We have finally concluded all of the core sampling for our demonstration test this production season. We have gathered all the data and Anna conducted a statistical analysis. In this analysis each location is treated as a replicate.
We had a total of 15 sites included in our test this year. We started this season with 5 locations designed to evaluate rww management tactics. An additional 5 sites were set up to evaluate colaspis management. We did not have any colaspis infestations in the test sites. We gained three more weevil test sites that had been planted out either by seed companies or a cooperator, who requested we take samples. We wound up with a total of 10 locations that were included in the overall data analysis. More than 500 core samples were processed to generate this dataset – that’s a lot of backbreaking work to pull all the cores and then to wash all that mud from the roots! Thanks to our cheerful, hardworking crew for completing this task without complaint.
We collected weevil cores from all sites 4 weeks post flood. Our standard method is to take 10 cores per treatment, in a zig-zag pattern across the field, making sure to pull cores from the edge and middle of the cut.
A few trends broke out in the dataset. In Acadia and Jeff Davis Parishes, we had a relatively light infestation with weevils, except at one location (Lawson Farm) where we had about 10 larvae per core in the untreated check. In Vermilion Parish we had low to moderate infestations. In Concordia Parish we had an average of 10 larvae per core in the untreated check. In Evangeline Parish we had a relatively severe infestation with untreated counts averaging from 10.8 rww larvae per core at the LaHaye farm to 15 larvae per core at the Morein farm site. Our highest population was in St. Landry Parish where we had an average of 21.9 larvae per core in the untreated check. While, in Tensas Parish (our most northern location) we had an extremely light infestation with zero larvae per core in the untreated check and the highest count of 0.15 larvae per core in the Dermacor X-100 treated cut. Interestingly at this location, we had a fairly severe infestation in the 2008 production season. The graph that follows summarizes the average number of rww larvae per core when we analyzed the entire dataset.
Overall, Dermacor X-100 provided the best level of weevil control, followed by pyrethroid (either Karate pre,Karate pre + mustangMax on fertilizer post, or Karate post) and CruiserMaxx. Dermacor X-100 provided significantly better control than the other two treatments. There was no signficant difference in the core sample average between the pyrethroid and the CruiserMaxx seed treatment.
Unfortunately, the results from the Hybrid test plots (25 pound or less seeding rate) did not provide any more clarity about the ability of CruiserMaxx to provide effective weevil control at the low seeding rates. We plan to repeat the demonstration test again next season, particularly focusing on the low seeding rate question. Mike Stout has some small plot replicated research that may also clarify the question of effectiveness of CruiserMaxx at low seeding rates as currently labeled.
This was certainly an interesting weevil season, and we learned a lot about weevil management, and just how difficult it can be to scout for adults and properly time insecticide applications.
We greatly appreciate the support and cooperation of all who are involved with the demonstration test. Please contact your local county agent, or me, if you have any questions about our observations this season.