Plant and Insect Diagnostic Clinic Update - May 12, 2010

The following are highlights and updates about samples and questions recently received in the Clinic:
Diseases


We are receiving blue spruce samples with sudden needle drop (SNEED) and  Rhizosphaera  needle  cast  disease.  It is not known if  treatment for Rhizosphaera  needle cast will help control SNEED.  More information about these two diseases can be found online in the January 7, 2009 Horticulture & Home Pest News and from the Missouri Department of Conservation.


Insects


Oystershell Scale. Several calls and samples this spring have involved large number of oystershell scales on maples and other trees. Oystershell scales are named for their elongate, curved appearance that resembles miniature oyster shells. See photos below. Oystershell scales are 2 – 3 mm in length and found on the stems of many different host plants. Contact insecticides are only effective for the control of scale insects right after egg hatch when the first instar nymphs (AKA, "crawlers") are present. See ISU Extension publication IC-415, Scale Insects on Ornamental Plants, for more information. 


 


Oystershell scales on maple twig.Oystershell scales on maple twig. Oystershell scale, close-up.Oystershell scale, close-up.

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