Choosing and packaging plant samples for testing by Grow Help Australia

Make sure your samples are suitable for testing:

  • Send correct and sufficient plant material for pathogen detection.
  • Package your samples as directed.

For advice about sampling, you can:

Choose suitable samples

If possible, send whole plants. Above-ground problems are often indicators of root rot or crown rot.

For plants that are too large to send whole, send sections such as the root ball and lower stem and stem dieback symptoms. Bag root balls and soil so they will not contaminate above-ground parts. For advice about which parts to send, email photographs to us.

If possible, send healthy and unhealthy plants so we can compare symptoms. This is particularly important for crops that are infrequently submitted. Sometimes after testing we find that a disease is present in both healthy and unhealthy plants.

Include the margin between healthy and dying plant tissue; this is the area where the pathogens are active and most easily detected.

Send multiple plants showing the symptoms, particularly when plants are small. The smaller the plants, the more plants we need.

Always follow the guidelines for different plant types and specific diseases and pests.

Guidelines for different plant types

  • What to send

    • Whole plants (number depends on size) showing initial and relatively advanced symptoms
    • Very small plants (such as from trays with more than 100 plants): 20 plants or a whole or half a tray if possible
    • Small seedlings and plants: 10 plants
    • Established tube stock plants: 4–6 plants
    • Medium-sized plants (such as in 140mm pots): 2–4 plants
    • Large plants: 1–2 plants or sections of plants (such as some or all of the root ball and stem or leaf symptoms) as for in-ground fruit and tree crops

    How to package

    • Wrap the roots of individual plants, then wrap the bases of all seedlings together.
    • Bag the container and/or root ball to stop media from contaminating the entire sample.
    Seedlings with roots and soil wrapped in soft plastic
    Best practice for packaging a diagnostic sample of seedlings

  • What to send

    • Depends on the type of symptoms observed and the age of the tree
    • Crown and root material (often required)
    • Stems with tip dieback (may be helpful but are most often a result of root rot, crown rot or problems in the graft)
    To test for dieback
    • Young in-ground trees: the root ball (bagged separately), lower stem and graft union
    • Mature trees: roots and soil (bagged separately), crown rot or canker material and/or branch dieback
    • Large branches or the main trunk (crown) of large trees: cross-sections or wedge-shaped pieces of wood (5–8cm wide) that contain the margin between healthy (normal wood colour) and unhealthy (discoloured) tissue

    Number of samples

    • Material from multiple trees, if possible

  • What to send

    • Seedlings and small plants: at least 10 whole plants
    • Mature crops according to symptoms:
      • Dieback: root ball, crown and at least the bottom 30–50cm of the plants, plus any stem tip dieback symptoms
      • Leaf spot: multiple stems with leaves attached, preferably with each stem from a different plant; can also indicate root rot, so check root and crown health
      • Unusual or deformed growth (including suspect virus infection): stems 30–50cm long including the growing tips; roots and crown (may be helpful)

    How to package

    • Ensure that soil and root balls are bagged to avoid contamination.

  • What to send

    • 5–10 whole fruit or vegetables if possible; fewer for very large fruit or vegetables such as watermelon
    • Specimens that show both diseased and adjacent healthy areas
    • NOT cut fruit or fruit that is likely to degrade into 'mush' during transport

    How to package

    • Contain the sample to avoid leakage.
    • Package it to avoid it being crushed or damaged in transport.

Guidelines for specific diseases and pests

  • Nematology testing is completed by the nematology team and may be charged separately. For information on testing of specific nematode pests, email growhelp@dpi.qld.gov.au.

    What to send

    • About 300g of field-moist soil to test for most pre-plant, plant-parasitic nematodes
    • Infested roots and adjoining soil to test for root nematode infection
    • 5–10 crowns with new growth showing deformity to test for foliar nematode infection

    How to collect

    • Randomly collect many smaller subsamples across the field, for example 20–30g of soil from each of 15–20 sites.
    • Do not refrigerate the soil or use icepacks.
    • Do not allow the soil to get hot once sampled.

    How to package

    • For nematode and Phytophthora testing, label and submit separate bags. Do not include icepacks.

  • What to send

    • About 1kg (in total) of samples of soil/media and roots, including symptomatic roots, from 5–10 collection points across the plot or under symptomatic trees
    • Symptomatic plants, if possible

    How to collect

    • Scrape the dry topsoil aside.
    • Collect relatively moist soil/media to a depth of 15–30cm.
    • Repeat for each subsample, preferably only from beneath symptomatic plants.

    How to package

    • For nematode and Phytophthora testing, label and submit separate bags.

  • If you suspect an exotic pest, report it using one of these methods:

    We cannot identify some groups of insects and mites because we do not have the required taxonomic expertise. Molecular tests can identify some insects and mites, but not all of them.

    Australia Post and most couriers do not allow postage of 70% ethanol, so do not use this with samples.

    Small insects

    • Send live insects present on plant foliage in a sealed ziplock bag, preferably double-bagged.
    • Send 20–100 leaves and/or stems with new growth, depending on the number of pests on the leaves.
    • Do not kill the insects.

    Large insects, or insects that readily move off the plant

    • Ensure the insects are contained and not crushed.
    • If the insects need to be reared out, submit enough plant material for them to develop.
    • If the insects are large and do not need to be reared:
      • Collect the insects and kill them in a freezer overnight.
      • Wrap the dead insects 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.

    For more advice, email growhelp@dpi.qld.gov.au or phone 13 25 23.

  • Virus symptoms can be confused with many different diseases and non-pathogenic disorders.

