Identification (GC and GC-MS) of unsaturated acetates inElasmopalpus lignosellus and their biological activity (GC-EAD and EAG)

Abstract

Two insect colonies of Elasmopalpus lignosellus were reared in our laboratory, the first being initiated from pupae obtained from a cornfield in the region of Sete Lagoas, Minas Gerais and the second from a cornfield in the region of Goiânia, Goiás. From the two colonies, two extracts were prepared from the pheromone glands of virgin E. lignosellus females. The extract obtained from the first colony was designated as extract 1 while the extract obtained from the second colony was designated as extract 2. Extract 1 was analyzed by gas chromatography-mass spectrometry (GC-MS) with (Z)-9-hexadecenyl acetate [(Z)-9-HDA] and (Z)-11-hexadecenyl acetate [(Z)-11-HDA] being identified and confirmed by the formation of DMDS derivatives. In addition, a third acetate, which could be either (E)-8-hexadecenyl acetate [(E)-8-HDA] or (E)-9-hexadecenyl acetate [(E)-9-HDA] was detected by GC-MS. Extract 2 was analyzed by gas chromatography (GC) and gas chromatography-electroannetography (GC-EAD) revealing the presence of (Z)-11-HDA and (Z)-9-TDA. In addition, the same compounds elicited a response with the E. lignosellus male antenna obtained from the second insect colony. Electroantennography (EAG) screening with the male E. lignosellus antenna (obtained from the second insect colony) was conducted with the 23 possible tetradecenyl acetates (TDA) and 22 hexadecenyl acetates (HDA) as standards. Out of the 23 TDA isomers evaluated, only (Z)-9-TDA elicited a response and out of the 22 HDA [(Z) and (E) isomers gamma2 to delta13] evaluated only (Z)-11-HDA elicited a response. The acetate compositions of two extracts obtained from insects originating from the two states (Minas Gerais and Goiás) of Brazil were different from one another as well as from that obtained from insects in Tifton, GA, USA. The bioactivity data (GC-EAD) of the extract 2 differed from those reported for the Tifton, GA, USA population. These data suggest polymorphism in relation to the insect populations found in Brazil and in the USA. The possibility of the existence of an E. lignosellus sub-species cannot be ruled out.

Identification of acetates in elasmopalpulus lignosellus pheromone glands using a newly created mass spectral database and kóvats retention indices

“…This led to the hypothesis that the pheromone blend of E. lignosellus in Brazil might be different due to regional differences. This hypothesis was confirmed since the acetate composition and activity of the pheromone extract varied from region to region in Brazil as well as from that in the USA 6 . However, in that study, it was not possible to identify the three acetates in the active extracts the gland extract obtained from insects in the state of Minas Gerais (extract 1).…”

“…GC-MS and GC-EAD (gas chromatography-electroantennography) analysis of active E. lignosellus extracts along with electroantennography (EAG) with puffs on the males´ antenna led to the identification of (Z)-9-HDA and (Z)-11-HDA in extract 1, and (Z)-9-TDA and (Z)-11-HDA in extract 2 6 . The composition was very different from the one reported for the same insect in Tifton, Ga, USA where the following ten compounds were identified by GC-MS 4 : (Z)-7-TDA (16.5%), (Z)-9-TDA (8.8%), tetradecyl acetate (3.8%), (Z)-9-HDA (28.8%) (Z)-11-HDA (7.4%), hexadecyl acetate (9.6%), (Z)-7-tetradecenol (2.1%), (Z)-9-tetradecenol (7%) and (Z)-11-hexadecenol (14%).…”

“…However, in that study, it was not possible to identify the three acetates in the active extracts the gland extract obtained from insects in the state of Minas Gerais (extract 1). We could identify only (Z)-9-hexadecenyl acetate (Z)-9-HDA and (Z)-11-hexadecenyl acetate (Z)-11-HDA and confirm their presence by DMDS derivative 6 . The third acetate, either (E)-8-hexadecenyl acetate [(E)-8-HDA] or (E)-9-hexadecenyl acetate [(E)-9-HDA] could not be identified based on its mass spectra or by comparison of the retention time (t R ) with standards.…”

“…The two pheromone extracts prepared in our previous study were used for this study 6 . Briefly, two Elasmopalpus lignosellus colonies were reared in our laboratory, the first being initiated from pupae obtained from a cornfield in the region of Sete Lagoas, Minas Gerais and the second from a sugarcane field in the region of Goiânia, Goiás.…”

Trichogramma pretiosum attraction due to the Elasmopalpus lignosellus damage in maize

“…Since the early 1980s, efforts have been directed to develop new alternatives based on semiochemicals and natural enemies to control E. lignosellus (Lynch et al, 1984;Pires et al, 1992;Jham et al, 2005Jham et al, , 2007. However, in Brazil, the currently used method is still based on pesticides.…”