Preliminary Study On Green Control For Snail In Production Of Dendrobium Officinale

Snail,a soft-bodied and omnivorous terrestrial mollusca,has been found all over the world.Also,it is a kind of agricultural pest which widely distributed in provinces of China with intermittent occurrence,particularly,the harms of snails are even more serious in the regions where it is warm,humid and rainy.Dendrobium officinale Kimura et Migo,a perennial epiphytic herb of Dendrobium species,is a traditional valuable Chinese herbal medicine,and it prefers warm and humid climate and partial shade condition which is similar to snail.Thus,places planted D.officinale are easier to be the activity and breeding sites of snails,and improper control on D.officinale may cause significant losses.What’s more,snail is difficult to control because of it’s hidden activities and the hard shell which are different from the general pest.And as a edible and medicinal herb,chemical pesticides are not suitable for D.officinale.Therefore,from the perspective of green control,this article does a preliminary study on prevention and control measures for snails on D.-officinale by indoor and field experiments,the results are as follows:1 The experiments of snail-dipping and snail-dipping coupled with leaf-dipping showed that,83.5%tea saponin had a good control efficacy to Bradybaena ravida B-enson.And at 96h,the control effect reached over 80%after treating snail with 12 g/L of 83.5%tea saponin in the two experiments mentioned above,while the contro-1 effect reached 96.67%when the concentration of 83.5%tea saponin was 13.5g/L in experiments of snail-dipping coupled with leaf-dipping;And the results of plant-spraying suggested that the feeding amount of control group was significantly higher than that of treatment group by snails.When plants were sprayed only,B.ravida was less likely to contact with tea saponin,which caused a lower mortality rate(3.33%～16.67%),but a very high antifeedant rate(96.36%～99.59%)was showed.For these reasons,tea saponin had an excellent protective function to plants.2 Experiment of applying Camellia oleifera seed cake on D.officinale demonstrated that different concentrations(600g/m2、300g/m2、150g/m2 and 75g/m2)of seed cake presented clear repellent effects to snails.And the penetrating rates of snails in D.officinale plots were both lower than 10%under two concentrations(600g/m2 and 300g/m2)at 3d after treatment.So seed cake of 600g/m2 and 300g/m2 showed the highest repellent effect to snails.3 Chinese cabbage trap crops had significant prevention and control effects when respectively putting snails outside or inside D.officinale plots.That is,Chinese cabbage could not only prevent snails outside from invading D.officinale plots,but also trap snails inside effectively.YWhile at 72h after treatment,snails inside D.officinale plots were all bellow 10%.4 The indoor experiment showed that 83.5%tea saponin had an excellent control effect to Microcystis hainanica,and the control effect reached 83.3%when treating M.-hainanica with 7g/L of tea saponin at 24h,and it was 86.7%at 96h.In addition,the field experiment indicated that 83.5%tea saponin and C.oleifera seed cake controled snails well.And the control effect in the field under all the concentrations of tea saponin was better than that of 80%Metaldehyde WP.,while the snail decrease rate and control effect were better than that of 6%Metaldehyde GR.and control group under 300g/m2 and 150g/m2 of C.oleifera seed cake,and when the concentration was 300g/m2,the snail decrease rate and control effect were both above 90%,which proved that seed cake was good in controlling snails.Thus,83.5%tea saponin and C.oleifera seed cake could be used in field for the substitution of molluscicide.5 To evaluate the safety of 83.5%tea saponin and Camellia oleifera seed cake to D.officinale with growth rate of bud number and average bud length,the number and length of D.officinale buds had been measured in the field experiment.Under the field experiment,it was found that slug and earthworm were dead in D.officinale cultivation area when 600 g/m2,300 g/m2 and 150 g/m2 seed cake were applied.And there was no difference in growth vigor between the treatment and control group,besides,all plants of D.-officinale grew well without any phytotoxicity.In conclusion,83.5%tea saponin and Camellia oleifera seed cake were safe to D.officinale.