IPS Engraver Beetle

The following information has been edited and adapted from an article by Dr. James Jarrett, Extension Entomology Specialist from Mississippi State University, and from other sources.

The southern pine beetle (SPB) is the first insect that probably comes to mind when there are problems with forest and landscape pines; however, other pine bark beetles are more commonly observed by the average forest landowner and homeowner. One of these is the Ips Engraver beetle. Some of these beetles are present every year in cut branches, logs, or in weakened or dying pines. In other years, populations will increase due to weather conditions such as hurricane, ice, or hail-damaged trees and, as populations increase, the incidence of damage to apparently healthy trees will increase. Damage is also greater following logging, fires, and, particularly, abnormally dry weather. Dry conditions will result in the death of single trees as well as groups of trees as they come under attack by the expanding Ips populations.

Drought conditions, such as those that occurred from 1999-2001 can allow Ips beetle populations to increase dramatically. During that period reports were coming in from all over the region concerning problems in pine sawlogs and pulpwood stands. The spots were often larger than normal and some had as many as 30 trees in one spot. As a general rule, landowners salvaged the sawlog trees and let the beetles have the pulpwood. Pine beetle experts do not recommend salvage operations in pine pulpwood stands except where spots are large enough to justify the harvest operation. See USDA Agriculture Handbook Number 558, "A Field Guide for Ground Checking Southern Pine Beetle Spots", by Ronald F. Billings and Herbert A. Pase III.

There are several distinctions between the Southern Pine Beetle and the Ips Engraver Beetle.

Ips Beetle Description. There are three species of Ips beetle (four-spined engraver, five-spined engraver, and six-spined engraver) in Mississippi, and all three can be found within the same infested tree or one or the other may predominate. The insects range in size from 2 to 3 tenths of an inch and are reddish brown in color. Size may dictate where the different species will be found within an infested tree. The smaller species tends to be found higher in the tree on small limbs and branches, while the larger species tend to be found on larger branches or the trunk. This will explain why many of the pine trees that are turning brown do not appear to be infested. The Ips beetle symptoms are further up the bole of the tree or maybe even in the branches.

Ips beetles are similar to the SPB; however, the Ips beetles have a number of projections (Fig.1) on the back edge of the insect's body, depending on species. The SPB beetles do not have these projections.

Male engraver beetles are the first to arrive at a potential host tree and will emit an attractant that draws other males and females to the tree. Mating takes place within the galleries, and the females will start excavating galleries for egg laying purposes. These galleries take the general shape of a Y and some will describe it as wishbone shaped (Fig.2.). In SPB the gallery is packed with frass.

By comparison, the galleries made by the southern pine beetle are generally "S" shaped. Eggs are deposited at points along the gallery made by the female (see egg niche, fig.2). Under favorable conditions, the eggs will hatch in about seven days, and the larva will make smaller feeding galleries left and right of the larger galleries. There may be 4 to 6 generations per year. If the egg laying and subsequent larval feeding continues over a period of time, the water and nutrient transporting system of the tree is eventually cut. This will lead to the death of the tree.

Ips beetle feeding may or may not produce "pitch tubes". These are red to white masses of sap that will accumulate at the point of entry by the beetle. A close inspection will show the entrance hole in the middle of the sap mass. Pitch tubes are usually missing if trees are extremely stressed like they were this past summer and fall.. Also, if the attack is in the crown of the tree, the pitch tubes will be difficult to see. If pitch tubes are not present, the first sign of an Ips beetle infestation may be a slight accumulation of reddish to whitish sawdust at the base of the tree or caught in spider webs. Many may confuse this sawdust with ambrosia beetles; however, the boring dust caused by these beetles is usually white and there will be a much deeper ring around the tree base than is found with an Ips beetle infestation.

As the attack progresses, needles on infested pines will fade from a dark green to a lighter green, then to yellow, red, and brown. This may occur from the top down. If the stressed conditions that bring about an Ips attack are related to drought conditions, the occurrence of rainy periods will generally end the attack. A word of caution--if a tree becomes infested late in the season, they may remain green over the winter period and death of the tree will not be evident until the following spring. If rains begin late in the fall, as they did in 2000, further attacks will probably not occur on other pines in the area following the emergence of these beetles in the spring.

Once an infestation is documented, it is practically impossible to control with chemical applications. The best approach, therefore, is to follow a sound management plan to prevent infestations from occurring. The following are some suggested tips:

(1) Thin pine stands as early in the rotation as feasible. Refer to MSU-ES Publication 2260, "Are My Pine Trees Ready to Thin?"

While we cannot do anything about drought, we can manage pine stands such that there will be less stress on trees when the dry conditions do occur. The "Ips" infestations are normally worse in unthinned plantations as opposed to those that have been thinned.

(2) When "bug spots" are detected, determine which pine bark beetles are involved. The following recommendations would apply to all species except the Southern Pine Beetle. If you need help to determine the species involved in the attack, consult a professional forester or see us for a copy of Agriculture Handbook No. 558. Salvage sawlog sized trees if possible. The purpose of the salvage is not so much to stop the infestation as it is to recover the value of the high value product.

Monitor Ips beetle infestations in pine pulpwood stands and salvage only if economically justified. Cut and leave to stop the infestation is not justified.

Southern Pine Beetles require a different management strategy since they are much more prolific. Please review the article on Southern Pine Beetles.