Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/31/2001
Publication Date: 12/31/2001
Interpretive Summary: Claviceps purpurea is an important floral infecting pathogen of about 400 species of grasses, including the cereal grains and forage and turf. The association of insects and the honeydew stage of C. purpurea (which includes the exudation of plant sap and spores of C. purpurea) and insects is established, although little quantitative data is available. A survey of insects in Kentucky bluegrass fields in the Pacific Northwest and their association with C. purpurea was conducted. Spores of C. purpurea were found on a diversity of insects, including moths, flies, leafhoppers, and thrips. Up to 100% of moths and 75% of flies were collected from some fields carried conidia of C. purpurea, indicating a high potential for these insects for spread of C. purpurea.
Technical Abstract: Insects in Kentucky bluegrass seed production fields in Oregon, Idaho and Washington were sampled just prior to harvest and their association with ergot conidia of Claviceps purpurea Fr. (Tul.) was evaluated during 1996 1998. A diversity of insects was observed at all three locations. The most abundant beneficial insects collected with sweep nets were Nysium spp., Nabis spp., ichneumon wasps, and Hippodamia spp. The cranberry girdler, Chrysoteuchia topiaria (Zeller), was the only important pest on grass seed collected by sweep net. Numbers of aphids such as Sitobion avenae (Fabricius), cicadellids and thrips such as Anaphothrips spp. and Aptinothrips spp. that were collected with an aphid sampler were below economic thresholds. Other insect groups occurred at low numbers. Noctuid moths collected in universal black light traps included 9 species of cutworms and armyworms. Protagrotis obscura (B. & McD.) was the most common cutworm species, and was present in all fields. The moth, Chortodes rufostrigata (Pack.) previously reported only from wet meadows in northeast and south central Oregon was found in Kentucky bluegrass fields in Central Oregon suggesting that irrigated Kentucky bluegrass seed production fields may simulate a montane meadow habitat. Conidia of C. purpurea were found on a diversity of insects, including moths, flies, leafhoppers, and thrips. Up to 100% of months and 75% of flies from some fields carried conidia of C. purpurea. No correlation between ergot honeydew present in a field and number of insects with conidia of C. purpurea was detected.