Chili Extracts (Capsicum frutescens L.) for the Control of Corn Weevil (Sitophilus zeamais Motschulsky)

Vasakorn Bullangpoti1 Jantra Pensook1 Porntip Wisarntanon2 Pintip Kanasutra1

and Suraphon Visetson1 3

  1. Department of Zoology, Faculty of Science, Kasetsart University. Bangkok, 10900. Thailand.

  2. Sub division of storage insect pest Research, Division of Entomology and Zoology, DOA. Bangkok, 10900. Thailand.
  3. Correspondent should be made to this author.

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ABSTRACT

Chili (Capsicum frutescens L.) seeds were extracted by soxhlet’s extraction using ethanol as a solvent at 70o C for 8 hours. The extraction was compared to the water stirring soaking method using water as a solvent at 25+ 2o C for 24 hours. Both extractions were trailed with adult corn weevils (Sitophilus zeamais Motschulsky) by the impregnated filter paper method against various extract concentrations. The weevil showed LC50 (24 hours) at 7.38% w/w (Y = 11.44 + 5.22X) for the extract from ethanolic soxhlet’s compared to 10.33% w/w (Y = 4.11 + 4.44X) for the extract from the water stirring soaking method. The in vitro enzyme studied indicated a 2 folds reduced esterase and glutathione-S-transferase. The inhibition revealed that these two enzyme systems may posses some roles in detoxification mechanisms in this weevil.

    

Table 1 Linear regression, LC50, correlation (r) and correlation determination (r2) of adult weevil

(Sitophilus zeamais Motschulsky) against 2 types of chili extractions after 12 and 24 hours

exposure.

Hour after exposure

Type of extraction

Water soaking

Ethanolic soxhlet's

12 hours

regression

Y = 0.66 + 1.05X

Y = 0.50 + 2.25X

LC50 (w/w)

46.71 b

22.44 b

r

0.80

0.93

.r2

0.64

0.88

24 hours

regression

Y = 4.11 + 4.44X

Y = 11.45 + 5.22X

LC50 (w/w)

10.32 a

7.38 a

.r

0.83

0.69

r2

0.68

0.48

In the same column mean followed by the same letter are not significantly difference at p>0.05 by DMRT.

1