Abstract
The rose aphid, Macrosiphum rosae L. (Hemiptera: Aphididae), is an important insect pest of rose plants because it damages the leaves and flowers. The entomopathogenic fungus, Beauveria bassiana Balsamo (Vuillemin), is environmentally safe in comparison with the chemical pesticides. The indigenous fungal isolates can be the best options in biological control because they are more adapted to the local environment. In the present study, four genetically different isolates of B. bassiana (isolates 1, 2, 3, and 4) were used to estimate LC50 for the rose aphid. Also, the same isolates were used to control the aphid’s infestation on rose plants in the field, and the efficacy was compared with a commercial strain (Naturalis®) with two concentrations for each isolate (2.3 × 106 and 4.6 × 106 conidia/ml). Bioassay results indicated that isolate 1 differed significantly (LC50 = 6.46 × 104) than the other three ones (LC50 = 1.46 × 105, 1.52 × 105, and 1.71 × 105). In field trials, the concentration of 4.6 × 106 conidia/ml, for indigenous as well as commercial strains, achieved the highest reductions of rose aphid infestation and the highest extraction of rose oil. Thus, this fungus can be recommended in organic rose production. Further investigations are needed for the improvement in utilization of these isolates with regard to UV radiations in the field.
Highlights
Rose plant, Rosa damascena trigintipetala Mill., is cultivated in Taif, Saudi Arabia, where a special local variety called Taify rose is well known for its oil contents and its suitability for growth under local climate
The differences in intercepts, slopes, and χ2 were insignificant (F = 0.088, 0.149, and 1.734, P = 0.965, 0.929, and 0.200, respectively). This result is in correspondence with previous findings of many studies such as of Selvaraj et al (2012) who found that the LC50 value of B. bassiana was 1.5 × 104 spores/ml to coriander aphid, Hyadaphis coriandri
Liu et al (1999) reported that LC50 values for six isolates of B. bassiana against M. persicae ranged from 1.2 × 104 to 1.55 × 106 spores/ml
Summary
Rosa damascena trigintipetala Mill., is cultivated in Taif, Saudi Arabia, where a special local variety called Taify rose is well known for its oil contents and its suitability for growth under local climate. Rose plants are infested by many insect pests especially rose aphids, thrips, whiteflies, and some lepidopteran larvae. These insect pests cause high damages to rose plants especially to buds, leaves, and flowers. The rose yields are reduced by infestations with these insect pests (Karlik and Tjosvold 2003). Entomopathogenic fungus (EPF), Beauveria bassiana Balsamo (Vuillemin), can be one of the best bio-control agents of the rose aphid. There is an increasing interest in utilization and mass propagation of EPF for controlling insect pests (Inglis et al 2001).
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