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Biological Control of Arthropod Pests
of the Northeastern and Northcentral Forests
in the United States


R. G. Van Driesche
University of Massachusetts
Fernal Hall, Department of Entomology
Amherst, MA 01003
S. Healy, and R. Reardon


The literature on 94 species of arthropod forest pests was reviewed with the objective of summarizing current knowledge about the role of biological control in the population dynamics of these pests. This was done for the purpose of identifying which species were the best candidates as future, new or reopened, projects of biological control. The report, to be published by the Forest Service in 1997, identified species for which opportunities for use of biological control existed through natural enemy importation, conservation or augmentation. Other species reviewed were felt to not be suitable as biological control targets. This information is summarized as follows (Tables 1-4).

Summary of Recommendations

Ninety four species of forest arthropods have been reviewed in this report. Other species, not reviewed, may be important pests from the perspective of more particular geographic areas or tree species. Consideration of application of biological control in such cases will require further review.

Of the species reviewed, 58 (62%) are believed to be native to North America. Of the remainder, the origins of two species (2%) (spruce mite and larch sawfly) are uncertain or disputed. The remainder include 29 species (31%) of non-native origin currently found in North America and three species (3%) not yet present in North America, but of concern (Ips typographus, Sirex noctilio, and Lymantria monacha). Finally, three species (Cooley spruce gall adelgid, Nantucket pine tip moth, and tuliptree aphid) are native to North America, but have spread into regions of North America outside their original ranges, and thus occur as non-native species in some areas.

Detailed recommendations of how biological control might be employed for the control of these pests are given as the concluding paragraphs in each species' section. These recommendations have been grouped into the following categories that correspond to the ways in which biological control can be employed:

  1. natural enemy introductions
  2. augmentation of natural enemies, through artificial propagation and release
  3. studies of population dynamics to clarify importance of natural enemies or identify modifications of silvicultural practices that enhance effects of existing natural enemies at production sites
  4. no role for biological control.


    Of the 29 species of non-native pests reviewed, 27 were judged to provide opportunities for their control via natural enemy introductions (Table 1). In some cases, these species have never been targets of natural enemy importations (e.g., beech scale, mimosa webworm, eastern spruce gall adelgid) or present opportunities for work additional to that which was done in the past. An example of the later would be searching new regions not considered or accessible in the past, e.g., the Caucasus Mts. for predators of the balsam woolly adelgid.

    Some species listed in this category have already been successfully controlled through natural enemy introductions (e.g., larch casebearer, European spruce sawfly, introduced pine sawfly, and Nantucket pine tip moth in California).

    Most of the pests listed in this category have invaded North America from other continents. A few, however, are native species (e.g., Cooley spruce gall adelgid, tuliptree aphid, Nantucket pine tip moth) that have invaded parts of the continent outside their historical ranges and become non-native pests locally.

    For the species that have invaded North America from abroad, it is important to identify the native homeland, which may be different from the area from which the pest came to North America. Many species, for example, appear to have moved from Russia or Asia to Europe and then to North America. In such cases, the species may lack important natural enemies in Europe as well as North America and Europe would thus be an inappropriate location in which to seek natural enemies able to suppress the pest.

    A small number of native species have been considered as possible targets for natural enemy introductions, using species collected from European or Asian species related to the pest at the generic level. Examples include spruce budworm and white pine weevil.


    For pests of high value sites (forest nurseries, shade trees, Christmas tree plantations), use of more expensive biological control products such as nematodes, predacious mites, or formulated pathogens is possible. Fourteen species were identified for which studies on the effectiveness of augmentative biological control seem useful (Table 2). Examples include the development of nematodes for the control of white grubs in forest nurseries, the use of Bacillus thuringiensis for control of defoliating Lepidoptera, and the use of nuclear polyhedrosis viruses for control of some species of sawflies.


    For some pests, insufficient information was found to judge the importance of natural enemies in the population dynamics of the species. In some cases there were needs to compare the importance of natural enemies between habitats (such as natural stands versus managed plantations) or locations (in North America versus the native range). A need for population dynamics studies of these sorts was identified for 17 species (Table 3). Examples include the need to clarify the importance of pipinculid parasitoids attacking the Saratoga spittlebug, a need to study the effect of different slash management practices on natural enemies of pine engraver beetle and larger pine shoot beetle, and studies of effects of vegetation diversity on various shoot borers.


    For 29 species (Table 4) no role for biological control was identified. These species were predominantly native (27) insects, for which natural enemy introductions were not likely to be relevant and for which augmentativebiological control methods were too expensive in view of the nature and distribution of the damage. While natural control by unmanipulated natural enemies is undoubtedly a factor to some degree in the population dynamics of these species, opportunities to intentionally employ silvicultural practices to increase biological control were not identified.

