Mass rearing method and utilization of the egg parasitoid Anagrus spp. for the control of the brown planthopper in rice fields

Abstract

The brown planthopper (Nilaparvata lugens (Stål)) is a major rice pest causing frequent and severe outbreaks in rice cultivation areas. Biological control using natural enemies is considered a safe, effective, and environmentally friendly approach. This research was conducted to develop a mass rearing technique for the egg parasitoids Anagrus spp. and to determine the appropriate release rate for controlling brown planthopper populations in paddy fields. Egg parasitoids (Anagrus spp.) were collected from paddy fields in Suphan Buri and Chai Nat provinces during 2022-2023 using brown planthoppers’ egg bait traps. Then, these parasitoids were mass reared under laboratory conditions using rice seedlings with brown planthopper eggs, with honey provided as food source. An average of 509.96 parasitoids/16 oz plastic cup was obtained, with an average emergence rate of 162.15 individuals/day. A single female parasitoid could parasitize an average of 22.33 eggs, with a sex ratio (male:female) of 1:3.3. To evaluate the efficiency of Anagrus spp. in controlling brown planthoppers during the wet season of 2024 and both the dry and wet seasons of 2025 using a randomized complete block design (RCBD) with four treatments and five replications. It was found that releasing five pairs of male and female parasitoids/10 plants containing brown planthopper eggs (15-20 days after transplanting), resulted in parasitism rates ranging from 48.97-68.24%, and produced the highest subsequent parasitoid populations. Therefore, when adult brown planthoppers are first detected in rice fields, the release of Anagrus spp. parasitoids at a rate of 76–265 pairs/m² is recommended during early morning or late afternoon to avoid high temperatures, to control brown planthopper populations and prevent outbreaks in rice fields.