential report.
2.11 MBS 359
| Programme Title: | Models for post border detection of visibly undetectable exotic plant pests |
| Programme Leader: | Gail Timmerman-Vaughan |
| Institution: | Crop & Food Research |
Summary
This project aimed to assist in defining the specifications for future disease surveys by evaluating a range of sampling strategies through simulation to estimate the probabilities of detection they provide under a range of assumptions regarding incidence and spatial distribution of the unwanted organism, using plum pox potyvirus and brown rot caused by Monilinia fructigena as models of diseases where significant aggregation is observed.
Background
The MAF National Plant Pest Reference Laboratory (NPPRL) has been active in carrying out studies to design and estimate the costs of surveillance schemes for high impact exotic plant pest species (Ganev and Braithewaite 2003, Stephenson et al. 2003). Fundamental research has shown that the spatio-temporal distribution of plant disease epidemics may be best described using different models (e.g. the binomial, beta-binomial or hypergeometric distributions), depending in particular on the degree of aggregation of the affected plants (Madden and Hughes 1999). Plum pox potyvirus and brown rot caused by Monilinia fructigena would be devastating to the stone and pome fruit industries, respectively, if they were introduced into New Zealand and became established. These were chosen as trial organisms for testing various sampling schemes for their statistical power to detect incursions when disease incidence, detection efficacy and detection probabilities were varied.
Approach & Outcomes
The possible behaviour of plum pox potyvirus and brown rot (M. fructigena) in the event of an incursion in New Zealand was characterised by surveying the published literature. The symptoms, host range, strains, transmission, epidemiology and diagnosis of these organisms were summarised to ensure that disease models to be developed, simulated epidemics, and estimates of detection costs reflected existing knowledge.
Existing equations to describe disease distributions do not consider both aggregation and orchard size, spatial layout, and spatial distribution of disease other than the extent of aggregation. Therefore, disease epidemics were simulated for a range of parameters including: disease incidence (from one tree/orchard to 10%), different pathogen dispersal (using four wind conditions), and different orchard shapes and sizes (square versus long, <50 trees to 10 ha). Each simulation was run 1000 times. Calculation of index of dispersion and the beta-binomial aggregation statistic (θ) showed that the extent of disease aggregation in the simulated orchards was appropriate for these two diseases. In addition, six sampling schemes were devised that either randomly sampled a fixed number of trees (50, 60 or 500) or sampled trees in regular patterns, sampling one-in-four or one-in-sixteen trees, either as individuals or in quadrats. The statistical power of the different sampling schemes to detect an infected orchard was determined by sampling the simulated orchards. The ability of the different sampling schemes to estimate disease incidence was also examined. Resources required to detect and diagnose disease incursions were then estimated using the sampling schemes that were the most powerful for the combination of three disease incidences (1 tree/orchard, 0.5% and 5%) and all the various orchard sizes.
Outcomes
For detection of relatively high disease incidence (5% or greater), we showed that effect of aggregation (θ=0.09) on the power to detect an infected orchard is only slightly reduced (dropping from 90% to 88%) using the sampling scheme described by Richmond et al. (1998) where relatively few trees (n=50) are randomly selected. By sampling 60 trees, the confidence of detection would increase to 90%. Therefore, even in the presence of a significant but low level of disease aggregation, the Richmond et al. (1998) approach will detect a high percent of infected orchards with 5% or greater disease incidence. The overseas literature on recent plum pox potyvirus outbreaks indicates that orchards with disease incidence as high as 10% occur by the time the disease has been detected (Hughes et al. 2002), therefore this level of sampling (n=50) may be appropriate for many diseases (where this degree of aggregation or less is observed) for conducting surveillance to determine whether an incursion has occurred.
However, to delimit the extent of a disease incursion or to ensure disease eradication, reliable detection of infected orchards with much lower disease incidences is required. The effect of disease aggregation is to increase the number of trees that must be selected to maintain a given confidence of detection. For example, if the distribution of trees fits the binomial distribution (ie they are randomly distributed), then 511 trees are required to detect an orchard with 0.5% incidence with a 90% confidence of detection and 90% detection efficacy. If modest aggregation is present (θ=0.09) then 600 trees must be selected to meet the same detection parameters. The most appropriate sampling schemes to detect infected orchards with aggregated disease at various disease incidences, and of various sizes, were determined. The most effective sampling strategies were still those that selected the largest proportion of trees in an orchard. Consequently, for small orchards, strategies that selected a fixed number of trees (50, 60 or 500) were most effective, while for large orchards the sampling strategies that selected the largest proportion of trees were most effective. In the presence of disease aggregation, the sampling scheme that selected one-in-four trees in quadrats was marginally more effective than a sampling scheme that sampled the same proportion of trees as single trees. In the case where the disease incidence was only one tree/orchard and the orchards were large, the best sampling schemes (selecting one-in-four trees) would at the best identify 25% of infected orchards.