Table 1. Species for which introductions of new species of natural enemies are needed or have previously controlled the pest.
Species Pest # Pest Origin Natural Enemy Needed, or Area to be Explored
1. eastern spruce gall adelgid 3 E Aphidoletes abietis
2. balsam woolly adelgid 4 E explore Caucasus Mts.
3. hemlock woolly adelgid 5 E explore China and Japan
4. Cooley spruce gall adelgid 6 N(but E in eastern N.A.) explore Colorado
5. Woolly beech aphid 11 E determine native range
6. tuliptree aphid 12 N(but E in CA) explore eastern U.S.
7. Norway maple aphid 13 E explore Europe
8. linden aphid 14 E explore China
9. beech scale 15 E determine native range
10. red pine scale 16 E Harmonia yedoensis in Japan
11. elongate hemlock scale 19 E explore Japan and China for parasitoids with better synchrony
12. oystershell scale 20 E explore Russian Far East
13. San José scale 21 E explore Russian Far East
14. Japanese beetle 32 E explore China and Japan for better parasitoids
15. imported willow leaf beetle 33 E explore China
16. elm leaf beetle 34 E explore Europe and Asia
17. smaller European elm bark beetle 36 E collect nematodes and microsporidia from Europe
18. black turpentine beetle 38 N re-release Rhizophagis grandis
19. Ips typographus 41 E collect in Europe, when needed
20. spruce budworm 42 N collect in Europe and Japan from congeneric species
21. gypsy moth 51 E explore Russia and China, but prepare detailed evaluation first
22. nun moth 52 E collect in Europe, when needed
23. mimosa webworm 57 E explore Asia and Australia
24. birch casebearer 58 E explore Europe
25. larch casebearer 59 E already controlled through natural enemy introductions
26. pine false webworm 63 E compare status in Europe and North America
27. introduced pine sawfly 67 E already controlled through natural enemy introductions
28. European spruce sawfly 68 E already controlled through natural enemy introductions
29. larch sawfly 69 E continue work in Europe on encapsulation-resistant parasitoids
30. European pine shoot moth 84 E reassess pest levels in North America, then explore in Europe
31. Nantucket pine tip moth 85 N(but E in CA) already controlled in CA by natural enemy introductions
32. white pine weevil 88 N collect in Europe from congeneric species
33. birch leafminer 93 E collect in Europe

Table 2. Species for which development of augmentative use of natural enemies is recommended.
Species Pest # Pest Origin Type of Natural Enemy
1. Phyllophaga spp. 28 N nematodes & fungi
2. Polyphylla variolosa 29 N nematodes & fungi
3. black vine weevil 30 E nematodes & fungi
4. strawberry root weevil 31 E nematodes & fungi
5. Japanese beetle 32 E nematodes & fungi
6. spruce budworm 42 N Bacillus thuringiensis
7. Bruce spanworm 46 N NPV
8. gypsy moth 51 E Bacillus thuringiensis or NPV
9. red headed pine sawfly 64 N NPV
10. swaine jack pine sawfly 65 N NPV
11. poplar borer 75 N nematodes
12. cottonwood borer 76 N nematodes
13. carpenterworm 81 N nematodes
14. spruce mite 94 ? predaceous mites

Table 3. Species which need basic studies of their population dynamics to clarify reasons for typical population densities, or to determine if modifications of silvicultural practices can enhance natural enemy effectiveness.
Species Pest # Pest Origin Aspect Needing Study
1. Saratoga spittle bug 22 N effect of pipinculid parasitoids
2. cottonwood leaf beetle 23 N population dynamics in natural stands vs. plantations
3. pine root collar weevil 25 N population dynamics in natural stands vs. plantations
4. pine engraver 40 N effect of slash management on natural enemies
5. jack pine budworm 43 N effects of stand conditions on natural enemies
6. large aspen tortrix 44 N basic population study
7. fall cankerworm 45 N basic population study
8. Bruce spanworm 46 N basic population study
9. spruce budmoth 55 N basic population study
10. balsam gall midge 62 N effects of Christmas tree plantation silvicultural practices on natural enemies
11. yellow-headed sawfly 70 N comparison of natural enemies in open versus shady sites
12. red oak borer 74 N woodpecker conservation methods
13. European pine shoot moth 84 E comparison of effects of stand age and vegetational diversity in Europe and North America
14. Nantucket pine tip moth 85 N effect of vegetational diversity on natural enemies
15. eastern pine shoot borer 86 N effect of vegetational diversity on natural enemies
16. cottonwood twig borer 87 N importance of natural enemies in natural stands versus plantations
17. larger pine shoot beetle 90 E effects on natural enemies of slash management practices

Table 4. Species for which no important role was identified for biological control
Species Pest # Pest Origin
1. pear thrips 1 E
2. introduced basswood thrips 2 E
3. pine bark adelgid 7 N
4. pine leaf adelgid 8 N
5. white pine aphid 9 N
6. woolly elm aphid 10 N
7. pales weevil 24 N
8. pitch-eating weevil 27 N
9. native elm bark beetle 35 N
10. spruce beetle 37 N
11. eastern larch beetle 39 N
12. spring cankerworm 47 N
13. forest tent caterpillar 49 N
14. eastern tent caterpillar 50 N
15. pine webworm 53 N
16. Zimmerman pine moth 54 N
17. bagworm 56 N
18. oak leafroller 60 N
19. saddled prominent 61 N
20. Virginia pine sawfly 66 N
21. two-lined chestnut borer 72 N
22. bronze birch borer 73 N
23. flatheaded apple borer 77 N
24. locust borer 78 N
25. white oak borer 79 N
26. whitespotted sawyer 80 N
27. banded ash clearwing 82 N
28. Columbian timber beetle 83 N
29. northern pine weevil 89 N
30. white cone beetle 91 N
31. arborvitae leafminer 92 N

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