May 15, 1998
NOW is the time to be checking pine trees for needle feeding damage by the larvae of the European pine sawfly. Pine sawfly larvae can be present any time after mid-May. The small larvae can only chew the edge from the needle, but as they grow, they consume more and more of the needle until eventually they are eating the entire needle down to the stub. Defoliation lasts for four to five weeks and usually peaks near the end of May.
A common weed in many lawns and gardens is ground ivy (Glechoma hederacea). Ground ivy is a low-growing, creeping, invasive perennial. It spreads by seed and the vining stems which root at their nodes. The leaves of ground ivy are round or kidney-shaped with scalloped margins. Stems are four-sided. Flowers are small, bluish-purple, and funnel-shaped. Ground ivy thrives in damp, shady areas, but also grows well in sunny locations. A member of the mint family, ground ivy produces a minty odor when cut or crushed. Ground ivy is also known as "creeping charlie."
Another common tree foliage problem being reported now is oak tatters. Oak tatters has become a moderately common and recurring problem in the spring. Affected oak leaves have a deformation that is distinctive - most of the leaf tissue which should be present is missing. Usually there is a thin strip of leaf tissue remaining along the major veins. Furthermore, the leaves often appear to have been stretched. This combination of thin strips of leaf tissue and stretched leaves give the foliage a strap-like appearance and the tree canopy a thin, lacy appearance.
An unusual and unexplained defoliation of hackberry trees has been reported around central Iowa during the past week. Reports of observations in other parts of Iowa are encouraged.
Reports of the problem have been confined to hackberry trees in an area from Newton to Carroll to Webster City. The symptoms appear to have followed this progression: