Studies On Screening Of Plant Attractive Toxicants To Reticulitermes Angustatus (Isoptera: Rhinotermitidae)

Termites belong to Insecta, Isoptera, Blattaria, which is an important pest group of agronomic, construction and furniture, plantations and forestry. In order to designate effective plant origin termiticide, toxic effects of the medicinal parts of the common Chinese herbs on Reticulitermes angustatus were studied and compared with that of chemical termiticide. Furtherly, to make plant origin termiticide preparations that may be the most suitable practically for the termite control, screening of bait for the termiticide preparations was also carried out with four plant materials. The main results are summarized as follows:1. The selection of bait-foodThe four pure plant materials, corn cob powder, fir wood powder, pine powder,waxberry wood powder, were tested in order to select the bait preferred by the termites. The mixed baits of the four pure ones with sugar, Auricularia aurcula, and millet powder as additives were tested respectively to determine preference of the termites. In four pure baits, feeding rate and amount of the corn cob powder were the highest at 15 d; the soil-cover on corn cob powder was relatively larger though there was no significant difference among the four pure baits. Comparing the pure and mixed baits, the one of corn cob powder with 20% sugar showed the best attraction for R. angustatus. It is therefore suggested that the corn cob powder is the best food bait with strong attraction for R. angustatus.2. The toxic effect of the common Chinese herbal medicine to R. angustatusIn the tested 16 kinds of common Chinese herbs, although most of them were weak in toxic effect to R. angustatus, the three, Rhododendron molle, Macleaya cordata and Pyrethrum cinerariifolium showed effective toxicity. The toxicity test with different mass fraction of the three herbs indicated that the toxicity of the herbs to the termites was increased with the increasing of the mass fraction. In these three kinds of Chinese herbs, the Pyrethrum cinerariifolium was distinctly more efficient than other two in both the corrected mortalities of the termite workers and LT50, at 7 d after treatment.3. Transfering of the Chinese herbs within population of R. angustatusThe results of the test on transfering of the three selected Chinese herbs within the population of R. angustatus showed a tendency that with the increase in the individual number of the initial poisoned termites, as time passed, mortality of the secondary poisoned termites increased and LT50 shortened. This indicated that the toxic transmission efficiency was positively proportional to the initial poisoned termite number and the secondary poisoning times. The toxicity of P. cinerariifolium was the most transmissible.4. Repellence the Chinese herbs to R. angustatusThe repellent test showed that the termites had certain aversion to the three selected herbs. The repellent effects of M. cordata to the termites was relatively weak and that of R. molle was strongest. In addition, the mortality rates of R. angustatus in the process of the repellent experiment also proved that the three kinds of Chinese herbal medicine have poison effect on R. angustatus.5. Toxic effect comparison of the Chinese herbs and Tianying termiticidal emulsionThe toxic effect of Tianying termiticidal emulsion to the termites test was propotional to concentration. 50μg/ml-2000μg/ml Tianying achived obvious termiticidal efficacy at 0 h and 36 h after treatment. LC50 of Tianying to termites at 12 h, 24 h, 36 and 48 h were 577.993μg/ml、38.249μg/ml、31.232μg/ml、28.1μg/m, respectively. The repellent test showed that Tianying had obvious repellent effect against R. angustatus. The transferred toxic effect of 50μg/ml Tianying was much better.Comparing with the Chinese herbs, the lethal effect of Tianying on R. angustatus were faster and better than the herbs. The toxic transmission efficiency of Tianying,having strong repellent effect, was limited with its concentration, but it could be used as contact termiticide to kill termites rapidly for reducing termite damage. The lethal effect of the Chinese herbs on the termites was a little less and acted relatively slower.Moreover, the toxic transmission efficiency of the herbs become better with the increase of mass fraction. These were promoted as advantages of the herbs to be used for making the bait termiticide, plant bait, which could be used for long-term prevention and control of the termites.6. Preparation of Plant Bait for termatesAntiseptic effects of three kinds of mould inhibitors on the corn cob powder with 20%sugar, the preferred diet of R. angustatus, were compared. Potassium sorbate was the best mould inhibitor that there was hardly mildew stain in the powder with 0.2% and0.4% of the nhibitor at 15 d after treatment. These amounts of potassium sorbate had no significant affect on R. angustatus. The effect tests proved that the applicable and effective plant bait could prepared with 25% pyrethrum mass fraction and the mixture of corn cob powder, 20% sugar and 0.2%-0.4% Potassium sorbate. Based on the studies above, a formula for making pyrethrum bait was proposed as: pyrethrum :corn cob powder : white granulated sugar≈5 : 11 : 4,with potassium sorbate 0.2% of the totle.