| ccording to the co-evolution between plants and phytophagous insects, aimed at finding out oviposition deterrents, antifeedants and developmental inhibitors of insect pests, this paper deals mainly with bioactivities of secondary plant metabolites of non-host plants against diamondback moth (DBM), Plutella xylostella (L.). Based on foregoing studies, interactions among the secondary plant metabolites were studied; their synergistic or antagonistic effects on the B.t. and their positive and negative effects on Cotesiaplutellae (CP) were investigated. With scanning electron microscopy and the ablation experiment, the involvement of sensilla in the oviposition and feeding was analyzed. Effects of secondary plant metabolites on DBM in the field were revealed with life tables and index of population trend (I) and interference index of population control (UPC) to explore the sustainable control potential for the ecological control of DBM in vegetable fields.In the oviposition deterrent assay, eggs laid on the vegetable plants treated with all kinds of non-host plant extracts were significantly different (P<0.01, T-test) from that on the control. The deterrent rates also varied among different treatments. When the ethanol extracts (Etho Exts) of Bauhinia variegata, Eucalyptus tereticornis, Euphorbia hirta, Duranta repens, Zanthoxylum bungeanum, Magnolia grandiflora, Nicotiana tabacum were applied respectively, the deterrent rates were all over 80.00%, whereas the deterrent rates were lower ranging from 30.00% to 40.00% when treated with 15% Nicotinamide and the Etho Exts of Centella asiatica, Salix babylonica, Commelina communis, Angeliaca pubescens, Lactuca saliva, Araucaria cunninghammi, Camelia oleifera, Bougainvillea glabra and Agastache rugosa. With treatments of the other non-host plant extracts, the deterrent rates were between that of previous two groups.In the antifeeding assay, when applied with all kinds of non-host plant extracts except that of L. saliva, the leaf areas consumed by DBM larvae were significantly (PO.01, Pair-Sample T test) more than the control at any alternative time. The antifeedant rates varied with different kinds of non-host plant extracts. Forty-eight hours after treatment, with presence of Aloperine, Theophylline, and the Etho Exts of E.pulcherrima, B.papyrifera, A.argyi, C.oleifera, S,babylonica, E.hirta, B.variegata, S.viridisa respectively, antifeedantrates of DBM larvae were all more than 80.00%, whereas the antifeedant rates were as low as 2.16% and 0.83% respectively when exposed to the extracts of A. rugosa and L. saliva. The antifeedant rates of DBM larvae treated with the rest of Etho Exts were between previous two groups' ranging from 50.00% to 80.00%.In the developmental inhibition assay, most of Etho Exts of non-host plants reduced pupation rate and pupal weight of DBM. Among these Etho Exts,15%Nicotinamide, the ones of C.oleifera, P. guajava, E. hirta, A. falcataria, M.haplocalyx, R. communis, D. repens were responsible for the lower pupation rates of less than 30% while the Etho Exts of A. tatarinowii, S. bahylonica, A.rivieri, M. indica, S.media, A.pubescens, E.tereticornis, S.viridis. M. charantia, A.cunninghammi, H.scandens resulted in the higher pupation rates of more than70.00%. The pupal weight of DBM was not significantly (P>0.05, Ducan's multiple range test, DMRT) inhibited by the Etho Exts of M charantia, A. conyzoides and M. grandiflora compared to the control though other had reverse story. Ten pupal weight of DBM was more than O.OSOOg when DBM was reared with Etho Exts of B. variegata, M.haplocalyx respectively, less than 0.0300g when reared with Etho Exts of C.asiatica, M.indica, B.papyri/era and E.tereticornis.Based on the orthogonal-regression-rotation design, the models were developed, which revealed the interactions among the Etho Exts of the non-host plants with the property of deterrent of oviposition and feeding. The model of oviposition deterrence showed that Etho Exts of Z.bungeaman had a synergistic interaction of deterring ovipositi... |
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