The Control Efficiency of Plant Alcohol Extracts on the Laboratory Populations of Myzus persicae(Sulzer)and Lipaphis erysimi (Kaltenbach)

The effects of semiochemicals extracted from 63 species of plants, on peach aphid (Myzus per-sicae) and mustard aphid (Lipaphis erysimi), were studied in laboratory. The deterrent rate, reproduction deterrent index and the interferential index of population control (IIPC) was used to evaluate the efficiency of semiochemicals on population control of the two target aphids. The results showed that the extracts of 34 species of common plants have noticeable effect on both aphid populations, especially, Xanthium sibiricum Petr. Et Widd. and Syngonium podophyllum Schott. These plant extracts could be used to construct the plant pro-tectant to protect crops.

Contact Activities of 20 Plant Extracts against Lipaphis erysimi Kaltenbach

[Objective] The aim was to screen out plants which had strong contact activity against Lipaphis erysimi Kaltenbach. [Method] Twenty plant species which were collected from Gupo Mountain in Hezhou of China were extracted with methanol by cold soaking method. Contact activities of 20 methanol plant extracts against L. erysimi were determined by capillary micro spot method. [Result] The methanol extracts from Mussaenda esquirolli Levi. and Folium trematis Orientalis had the highest contact activities against L. erysimi at the dose of 10 p^g/head, and their 24 h corrected mortality rates were 92.22% and 92.15%, respectively; followed by Folium trematis and Viola hossei, with 24 h corrected mortality rate of 87.59% and 82.95%, respectively. The methanol extract of Hedyotis lancea had medium activity, with 24 h corrected mortality rate of 65.52%. Methanol extracts of the other plants had low contact activities against L. erysimi, with the corrected mortality rate lower than 50%. The methanol extracts of M. esquiroUi, F. variolosa and F. trematis had high contact toxicity, with LDS0 of 0. 768 6, 0.784 1 and 1. 504 4 μg/head, respectively. [ Conclusion] M. esquirolli, F. variolosa and F. trematis show exploitation potential, and they are worth further studying.

Positive correlation of methamidophos resistance between Lipaphis erysimi and Diaeretilla rapae and effects of methamidophos ingested by host insect on the parasitoid

Temporal and spatial correlated variations on the methamidophos resistance and biomolecular rate constant of acetylcholinesterase to insecticides were found between the turnip aphid, Lipaphis erysimi and its endoparasitoid, Diaeretilla rapae, collected from field colonies and an insecticide-free field insectarium in Fujian, China. Compared to the related susceptible insectarium population, L. erysimi and D. rapae displayed 7.4-29.2- and 2.6- 9.2-fold resistance ratios, respectively. In addition, two populations ofL. erysimi with different methamidophos resistance levels, that is, a field （with 5.8-fold resistance ratio） and an insectarium population, were used to study the effects of methamidophos ingested by the host insect on D. rapae development. The percentage of D. rapae cocoon formation decreased significantly when the parasitized L. erysimi were fed on cauliflower leaves treated with methamidophos at lethal concentration dosages 10 （LC50） or LC520. At LC50 dosages the percentage of D. rapae cocoon formation and adult emergence decreased significantly. When the parasitized L. erysimi were fed on methamidophos at LC50 dosage, no D. rapae cocoons were found. When the field or insectarium L. erysimi were treated with methamidophos at LC50, the susceptibility to methamidophos in the adult D. rapae emerged from the treated host insect was similar to the control. However, the susceptibility to methamidophos in the adult D. rapae became lower than the control when the host insects were treated at LC50 dosages. The data thus suggested that the methamidophos ingested by the host insect L. erysimi could be an important factor in the endoparasitoids＇ insecticide resistance development. The natural selectivity would favor the parasitoids that had developed an insensitivity to the insecticide（s）.

Effect of SO_2－polluted rape plant on growth and reproduction of the turnip aphid，Lipaphis erysimi（Kaltenbach）

A series of experiments using open-top fumigation chambers was carried out to investi gate the effect of SO2-polluted rape on performance of the turnip aphid, Lipaphis erysimi(Kaltenbach).Proper SO2 concentrations significantly enhances growth and reproduction of the aphid. Nymph MRGR and adult fecundity reached their maxima at 116 nl/L and 80 nl/L of the pollutant, respectively. Potential of the population growth got fully displayed at the latter dose because the highest survival rate of the nymphs also took place at this concentration.It is suggested according to changes in the plant chemistry that this indirect effect of SO2 pollution on the turnip aphid might involve variation in content of individual key free amino acid rather than total amount of all the amino acids in the leaves induced by the air pollutant.

Olfactory responses of Aphidius gifuensis to odors of host plants and aphid-plant complexes

The olfactory responses ofAphidius gifuensis to odors from two host plants （Nicotiana tabacum and Brassica napus ssp.） and their complexes with different infestation levels of two host aphids （Myzuspersicae and Lipaphis erysimi） were respectively examined in an olfactometer. The results showed that female A. gifuensis did not respond to odors of undamaged or mechanically damaged host plants, but significantly responded to odors of aphid/plant complexes. Moreover, A. gifuensis responded significantly to odors of both M. persicae and L. erysimi/plant complexes when host plants were infested by high levels of aphids, suggesting that quantity of aphid-induced volatiles could be important for attracting A. gifuensis. When tested between aphid/plant complexes, .4. gifuensis did not show its preference for either complex. The efficiency of.4. gifuensis against aphids in open fields potentially could be improved by using its olfactory response to aphid/plant complexes.