Inspect Incoming Plants

Thursday, 02 February 2012 14:48

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Vegetative plugs and seedlings are arriving (or will be soon) in greenhouses and it is important to prevent pest outbreaks right from the start. Inspecting incoming plants is probably the most important and effective way to monitor for pests and diseases. Inspecting incoming plants is often overlooked due to lack of time or the assumption that "I know my suppliers and they always provide me with excellent plant material". Yes, that is often true, but it may not always be the case, in spite of the best intentions. Often times, pests are suppressed, but not completely eradicated, leaving overlooked one or two small aphid nymphs or a few two spotted spider mite eggs or larvae or thrips when plants are shipped. If you see whitish spray residue, yes, that means the plants were sprayed, but how well did the spray actually work? Did they obtain thorough plant coverage or were the pests resistant?
Take the time to use a handlens and look on the underside of the leaves for:

You will need a hand lens (10 to 16X) to see these small insects, and mites.

If the incoming plugs are somewhat lush, tap the plant material over a sheet of white paper to help you detect aphids and thrips.

Don't forget to inspect the roots – to insure that they are white and healthy. Look for signs of disease (discolored, brown or blackened roots or if the outer cortex sloughs off leaving a central core.) Occasionally, root aphids and root mealybugs can also be introduced on plant material that appears healthy.

If you see symptoms that may indicate a disease such as downy mildew, try placing the leaves in a "moist chamber " or moistened plastic bag, overnight. The next morning, look for the characteristic fungal sporulation using a hand lens or microscope.

Leanne Pundt, UConn Extension
Tina Smith, UMass Extension