Pests of the home & landscape

November 28, 2000
Ips Beetle

The southern pine beetle (SPB) is the first insect that probably comes to mind when there are problems with landscape pines; however, other beetles will cause as many problems as the southern pine beetle. One of these is the Ips or 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.

Fig. 1.  Back edge of Ips beetle showing projections.

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 c to 3 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. Ips beetles are similar to the SPB; however, the Ips beetles have a number of projections (Fig. 1) on the back edge of the insects body, depending on species. The SPB=s beetles do not have these projections.

Damage. Male engraver beetles are the first to arrive at a potential host tree and will emit an attractant which 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. 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.

Fig. 2.  "Y" shaped gallery of an Ips beetle-- egg galleries (tunnel) are free of frass.  In SPB the gallery is packed with frass.

Ips beetle feeding may or may not produce Apitch 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 or if large numbers of beetles attack trees. Also, if the attack is in the crown of the tree, the pitch tubes may not be present or they 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 which bring about an Ips attack is 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.

Controls. 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 for ornamental pines in an attempt to prevent infestations from occurring. The following are some suggested tips:

  • Keep the area under pines free of broken limbs and debris.
  • Prune out dead or dying limbs as soon as possible
  • Remove pruned limbs from the area immediately after they are cut from the tree.
  • If trees have to be removed, the tree should be cut and removed from the site without delay.
  • Grind stumps after the tree is removed or cut the stump very low to the ground.
  • Do not damage the trunks of trees during lawn maintenance operations.
  • If additions are made to a home, protect the root system of pines during the construction.
  • Do not allow cement trucks or other heavy equipment to run repeatedly over the root zone of the tree.
  • Keep trees in a healthy state of growth at all times--follow a sound fertilization and water management plan. Water is especially important during periods of drought.

References:

Speers, Charles F. 1971. Ips bark beetles in the South. U.S.D.A., Forest Service. Forest Pest Leaflet 129.

Driestadt, Steve H. et. al. 1994. Pests of landscape trees and shrubs, an integrated pest management guide. Univ. Calif., Division Agri. and natural Resources, pub. 3359.

James H. Jarratt
Extension Entomologist

Evan Nebeker
Professor of Entomology

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