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Co-Colonization of Red Pine in Central Minnesota by Ips. spp.

By Camille Jensen and Dr. Steven Seybold
Departments of Entomology and Forest Resources
University of Minnesota
St. Paul, MN 55108-6125

Introduction

In the North Central United States, three species of Ips (Coleoptera: Scolytidae) are known to infest pines. The most common of these is Ips pini (Say)(Schenk and Benjamin, 1969; Kennedy, 1969; Raffa, 1991). Additionally, Ips perroti (Swaine)(Ayres et. al. 2001) and Ips grandicollis (Eichhoff)(Lanier 1970, 1987) colonize pines in this region of North America. The latter species has been commonly collected from Scots pine, Pinus sylvestris, planted in shelter belts across the state of Iowa (Mark Shour personal communication). All of these species of Ips have been collected in Minnesota (Dodge, 1938). A recent infestation of Ips spp. in a red pine, Pinus resinosa, plantation in Central Minnesota gave us the opportunity to investigate the colonization behavior of Ips spp. in this region.

Methods

In late June 2001 a stand of red pine, Pinus resinosa, in the Sand Dunes State Forest (Sherburne Co., MN - SE SE Sec.17 - T 034 - R 27) was determined to be infested with Ips spp. and was treated using four possible bark beetle management options. Fifty trees were studied, only 18 trees were colonized by bark beetles. The treatments followed by their GPS coordinates and the number of sample trees included:

  1. Girdling (N 45 25' 52.7" W 93 43' 0.40")(n=3);
  2. Girdling followed by treatment withIps pini aggregation pheromone (racemic ipsdienol and lanierone, Phero Tech Inc., Delta British Columbia) stapled to the bark at breast height (1.3 meters)(N 45 25' 53.4" W 93 43' 6.5")(n=1);
  3. Girdling and felling trees (N45 25' 52.9" W 93 42' 57.6")(n=10); and
  4. Untreated standing trees near the girdled trees (N 45 22' 52.6" W 93 42' 54.4") (n=4).

Trees were girdled at 1.3 meters above ground with a chain saw. Entire rows of trees were treated because the entire stand was infested. On July 25 through 27, 2001 the experimental trees that remained standing were felled for examination. Samples of bark and phloem (approximately 25 cm by 12 cm) for each treatment were collected from each of five trees. Samples were taken from the basal one-third, middle one-third, and upper one-third of the bole of each tree. There were a total of 18 samples with evidence of bark beetle colonization. All of these samples were examined, beetles recovered, and identified. Population densities were calculated for each sample and expressed as the number of beetles per dm2. Specimens were pinned and deposited in the University of Minnesota Insect Collection, St. Paul, Minnesota, and in the California Academy of Sciences, San Francisco, California.

Results

A total of 201 Ips pini and 96 Ips grandicollis were recovered from the samples, but no Ips perroti were found in the samples. Across all treatments, Ips grandicollis was more abundant in the base of the trees and I. pini was abundant throughout all three tree sections and perhaps slightly more abundant in the middle and top sections of the trees (Figure 4). The tendency for I. grandicollis to colonize the basal third of the trees was evident not only from the cumulative data set, but also from the data sets from the groups of felled and girdled trees, felled trees, and standing trees (Figures 1-3). Only in the group of girdled P. resinosa (Figure 1) did the density of I. grandicollis increase with height. In all treatment groups and in the cumulative data set, the density of I. pini was lowest in samples from the basal section and higher in the mid-range and top samples. We also found a beetle associate of Ips (Family Tenebrionidae, Corticeus spp.) to be fairly common in the samples and evidence of cerambycid wood-borer galleries in the samples.

graph showing density of Ips collected from girdled red pine

Fig. 1: Density of Ips pini [dark bars] and Ips grandicollis [white bars] collected from bark samples taken at three heights of girdled red pine, Pinus resinosa, near Zimmerman, Minnesota (July 25-27, 2001).


graph showing density of Ips collected from felled red pine

Fig. 2: Density of Ips pini [dark bars] and Ips grandicollis [white bars] collected from bark samples taken at three heights of felled red pine, Pinus resinosa, near Zimmerman, Minnesota (July 25-27, 2001).


graph showing density of Ips collected from standing red pine

Fig. 3: Density of Ips pini [dark bars] and Ips grandicollis [white bars] collected from bark samples taken at three heights of standing red pine, Pinus resinosa, near Zimmerman, Minnesota (July 25-27, 2001).


graph showing density of Ips collected from red pine

Fig. 4: Density of Ips pini [dark bars] and Ips grandicollis [white bars] collected from bark samples taken at three heights of red pine, Pinus resinosa, near Zimmerman, Minnesota (July 25-27, 2001).

Acknowledgements

We thank Jana Albers, Mark Platta, and Bob Tiplady for their assistance with data collection.

Ayres, B. D., Ayres, M. P., Abrahamson, M. D., and Teale, S. A. 2001. Resource partitioning and overlap in three sympatric species of Ips bark beetles (Coleoptera: Scolytidae). Oecologia 128: 443-453.

Dodge, H. R. 1938. The Bark Beetles of Minnesota (Coleoptera: Scolytidae). Univ. of Minn. Agr. Exp. Sta. Tech. Bull. 132, 60 p.

Kennedy, P. C. 1969. Causes of the 1966 Ips pini outbreaks. Mich. Acad. 2: 87-92.

Lanier, G. N. 1970. Biosystematics of North American Ips (Coleoptera: Scolytidae): Hopping's group IX. Can. Entomol. 102: 1139-1163.

Lanier, G. N. 1987. The validity of Ips cribricollis (Eich.) (Coleoptera: Scolytidae) as distinct from Ips grandicollis (Eich.) and the occurrence of both species in Central America. Can. Entomol. 119: 179-187.

Raffa, K. F. 1991. Temporal and spatial disparities among bark beetles, predators and associates responding to synthetic bark beetle pheromones:Ips pini (Coleoptera: Scoytidae) in Wisconsin. Environ. Entomol. 20: 1665-1678

Schenk, J.A., and D.M. Benjamin. 1969. Notes on the biology ofIps pini in central Wisconsin jack pine forests. Ann. Entomol. Soc. Am. 62: 480-485