The fields were scouted weekly, and percent parasitism was assessed by taking any egg masses we found back to the lab to see if they turned black. If unparasitized egg masses were found when scouting, they were held for 2-4 days to see if they turned black due to Trichogranima parasitization, and parasitized egg masses were excluded from the calculation when deciding if a field was over threshold. Bt products were applied at the maximum label rate. The results are summarized below in Table 1. It was not possible to have untreated controls for comparison in these demonstrations because the wasps disperse from field to field so readily.
Further research is needed to determine the optimal numbers.
Initial research was conducted in individual fields and established that, after the initial release, the wasps were able to move up to 340 feet and persist in a field for up to 30 days. In 1999, a single release of 30,000 wasps was made per field, and egg masses were sampled in fields throughout the season. At harvest, the infestation level in ears was similar in release and non-release fields regardless of whether insecticides were applied or not. The wasps were able to persist throughout the season even in fields receiving insecticide applications. They disappeared from only one release site, which had very low numbers of ECB eggs.