Toxicity of <i>Cymbopogon flexuosus</i> essential oil and citral for <i>Spodoptera frugiperda</i>

Oliveira, Ellison Rosario de; Alves, Dejane Santos; Carvalho, Geraldo Andrade; Oliveira, Bárbara Maria Ribeiro Guimarães de; Aazza, Smail; Bertolucci, Suzan Kelly Vilela

doi:10.1590/1413-70542018424013918

ABSTRACT

Fall armyworm (FAW) (Spodoptera frugiperda) is a polyphagous insect responsible for damage to several crops. Synthetic chemical insecticides and genetically modified plants are the most commonly used methods for FAW control. However, the selection of resistant populations has been reported in several studies, justifying the search for new molecules to be used in the control of S. frugiperda. The aim of the present study was to evaluate the toxicity of lemongrass (Cymbopogon flexuosus) essential oil (LEO) and its major component (citral) in relation to FAW. Additionally, the anticholinesterase activity of LEO and citral was evaluated using acetylcholinesterase (AChE) from Electrophorus electricus. The LEO was toxic to FAW when added to an artificial diet (LC₅₀ = 1.35 mg mL^-1) at the highest concentrations tested, and the median lethal time (LT₅₀) was 18.85 h. Major components of LEO were identified by gas chromatography-mass spectrometry, and citral, the most abundant component, was used in FAW bioassays. The insecticidal activity of citral was statistically similar to that of LEO, demonstrating that citral was responsible for the insecticidal activity of LEO. Inhibition of AChE was measured, and the mean inhibitory concentration (IC₅₀) values for LEO and citral were 650- and 405-fold higher, respectively, than that verified for the positive control (methomyl insecticide), suggesting selectivity for non-target organisms. Based on these results, citral and C. flexuosus have the potential to be applied in the development of new products for the control of S. frugiperda.

Index terms:
Lemongrass; (2Z)-3,7-dimethylocta-2,6-dienal; monoterpenes; botanical insecticide; fall armyworm.

[1] ^*Corresponding author: agronomellison.oliveira@yahoo.com.br

	Constituent	RT	RI*	Area %
1	5-Hepten-2-one, 6-methyl-	7.820	985	1.58
2	Myrcene	7.971	990	0.45
3	Trans-linalool oxyde	11.711	1088	0.14
4	Linalool	12.171	1100	2.79
5	Exo-isocitral	14.127	1144	0.42
6	Photocitral A	14.345	1149	0.38
7	Citronellal	14.493	1152	0.29
8	Z-isocitral	15.003	1164	0.98
9	E-isocitral	15.815	1182	1.28
10	Estragole	16.513	1198	0.35
11	n-decanal	16.843	1205	0.42
12	Neral	18.523	1242	32.59
13	Geraniol	19.061	1254	0.93
14	Geranial	19.897	1273	44.65
15	Nerolic acid	22.168	1323	0.54
16	Ni m/z = 168	22.850	1339	2.31
17	Geranic acid	23.939	1363	0.18
18	Ni m/z = 169	24.479	1375	3.41
19	Geranyl acetate	24.882	1384	1.92
20	Ar-curcumene	29.165	1483	0.46
21	Sandacopimara-8(14), 15-diene	47.356	1966	0.22

Treatment	Larval period (days)	Pupa weight (mg)^ns
Water + Dye	16.90±0.16 a	243.83±2.25
Water + Dye + 1% Tween^® 80	17.32±0.14 a	243.12±2.75
C. flexuosus - 0.675 mg mL^-1 diet	18.36±0.37 b	242.17±3.32
C. flexuosus - 1.35 mg mL^-1 diet	20.85±0.72 c	241.81±4.25
р ≤ 0.05	0.0000	0.968
F	24.472	0.0855
df	3	3

Concentration	% Inhibition ± SD	% Inhibition ± SD	% Inhibition ± SD
(mg.mL^-1)	C. flexuosus	Citral	Control (methomyl)
0.01	3.88 ± 2.14	3.70 ± 0.51	73.64 ± 0.23
0.02	5.81 ± 0.91	4.11 ± 0.99	79.86 ± 0.12
0.04	6.41 ± 1.11	7.05 ± 0.28	90.09 ± 0.25
0.07	10.48 ± 1.57	8.55 ± 0.24	98.35 ± 0.18
0.14	18.71 ± 0.05	16.08 ± 0.86	99.89 ± 0.37
0.28	25.59 ± 0.67	31.06 ± 0.52	99.99 ± 0.09
0.56	40.22 ± 0.15	51.57 ± 0.77	99.99 ± 0.07
1.12	61.30 ± 0.21	64.40 ± 0.36	99.99 ± 0.05
2.24	74.36 ± 0.37	75.57 ± 0.56	99.99 ± 0.05

Brasil

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Toxicity of Cymbopogon flexuosus essential oil and citral for Spodoptera frugiperda

Toxicidade do óleo essencial de Cymbopogon flexuosus e do citral para Spodoptera frugiperda

ABSTRACT