Insect Infestation

Elm spanworms, the adults Ennomos subsignarius known as snow-white linden moths, adversely affect elm trees by repeated defoliation. Spanworms, called loopers, march along a branch to feed on new succulent foliage. The loop made by the larvae resembles the Greek letter omega. Longdistance migration by adults accounts for the spanworm's rapid spread." The insects do not attack yellow-poplar almost alone among non-susceptible species. (See Chapter 6.)

Closely related to the elm spanworm in damage done is the gypsy moth (Lymantria dispar), so named because it extends its range as a hitch-hiker. Camping gear and motor vehicles carry the insect throughout the hardwood forests of the Appalachian region. Females, unable to fly, sail with the wind to infest nearby woodlands. They prefer various species of oak, birch, willow, and cottonwood.

Entrepreneurs imported gypsy moths into this country via Europe from the Orient for silk production. The industrialists intended to use the larvae to produce silk for the North American textile industry, as the silkworm serves in China. Importation from France occurred in 1869; serious damage was observed as early as 1889 near Boston.

Hickory twig girdlers and hickory spiral borers attack the terminal shoots of young trees, often killing them. If the seedlings live, trees become misshapen as their lateral branches bend upward, exhibiting phototropism, to assume dominance. Numerous parasites keep these insects in check.

Figure 4.11 The hickory horned devil. Larvae, up to 5 inches long and as stout as a thumb, feed on deciduous trees. Ferociously appearing because of the hornlike appendages in this stage, they are harmless to people. The larvae feed on many deciduous trees, especially Fraxinus and Juglans species, throughout the South. The adult is called the regal moth. (Texas Forest Service photo by R. Billings)

Figure 4.11 The hickory horned devil. Larvae, up to 5 inches long and as stout as a thumb, feed on deciduous trees. Ferociously appearing because of the hornlike appendages in this stage, they are harmless to people. The larvae feed on many deciduous trees, especially Fraxinus and Juglans species, throughout the South. The adult is called the regal moth. (Texas Forest Service photo by R. Billings)

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