Army Worms & Pine Trees

Armyworms feed on the foliage of pine trees, causing extensive damage.

Armyworms are pests of many species of plants, shrubs and trees. These pests are members of the family Noctuidae, and are related to cutworms. Pine trees are often hosts to armyworms, sustaining damage from feeding of armyworm larvae. Early detection is the key to reducing damage to pine trees from armyworm infestations.

Identification

Armyworm larvae is responsible for the damage to host trees. The adult stage of this pest is a moth, which is nocturnal in nature but does not feed on host plants. Armyworms feed on a wide range of hosts, including conifers, vegetables and turfgrass. Most armyworm species experience five larval stages, which occurs over a 14- to 21-day period. The larger the armyworm grows, the more plant tissue it can consume and the more damage it inflicts on host plants. Once the larvae matures, it buries itself in the soil, emerging as an adult moth after seven to 14 days.

Types

The fall armyworm is particularly damaging to host trees, reaching 1 to 1 1/2 inches in length at larval maturity. This pest is tan, gray or green in color. Another species of armyworm is the southern armyworm, which is known to climb host plants to feed on foliage. Southern armyworms are pink or gray in color and often exceed 1 to 1 1/2 inches in length. The beet armyworm, the true armyworm and the yellow-striped armyworm are also damaging pests to many species of trees.

Effects

Pine trees with armyworm infestations sustain damage to foliage from larval feeding, which occurs most often at night or on overcast days. Armyworms often multiply in number, defoliate the host tree and quickly move to another tree to feed. Armyworms received their name for the tendency to migrate in large groups from tree to tree. Pine trees with heavy infestations of armyworms can die from repeated or severe defoliation.

Control

Armyworm control in pine trees is most successful when treated while armyworm larvae is small. The larvae is most susceptible to control methods while it is young and damage to the host tree is minimal. Chemical control products are available at your local garden center for armyworm control and elimination. Apply all insecticides according to the directions on the label for best results.

References

• University of Florida: Armyworms: F.A Johnson, J.L Castner
• MDNR: Forest Disease Newsletter: Armyworms
• NDSU: The Armyworm And The Cutworm; Philip Glogoza: April 2000