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Within the framework of finding new biological control methods to suppress allergic effects of pine processionary moth (PPM), Thaumetopoea wilkinsoni Tams, less toxic and environmentally friendly, entomopathogenic fungi and essential oils are considered to be an alternative to chemical insecticides. The aim of the present study was to investigate the effects of essential plant oils and two isolates of Metarhizium brunneum (V275 and ARSEF4556) on PPM larvae and pupae under field and controlled laboratory conditions. PPM larvae inside the nest and late instar larvae preparing to pupate were highly susceptible to both strains of M. brunneum, which caused 100% mortality in the laboratory and 45–100% mortality in field trials. The insecticidal effects of essential oils (ginger, eucalyptus and rosemary) on the first, third and fourth instar larvae of PPM were proportional to dosage and life stage of insect. Ginger oil diluted in water was toxic to first instar larvae even at a dose as low as 1% and 3% (v/v). Field trials showed that injection of essential oils into nests of third instar larvae caused significant mortality (87.4%) but <5% mortality of fourth instar larvae. Surface application of all essential oils at a concentration of 5% killed half of the larvae in one day, while 1% concentration caused from 0% to 20% mortality. Only 1% ginger caused 63% mortality at the end of the trial. This study shows that ginger oil and M. brunneum strains ARSEF 4556 and V275 show promise for the control of PPM larvae under field conditions. [ABSTRACT FROM AUTHOR]