Using the statistically most powerful sampling schemes for each orchard size, the costs of surveying for plum pox potyvirus by visual observation, ELISA and IC-PCR (immunocapture-PCR) were estimated; and the costs of surveying for brown rot (Monilinia fructigena) of pome fruits by visual observation were estimated. For example, sampling one 10 hectare orchard to detect a 0.5% disease incidence of plum pox potyvirus with a probability of detection nearing 100% of infected orchards will require 86 hours of surveying, either 5.5 days (ELISA, based on 300 tests/day) or 13.8 days (IC-PCR, based on 120 tests/day) of laboratory diagnostics, and either approximately $2500 or $5000 in consumable reagents.
Summary
This project aimed to evaluate sampling methods through simulation to estimate the probabilities of detecting either plum pox potyvirus or brown rot caused by Monilinia fructigena under a range of assumptions regarding incidence and spatial distribution of the unwanted organism in order to assist in defining the specifications for future disease surveys.
Following literature surveys to identify key characteristics of the pathogens and their epidemics, diseased orchards with the relevant spatial distributions were generated by simulation. In particular, the aim was to achieve a mean aggregation of disease consistent with the aggregation that has been observed in overseas studies. Existing equations to describe disease distributions do not consider both aggregation and orchard size, spatial layout, and spatial distribution of disease other than the extent of aggregation. Therefore, diseased orchards were simulated for a range of parameters including disease incidence (from 1 tree/orchard to 10%), different pathogen dispersal (using four wind conditions), and different orchard shapes and sizes (square versus long, <50 trees to 10 ha). The power of different sampling schemes to detect infected orchards was determined by sampling the simulated orchards.
The most appropriate sampling schemes to detect infected orchards with aggregated disease at various disease incidences, and of various sizes, were summarised. The most effective sampling strategies were still those that selected the largest proportion of trees in an orchard therefore different sampling schemes would be chosen for small versus large orchards. Using the statistically most powerful sampling schemes for each orchard size, estimates were presented of the costs of surveying for plum pox potyvirus by visual observation, ELISA and IC-PCR (immunocapture-PCR); and the costs of surveying for brown rot (Monilinia fructigena) of pome fruits by visual observation.
2.12 MBS 360
| Programme Title: | Fusarium circinatum – Year 2 (2004/05) |
| Programme Leader: | Tod Ramsfield |
| Institution: | Forest Research |
Summary
To extend the utility of the PCR primers developed during 2003/2004, a system was developed to identify F. circinatum in soil.
Background
If F. circinatum arrives in New Zealand, it will likely appear first in the nursery environment as it did in Chile and South Africa, therefore a DNA based detection system that is able to identify the pathogen in soil will allow a rapid survey of New Zealand nurseries.
Approach & Outcomes
In this experiment, F. circinatum was grown on millet grain and then conidia were harvested and inoculated into both sterile and non-sterile soil and potting mix at known concentrations. Immediately following inoculation, DNA was isolated from the soil and potting mix. It was then attempted to detect F. circinatum DNA extracted from the inoculated soil and potting mix to test the sensitivity of the PCR detection method.
Outcomes
This research was conducted to test the efficacy of the DNA based identification system for Fusarium circinatum in soil and potting mix that was inoculated with known concentrations of F. circinatum conidia. DNA was extracted from the soil and potting mix using a FastDNA® SPIN kit for soil and then the DNA was PCR amplified with the specific primers that were developed in prior studies. After two rounds of PCR, it was found that the technique could detect F. circinatum condia at a concentration of 105 conidia / gram. The technique was shown to be specific as the PCR primers did not cross react with the high levels of background DNA present in non-sterile soil and potting mix. It was observed that F. circinatum was a poor competitor in the soil environment; the fungus was recovered from sterile soil and potting mix that was inoculated with all concentrations of the pathogen that were tested (106, 105, 104, 103, 102, and 101 conidia / gram) but recovery from non-sterile soil and potting mix only occurred from the 106, 105, and 104 conidia / gram concentrations in non-sterile soil and from the 106 conidia / gram concentration in non-sterile potting mix.
Publications
Publication of the method and results in an international journal anticipated.
2.13 MBS 363
| Programme Title: | The relative attractiveness of baits to Paratrechina longicornis |
| Programme Leader: | Margaret Stanley |
| Institution: | Landcare Research |
Summary
To trial the relative attractiveness of various baits and food types to determine optimal bait acceptability by Paratrechina longicornis.
