Association of insects and ergot (Claviceps purpurea) in Kentucky bluegrass seed production fields

Abstract

Insects in Kentucky bluegrass seed production fields in Oregon, Iaho, and Washington were sampled just before 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., ichneumonid 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 (F.), 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 in low numbers. Noctuid moths collected in universal blacklight traps included nine 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 moths and 75% of flies collected 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.