St. John's wort and fall web worm

St. John's wort

Many varieties of the yellow flowing plant exist through out the world. The bushy St. John's wort (Hypericum densiflorum) while native to this area is not commonly seen in the wild. It is classed as endangered in New York and threatened in Pennsylvania. The bushy variety can grow as high as 6 feet, thrives in wetter areas and stream banks and displays small bright yellow flowers in summer. The native shrub is available in nurseries as are several related cultivars.

St. John's Wort

Photo by Ginny Brace

More often seen in bloom in July in Frederick County, common St. John's wort (Hypericum perforatum) is a non-native perennial plant with yellow flowers similar to the native variety. It spreads through a type of underground stem called a rhizome and by seed. Its one inch diameter yellow flowers start blooming about the time of St. John's day, June 24th. The green, yellowish oblong leaves grow opposite on the stems and are about a half inch in length. When examined closely, the leaves can show tiny clear spots that are oil glads. Dating back to ancient Greece, St. John's wort extracts have been used as herbal remedies for mild depression and for topical treatment of skin wounds, pain and burns. It is native to Europe, yet is widespread in temperate areas, including North America.

Although it has been planted as a ground cover, common St. John's wort is somewhat invasive and can spread quickly in disturbed ground. It is not as difficult to control as many invasive species, as it does not rapidly take over undisturbed areas. While constituent chemicals in the plant have been used as herbal remedies, the plant can be a hazard to livestock when it invades pastures. Consumption by animals has been observed to contribute to sunlight sensitivity, spontaneous abortion, reduced responsiveness and even death. As a result, the plant is considered a noxious weed in many areas.

Fall web worm

The silky nests that are showing up on trees now were made by the Fall Webworm (Hypantia cuneu). Fall Web Worm is a native Lepidopterous insect that becomes a moth at adulthood. The larval stage of this insect builds the nest and feeds on a wide range of tree foliage particularly black walnut and hickory. The larvae become active spinning their nests and feeding in early August; about mid-September they pupate and emerge as adults. Eggs are laid and hatch within about 10 days. The small larvae will overwinter in bark crevices or in leaf litter beneath the tree.

Fall web worm

Courtesy photo

Fall web worm tent

Photo by Mike Kay

Fall web worms are considered more of an eyesore than a serious threat to tree health. It is not very often that these insects are found in large enough numbers to defoliate a tree. Furthermore, like many leaf eating insects that occur in the fall, the damage they inflict does not seriously impact deciduous trees that are getting ready to drop their leaves anyway. Fall web worm was first identified in Hungary in 1940 and has become a serious insect pest across much of Europe over the years. The fact that this imported pest does not have any natural predators in Europe results in larger damaging populations. Fall web worm is an example of one of our native insects that has become a problem overseas.

Nature Note for 8/11/2013