Tips for Submitting Greenhouse Samples to the Purdue Plant and Pest Diagnostic Lab (PPDL) – Vegetable Crops Hotline

Tips for Submitting Greenhouse Samples to the Purdue Plant and Pest Diagnostic Lab (PPDL)

Samples in plug trays, as well as unrooted and rooted cuttings, and plants in pots require extra care when they are packaged for submittal to a diagnostic lab. Before you mail the next sample, please take a few minutes to review these suggestions for packaging and submitting samples. This will help preserve the integrity of the sample during shipment and increasing the likelihood of a more accurate diagnosis.

Plugs – keep them in the tray

If possible, do not remove the plugs from the plug tray. Submitting either an entire tray or cutting off a section of the tray helps keep the soil off the foliage where most symptoms are observed. (Figure 1) Secondary decay often occurs when soil is allowed to come in contact with the foliage, interfering with accurate diagnosis. When possible, submit at least 5-10 cells with plugs. This provides the diagnostician with ample material for microscopic observation, culturing, and virus testing if necessary.

Fig 1.Wrappedflat

Figure 1. Plug flat wrapped and ready for shipment to the diagnostic lab.


Cuttings – separate foliage from media with a plastic bag

The primary concern is to keep the growing media separate from the foliage to prevent contamination and rotting. Put the cuttings into a plastic bag, and seal the bag with a twist tie (Figure 2) at the soil line. Do not seal the foliage in a plastic bag. Next, wrap the sample in newspaper to prevent additional drying out of foliage before it is received. Newspaper is one of the best packing materials for plant samples.

Fig 2. Media and roots properly secured

Figure 2. Media and roots on left are properly secured for shipment.


Potted Material – pack around the plant

Take into consideration that the mail carrier will not necessarily keep these packages right side up even when those directions are written on the outside of the box. Place plastic wrap, clear packing tape or paper (Figure 3) over the pot surface, or put the pot in a bag and seal it with a twist tie around the base of the plant. Fill any extra space in the shipping box with newspaper, styrofoam peanuts, or another space filling packing material (Figure 4) to prevent jostling of sample during shipment.

Fig. 3 soil secured in pot

Figure 3. Tape keeps soil in the pot during shipment.

Fig 4 Packing in box

Figure 4. Use Styrofoam, packing peanuts, or crumpled newspaper inside a crush proof box to protect the sample during shipment.


If you are delivering the sample to our building…

We welcome delivery of samples in person! There are two short-term metered parking spaces on the west end of our LSPS building. (Figure 5) Samples may be dropped off from 8am-5pm in room LSPS 116 in the two-story brick building (Life Sciences Plant and Soils) located in-between Lily Hall of Life Sciences and the Life Science Greenhouses. A completed submission form must accompany all samples. Sample submission forms can be downloaded from our website ( and filled out ahead of time or are available at the drop off point.

Fig 5 PPDL Parking

Figure 5. Short-term metered parking spaces on the west end of the LSPS building at Purdue are reserved for PPDF customers.


Shipping – watch the weekend

Do not mail or ship samples on Friday, as we are not here to receive them over the weekend. Samples can be sent via US mail, UPS, FedEx, etc. We encourage you to send samples with priority or express delivery so we receive them in the best condition possible to provide you with the most accurate diagnosis.

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