Essential oils from botanical extracts used for insect pest control should be both effective and have low impact on natural enemies. The objective was to evaluate the effects of ten essential oils on the biological and reproductive parameters in two Trichogramma galloi Zucchi (Hymenoptera: Trichogrammatidae) generations. The emergence F 1 generation of T. galloi was reduced by more than 30% with Allium sativum, Carapa guianensis, Citrus sinensis, Neem and Syzygium aromaticum. Zingiber officinale reduced the T. galloi emergence of the F 1 and F 2 generations by between 30 and 99%. The longevity of the F 1 generation was reduced by more than 50% with Z. officinale at the pre-pupae and pupae stages. All oils reduced the parasitism rate of the F 1 generation in the egg-larva and pre-pupa stages. Allium sativum, C. guianensis and C. sinensis, Neem and Origanum vulgare reduced parasitism by between 30 and 79%. Zingiber officinale was slightly and moderately harmful to the F 1 and F 2 generations, respectively, for the T. galloi parasitism. The sex ratio of the two T. galloi generations was not affected by the essential oils. The low side effects of the oils on the F 2 generation, except for Z. officinale (the most harmful oil), suggest that T. galloi developed some post-transgenerational tolerance/resistance mechanisms to these oils and/or their components. The A. sativum, C. guianensis, C. sinensis, Neem, O. vulgare, S. aromaticum and Z. officinale oils were not selective for T. galloi. Mentha piperita, Piper nigrum and Thymus vulgaris essential oils can be included in integrated pest management programs for this parasitoid.

The use of chemical insecticides and non-selective natural products authorized for use in organic farming may reduce the effectiveness of egg parasitoids. The side-effects of ten plant essential oils on immature stages of Trichogramma pretiosum were evaluated. Carapa guianensis, Origanum vulgare and Zingiber officinalle during the F generation, and Azadirachtin and Mentha piperita in the F generation were slightly harmful (class II: 30-79%) to the emergence of this parasitoid. All essential oils affected the longevity of females of the F and F generations. Thymus vulgaris and Z. officinalle were the oils most harmful to female longevity. Carapa guianensis proved slightly harmful (class II: 30-79%) to parasitism in the F generation when applied during the egg-larval and pre-pupal stages and O. vulgare in the F generation in the pre-pupal stage alone, of this parasitoid. The sex ratio was lower than 0.5 during the pre-pupal stage of the F generation with Azadirachtin, C. guianensis, O. vulgare, Piper nigrum and Syzigium aromaticum, but this parameter was not affected for the other biological stages of T. pretiosum in the F and F generations. The Azadirachtin, C. guianensis, M. piperita, O. vulgare, T. vulgaris and Z. officinalle oils revealed a mild toxic effect to the immature stages of T. pretiosum and, therefore, it should be used according to patterns of ecological selectivity. Allium sativum and Citrus sinensis essential oils were not harmful to T. pretiosum, and can be used in Integrated Pest Management.

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