Small concentrations of Lippia spp. can help in the control of the bean weevil, Acanthoscelides obtectus Say

Acanthoscelides obtectus (Coleoptera: Chrisomelidae: Bruchidae) is an insect pest which attacks the common bean (Phaseolus vulgaris, L.). It has been suggested that plant products, e.g. essential oils, may be a suitable alternative for controlling insect pests¹, including A. obtectus ². The objective of this study was to determine the capacity of essential oils of Lippia spp. to control A. obtectus adults under laboratory conditions. One millilitre of solution (6µL of Lippia orinanoides and Lippia alba diluted in 994µL of ethanol) was sprayed (Potter tower) directly on Petri dishes (90 mm in diameter) covered with sterile filter paper. One hour after, twenty A. obtectus adults were placed in these Petri dishes. Four replicates were used for each Lippia spp. Daily monitoring of insect mortality was performed for 15 days.

Results (Figure 1) show L. orinagoides accumulated an insect mortality of 54%, significantly different from L. alba, which achieved a mortality of 43%. Both Lippia spp. treatments were significantly different from control treatment, with an accumulated mortality of 16%.

Fig. 1: Accumulated daily A. obtectus adults mortality by Lippia spp. essentials oils (day 1 represents 24 hours after treatment). Upper and lower error bars are represented. (Fisher's LSD. p < 0.05).

The ability of both essential oils of Lippia spp. to paralyze the adults and kill them make these essential oils a new suitable tool for the control of adults of this insect pest in small storages.

[1] Pavela RInd. Crops Prod. 2011, 34: 888 – 892.

[2] Papachristos DP, Karamanoli KI, Stamopoulos DC, Menkissoglu-Spiroudi U. Pest Manag. Sci. 2004, 60: 514 – 520.