Population Status of Biological Control Agent: Sphegigaster spp (SPINO.) (Hymenoptera, Pteromalidae) as a Parasitoid on Soybean Stem Fly Melanagromyza sojae (ZEHNT.) (Diptera, Agromyzidae) in the Nubaria Region of Egypt

Abstract

The soybean stem fly (SSF), Melanagromyza sojae (Zehntner) (Diptera: Agromyzidae), is highly polyphagous and attacks various host plant species in the family Fabaceae, such as soybean and other beans. A field survey was conducted during the 2016 and 2017 seasons at the Nubaria Agriculture Research Station, Egypt, to follow populations of the SSF on soybean cultures. The parasitoid Sphegigaster spp was identified and recorded for the first time as a solitary parasitoid on SSF pupa. The parasitoid's morphology was studied by using The scanning electron observations of the morphology confirms the genus of the parasitoid. The insect injurious stage of SSF on soybean plantations was larva that feeds inside the plant stem then convert to pupa during Jun.-Sept. (2016-2017). The level of SSF infestation was severe compared with insect pests orders Hemiptera and Lepidoptera. The infested plants by M. sojae and the level of parasitism (non-parasitized and parasitized SSF pupae) were estimated during 2016 and 2017 seasons. The results indicate that the exit hole of M. sojae is associated with the entry of the parasitoid into a pupa. The Parasitism percentages on SSF pupae by Sphegigaster parasitoid increased gradually up to 38.7% in August 2016, while it is 34.3% in August 2017. In September 2016 and 2017, respectively and then started to decrease in September where it was 16.7%, 22.2% in two successive seasons. Finally, the average of parasitism percentages on SSF pupae by their parasitoids Sphegigaster spp was 23.4% in 2016, while it is 26.7% in 2017. The Sphegigaster spp sex ratios were male biased, being respectively 52% (14 females and 15 males) in 2016 and 62% (12 females and 20 males) in 2017. The result point to the first record of the parasitoid Sphegigaster spp in Egypt on SSF pupae offers a promising opportunity for a biocontrol of soybean stem fly under local agronomic and climate conditions. Therefore, the presence of the parasitoids of M. sojae in Egypt was useful for the development of biocontrol methods to limit its impact on regional soybean production.