    Preliminary advice

    For advice about whether a plant may be infected with a virus, email the following to growhelp@dpi.qld.gov.au:

    • multiple in-focus photographs of a suitable size (larger than 500KB)
    • information about the host
    • details of where the crop is grown
    • the incidence (frequency) and area over which symptoms occur.

    This will help us determine the likelihood of a viral infection and the cost of testing.

    Virus testing

    If you suspect your plants are infected, you can send samples for testing to confirm a virus infection.

    • Select 6–10 stems, each about 30cm long. Include growing tips, each from a different plant.
    • Wrap the stems in dry paper and place them in a ziplock bag.
    • Package the stems carefully to prevent crushing in transport.
    For large leaves
    • Select 10 symptomatic leaves, preferably each from a different plant.
    • Place a paper towel under and between each leaf.
    • Place all leaves into a ziplock bag and package them in a box to stop them from being crushed.

    For more advice, email growhelp@dpi.qld.gov.au or phone 13 25 23.

  • Many pests and pathogens (such as Phytophthora) can cause dieback of particular plant species, or groups of plant species, across environmental landscapes.

    If you are a ranger or local government worker and have observed widespread or localised but spreading dieback, email to growhelp@dpi.qld.gov.au:

    • the history of your observations
    • photographs of the symptoms.

    If you suspect an exotic pest is causing dieback, report it using one of these methods:

  • Testing mature trees in urban and parkland settings for plant pathogens (such as Phytophthora, Phellinus and fungi from the family Botryosphaeriaceae) can be challenging and time-consuming. Also, testing may not detect a pathogen even if it is the cause of dieback.

    However, if you are a professional arborist, you can request pathogen testing.

    What to send

    • Soil for Phytophthora testing
    • Rotting roots, if present, preferably including roots with the margin between healthy and dead tissue (though these can be difficult to find)
    • Roots with soil 'stuck' to them (this is called 'stocking'). Stocking can appear above or below ground and often will have white fungal growth within it, beneath it or within the root itself. These symptoms may indicate the presence of Phellinus
    • Piece of tree root, with a portion of the stocking removed showing fungal growth underneath
      Large root with stocking, but with a portion of stocking removed to show fungal growth (Phellinus)
    • Wood sections with a honeycomb look about them and/or black lines or shoestring-like structures in the wood. This could be fungal growth moving up the bark of the tree trunk from ground level and is known as 'stocking'. These symptoms may indicate the presence of Phellinus or Armillaria
    • Cross section of tree lying flat on black plastic, showing black fungal growth
      Clean section of wood (about 30cm in diameter) with black fungal growth (Phellinus) present
    • Wedges or cross-sections (5–10cm thick) of large stems or branches with internal discolouration. Discolouration may appear as a blue stain or dark regions in the centre or outer areas of the heartwood. If the stem is more than about 30cm in diameter, submit only a portion of the cross-section (a wedge or half). Include both healthy and dark, unhealthy tissue
    • Five cross sections of a tree showing fungal growth lying flat in plastic container
      Stem cross-sections with necrotic heartwood containing fungi from the family Botryosphaeriaceae

    How to package

    • Bag roots and soil to stop soil from contaminating the rest of the sample.
    • Do not include soil or small bits of wood that can contaminate wood tissue unless they are bagged separately.
    • Wrap individual pieces of wood in clean paper, paper towel or newspaper to keep them relatively fresh and free of debris.

Do not submit

  • Dead plants. They are full of bacteria and fungi feeding on the decaying organic matter. The bacteria and fungi inhibit our ability to isolate a pathogen.
  • Uncontained soil or growing media (including loose soil and media). These can contaminate the above-ground plant parts, seedlings or plugs.
  • Saturated samples. Wet samples increase the growth of secondary bacteria and fungi—these inhibit our ability to isolate a pathogen. Also, foliage generally survives transport better when dry.
  • Samples with icepacks (unless icepacks are critical). Generally, icepacks in samples create condensation, which promotes sample breakdown and contamination. Also, if they are not packaged with care, icepacks can damage samples during transport.
  • Degraded fruit. This turns to 'mush' in even the best packaging.
  • Easily crushed samples. Include protective packaging to keep samples intact and in good condition.
  • Bark from dying trees. We require the heartwood, as the pathogen will not be active in the bark. Only send bark if it also has some heartwood present and has the margin of the disease.
  • Samples that have been treated with fungicides (particularly systemic products) in the last 14 days. Fungicides inhibit fungal growth, making it harder for our tests to detect the pathogen. Samples that have been recently treated with fungicide are more likely to produce false negative results. Copper products can also inhibit detection of bacterial pathogens.

Package samples correctly

Use protective, safe packaging

  • Choose packaging that will not compress or damage your sample, especially if you are submitting fruit or delicate plant material.
  • Do not send large glass containers. Small tissue culture tubes are acceptable.
  • Ensure the sample container weighs less than 15kg and can be lifted by 1 person.
  • Protect your samples from degrading and from extremes in temperature.

As a general guideline, treat your plant sample as though it is an egg in the package. If you can pick up the package and shake it without damaging the 'egg', you have packaged your sample well.

Keep samples dry and uncontaminated

  • Bag the root ball and contain the soil or growing media so that it does not contaminate foliage. Cling film is useful for wrapping the roots and growing media of smaller plants. The root ball can be moist.
  • Make sure the other plant material (especially mature fruit) will stay as dry as possible. Wrap samples in paper (such as newspaper, paper towel or tissues) and contain them in a ziplock bag.
  • If icepacks must be included:
    • wrap them in paper to minimise condensation.
    • pack them so they do not have direct contact with the samples.
    • wrap the samples in enough dry paper to soak up any condensation from the icepacks.