Selecting and packaging plant samples for testing

Ensure you send correct plant material for pathogen detection and package your samples well. If you select poor samples and/or package them inadequately it may result in the sample being unsuitable for testing.

After you have read this page, if you are unsure or need more information, send photographs of the symptoms to growhelp@daf.qld.gov.au or phone us on 13 25 23.

Choosing suitable samples

We prefer to receive both healthy and unhealthy plant specimens as these can provide a valuable comparison and increase our capacity to complete accurate and thorough diagnostic tests. For many of the tests we complete, it’s essential that the sample includes the margin between healthy and dying plant tissue. This is the area where the pathogens are active and most easily detected. Sending multiple plant samples is usually beneficial.

Do not submit the following types of samples:

  • Dead plants. They are full of bacteria and fungi feeding on the decaying organic matter which inhibits our ability to isolate a pathogen.
  • Uncontained soil/growing media with plants, including loose soil and media contaminate above ground plant parts, seedlings or plugs. Bag the root balls and/or containers as per below.
  • Saturated samples. Wet samples increase the growth of secondary bacteria and fungi which inhibits our ability to isolate a pathogen. Most often, foliage survives transport better when dry. Wrap samples in paper (e.g. newspaper, paper towels, tissues) as required and contain them in a zip-lock bag.
  • Samples with ice packs. Generally, ice packs in samples create condensation that promotes sample breakdown and contamination. If ice packs are critical, ensure you wrap samples in sufficient dry paper to soak up the condensation. Also, pack the sample to ensure the ice pack does not damage the sample in transport.
  • Degraded fruit. This turns to 'mush' in even the best packaging.
  • Easily crushed samples. Include packaging to keep the sample intact and in good condition.
  • Samples requiring 2 people to lift. Each package must be less than 15kg.
  • Bark from dying trees. We require the heartwood, as the pathogen will not be active in the bark.
  • Select multiple pots/plants showing initial and relatively advanced symptoms.
  • Where possible, send multiple unhealthy plants of the same variety; this can increase our confidence that the problem is consistent across symptomatic plants.
  • The smaller the plants, the more plants we require:
    • For small seedlings and plants we require at least 10 plants to optimally test the sample.
    • For medium-sized plants (e.g. in 100mm pots) 4 plants are usually sufficient.
    • For large plants, 1–2 plants are usually sufficient.
    • Regardless of the size of the container, bag the container and/or root ball to stop media from contaminating the entire sample.
    • For tall plants, we only require the root ball, root crown (up to about 30–50cm above the ground) and growing tips if showing dieback or unusual symptoms.
    • If in doubt, phone or email us with photographs.
Best practice for packaging a diagnostic sample of seedlings. Wrap the roots of individual plants then wrap the bases of all seedlings together.
  • For young in-ground trees experiencing dieback, we require he root ball (bagged separately), lower stem and graft union.
  • Stems with tip dieback may also be helpful but are most often a result of root rot, crown rot or problems in the graft.
  • Send material from multiple trees, if possible.
  • Ensure root ball and soil is bagged to avoid contaminating the sample.
  • For mature trees with dieback, sending whole plants is not feasible but we require roots and soil (bagged separately), crown rot or canker material and/or branch dieback.
  • The exact tissue is dependent on the type of symptoms observed and the age of the tree.
  • Where dieback is occurring on large branches or in the main trunk (crown) of large trees it’s necessary to cut cross sections or pie-wedge-shaped pieces of wood that contain the margin between healthy and unhealthy trees. Ensure pieces are about 10cm wide.
  • If in doubt, phone or email us with photographs.
  • For seedlings and small plants, we recommend sending at least 10 whole plants.
  • For more mature crops, the sample may vary depending on the symptoms:
    • For crops experiencing dieback it's necessary to submit the root ball, crown and at least the bottom 30–50cm of the crop. Stem tip dieback can also assist.
    • For identifying leaf spot, we recommend submitting stems with leaves attached. Submit multiple stems, preferably with each stem from a different plant.
    • For plants showing unusual or deformed growth (including suspect virus infection) we recommend submitting stems about 30–50cm long including the growing tips. However, sometimes including the roots and crown can be helpful.
  • Ensure that soil and root balls are bagged to avoid contamination.
  • If in doubt, phone or email us with photographs.
  • Submit 5–10 fruit/vegetables whenever possible (where fruit are very large submit fewer, e.g. watermelon):
    • avoid submitting cut fruit/vegetables as this will increase the rate at which they degrade
    • do not select fruit that is likely to degrade into 'mush' during transport.
  • Select specimens that show both diseased and adjacent healthy areas.
  • Contain the sample to avoid leakage and package it to avoid it being crushed or damaged in transport.

Nematology testing is completed by the nematology team and may be charged separately.

  • Collect about 300g of field moist soil to test for most pre-plant, plant-parasitic nematodes.
  • Ensure that the sample is made up of many smaller subsamples, randomly collected across the field.
  • Do not refrigerate the soil; ice packs are not necessary.
  • Do not allow the soil to get hot once sampled.
  • If plants are to be tested for root nematode infection, submit infested roots and adjoining soil.
  • For suspect foliar nematode infection, submit 5–10 crowns with new growth showing deformity.
  • If both nematode and Phytophthora testing is required, please submit bags labelled separately.

For information on testing of specific nematode pests, email Jennifer.cobon@daf.qld.gov.au in the nematology team

Collect sub-samples (adding up to a total of about 1kg) from across the plot/block by collecting a handful of soil/media and roots from at least 5–10 collection points or from compass points around large trees:

  • scrape the dry topsoil aside
  • collect relatively moist soil/media to a maximum depth of 15–30cm
  • repeat for each sub-sample, preferably only from beneath symptomatic plants
  • include symptomatic roots to increase our ability to detect Phytophthora. Also submit symptomatic plants, if possible
  • if both nematode and Phytophthora testing is required, please submit bags labelled separately.

