Who Spit on My Trees

Robert Bishop 
Frederick County Master Gardener Program

If you notice numerous masses of a foamy, spit-like substance in your evergreen trees this year you are not alone. I have received well over thirty phone calls and have been brought at least seven branch samples this week exhibiting this condition. Deep inside the foam is an insect commonly called a Spittlebug or froghopper. Spittlebug is not considered a serious pest, although this year we are seeing unusually high populations.

There are several species found in Maryland. One of the most common is the pine Spittlebug. As it's name suggests is primary host is pine, but will also attack Norway, white and red spruce, Douglas and Balsam fir, larch, eastern hemlock, and Leyland cypress. Other Spittlebug species can be found on dogwood, birch, witch-hazel, cherry, redbud, alder, holly and herbaceous perennials.

Spittlebug eggs hatch in spring and the nymphs begin feeding on plant sap. As they feed, they continually excrete undigested sap (honeydew) and pump air into as it exits their bodies thus forming the foamy masses (spittle) that surround them. The nymphs are active in May and June. Adults appear in July and August and also feed on plant sap but do not produce spittle. There is only one generation per year for most species.

Damage symptoms include leaf distortion and or stunting, and in heavy infestations twig dieback. Further plant problems may occur when disease causing pathogens enter plants through the holes left from spittlebug feeding. Diplodia tip blight is an example of a disease that can infect pines through this mechanism. Control is only recommended for large infestations, apply a residual insecticide in May for best results.

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