Abstract

MATHULWE, LL; MALAN, AP  and  STOKWE, NF. The occurrence of entomopathogenic fungi in apple orchards and their biocontrol potential against Eriosoma lanigerum. AE [online]. 2023, vol.31, pp.1-9. ISSN 2224-8854.  http://dx.doi.org/10.17159/2254-8854/2023/a13728.

Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae), woolly apple aphid (WAA) is an important pest on apples globally and a key pest of apple production in South Africa. The aphid has developed some level of resistance against several chemical insecticides. Entomopathogenic fungi (EPF) have been identified as promising biological control agents against a wide array of insect pests. The main aim of this study was to conduct a survey in local apple orchards in the Western Cape province for EPF and to use isolates to test the susceptibility of WAA under optimum laboratory conditions. Soil samples were collected from apple orchards and baited using larvae of Galleria mellonella and Tenebrio molitor to isolate EPF. Six EPF species: Beauveria bassiana, Cordyceps fumosorosea, Metarhizium brunneum, M. pinghaense, M. robertsii and Purpureocillium lilacinum were identified from the soil samples. The results from bioassays showed that Metarhizium robertsii and M. pinghaense isolates were the most effective with an average percentage mortality of > 90%. Metarhizium brunneum also proved to be effective when used against the insect with an average percentage mortality of > 80%, while B. bassiana and C. fumosorosea were the least effective with average percentage mortality of 52% and 48%, respectively. The lethal time required to kill 50% and 90% of the colony at a concentration of 107 conidia/ml over five days, LT50 and LT90, of M. robertsii (2.12 and 4.19 days, respectively) and M. pinghaense (2.05 and 4.45 days, respectively) showed to require similar mortality time in days of E. lanigerum. The results obtained in the study have provided an insight into the diversity of EPF species across apple orchards of the Western Cape and shown the efficacy of the Metarhizium isolates as potential biological control agents of the E. lanigerum.

Keywords : biological control; Metarhizium; pathogenicity; Beauveria; woolly apple aphid.

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