Preliminary Exploration On The Parasitic Behavior And Interspecific Competition Of Two Egg Parasitoid Wasps On Brown Rice Planthopper Nilaparvata Lugens(St(?)l)

The brown rice planthopper(BPH),Nilaparvata lugens(St(?)l),a monophagous phytophagous insect,which is acknowledged as one of the most important pests of rice,could lead to millions of tons of rice being dam-aged or even complete losses.Currently,the main method of controlling BPH is through integrated management,among which the use of parasitic wasps to control BPH has received widespread attention due to its green and efficient ecological advantages.Previous studies have shown that Anagrus nilaparvatae and Pseudoligosita yasumatsui are parasitic wasps of BPH,both of which can parasitize BPH eggs,and A.nilaparvatae has a good control effect on BPH,but there are few reports on the control of BPH by P.yasumatsui.In order to compare the control effect of A.nilaparvatae and P.yasumatsui on BPH,evaluate the application value and interspecific competition of the two egg parasitic wasps,this study used A.nilaparvatae and P.yasumatsui to parasitize BPH eggs,compared the morphological characteristics,reproductive modes,and parasitism of the two egg parasitic wasps on BPH eggs(including parasitic preference,oviposition regularity,probing behavior,and interspecific competition),and obtained the following main conclusions:In this study,A.nilaparvatae has both gamogenesis and parthenogernesis.During gamogenesis,the offsprings produced by A.nilaparvatae are mostly female;during parthenogernesis,all offspring develop into males.Both species of egg parasitoid wasps can parasitize both fertilized and unfertilized BPH eggs,but they prefer to parasitize fertilized BPH eggs.The preference for parasitizing BPH eggs decreases with egg age,with a greater preference for parasitizing eggs aged 1-4 days.The oviposition activity of both egg parasitoid wasps mainly occurs during the day,with the parasitic peak of A.nilaparvatae occurring mainly between 7:00-15:00 and the parasitic peak of P.yasumatsui occurring mainly between 7:00-13:00.During the 30-minute probing behavior observation,the probing time required by P.yasumatsui was significantly higher than that of A.nilaparvatae,and the number of probes was lower than that of A.nilaparvatae,and the parasitized quantity of BPH eggs was also lower than that of the latter.So the parasitic ability of A.nilaparvatae is superior to P.yasumatsui.P.yasumatsui has strong inter and intraspecific competition and exhibits frequent behavior in competition for host eggs.In contrast,competition is relatively weak for A.nilaparvatae,and it avoids confrontation with the P.yasumatsui when parasitizing on the same BPH egg mass but will parasitize the same egg mass when the P.yasumatsui is undistinguished.Both species of egg parasitic wasps can parasitize the same mass of BPH egg.When two species of parasitoid wasps parasitize the same BPH egg mass,their respective parasitism ratios vary under different parasitism sequences: when parasitizing simultaneously,the average proportion of eggs of the parasitoid A.nilaparvatae in egg masses co-parasitized by both parasitoid species is significantly higher than that of the P.yasumatsui;when A.nilaparvatae parasitizes after P.yasumatsui,there is no significant difference in the average proportion in co-parasitized egg masses;when P.yasumatsui parasitizes after A.nilaparvatae,the average proportion of P.yasumatsui in co-parasitized egg masses is significantly higher than that of A.nilaparvatae.