Abstract
The rose aphid, Macrosiphum rosae (L.) causes a high damage for rose plants. In the present study, efficacy of the native Saudi Arabian and widely distributed coccinellid species; Hippodamia varigata (Goeze) and Coccinella undecimpunctata L. were evaluated for suppressing M rosae on Taif rose plants. The experiment was carried out in a rose farm at Alhada, Taif Governorate (Saudi Arabia) using a Randomized Complete Block Design. Three release rates; (10, 20 and 30 of 2nd instar larvae/ plant) were conducted weekly for 6 weeks for each of the coccinellid species. Results showed that the aphid population reduction (%) varied and significantly was influenced by the release rate of both predators and the counting date, whether on leaves or on flower buds. The release rate of 30 larvae of H. variegata achieved about (87 and 83%) aphid reduction on leaves and flower buds, respectively, 2 weeks post the 1st release, while they reached more than (95%) after 3 releases. Moreover, this value was' achieved after 4 releases on leaves at the release rates of: 20 larvae of H. variegata or 30 larvae of C. undecimpunctata, while it was detected with these release rates for both species after 5 releases on flower buds. It could be concluded that the release of 20 larvae of H variegata for 3 weeks can be effective for suppressing the population of M rosae on rose plants during flowering stage and can be recommended in organic production of rose.