The twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), is one of the most important and highly polyphagous pests of vegetables and other crops worldwide. Experiments were conducted in the laboratory and greenhouse to evaluate corn (Zea mays L.) as a banker plant for the predatory gall midge, Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) to potentially control T. urticae. Choice and no-choice experiments were carried out to determine the host plant preference of an alternative prey, Oligonychus pratensis (Banks)(Acari: Tetranychidae) to corn and green bean (Phaseolus vulgaris L.). Results showed that O. pratensis adults strongly preferred corn as a host plant and posed no risk to green bean. F. acarisuga was found to fly at least 7.0 m to search for new preys on green bean plants, and over 176 F. acarisuga larvae per leaf were recorded at 14 d after dispersal. F. acarisuga proved to be an excellent predator of both T. urticae and O. pratensis. The predation by F. acarisuga to T. urticae and O. pratensis ranged from 43.7 to 67.9% and 59.2 to 90.3%, respectively, under laboratory conditions. In a non-cage study, 81.2% of T. urticae population was suppressed by F. acarisuga in reference to the control (cage treatment). The results showed that this banker plant system has potential for controlling T. urticae in greenhouse vegetable production. 相似文献
Medicago archiducis-nicolai Sirjaev and M. ruthenica (L.) Ledebour are two phylogenetically closely related species in the section Platycarpae within Medicago. M. archiducis-nicolai is endemic to the Qinghai–Tibetan Plateau (QTP), shows more tolerance to abiotic stress than M. ruthenica, which inhabits relatively temperate areas, and has the potential to be domesticated and used as a legume forage germplasm in alpine meadows. Here, we analyzed the population genetic structure and genetic diversity of these species using 20 putatively neutral EST-SSR markers. Twenty-four wild populations, including 21 M. archiducis-nicolai and 3 M. ruthenica, were divided into two clusters that were consistent with current taxonomy. The 21 M. archiducis-nicolai populations were clustered into two geographically related groups. Positive relationships between population genetic distance and geographical factors, including geographical distance and altitudinal difference, revealed that the genetic differentiation of M. archiducis-nicolai populations was driven by both geographical distance and the complex topography of the QTP. Medicago archiducis-nocilai, a narrow-range endemic on the QTP, had lower genetic diversity than the more widespread M. ruthenica. Medicago archiducis-nicolai populations from the central platform of the QTP had relatively high genetic diversity, whereas those occupying the east platform and edge of the QTP showed variable levels of genetic diversity, implying the presence of refugia on the central platform. These results have implications for the genetic resource management and exploitation of M. archiducis-nicolai and provide novel insights into the mechanisms underlying the adaptation of this species to the harsh environment of the QTP.