Application of trait-mediated indirect effects to pest control: why does pest crop damage decrease in the presence of predators?

Research Project

Project/Area Number	17K20074
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Research Field	Environmental conservation measure and related fields
Research Institution	National Agriculture and Food Research Organization
Principal Investigator	Baba Yuki 国立研究開発法人農業・食品産業技術総合研究機構, 農業環境研究部門, 上級研究員 (70629055)
Co-Investigator(Kenkyū-buntansha)	坂本洋典国立研究開発法人国立環境研究所, 生物・生態系環境研究センター, 研究員 (70573624)
Project Period (FY)	2017-06-30 – 2023-03-31
Project Status	Completed (Fiscal Year 2022)
Budget Amount *help	¥5,850,000 (Direct Cost: ¥4,500,000、Indirect Cost: ¥1,350,000) Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000) Fiscal Year 2018: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000) Fiscal Year 2017: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000)
Keywords	形質介在効果 / クモ / ヒメトビウンカ / 化学分析 / GS/MS / カトウツケオグモ / 植食性昆虫 / 体表物質 / 害虫 / 害虫防除 / クモ糸 / 化学物質 / 行動 / 忌避 / 植食者 / クモの糸 / コモリグモ / ウンカ / アシナガグモ属 / イネ害虫 / 群集生態学
Outline of Final Research Achievements	A trait-mediated effect, whereby the presence of natural enemies itself changes the insect pest's behaviour and affects the crop production, was tested. Field studies in rice paddies showed a negative relationship between the abundance of the spiders and an insect pest, small brown planthopper. Next, laboratory experiments presented spider threads and excrement to potential prey insects of spiders (e.g. brown planthopper and European house crickets), but no clear repellent behaviour was observed. As it has been suggested that spiders may rather lure prey with body surface chemicals, body surface substances were analysed for the crab spider, Phrynarachne katoi; GS/MS analysis revealed nearly 50 peaks and 19 chemical substances, including Hexadecanal, were detected.
Academic Significance and Societal Importance of the Research Achievements	クモを対象とした形質介在効果に関していくつか代表的な既往研究が存在するが、具体的にどのような化学物質が昆虫の行動を変化させているか、その至近的要因は明らかにされていない。本研究では、形質介在効果の存在は明らかにできなかったが、化学分析によって特徴的なクモの体表物質の組成を明らかにできた点は意義深い。また日本ではクモによる害虫の抑制効果を示した事例が限られているため、水田における調査データを基に、クモによる害虫抑制の証拠を提示できた点も意義深いと考えられる。