Insecticidal activities of a Diospyros kaki root-isolated constituent and its derivatives against Nilaparvata lugens and Laodelphax striatellus

a b s t r a c t a r t i c l e i n f o Diospyros kaki root-derived materials were examined for insecticidal properties against Nilaparvata lugens and Laodelphax striatellus. Based on the LD 50 values, the chloroform fraction of D. kaki extracts showed the most activity against N. lugens (3.78 μg/female) and L. striatellus (7.32 μg/female). The active constituent of the chloroform fraction was isolated by various chromatographic methods and was identified as 5-hydroxy-2-methyl-1,4-naphthoquinone by spectroscopic analyses. To establish the structure-activity relationships, the insecticidal effects of 5-hydroxy-2-methyl-1,4-naphthoquinone and its derivatives against N. lugens and L. striatellus were determined using micro-topical application bioassays. On the basis of LD 50 values, 5-hydroxy-1,4-naphthoquinone was the most effective against N. lugens (0.072 μg/female) and L. striatellus (0.183 μg/ female). 2-Bromo-1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, and 5-hydroxy-2-methyl-1,4-naphthoquinone also had potent insecticidal activities against N. lugens and L. striatellus. In contrast, no insecticidal activity was observed with 2-methoxy-1,4-naphthoquinone or 2-methyl-1,4-naphthoquinone. These results indicate that the functional group (bromo-and hydroxyl-) at the C-2 position of the 1,4-naphthoquinone skeleton and the change in position of the hydroxyl group play important roles in insecticidal activity. Therefore, naturally occurring D. kaki root-derived 5-hydroxy-2-methyl-1,4-naphthoquinone and its derivatives may be suitable as insecticides

Prediction of Adult Emergence Time and Generation Number of Overwintered Small Brown Planthopper, Laodelphax striatellus According to RCP8.5 Climate Change Scenario

ABSTRACT: Recently, climate change scenarios were substituted by the Special Report on Emission Scenarios (SRES) for Representative Concentration Pathway (RCP). Using the RCP scenario, the World Meteorological Organization (WMO) produced new climate change scenarios. Further, the National Institute of Meteorological Research (NIMR) of Korea produced new climate change scenarios for the Korean Peninsula. In this study, emergence time of small brown planthopper (SBPH), Laodelphax striatellus and the number of generations a year were estimated during climatic normal year with previous studies and they were predicted during 2050s (2045-2054) and 2090s (2085-2094) by means of RCP8.5 climate change scenario. In comparison with 176.0±0.97 Julian data in the climatic normal year, the emergence time of overwintering SBPH was predicted to be 13.2±0.18 days (162.8±0.91 Julian date) earlier in 2050s and 32.1±0.61 days (143.9±1.08 Julian date) earlier in 2090s. The SBPH was expected to produce an additional 2.0±0.02 generations in 2050s and 5.2±0.06 generations in 2090s