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EB1718 
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| The silver-spotted tiger moth, Lophocampa argentata, or silver-spotted halisidota, as it is sometimes called, is an occasional pest of ornamental conifers. Its main host is Douglas-fir, but it will sometimes feed on spruce, pine, and other conifers. This insect is often confused with tent caterpillars because both make tents; however, they do not feed on the same kinds of trees. | ||
| Description and Life History | ||
| The silver-spotted tiger moth has four stages: egg, larva, pupa, and adult. The adult is a large moth with a wingspread of about 2 inches. The forewings are reddish brown with many silvery spots. The hind-wings are white to tan. | ||
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| The larva or caterpillar is the damaging stage. Mature caterpillars are about 11/2 inches in length and covered with a combination of dense black, reddish brown, and yellowish hairs. It is said that these hairs are poisonous and upon contact may cause rash, itching, or a burning sensation. Many people, however, have handled these caterpillars without any such reaction. | ||
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In mid-June, the larvae leave the trees to seek sheltered pupation sites, such as among the needles, bark, and under the eaves of houses. The dirty-brown cocoons are constructed from silk and body hairs; inside is a shiny, red-brown pupa. The oval eggs are pea green. They are laid in clusters by the female on needles and twigs of host trees in mid to late summer. The eggs hatch in 10 to 14 days. The small, furry, rusty brown or blackish caterpillars feed on the needles in large numbers. They feed well into fall until cold weather begins. Young caterpillars hibernate during winter in dense webs which they spin. They resume their feeding in early spring. On warm days you may even find them feeding as early as January. When they are about two-thirds grown, they become less gregarious and begin to disperse and feed throughout the tree singly or in small groups of two or three. Feeding during this period is usually not very harmful to the trees or noticeable since the damage is widely scattered. |
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| Damage | ||
| Feeding is restricted to the needles at the ends of the lateral branches. Whole branches are often stripped of their leaves, making individual trees appear quite unsightly at times. Cases of total defoliation are rare. Most commonly, damage occurs as defoliation in one or a few limbs of a tree. Since the buds are not harmed, the new growth will cover the damaged area by early summer. | ||
| Management Options | ||
| Biological |
In general, the caterpillar is not considered to be a serious pest. It is generally reduced by the same parasitic Tachinid flies that attack tent caterpillars, and these parasites keep populations under control. However, in some years the caterpillars are more numerous and may not be adequately reduced by the parasites, resulting in some necessary action by you. Home garden formulations of Bacillus thuringiensis, a bacterial insecticide, are available for use against caterpillar pests. The caterpillar must feed on sprayed foliage before this material will be effective. |
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| Cultural |
Simple removal of the infested limb, tent, and caterpillars is frequently all that is necessary. If removal of the limbs threatens the tree's symmetry, then removal of the caterpillars alone is an option. This is tedious and practical only with limbs that can be reached easily. Branches that are too high to prune can be left to recover on their own. |
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| Chemical |
There are a number of garden type pesticides available for controlling this pest if it is really necessary. Your local county Cooperative Extension agent or Master Gardener clinic can provide current recommendations. |
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