Insecticidal Effects and Chemical Composition of Lemongrass and Peppermint Essential Oils Against the Coconut Mealybug, Nipaecoccus nipae (Maskell), (Hemiptera: Pseudococcidae)

Document Type : Original Article

Authors

1 Economic Entolomgy and Pesticide Department, Faculty of Agriculture, Cairo University, Giza, Egypt.

2 Plant Protection Research Institute, Agricultural Research Centre, Dokki, Giza, Egypt

3 Plant Protection Research Institute, Agricultural Research Centre, Dokki, Giza, Egypt.

Abstract

Plant essential oils have been found to exhibit pesticidal activity against many insects including mealybugs. The present study was conducted to evaluate the efficiency of different concentrations of two essential oils namely, lemon grass (Cymbopogon citratus (DC. Stapf.)) (Poales: Poaceae), and peppermint (Mentha piperita L.) (Mentha: Lamiaceae) on the populations of nymphs and adults of the mealybug Nipaecoccus nipae (Hemiptera: Pseudococcidae) under laboratory conditions after 24, 48 and 72 hrs. Additionally, analyzes and determines the chemical constituents of the two essential oils using GC-MS analysis. The results showed that the essential oils of lemongrass and peppermint recorded highly toxic effects against N. nipae after 72hrs.with lethal concentrations LC50 values at 5.69 and 4.95 ppm for nymph populations, respectively. In the case of N. nipae adults, the LC50 values were 6.45 and 2.99 ppm for lemongrass and peppermint essential oils after the same time, respectively. At the highest concentration (10000ppm), the percentages of N. nipae nymphs and adults mortality recorded the highest mortality percentage (100%) for lemongrass and peppermint essential oils after 72hrs. of treatment. Mealybug mortality increased with the increase in exposure time and oil concentration. Both essential oils were proved to be very toxic to N. nipae nymphs and adults. The GC-MS analysis results showed that twenty-two compounds were identified in the lemongrass essential oil representing 99.39% of essential oil compositions. These compounds mainly consisted of geranial (41.23%) and neral (34.51%) as major constituents. Other major compounds were geraniol (6.01%), Geranyl acetate (5.48%), while nineteen chemical constituents representing 99.99% of the M. piperita essential oil and the most abundant constituents of were menthol (36.94 %), menthone (22.62%), menthyl acetate (10.55%), and menthofuran (9.18%) and others are minor components such as β-pinene and β-caryophyllene. These monoterpenes compounds present in lemongrass and peppermint essential oils may responsible for the highly insecticidal activities against N. nipae. Our studies suggest that the lemongrass and peppermint essential oils can be useful as a botanical insecticide for an IPM strategy for mealybugs and protect crops against their at­tacks. 

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