Evaluation of Two Parasitoids in Dairy Calf Greenhouses

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Project Leaders: D. A. Rutz¹, P. E. Kaufman¹, and J. K. Waldron²

¹Department of Entomology, Cornell University, Ithaca, NY

²New York State IPM, Cornell University, Geneva, NY

Type of Grant: Biological control and pest biology

Project locations: Cayuga, Cortland, Onondaga and Tompkins Co. Results applicable throughout the Northeast

Abstract:

Parasitoids are a critical component of a successful dairy IPM program. In the first year of this two-year study we compared individual species parasitoid releases. During Year 2 we will compare the best individual parasitoid from Year 1 to a 50:50 ratio of M. raptor and M. raptorellus.

House fly levels were similar throughout the study and in no time period did fly numbers exceed the threshold level of 100 spots per card. In general, producers were very good stewards of the bedding areas. Stable fly numbers increased throughout the summer and numbers were highest in the post-release period on all nine farms.

On "no-release" farms, M. raptor, a native NY parasitoid, accounted for 60.5% of successful parasitism with the ichneumonid wasp, Phygadeuon spp., another native parasitoid, accounting for 28.7%. On M. raptor-release farms, the released parasitoid accounted for 93.8% of successful parasitism, while M. raptorellus and Phygadeuon spp. accounted for 3.9% and 3.0% of pupae, respectively. On M. raptorellus-release farms, the released parasitoid accounted for 84.9% of successful parasitism, while M. raptor accounted for 15.0% of pupae that produced a live parasitoid. No to very low parasitism was identified during the pre-release period and the first week of releases. Successful parasitism immediately increased on the six release farms and remained low on the no-release farms for the duration of the release period. Successful parasitism averaged 3.6%on the no-release farms, 22.4% on M. raptor farms and 50.0% on M. raptorellus farms during the release period. Total parasitism is the number of pupae killed by parasitoids and represents the benefit (dead flies) to farmers that the parasitoids are providing. Total parasitism averaged 9.6% on no-release farms, 37.1% on M. raptor-release farms and 63.7% on M. raptorellus-release farms. These data indicate that the parasitoids were removing from 50 to 64% of flies from the calf bedding areas on M. raptorellus-release farms.

The apparent similarity in fly densities on farms combined with the decidedly varied response in sentinel data among release and no-release farms suggests that a substantial number of house flies were being produced from sites on the farms other than the calf bedding areas. In total, however, fly numbers did not exceed the treatment threshold in any study period, lending credence to successful producer-driven fly management across the farm. Based on these results, M. raptorellus out-performed M. raptor in 2003. According to our protocol, we plan to compare M. raptorellus only releases to combined releases of 50% M. raptor and 50% M. raptorellus in 2004.