Contact Toxicity, Fumigant Toxicity And Repellence Assessment Of Thymus Vulgaris And Cymbopogon Winterianus Against Blattela Germanica

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G.K. Sedikelo , G.G. Lenetha , N.J. Malebo and F. Chidawanyika


Background: Natural materials such as plant essential oils provide an exceptional alternative to synthetic
pesticides to control pests and decrease the negative impact the environment and human health. The move
towards using green products and the continuing need to develop new methods to control and prevent pest
infestation is increasing. Pests such as cockroaches have demonstrated a growing resistance against the
common synthetic pesticides. However, synthetic pesticides have been shown to have detrimental effects
on humans and the environment. Thus, the need to develop safer ways for pest management.
Materials and methods: This study evaluated the effect of Java citronella and red thyme essential oils against
the German cockroach, Blatella germanica, using three bioassay methods to determine the contact toxicity,
fumigant toxicity and repellent activity. The essential oils were diluted in hexane. The dilutions were 5%,
10%, 15%, 30%, and 100% essential oil for all Java citronella and red thyme assays. Aliquots of 2.5 ml were
used for every assay to treat the filter papers.
Results. Generally, the results showed a higher insecticidal effect in test groups treated with Java citronella
oil than in groups treated with red thyme essential oil.
Conclusion: Java citronella and red thyme have been shown to have an insecticidal effect against the German
cockroach, with Java citronella showing more affinity over red thyme as a potential cockroach repellent. This
further proves that essential oils can be explored as a safer alternative pesticide.

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