Plant Allelochemicals On The Control Of Pests Of Cruciferous Vegetables

According to the co-evolution between chemical defense of plants and behavior of phytophagous insects, semiochemicals of non-preferable plants on major insect pests of cruciferous vegetable are emphasized. The semiochemicals of non-preferable plants play an important role on protecting the target plants, including the effects of repelling insect pests away from the plant, deterring the egg laying of adults, continually feeding of larvae, or killing with toxicity. Based on the life table method and the index of population control, an index system was suggested to evaluate the effects of semiochemicals of non-preferable plants on population control of major pests, diamondback moth Plutella xylostella L., the striped flea beetle Phyllotreta striolata (F.) and mustard aphid Lipaphis erysimi (Kaltenbach) in cruciferous vegetable field. Interaction of 5 alcohol extracts, interaction of alcohol extract of Eucalyptus robusta, alcohol extract of Wedelia chinensis and Bacillus thuringiensis and influence of the 10 extracts on three parasitic wasps of diamondback moth, Cotesia plutellae Kurdjumov, Oomyzus sokolowskii Kurdjumov and Trichogramma confusum Viggiani were studied on the bases of preliminary results. An interference index of population control (IIPC) was improved as follow: Notes:IIPC-interference index of population control; N1Tr, N1Ck-Number of next generation of the treatment and control; N0Tr, N0Ck-Number of that generation of the treatment and control; SETr, SSTr, SLTr, SPTr-Survival rates of egg, small larva, large larva and pupa of the treatment; SECk, SSCk, SLCk, SPCk-Survival rates of egg, small larva, large larva and pupa of the control; F-proposed egg number per female; PFTr, PFCk-the proportion of egg achieved per female of the treatment and control; P♀Tr, P♀Ck-proportion of female of the treatment and control; PhTr, PhCk-proportion of habitant adult after flying of the treatment and control; PfdTr, PfdCk-Proportion of fecundity per day(d=1,2,3,…) of the treatment and control; (SAaTr)d, (SAaCk)d-Survival rate of adult per day(d=1,2,3,…) of the treatment and control. Effects of 30 extracts or chemical compounds extracted or separated from 27 plants, which belonged to 15 families (Myrtaceae: Eucalyptus robusta Smith, E. camaldulensis Dehnhardt, E. maculata citriodora Bailey, Melaleuca leucadendra L., Eugenia caryophyllata Thunb.; Compositae: Wedelia chinensis (Osb.) Merr., Bidens pilosa L., Tagetes erecta L., Ageratum conyzoides L., Conuza canadensis (L.) Cronq., Artemisia apiacea Hande, Xantgium sibiricum Patrin, Siegesbeckia orientalis L. ; Solanaceae: Solanum Nigrum L., Lycopersicum esculentum Mill.; Polygonaceae: Polygonum hydropiper L.; Amaranthaceae: Amaranthus viridis L.; Rutaceae: Citrus reticulata Blanco; Araceae: Alocasia macrorrhica (L.) Schott.; Meliaceae: Azadirachta indica A. Juss; Ericaceae: Rhododendron molle G. Don.; Lauraceae: Cinnamomum parthenoxylon(J.) N.; Labiaeae: Leonurus sibircus L.; Verbenaceae: Lantana camara L.; Malvaceae: Gossypium hirautum L.; Gleichiniaceae: Dicranopteris dichotoma (T.) B.; Osmundaceae: Osmunda japonica Thumb.), on major insect pests of cruciferous vegetables were studied. The experimental results of 30 reagents showed 28 deterred the egg laying of adults, 11 reduced hatchability of treated eggs, 22 and 17 decreased the survival rate of the first and second instar larva of diamondback moth evidently; 21 could antifeed the adults of the striped flea beetle respectively. The effects of semiochemicals of non-preferable plants on population control of diamondback moth and the striped flea beetle were promoted with the increase of experimental concentration. They were weakened with hours after the reagents sprayed. The experimental results of 8 reagents on mustard aphid and green peach aphid Myzus persicae (Sulzer) showed that majority possessed antifeedant and deterrent bio-activity of reproducing nymph aphid on mustard aphid, but only petroleum spray oil possessed those on green peach aphid. 