Australia Post and most couriers do not allow postage of 70% ethanol; therefore, we recommend you send live small insects present on plant foliage in a zip-lock bag. Do not kill them.

If they are suspected to be an exotic pest phone the Exotic Plant Pest Hotline on 1800 084 881.

Relatively large insects, or insects that readily move off the plant, can be collected and killed in the freezer overnight:

  • after they are dead, wrap them in tissue paper and place them in a small container that will not be crushed or damaged in transport
  • ensure that the insects will stay dry
  • where foliage is malformed, ensure that you include stems with growing tips in the sample.

Contact us if you are unsure of the best method to send us insects or mites.

Some groups we cannot identify as we do not have the required taxonomic expertise. Molecular tests sometime are successful in identifying insects, but not always.

Virus symptoms can be confused with many different diseases and non-pathogenic disorders. Visual symptoms can provide a substantial amount of information as to whether further testing is worthwhile.

If you are unsure if the plant is infected with a virus, we recommend you email growhelp@daf.qld.gov.au with:

  • multiple photographs—ensure they are in focus and of a suitable size (e.g. larger than 500KB)
  • information about the host, where the crop is grown, and an indication of the incidence (frequency) and area over which symptoms occur. This may initially inform the likelihood of a viral infection and also the cost of testing.

If you have experience and suspect your plants are infected and would like to confirm a virus infection, we recommend:

  • sending 6–10 stems, each about 30cm long
  • including growing tips, each from a different plant
  • wrapping stems in dry paper placed in a zip-lock bag
  • packaging stems to prevent crushing in transport
  • contacting us, if in doubt.

Our service can complete bulk testing to assist in gaining market access and certification. Please enquire for a quote.

A range of pests and pathogens can cause dieback of particular plant species, or groups of plant species, across environmental landscapes (e.g. Phytophthora dieback). If you suspect an exotic pest is causing dieback, phone the Exotic Plant Pest Hotline on 1800 084 881.

You may choose to report such observations to a local ranger or council worker; they can let you know if threat abatement plans are already in place or being implemented.

If you are a ranger or council worker observing widespread, or localised but spreading dieback, email growhelp@daf.qld.gov.au with the history of your observations and photographs of the symptoms.

Mature trees in urban and parkland settings can decline suddenly or over long periods of time. Testing these trees for the presence of plant pathogens (e.g. Phytophthora, Phellinus and fungi from the family Botryosphaeriaceae) can be challenging and time consuming. Furthermore, testing may not result in the detection of a pathogen even if it was responsible for death and decline of the tree.

For professional arborists seeking pathogen testing, we recommend submitting the following material:

  • soil for Phytophthora testing (as per above), bagged to contain the soil and stop contamination of the sample
  • rotting roots, if present, preferably including roots with the margin between healthy and dead tissue (though this can be difficult to find). Bag roots to stop soil from contaminating the rest of the sample
  • roots with soil ‘stuck’ to them (this is termed ‘stocking’). Stocking can appear above or below ground and often will have white fungal growth present within, beneath it or within the root itself. These symptoms may indicate the presence of Phellinus
  • wedges or cross-sections of large stems/branches with internal discolouration. Discolouration may appear as a blue stain or dark regions in the centre or outer areas of the heartwood. Cross sections should be about 5-10cm thick. If the stem is more than about 30cm in diameter, submit only a portion of the cross section (e.g. a wedge or half). Regardless, ensure that the section includes both healthy and dark, unhealthy tissue
  • do not include soil or small bits of wood that can contaminate wood tissue unless they are bagged. We recommend wrapping individual pieces of wood in clean paper, paper towel or newspaper to keep them relatively fresh and free of debris.
Stocking removed to show fungal growth

Large root with stocking. A portion of the stocking has been removed to show fungal growth present underneath from which Phellinus was detected

Section of wood with black fungal growth

Clean section of wood (about 30cm in diameter) with black fungal growth present. Phellinus was detected from this sample

Necrotic heartwood showing fungi

Stem cross sections with necrotic heartwood from which fungi from the family Botryosphaeriaceae was detected

Samples and fungicides

Ensure you send samples which have not been treated with fungicides for at least 14 days before sending, particularly systemic products. Therefore, collect samples before applying fungicides whenever possible.

Fungicides inhibit fungal growth and can stop or reduce our ability to detect the pathogen, though it may still be present and cause disease. Similarly, copper products can inhibit detection of bacterial pathogens. While some pathogens can still be detected, samples that have received recent fungicide applications are more likely to produce false negative results.

Packaging samples

  • Choose packaging that will not compress or otherwise damage your sample. This is particularly important if submitting fruit or delicate plant material.
  • Make sure the plant material will stay dry (the root ball can be moist). Add newspaper or paper towel as necessary to keep sample dry.
  • Bag the root ball and contain soil/growing media so that it does not contaminate foliage.
  • Protect your samples from degrading and from extremes of temperature. Including ice packs may cause more problems with condensation promoting breakdown of the sample. If ice packs are critical, ensure you wrap samples in sufficient dry paper to soak up the condensation. Also, pack the sample to ensure the ice pack does not damage the sample in transport.
  • Complete a sample submission form and include at least the first page with the actual sample. Samples without a completed form may be delayed.
  • Do not send large glass containers (small tissue culture tubes are acceptable).
  • Ensure the sample container weights less than 15kg and can be lifted by 1 person.
  • Address your sample correctly. Using an incorrect address will significantly delay your sample. Read about delivery options.
  • Post samples on Monday, Tuesday or Wednesday, if possible. Samples that sit in transport over weekends can become degraded.