Send as much of the plant as possible. Many diseases are the result of damage to or infections in parts of the plant that are distant from the parts of the plant that show symptoms. If possible, send in roots, stems, leaves, flowers, and even the soil around roots.
Submitting healthy plant samples is useful for comparisons.
To make an accurate and timely disease diagnosis, it is important that plant disease samples being sent to the lab arrive in the best condition possible.
Put plants in a paper bag and put paper bag in a box for shipping. Pack brittle samples in dry packing material (paper towels) so they aren’t crushed during shipment.
Do not put samples in wet paper towels or in sealed plastic bags, this will cause the plant tissue to rot and will make diagnosing the problem difficult or impossible. If you are concerned that the sample will dry out before it gets to the bands. Keep samples cool until shipping and mail samples early in the week.
Take 4-10 small samples from different parts of the area of concern and combine them in a sealable plastic bag or soil sample bag of appropriate size. Usually 100 grams (~one quart) of soil is enough to run all soil fungi tests.
For large areas such as agriculture fields, it might be useful to submit more than one soil sample per field. For example, one sample from the north, south, east, and west quadrants of the field. If submitting soil from a diseased area, take another soil sample from an area where plants are healthy.
Put sample bags in a sturdy box and be sure to secure the sample bag opening so it doesn’t open during shipment.
The optimum sample size is 0.1 to 1 Liter. Keep samples cool until and during shipment.