Chi Defu

Pesticidal character of phytoecdysteroids fromAjuga multiflora Bunge (Labiatae) on larvae ofCryptorrhynchus lapathi L. (Coleoptera: Curculionidae)

Eight kinds of phytoecdysteroids extracted from different parts ofAjuga multiflora Bunge (Labiatae) that were collected from different places at different time were tested for killing effects on the 2-instar larvae ofCryptorrhynchus lapathi L by adding them to the artificial diet of larvae. The experimental results indicated that adding 1–3-mL phytoecdysteroids to the artificial diet could lead 58%–100% of 2-instar larvae ofC. lapathi to death within 24 days. The phytoecdysteroids extracted from the whole plant ofA. multiflora which was collected before flowering time were much more effective than those extracted from the plants collected at flowering and after flowering periods, and the modified mortality rate of larvae reached 65.22%, 85.07%, and 98.11% at the dosage level of 1-mL, 2-ml, and 3-mL extracts, respectively. The extract made from root ofA. multiflora plant was more effective in killing efficiency than those from stem and leaves, and the average death rates of larvae were up to 100%, 98.20% and 98.32% at dosage levels of 1-mL, 2-mL, and 3-mL extracts, respectively. The killing speed of the extracted phytoecdysteroids was slower than that of triflumuron, hexaflumuron or deltamethrin emulsifiable concentrate. The mortality rate of larvae is closely related to the feeding duration on the diets containing phytoecdysteroids. Feeding on the diets with addition of phytoecdysteroids for 16 days, more than 80% of treated 2-instar larvae ofC. lapathi were led to death. The killing effect of the extracts was little affected by the growth areas ofA. multiflora plant and the adding way to artificial diet.

Control ability of extrats fromAjuga plants on some pests

Several phytoecdysteroids have been found in the extracts ofA. multiflora andAlinerifolia using HPLC analysis. Those were 20-OH ecdysone, cyasterone. 3-acetate-20-OH ecdysone. 2-acetate-20-OH edysone, ajugalactone. We found out that those phytoecdy steroids could lead the second instar larva ofClostera anastomosis andStilpnotia candida to death. The modified mortality rate was from 44.64% to 96.24%. Those extracts could significantly reduce the amount of nymph produced by the femaleTuberolachnus salignus. The number of the nymph produced after treating with those extracts was only 20% to 70% of that produced by the untreated group. The death rate of the newly produced nymph which treated was among 33.33% to 58.82%. It was much higher than the death rate of the control group (17.57%).

Foraging behavior of parasitoid chalcid to the essential oil from bark ofPopulus pseudo-simonii×P. nigra andQuadraspidiotus gigas

Four-armed airflow olfactometer was used to determining the foraging behavior ofPteroptrix longgiclava (Girault) (Hymenoptera: Aphelinidae) andEncarsia gigas (Tshumakova) (Hymenoptera: Aphelinidae) to the essential oils which emitted from the healthy bark ofPopulus pseudo-simonii×P. nigra, the infested bark injured byQuadraspidiotus gigas (Thiem & Gerneck), the body and scale of fixed 1st-instar-nymph ofQ. gigas. The results from these experiments showed that the volatile oils produced from the injured bark and from the scale of fixed 1st-instar-nymph had a higher attractive ability to female adults of the two species of wasps. The essential oil produced from the scale of the pest at dosages of 3–7 μL and the essential oil emitted by injured bark at dosages of 5–9 μL had a stronger alluring effect on the host searching behavior ofPteroptrix longgiclava. The essential oil from the body of fixed 1st-instar-nymph ofQ. gigas also had certain effect on the host locating effort ofPteroptrix longgiclava andEncarsia gigas. Those two wasps did not shown any reaction to the essential oil produced by the healthy bark of poplar.