The rose sawfly, Arge rosae L. (Hymenoptera: Argidae), is one of the most destructive pests of roses grown both indoors and outdoors in Antalya province (south-western part of Turkey). Especially in greenhouse rose cultivation, growers depend heavily on synthetic pesticides to control this pest along with other arthropod pests in their crops. The aim of this study was to evaluate biocontrol potential of some indigenous soil-borne entomopathogenic fungi (EPF) against the pest. In pathogenicity assays, a total of 17 EPF isolates, belonging to three species [Beauveria bassiana (Bals.) Vuill. -14, Clonostachys rosea (Link) Schroers -2 and Isaria farinosa (Holmsk.) Fr. -1] were tested against the 4 th instar larvae of A. rosae under laboratory conditions. All the isolates were applied at a conidial suspension of 1 × 10 7 conidia/ml, using the spray method. The results from the assays showed that bioefficacy of tested isolates increased significantly with elapsed time up to 9 days after inoculation. Of the 17 isolates tested, 5 isolates of B. bassiana (BbDm-1, BbKp-1, BbMp-1, BbSr-1 and BbMg-2) and 1 isolate of I. farinosa (IfGp-1) appeared to be most promising, causing mortalities between 76.7 and 86.7% 3 days post treatment. Probit analysis of mortality data showed that there were significant differences in the susceptibility of 4 th instar larvae of A. rosae to tested EPF isolates. The above-mentioned six isolates had the lowest LT50 and LT95 values (ranged from 1.66 to 7.50 and 4.81 to 8.49 days, respectively), implying their high virulence and their biocontrol potential against the pest. Phylogenetic analysis based on the ITS region sequence revealed that all tested isolates showed high similarities (ranged from 99 to 100%) with other isolates of their respective fungal species in GenBank.Overall results suggested that the most virulent above-mentioned six isolates had significant potential as biological control agents against A. rosae.
Background
The Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae) is one of the most damaging pests of potatoes all over the world as well as in Turkey. Both adults and larvae of this pest feed on the foliage of potatoes, and often cause complete defoliation of potato plants, with considerable yield losses of up to 60%. Chemical control of this pest has induced the selection of resistant CPB populations and negative environmental impact. The aim of the present study was to evaluate the pathogenicity of 14 Turkish isolates of Beauveria bassiana (Balsamo) Vuillemin (Deuteromycota: Hyphomycetes) against different stages of CPB under laboratory conditions.
Results
All isolates were tested as conidial suspensions of (1 × 107 conidia/ml), using spray method. The results from pathogenicity assays showed that virulence of tested isolates was variable, and mortality increased with the time of exposure. The highest mortality was seen in larvae of CPB; however, young larvae (1st and 2nd instars) were more susceptible to fungal isolates than older ones (3rd and 4th instars). Four isolates (BbDm-1, BbDs-2, BbMg-2, and BbMp-1) were more pathogenic than others against L. decemlineata, causing mortalities between 96.7 and 100% in the 2 youngest larval instars, respectively, between 91.7 and 96.7% in the 2 oldest larval instars, respectively, and between 93.3 and 96.7% in 0–48-h-old adults, respectively, 9 days post treatment. Furthermore, these 4 isolates had the most potent egg-hatching inhibitory effects (66.7–90%). The results of molecular phylogenetic analyses based on the ITS region sequence indicated that all tested B. bassiana isolates showed a high similarity (99%) with other B. bassiana isolates in GenBank.
Conclusions
Results suggested that the 4 B. bassiana isolates were highly virulence and had the potential for biological control of CPB. Further tests under field conditions are recommended to validate the laboratory results.
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