The following are highlights and updates about samples and questions recently received in the Plant and Insect Diagnostic Clinic. Visit the PIDC's Facebook page to ask questions and for updates and more pictures.
We continue to receive conifers with winter burn, abiotic needle drop and root problems. This spring we received perennial plants with root problems associated with excessive moisture and low or lack of soil oxygen (or anoxia).
We have also received tree samples that suffered frost cracks. See the photo below). These cases are a good reminder to always select shrubs and trees adapted for USDA hardiness zones 4 and 5. Even though beautiful, Japanese flowering cherry (Prunus serrulata) and Japanese maple (Acer palmatum), are susceptible to winter damage. Damage can vary from dead twigs and branches to tree death (more info: Yard and Garden: Plants Affected by Frigid Temperatures).
Other diseases diagnosed this week include Sphaeropsis tip blight in arborvitae (Thuja spp.) and Stigmina in spruce. General cultural recommendations for disease management in conifers include increase airflow by pruning and, removing infected tissue during dry weather conditions. This will reduce the pathogen that can overwinter in plant debris. If in doubt, send a sample to the ISU Plant and Insect Diagnostic Clinic. When disease diagnosis has been confirmed, consider the application of fungicides early in the spring to protect new growth.
It's spittlebug time again. See the photos below. Spittlebugs are recognized by the foamy, viscous mass of fluid surrounding the sap-feeding nymph. The "spittle" is the insect's excrement which consists of excess plant sap (so not that unpleasant!) The spittle protects the nymphs from enemies as well as desiccation.
Frost crack on weeping Prunus sp.
The mass of "spittle" on a wide variety of plants makes it easy to identify the spittlebug.
Spittlebug nymphs feed on plant sap while concealed within the foamy mass of "spit."