Like other pine bark beetles, Ips pine engravers live predominantly in the inner bark, where they breed and feed on phloem tissue. Pines successfully colonized by Ips engravers, if not already dead, are killed by adult and larval feeding in the phloem (which can girdle the tree) and by colonization of the sapwood with blue-stain fungi that the beetles introduce. The blue-stain fungi spread into the xylem and block water flow, serving to hasten tree mortality (Connor and Wilkinson 1983, Kopper et al. 2004).
Ips beetles usually colonize only those trees that are already stressed, declining, or fallen due to other environmental or biotic factors. Ips also readily colonize cut logs and slash, and are attracted to fresh pine odors. Infestations may occur in response to drought, root injury or disease, timber management activities, lightning strikes, or other stresses, and sometimes occur in association with attacks by D. frontalis or D. terebrans (Anderson and Anderson 1968, Lovelady et al. 1991, Miller 1983). When populations of Ips beetles are sufficiently high, they can overcome the defenses of apparently healthy trees by attacking in large numbers. However, Ips outbreaks are greatly limited in duration and spatial scale compared to outbreaks of the more aggressive D. frontalis (Anderson 1977).
The distributions of both I. c. calligraphus and I. grandicollis north of the southern pines coincide with the range of pitch pine (Pinus rigida Mill), although they will affect any pine species within that range. I. avulsus is restricted to the southeastern states, from southern Pennsylvania to Florida and Texas (USDA Forest Service 1985).
The three southern species can be distinguished by body length and number of spines along each side of the elytral declivity:
Sixspined ips, I. calligraphus, 3.5 to 6.5 mm long, six spines per side
elytral apices, I. calligraphus
Eastern fivespined ips, I. grandicollis, 2.8 to 4.7 mm long, five spines per side
elytral apices, I. grandicollis
Small southern pine engraver, I. avulsus, 2.3 to 2.8 mm long, four spines per side
Dorsal comparisons of the elytral apices under magnification may also aid in distinguishing species.
Eggs: Eggs are oblong (ca. 1.0 mm x 0.5 mm) and pearly white.
Larvae: Larvae are small, whitish, legless, and grublike with reddish colored heads that are <1 mm wide.
Pupae: Pupae are waxy-white and similar in size to adults
(All descriptions from USDA Forest Service 1985, Connor and Wilkinson 1983).
The adult male bores into the phloem and excavates a nuptial chamber, where it mates with one to five (commonly three) females. After mating, each female excavates an egg gallery that extends away from the nuptial chamber and usually parallel to the wood grain, resulting in an overall I-, H- or Y-shaped gallery pattern.
Eggs are deposited in niches along the sides of the egg galleries. Larvae tunnel in the phloem perpendicular to the egg galleries and eventually pupate in individual cells excavated in the inner bark. After pupation, the adult will feed for a short time in the phloem before emerging through the bark, leaving small scattered emergence holes (USDA Forest Service 1985). Newly-emerged adults can fly as far as four miles in their first dispersal flight to find a new host tree (Kinn 1986).
Development is slower in cool temperatures and the time required to complete the life cycle varies from a few weeks in the summer to several months through the winter. I. calligraphus and I. grandicollis can complete their life cycles within 25 days during the summer and can produce eight generations per year in Florida (Dixon 1984), while the I. avulsus life cycle can take as little as 18 days, producing 10 generations per year. Generations commonly overlap and all life stages may overwinter in the tree (Connor and Wilkinson 1983).
The three species of Ips tend to colonize different parts of the tree, although there is considerable overlap between these territories (Coulson and Witter 1984). I. calligraphus usually attacks the lower bole or portions of stumps, trunks, and large limbs greater than 10 cm (4 in) in diameter (Connor and Wilkinson 1983). I. grandicollis prefers to infest recently felled trees and slash, but also can be found infesting weakened living trees, most heavily on large limbs and the mid to upper bole of the host. I. avulsus prefers small-diameter slash, but will attack groups of young trees and the crowns of large trees (USDA Forest Service 1985). I. avulsus shows a higher degree of aggregation behavior than some other Ips species (Mason 1970).
These color changes can occur in two to four weeks in warm weather, but may take several months in the winter. In cooler weather, the beetles have frequently vacated the tree by the time the needles fade. Early signs of attack include the accumulation of reddish-brown boring dust on the bark, nearby cobwebs, or understory foliage.
If there is sufficient resin pressure within the host, attacked trees will exhibit dime-sized, whitish or reddish-brown globs of resin and boring dust called "pitch tubes" on the bark at each point of beetle attack.
Unlike those of the southern pine beetle, Ips pitch tubes are more commonly seen on the surface of bark plates than in bark crevices. After beetles emerge from the tree, scattered circular emergence holes (1 to 3 mm diameter) can be observed on the outer bark. By removing a section of the outer bark, the characteristic Y-, I- or H-shaped galleries may be observed in the phloem or engraved on the outer sapwood (Connor and Wilkinson 1983).
These gallery patterns are sometimes obscured by larval galleries of other phloem borers in the families Cerambycidae (roundheaded borers) and Buprestidae (flatheaded borers) that readily colonize dead pines.
Preventative strategies in forest stands include:
As for control, when Ips infestations are small and/or sparsely scattered throughout a stand, the best course of action is often to let them die out on their own. Cutting and removal of isolated infested trees or small "spot" infestations with buffer strips (as is done to control D. frontalis infestations) is not recommended. Observations in Florida suggest that such selective removals may increase the likelihood of Ips problems by producing fresh host odors, logging slash, and additional stress or injury to the residual stand. If scattered mortality is progressing to unacceptable levels, a stand-level clearcut or a contiguous block removal of a generally infested area may be preferable to selection harvests.
For urban and residential landscape trees, preventative strategies include the following:
In some cases, the application of an approved insecticide that coats the entire tree bole may be warranted to protect high-value landscape trees from infestation; contact your local county Cooperative Extension Service office for current insecticide recommendations.
Insect Management Guide for insect borers of trees and shrubs
When infested trees are removed, care should be taken to avoid injury to surrounding pines. There is no effective way to save an individual tree once it has been successfully colonized by Ips beetles (Connor and Wilkinson 1983, Dixon 1984, Thatcher et al. 1978).
Authors: Jeffrey M. Eickwort and Albert E. Mayfield III, Florida Department of Agriculture and Consumer Services ( DOACS ) - Division of Forestry; and John L. Foltz, University of Florida
Originally published as DPI Entomology Circular 417.
Photographs:David T. Almquist and John L. Foltz, University of Florida; Jeffrey M. Eickwort, Albert E. Mayfield III, and Wayne N. Dixon, Florida DOACS; Ronald F. Billings, Texas Forest Service;
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-388
Publication Date: September 2006
Copyright 2006 University of Florida
Featured Creatures
Department of Entomology and Nematology
Division of Plant Industry
Electronic Data Information Source
I. calligraphus
I. grandicollis
I. avulsus
elytral apices, I. avulsus
I. calligraphus gallery
I. grandicollis gallery
I. avulsus gallery
fading crown
blue-stain fungi
boring dust
pitch tube