The flower thrips Frankliniella intonsa (Trybom) is one of the most economically important pests in cowpea greenhouses in China. Widespread pesticide resistance of thrips and the negative environmental effects limit the application of pesticides for thrips control. Two commercial cowpea greenhouse experiments were designed to determine the color preference of F. intonsa to colored cards, including white, pink, pale green, light yellow, powder blue, crimson, yellow green, deep sky blue, dark slate blue, dark orange, medium orchid, gold, and black. Clear pieces of plastic were used as the control cards. Additionally, the effects of placement height and orientation (cardinal direction) of the cards were also studied. Both greenhouse trials showed that white cards were significantly more attractive to F. intonsa than the other 13 card colors, followed by deep sky blue cards. White or deep sky blue cards placed low to the ground were found to be most attractive to F. intonsa. Orientation of the colored cards also affected the attractiveness to F. intonsa. The results indicate that white sticky cards were significantly more attractive to F. intonsa than blue cards and therefore can be recommended to monitor F. intonsa population densities and to control them in cowpea greenhouses as part of integrated pest management programs.

Camptothecin (CPT), a natural alkaloid isolated from Camptotheca acuminata Decne, is found to show potential insecticidal activities with unique action mechanisms by targeting at DnA-topoisomease I (Top1) complex and inducing cell apoptosis. To improve the efficacy against insect pests, two camptothecin (CPT) derivatives were synthesized through introducing two functional groups, 2-nitroaminoimidazoline and 1-chloro-2-isocyanatoethane by esterification reaction. The insecticidal activities of these two derivatives were evaluated at contact toxicity, cytotoxicity and topoisomerase I (Top1) inhibitory activities comparing with CPT and hydroxyl-camptothecin (HCPT). Results showed that compound a, synthesized by introducing 2-nitroaminoimidazoline to CPT, apparently increased contact toxicity to the third larvae of beet armyworm, Spodoptera exigua, and cytotoxicity to IOZCAS-Spex-II cells isolated from S. exigua. However, the inhibition on DNA relaxation activity of Top1 was reduced to less than 5 percentage even at high concentrations (50 and 100 μM). For introducing 1-chloro-2-isocyanatoethane to HCPT, the contact toxicity, cytotoxicity and Top1 inhibitory activity of synthesized compound b were increased significantly compared to CPT and HCPT. These results suggested that both synthesized compounds possessed high efficacy against S. exigua by targeting at Top1 (compound b) or novel mechanism of action (compound a).Plant secondary metabolites have a long history as a source of, and inspiration for, novel insect control agent. Examples include pyrethrum, nicotine, rotenone, which were used directly for pest control and/or as the lead compounds to develop insecticides. Camptothecin (CPT, 1, Fig. 1) is a naturally occurring alkaloid believed to serve as a defense against insect herbivores 1,2 . In China, the farmer had applied historically the crude extract of C. acuminata to control insect pests 3 . Recently, much interest has been focused on CPT due to its bioactivities to some important pest insects and unique action mechanisms by targeting at DNA and topoisomerase I (Top1) complex and inducing cell apoptosis 4-6 .Several studies have demonstrated that CPT shows toxic effects on fruit flies (Drosophila melanogaster Meigen) 7 , house flies (Musca domestica Linnaeus) 2 , and several important agricultural pest species including Spodoptera exigua Hübner 3 , Nilaparvata lugens Stål, Brevicoryne brassicae Linnaeus, and Chilo suppressalis Walker 8 . Interestingly, Sun et al. evaluated CPT synergistic effects on Bacillus thuringiensis (Bt) var. kurstaki and nucleopolyhedroviruses against Trichoplusia ni (Hübner) and S. exigua 9 . Results showed that CPT enhanced significantly the toxicity of Bt var. kurstaki to S. exigua and T. ni, and the infectivity of Autographa californica (Speyer) multinucleocapsid nucleopolyhedrovirus (AcMNPV) and S. exigua nucleopolyhedrovirus (SeMNPV). CPT and its derivatives, hydroxylcamptothecin (HCPT, 2, Fig. 1) could induce apoptosis in insect cell lines, such as IOZCAS-Spex-II (established fr...