Fumigant Toxicity of four Essential Oils Against Two Major Stored Date Fruit Insects and Microbial Load

Abstract

Dates are among the most important fruits with high nutritional value. These fruits are exposed to many pests that reduce their market value which include Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae), Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), in addition to a microbial load. This work aimed to investigate the effect of four crude essential oil fumigants: lavender (Lavandula officinalis), orange (Citrus sinensis), marjoram (Majorana hortensis), and eucalyptus (Eucalyptus citratus), as a safe alternative to manage these pests. Five concentrations of each oil (62.5 to 1000 mg/l of air) were evaluated at 3, 5, and 7 days after treatment. Results obtained indicated that the fumigant toxicity increased with the increase of oils concentration and exposure time. L. officinalis essential oil had the highest toxic effect against the 4^th larval stage of P. interpunctella and the O. surinamensis adults followed by C. sinensis which was much more toxic as fumigant than M. hortensis oil, whereas E. citratus oil was the least effective on the two tested insects. Results obtained also indicated clearly that Surinam adults were more tolerant to the four tested essential oils than the P. interpunctella larvae. The four tested essential oils had high antibacterial and antifungal activity in the treated stored date fruits. This work clearly confirmed that lavender, orange, marjoram and eucalyptus oils can be used to protect stored date fruits due to their ability to control P. interpunctella and O. surinamensis insects as well as their ability to act as antibacterial and antifungal agents on stored date fruits.

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Keywords:

Phoenix dactylifera, essential oils, Plodia interpunctella, Oryzaephilus surinamensis, date fruits, microbial load.