6 compounds, which were extracted by n-hexane (Fr1), chloroform (Fr2), ethyl acetate (Fr3), n-butanol (Fr4-1), emulsification layer of n-butanol (Fr4-2) and alcohol (Fr5-2), possessed repellent and antifeedant bio-activity on diamondback moth in 16 separated from W. chinensis. Fr2, Fr3, Fr4-1 and Fr5-2 influenced the eggs on treated B. parachinensis, hatchability and survival rate of the 1st ~2nd instar larvae of diamondback moth evidently. Fr1 and Fr4-2 influenced their eggs on treated B. parachinensis and survival rate of the 1st ~2nd instar larvae evidently, but hatchability's was not evident. The effects of caierdi and alcohol extracts of several plants on population control of diamondback moth were promoted with the increase of experimental concentration. There was evident synergism between alcohol extract of E. robusta and W. chinensis, betweenalcohol extract of E. robusta and Lantana camara L., or among alcohol extract of E. robusta, alcohol extract of W. chinensis and caierdi. There was evident antagonism between alcohol extracts of W. chinensis and Lycopersicum esculentum. They could not be mixed. Semiochemicals of non-preferable plants used as pesticide synergist is an important field of plant protection. C. plutellae Kurdjumov, O. sokolowskii Kurdjumov and T. confusum Viggiani are 3 major parasitic wasps of diamondback moth. The emergence rate, female and male longevity and parasitization of C. plutellae, the emergence rate and parasitization of O. sokolowskii and parasitization of T. confusum were not influenced evidently by the alcohol extracts of E. robusta, E. camaldulensis, W. chinenssis, Bidens pilosa, Lycopersicum esculentum, Polygonum hydropiper and Lantana camara. 7 alcohol extracts above did not kill the adults of 3 parasitic wasps within 72 hours. The emergence rate of 3 parasitic wasps was not influenced by azadirachtin and ethyl acetate extract of Rhododendron molle flower, but female and male longevity and parasitization of C. plutellae and parasitization of O. sokolowskii were influenced evidently by both of them. Accumulative mortality of C. plutellae and T. confusum was not evidently different with control within 2~48h, but higher than control evidently at 72h; those of O. sokolowskii was not evidently different within 2~36h, but higher evidently within 48~72h. The emergence rate, parasitization and accumulative mortality of 3 parasitic wasps were all higher than control evidently treating with methanol extract of Tagetes erecta roots. The feed areas of larvae, weight of pupae and female adults and fecundity of female of diamondback moth were higher than their control evidently treating with alcohol extracts of E. robusta, E. camaldulensis, W. chinenssis, B. pilosa, Lycopersicum esculentum, P. hydropiper and Lantana camara. Development duration of diamondback moth was not influenced by all of them. The interference index of experimental population control of diamondback moth treating with 7 alcohol extracts was as follows: E. robusta, 0.0546; E. camaldulensis, 0.0879; W. chinenssis, 0.1185; B. pilosa, 0.2844; Lycopersicum esculentum, 0.1101; P. hydropiper, 0.0788 and Lantana camara, 0.2510 respectively. The interference index of natural population control of diamondback moth was 0.2824, 0.4499, 0.5662 and 0.2020 respectively treating with alcohol extracts of E. robusta, W. chinenssis, Lantana camara and mixture of three above. In the natural population life table of diamondback moth, the major stages causing the decrease of interference index of population were egg, the first instar larva and adult period; the major factors were oviposition repellence, hatchability, death of neonate and probability of arriving standard egg numbers.Semiochemicals of poisonous plants are studied extensively in China or abroad at present. It has not been paid attention to enough as yet that practical research of semiochemicals of non-preferable plants with evident repellent and antifeedant bioactivity in ecological pest control. Compounds with repellent bioactivity are very important in pest control. The sequence of "toxicity→antifeedance→repellence"should be changed as "repellence →antifeedance →toxicity". New indices of studying plant protectant ought to be established by taking repellent and antifeedant bioactivity as the first and toxicity as the second. The plant protectant must be supplemented to chemical pest control. This research suggested a new way for overcoming "3R"problems and exerted a great influence in pest population control.