Ips beetles in Georgia, USA

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Arthropoda
Subphylum	Hexapoda
Class	Insecta
Subclass	Pterygota
Infraclass	Neoptera
Order	Coleoptera
Suborder	Polyphaga
Infraorder	Cucujiformia
Superfamily	Curculionoidea
Family	Curculionidae
Subfamily	Scolytinae
Tribe	Ipini

Scientific Name

Ips

Scientific Name Synonyms

Ipsi

Common Name

Ips engraver beetles

Author: G. Keith Douce, University of Georgia

Ips beetles (Ips species) vary in size by species. Adults are cylindrical in shape, usually dark brown-to-black and range in length from 2 to 7 mm (0.1-0.3 inch). The rear end of Ips beetles are sunken, or "chopped off" in appearance, with four to six spines along each side of the sunken area.

Although this group contains several species, all Ips beetles have the same general appearance and similar habits. Male Ips beetles initiate attack by boring through the bark of pines and constructing mating chambers. From two to four females (depending on species) join each male. These females excavate rough Y-, H- or I- shaped egg galleries in the phloem.

Pitch tubes formed at the point of attack are normally less than 12 mm (½ inch) in diameter and look like those associated with Southern pine beetle Dendroctonus frontalis attacks. As with the Southern pine beetle, often the only visible sign of attack on severely weakened trees is the presence of brown boring dust in bark crevices and on spider webs, since pitch tubes may not form.

Egg galleries radiate out from the mating chamber, usually parallel to the grain of the sapwood. Eggs are deposited at regular intervals along the sides of the galleries. The galleries usually groove the sapwood and generally are free of boring dust. Ips beetles complete their life cycle in 25 days or more depending on species and temperature.

The bark of infested trees can be covered with large numbers of holes bored by emerging beetles. However, serveral newly emerged Ips beetles often emerge from a common exit hole, resulting in far fewer emergence holes in the bark than with Southern pine beetles. Emergence hole size varies with the species of Ips.

Once beetles successfully attack trees and constuct egg galleries, the blue-stain fungus they carry has usually been introduced. These trees cannot be saved, even if treated with an insecticide to kill the larvae.

Ips beetles and black turpentine beetle Dendroctonus terebrans are present throughout Georgia virtually every year but seldom kill large numbers of trees in one spot. However, under certain conditions, both the Southern pine beetle and Ips beetles can reach outbreak levels and cause widespread damage.

Of the bark beetles in Georgia, the Southern pine beetle is the most damaging and most subject to wide-area outbreaks. It is common for more than one species of bark beetles to infest individual trees, especially in beetle outbreaks. A large number of other insects are also associated with bark beetle attacks and/or dead and dying pine trees.