Background
Biosecurity New Zealand (BNZ) is currently responding to a series of incursions of exotic invasive ant species, and to date, has relied heavily on a small number of baits and toxins for control of incursions. The success of responses to new incursions of invasive ants may be compromised in the absence of effective toxic baits. As a first step to ensuring effective incursion response, BNZ commissioned Landcare Research to review international information on baits and toxins used for ant control (MBS356). This review recommended that highest research priority should be given to identifying effective toxic baits with which to manage P. longicornis (crazy ant) incursions (Stanley 2004). BNZ frequently detect P. longicornis incursions around New Zealand and there are no toxic baiting strategies of proven effectiveness. Ant preferences for different food types (protein, carbohydrate, lipids) determine how appropriate toxic baits are for use against particular ant species. There is very little information on the diet and bait preferences of P. longicornis, and no formal testing of the attractiveness of commercial ant baits to P. longicornis. The aim of this project was to trial the relative attractiveness of various food types and baits to P. longicornis, with the ultimate aim of determining the appropriateness of various commercial ant baits for P. longicornis management.
Approach & Outcomes
Given the lack of established P. longicornis populations in New Zealand, the attractiveness of seven bait types to P. longicornis was tested in field trials on Fraser Island, Queensland, Australia, where abundant populations of P. longicornis have established. Summer and autumn trials were performed with autumn climatic conditions expected to approximate a northern New Zealand summer. Recruitment of P. longicornis workers to the baits in the presence of competitors was also investigated.
Baits trialled were a range of commercially available products Amdro®, Maxforce®, Xstinguish™ (non-toxic monitoring version), and Presto®, as well as tuna (in spring water), sugar water (25%), boric acid (1%) in 25% sugar water, and deionised water. This ensured all major food types (protein, carbohydrate, lipids) were included. Seven baits were used in each trial, and tuna was used where Presto® was unavailable. During each trial, replicate bait stations were positioned at least 10 m apart at the trial site. At each bait station, each of the seven bait types were positioned randomly in a circular pattern with at least 30 cm between dishes. Recruitment (number of workers) to each of the seven baits was recorded at each bait station at least three times over the next 1.5–2.5 hours. The presence and abundance of other ant species were also recorded.
Outcomes
Tuna and Xstinguish™, along with sugar water and sugar water + boric acid, were the most attractive baits to P. longicornis workers. The granular baits (Maxforce®, Amdro®, Presto®) were relatively unattractive to P. longicornis foragers. Tuna is not practical for use as a control tool in terms of toxin incorporation and bait delivery, but was highly attractive, which suggests forager preference for protein and potential use as a cost-effective monitoring bait for P. longicornis. Sugar water was attractive to P. longicornis and other ant species, but care would be required in situations where potential non-target species, such as honeybees, are present. Bait delivery in liquid form is also more difficult than a solid bait, but can be used efficiently during small scale incursion events. Xstinguish™ combines both protein and carbohydrate (sugar) attractants and was consistently more attractive to P. longicornis than the sugar water. Because Xstinguish™ is produced as a commercial ant bait, it is more practical to use than liquid baits in both small and large scale incursions.
Given the attractiveness of sugar water + 1% boric acid baits to P. longicornis in this study, the effectiveness of boric acid-based, sweet liquid baits (commercially available in New Zealand) in eliminating P. longicornis colonies requires testing. The effectiveness of the toxic version of Xstinguish™ at attracting P. longicornis foragers and eliminating colonies also requires testing. Xstinguish™ is not registered for use in Australia, and an experimental use permit would be required for testing the effectiveness of the toxic version in Australia. As an alternative, a carefully designed research by management approach could be adopted by BNZ to quantify the effectiveness of this product against P. longicornis incursions in New Zealand.
Summary
The aim of this project was to trial the relative attractiveness of various food types and baits to crazy ants, P. longicornis, to determine the appropriateness of various commercial ant baits for P. longicornis management. Given the lack of established P. longicornis populations in New Zealand, the attractiveness of seven bait types to P. longicornis was tested in field trials in Queensland, Australia. Baits trialled were commercially available products Amdro®, Maxforce®, Xstinguish™ (non-toxic monitoring version), and Presto®, as well as tuna (in spring water), sugar water (25%), boric acid (1% in sugar water), and deionised water. At each of the replicate bait stations (10 m apart), each of the seven bait types were positioned randomly in a circular pattern. Recruitment to each of the seven baits was recorded at each bait station at least three times. The presence and abundance of other ant species was recorded. Tuna and Xstinguish™, along with sugar water and sugar water + boric acid, were the most attractive baits to P. longicornis workers. The granular baits (Maxforce®, Amdro®, Presto®) were relatively unattractive to P. longicornis foragers. Without further research, and given the results of these bait preference trials, P. longicornis incursions should continue to be managed using Xstinguish™ and Exterm-An-Ant® (8% boric acid + 5.6% sodium borate in a sweet solution). Laboratory and field trials are required to confirm the effectiveness of toxic Xstinguish™, Exterm-An-Ant® and 25% sugar water + 1% boric acid, in eliminating P. longicornis colonies.
Publications
Stanley, M; Robinson, W; Nicholls, Z; Collier, P (2005). The relative attractiveness of baits to Paratrechina longicornis. Landcare Research Contract Report: LC0405/132.
Contact for Enquiries
Farm Monitoring Programme Manager
Monitoring and Evaluation
MAF Policy
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0623
Fax: +64 4 894 0741
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