Susceptibility of rose (Rosa spp.) to infestation by the pubescent rose chafer, Tropinota squalida (Scop.) and its relationship with rose cultivars and climatic changes in Southern Egypt.

摘要

The present work aimed to study susceptibility of rose (Rose spp.), an economically important ornamental and aromatic plant, to infestation by the pubescent rose chafer, Tropinota squalida (Scop.) causing a great damage in flowers yield and its relationship with climatic changes and rose cultivars. Two experiments were carried out in Agricultural Experimental Farm of Sohag University, Egypt during 2007 and 2008 years. The first experiment was conducted to study the seasonal abundance of T. squalida on the hybrid tea rose cultivar "Eiffel tower" and its relationship with weather factors. The second one was to investigate the susceptibility of five rose cultivars different in flower color and fragrance (pink and very fragrant, pink blend and fragrant and three cultivars of yellow, orange and red color and little fragrant) to infestation by T. squalida and its relationship with rose cultivars. Weakly observations of captured beetles showed that T. squalida have three field generations on rose starting from January to April for both tested years. The first peak of activity occurred during January while the second occurred during February and the third occurred during March. It was found that minimum temperature and relative humidity are the most important weather factors affecting population density of T. squalida. Rose cultivars significantly differed in their susceptibility to T. squalida infestation. The rose cultivar Eiffel tower of pink and very fragrant flowers was the most sensitive one followed by the pink blend and fragrant cultivar with infestation percentage of 63-73% and 51-59% respectively for both years. These two cultivars also showed the highest beetles number, 48-51 and 19-26 adults per 5 flowers. The highest infestation percentage and beetles number was recorded in February followed by March for all studied cultivars in both tested years. Perfect positive correlations of 0.92 to 0.99 were found between essential oil content and infestation by T. squalida which gave an explanation to rose susceptibility. The obtained results could be useful in prediction of susceptibility of rose cultivars and control of T. squalida using traps containing drops of rose essential oil to avoid use of insecticides and save environment.