Winter 1995 (v7n1)
E. W Riddick and N.J. MiII5
Environmental Entomology 23:1338-1345. 1994
Codling moth is a serious pest of several crops including apples, pears and walnuts. In semidwarf apple orchards, the smooth bark of the trees affords few pupation sites so codling moth typically pupates on the ground in leaf litter, or in the soil. This habit renders the larvae susceptible to predation by ground-dwelling predators, including carabid beetles. In apple orchards in Sonoma and Contra Costa counties of California, the investigators conducted observations on predators attacking fifth-instar codling moth tethered on the orchard floor. Tethering was by means of heavy-duty black cotton thread fastened either to a 9-cm disk of sandpaper or to an inverted petri dish of 9.5-cm diameter that was flush with the soil. Laboratory studies were also conducted on killing success, degree of carnivory, and consumption patterns.
Carabidae attacking tethered codling moth larvae in the field included Agonum punctiforme Say, Calathus ruflcollis Dejean, Harpalus pensylvanicus DeGeer, and Pterostichus (Hypherpes) spp. In the field, predation rates were high during early June, but declined during later June and July. In the laboratory, 75 percent of the individuals tested of each of the following species were capable of killing fifth-instar codling moth: Pterostichus lustrans LeConte, Pterostichus cursitor LeConte, Pterostichus (Hypherpes) spp., Harpalus pensylvanicus DeGeer, and Anisodactylis californicus Dejean. Pterostichus spp. were particularly effective predators.
Reviewer's Note
This article explores the role of carabids in apple orchards, but ground beetles may also be active predators in walnut orchards. In walnuts, codling moth larvae overwinter under loose scales of bark or in trash on the ground near the trunk. Samples collected by Robert Bugg and John Dunley during July 1994 from organic walnut orchards near Winters, California, were sent to Riddick for identification. Table 1 shows the carabid species found in that sampling (Orchard 1). A collection made in late August at the edge of another organic walnut orchard near Winters yielded 22 specimens. These are also listed in table 1 (Orchard 2).
In addition to the paper reviewed here, other studies in both Europe and the U.S. are exploring the potential importance of ground beetles (Carabidae) as biological control agents. Several recent papers have looked at the ability of ground beetles to control pests (codling moth and others) that pupate in the soil; other papers suggest possibilities for increasing their abundance in agronomic crops.
For more information write to: E.W. Riddick, Department of Entomology, Symons Hall, University of Maryland, College Park, MD 20742.
(DEC.522) Contributed by Robert Bugg
| Table 1. Carabid species collected from two walnut orchards near Winters, California. | |
| Species | Number of Adult Individuals Collected |
| Orchard 1 (July, 1994) | |
| Amara sp. | 2 |
| Agonum punctiforme | 14 |
| Agonum (varioatum?) | 3 |
| Calathus ruficollis | 2 |
| Harpalus pensylvanicus | 1 |
| Pterostichus cursitor | 2 |
| Trechus obtusus | 3 |
| Orchard 2 (August, 1994) | |
| Amara spp. (2 species?) | 4 |
| Calathus ruficollis | 7 |
| Harpalus pensylvanicus | 9 |
| Harpalus sp. | 1 |
| Pterostichus (Hypherpes) algidus | 1 |
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