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Selecting and packaging plant samples for testing

COVID-19 and Grow Help Australia service update

We anticipate that Grow Help will remain open indefinitely. However, there may be delays in testing and completing reports. We will do everything we can to get results to you promptly.

Email growhelp@daf.qld.gov.au for further information.

We can only make an accurate diagnosis if your specimens are:

  • carefully selected and packaged—follow the advice below
  • rapidly delivered
  • sent together with a history of the crop and problem.

After you have read this page, if you are still unsure about correct sampling procedures or need more information:

  • email images of the symptoms to growhelp@daf.qld.gov.au for further advice on what to submit. Check to make sure that all images are in focus and include your phone number in the email
  • phone us on 13 25 23.

Choosing suitable specimens

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. Never send dead plants—dead plants are full of bacteria and fungi feeding on the decaying organic matter that inhibits our ability to isolate a pathogen.

Nursery plants and hydroponic crop plants

Select different pots or plants showing initial and advanced symptoms. Where possible, send multiple unhealthy plants; this can help diagnose the problem and increase our confidence that the problem is consistent across symptomatic plants.

When packaging:

  • small to medium container plants—place the pot or root ball with growing media in a bag or wrap in such a way as to stop media from contaminating the entire sample
  • very large plants—if may be possible to send only a portion of the above-ground parts, perhaps with a separate bag of some roots and growing media. Contact us for the best way to proceed with large plants.

Seedlings and cuttings

Send a minimum of 3 plants. However, more may be required where plants are very small or when plants are dying back. We suggest submitting 12 or more, particularly for stem dieback problems on small plants or plugs.

Seedlings placed loosely in bags become degraded rapidly. We recommend you:

  1. wrap roots of individual plants in cling wrap
  2. wrap cling wrap around the bases of all seedlings of a particular type
  3. wrap in paper towel and place in a zip-lock bag.
Best practice for packaging a diagnostic sample of seedlings. Wrap the roots of individual plants then wrap the bases of all seedlings together.

In-ground fruit and vegetable crops

To increase our ability to accurately diagnose the problem:

  • submit whole plants together with soil/media around roots, if possible. Often above-ground symptoms are a result of root and stem vascular problems
  • bag soil and root ball so it doesn't contaminate the entire sample
  • for trees grown in-ground, email images of the problem to growhelp@daf.qld.gov.au, so we can specifically advise you. For example, for:
    • younger trees (particularly)—we will often need the entire plant. We may advise cutting the stem into sections of about 50–100cm for transit
    • older and larger trees—we may only need you to send a sample of the soil and roots together with sections of stems and foliage, including images of the tree in its existing position
    • trees with stem or branch cankers—we recommend that you submit entire branches, as small portions of bark or woody tissue are unlikely to be useful.

Postharvest fruit and vegetables

To assist diagnosis:

  • submit at least 6 fruit or vegetables whenever possible, or possibly fewer if the fruit is large
  • avoid cutting fruit/vegetables as this will increase the rate at which they degrade
  • select specimens that show both diseased and adjacent healthy areas. Do not select fruit that is likely to degrade into 'mush' during transport. Contain the sample to avoid leakage
  • provide information on harvest times (e.g. whether it was early or late), about any problems encountered earlier in the season (e.g. pests or diseases) and any suspected post-harvest storage problems (e.g. chill or heat damage).

Testing soil for nematodes

When collecting soil samples:

  • provide about 300g of moist field soil to test for most pre-plant, plant-parasitic nematodes
  • sample randomly across the field
  • do not refrigerate the soil
  • do not allow the soil to get hot once sampled
  • if plants are to be tested for nematode infection, submit infested roots and adjoining soil.

Nematode testing only

If your samples are only to be tested for plant parasitic nematodes, you should email Jennifer.Cobon@daf.qld.gov.auat the Nematology Diagnostic Laboratory before you send your samples to find out about:

  • additional sampling procedures for specific nematodes
  • methods and addresses for sending or delivering your sample.

Nematode and other tests

If your samples are to be tested for nematodes and other problems, submit the sample to Grow Help Australia using our methods, contacts and addresses for submitting samples. We will liaise with the nematology team as required.

Testing soil for Phytophthora

Collect a number of sub-samples from across the plot by collecting a handful of soil/media and roots from at least 5–10 collection points or from compass points around large trees.

Phytophthora is difficult to isolate from very dry soil; therefore:

  1. scrape the very dry top soil aside
  2. collect from relatively moist soil underneath to a maximum depth of 15–30cm
  3. repeat for each sub-sample, preferably only from beneath symptomatic plants
  4. bulk each sample together to make a representative sample (approx. 500g) for each plot
  5. include symptomatic roots to increase our ability to detect Phytophthora. Also submit symptomatic plants, if possible.

Insects and other pests

For foliar mites and insects:

  • wrap as much foliage as possible in a dry paper towel/newspaper
  • place in a zip-lock bag
  • ensure sample will not be crushed
  • where foliage is malformed, ensure that you include growing tips in the sample.

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

Suspect virus infections

To diagnose viral infections, email growhelp@daf.qld.gov.au:

  • multiple images of symptoms—ensure they are in focus and the file size is at least 500KB or greater
  • information on the region where the crop is grown
  • an indication of the incidence (frequency) and area over which symptoms occur. This may initially indicate the likelihood of a viral infection and also the cost of testing.

When we receive your email, we will advise you, but we generally recommend that you:

  • send 6–10 stems, each about 30cm long
  • include growing tips, each from a different plant
  • wrap stems in dry paper placed in a zip-lock bag
  • package stems to prevent crushing in transit.

Environmental dieback

A range of pests and pathogens can cause dieback of particular plant species, or groups of plant species, across environmental landscapes, for example Phytophthora dieback.

You may choose to report such observations to a local ranger or council worker; they can let your 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 images of the symptoms.

Home gardens and street trees

If you are a homeowner, we recommend you review our resource list and guidance to help identify plant health problems.