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Evaluation of Two Parasitoids in Dairy Calf Greenhouses 2006

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Project Leaders: D. Rutz, Department of Entomology, Cornell University, Ithaca, NY; J. K. Waldron, NYS IPM Program, Cornell University

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 compared the best individual parasitoid from Year 1 (M. raptorellus) 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 calf bedding areas.  In 2006, the average spots per card were a little higher than normal, but that can be attributed to NY having one of the rainiest summers on record.  These wetter than normal conditions would have easily produced ideal conditions for more flies to be produced on these farms.  Stable fly numbers increased throughout the summer on no-release farms and numbers were highest during the release period on all of the release farms.

On no-release farms, M. raptor, a native NY parasitoid, accounted for 97.9% successful parasitism and M. raptorellus accounted for 2.1%.  On M. raptorellus-release farms, the released parasitoid accounted for 90.1% successful parasitism, while M. raptor accounted for 9.9%.  On M. raptor/M. raptorellus-release farms, M. raptor accounted for 52.5% successful parasitism, while M. raptorellus accounted for 47.5%.  None 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 study.  Successful parasitism averaged 5.2% on the no-release farms, 62.5% on M. raptorellus farms and 57.4% on M. raptor/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 21.8% on no-release farms, 65.9% on M. raptorellus-release farms and 67.2% on M. raptor/M.raptorellus-release farms.  These data indicate that the parasitoids were removing 69-76% of flies from the calf bedding areas on M. raptorellus-release farms and 71-78% of flies from M.raptor/M.raptorellus release farms.

Based on these results, M. raptorellus and the 50:50 mix of M. raptor and M.raptorellus gave very similar control of the fly populations on their respective dairy farms.  With the similarities taken into consideration, it merely comes down to the cost effectiveness of each parasitoid release to the farmer.  To release the M.raptorellus, it costs less then half of what it would to release the 50:50 mix.  However, it would be most beneficial to have another year to fully compare and understand the differences between the two types of parasitoid releases in the 2006 study and to make certain that the record breaking NYS rainfall in 2006 was not a factor in how the parasitoids performed.  We hope to be able to accomplish this in 2007.