Abstract:

The purpose of this study was to evaluate the effect in field of Trichogramma chilonis Ishii release and to provide some reference for promoting biocontrol techniques on controlling the Spodoptera frugiperda. We set up 2 experimental districts. One was in the Gutong village, Mashan County, Nanning, and the other was in the cornplanting base of Jinguang Company in the Tanluo village, Xixiangtang District, Nanning. Each district released T.chilonis 3 time, and use 150 bee cards which contained 1000 Trichogramma chilonis Ishii in a card per hectare at a time. The injury rate, amount per100 plants and egg parasitzed rate of Spodoptera frugiperda were investigated before and everytime after releasing. In Gutong, when the release was over, the average injury rate decreased from 36.33% to 7.60%, the amount per100 plants decreased from 11.27 to 3.33, and the average egg parasitized rate increased from 20.08% to 100%. The damage was controlled and the egg parasitized rate increased significantly. In Jinguang, when the release was over, the average injury rate increased from 68.40% to 88.37%, the amount per100 plants decreased from 43.56 to 43.23, and egg parasitzed rate increased from 0 to 3.96%. The damage situation was not improved and the egg parasitzed increased. It was also found that Trichogramma chilonis Ishii was co-parasitized with the Telenomus remus Nixon. The two wasps sent 56 eggs in total after 8 days of 3 times of parasitism in Gutong village, and the parasitism rate was 100%. We found that, Telenomus remus Nixon and Trichogramma chilonis Ishii preferred to co-parasitise the egg mass of Spodoptera frugiperda. In conclusion, releasing Trichogramma chilonis Ishii when the infestation of Spodoptera frugiperda was mild could effectively control the population density of armyworm in the field, reduce the infestation rate and increase the egg parasitism rate, which was one of the effective biological measures to control Spodoptera frugiperda in the field. Only release of Trichogramma chilonis Ishii could not achieve good control effect when the field damage was heavy. Release of Trichogramma chilonis Ishii to control Spodoptera frugiperda needs to seize the moment.

Key words: Spodoptera frugiperda, Trichogramma chilonis Ishii, biological control, effect, natural enemies