A Short Course for the Field Identification of SPB and its Damage
Contents:
In southern pine forests the southern pine beetle (SPB) is commonly found competing for the same resources with other bark beetles. Proper identification of SPB is essential to verifying the cause of tree mortality and making correct decisions regarding control. Three species of engraver beetles (Ips spp.) are close associates of the SPB:
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When you ground check SPB spots in the field, you generally will encounter only two Ips species within the same infested tree - the four- and six-spined engraver. The five-spined engraver is not usually observed during a ground check because it concentrates its attack in the tree crown. For purposes of this workshop, only the differentiating characteristics of the four- and six-spined engravers are addressed in relation to SPB. Keep in mind, however, that the proper identification of each Ips species is not the focus here, but simply the accurate identification of SPB and its damage.
Although peak arrival of the four- and six-spined engravers usually occurs one to two weeks after the peak arrival of SPB, it is important to remember that all three may occupy the host at the same time. Under these circumstances the resource manager must be able to differentiate between evidence of SPB and evidence of Ips. Spatial distribution among the three species differs within the host, and some overlap may occur. Finding Ips and SPB together may not always be common but it is not unlikely either.
In general, the peak arrival and spatial concentration of SPB and the four-and six-spined engravers following initiation of attack are as follows:
| Species | Peak Arrival (Days)* | Location in Tree |
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| SPB | 3 5 | lower and middle bole |
| Four-spined Engraver | 12 | middle and upper bole, limbs |
| Six-spined Engraver | 21 | lower, middle, and upper bole |
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*after initial arrival of SPB
Adapted from Dixon, W.N., and Payne, T.L. 1979. Sequence of arrival and spatial distribution of entomophagous and associate insects of southern pine beetle-infested trees. Texas Agric. Exp. Stn. Misc. Publ. 1432. 28pp. |
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The following table lists nine identifying characteristics to differentiate Ips and SPB in the field. Some characteristics assume the use of a 10x hand lens.
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| Adult galleries of six-spined engraver are "H" or "Y" shaped and predominently vertical* | Adult galleries of SPB are "S" shaped and not predominantly vertical* |
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| Adult galleries of four-spined engraver are "I" shaped and predominently vertical* | Adult galleries of SPB are "S" shaped and not predominantly vertical* |
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| Pitch tubes of six-spined engraver often found on bark plates along bole | SPB pitch tubes are usually found in bark crevices |
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| Late larval and pupal stages occur between bark and sapwood | Late larval and pupal stages hidden in outer bark |
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| Adult galleries usually are not packed with frass | Adult galleries usually are packed with frass |
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| Six-spined engraver is larger than SPB | SPB is smaller than the six -spined engraver |
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| Four-spined engraver is smaller than SPB | SPB is larger than the four-spined engraver |
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| Hind end (abdomen) is scooped out and spined | Hind end (abdomen) is smooth and rounded |
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| Head is not visible from above | Head is visible from above |
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| *The most common and reliable characteristics for differentiating
SPB & Ips in the field.
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