Predatory and parasitic wasps (Hymenoptera) feeding at flowers of sweet fennel (Foeniculum vulgare Miller var. dulce Battandier & Trabut, Apiaceae) and spearmint (Mentha spicata L., Lamiaceae) in Massachusetts.
Maingay, Hilde M., Robert L. Bugg, Robert W Carlson, and Nita A. Davidson

Biological Agriculture and Horticulture 7:363-383. 1991

Reviewer's note: Parasitic wasps are important in the biological control of various insect pests. Adult wasps are often reliant on nectar. Sweet fennel is a common roadside weed in much of California so this study, conducted in Massachusetts, may find application here.

Sweet fennel (Foeniculum vulgare Miller var. dulce) and spearmint (Mentha spicata) grew and flowered in 0.5 X 1 .0-m, plots located amid an organic market garden (Site 1). During 1985, 12 approximately-weekly sets of aerialnet collections were made from August 7th through October 22nd from single experimental plots planted to each of the two species. On each date, samples were taken during three-minute episodes at hourly intervals from 0830-1630 EDST. Additional nearby plantings of sweet fennel in an herb garden (Site 2) were used for occasional supplemental sampling of flower visitors.

Sweet fennel flowered throughout the 12 weeks of sampling. Four hundred and ninety-seven insect specimens were collected from a small plot of sweet fennel occurring in Site 1, with 195 representing taxa that are at least in part predatory, and 105 representing groups that are at least partially parasitic. Wasps (Hymenoptera) collected from sweet fennel at Sites 1 and 2 included four species of Sphecidae and four of Vespidae (including yellowjackets and paper wasps). Eighty-seven specimens of Ichneumonidae were collected, representing 48 distinguishable species and eight subfamilies. In addition, 11 adult Coccinellidae, representing five species, were observed feeding at sweet fennel flowers. Spearmint flowered from about August 21st until September 25th, during which time 277 insect specimens were collected, including 53 from mainly-predatory taxa and 33 representing principally-parasitic groups. Wasps included six species of Sphecidae, two of Eumenidae, two of Vespidae, and two of Ichneumonidae.

Few Ichneumonidae occurred at Site 1 before August 21st; peaks of attendance occurred on September 25th and October 16th. Vespidae showed highest visitation rates on August 28th. Sphecidae were most abundant on September 3rd. Peak attendances by ichneumonids and vespids were at 0900 hours, followed by apparent reduced foraging during midmorning, and relatively high visitation rates from late morning through early afternoon. Sphecidae peaked during late morning, was lower during early afternoon, recovered somewhat during mid afternoon, and again dropped during late afternoon.

Flowering herbs such as sweet fennel and spearmint are often grown in close proximity to vegetable crops on diversified organic truck farms and in community gardens. Of the ichneumonid species collected, eight are known parasites of significant agricultural pests. Several of the predatory wasps observed also attack pests. Future studies could determine whether these or other flowering herbs could contribute to enhanced biological control of insect pests.

For more information write to: (Bugg) Information Group, UC Sustainable Agriculture Research and Education Program, University of California, Davis, CA 95616

(DEC.332) Contributed by Robert Bugg