| Summary: | Spodoptera exigua is a polyphagous pest in the warmer regions of the
world. Although has plenty of host plants, S. exigua has become a serious pest in
shallot field in Indonesia, especially in lowland area. As a kind of polycultures,
intercropping can provide the best condition for shallot to express its potential
yield and may offer increased yield per unit of land. The aim of this research are
to know the influence of intercropping shallot with groundnut or cowpea to the
level of damage caused by S. exigua and to understand the mechanisms behind
these level of damage changes. This research was conducted in the green house
and laboratory of Applied Entomology Faculty of Agriculture Universitas Gadjah
Mada Yogyakarta from April 2010 until June 2011. The GC-MS analysis was
done in Organic Chemistry Laboratory of Universitas Gadjah Mada. Twenty four
hours old adults were used in this research. There were two treatments:
monoculture (shallot monoculture, groundnut monoculture, and cowpea
monoculture), and intercropping (shallot with cowpea intercrop and shallot with
groundnut intercrop). Three replicates were included per treatments where there
were twenty plants inside each cage. The results show intercropping shallot with
groundnut or cowpea has significant influence in decreasing number of egg
masses, decreasing the level of damage and increasing the weight of shallot.
Intercropping shallot with groundnut is also more advantageous than
intercropping shallot with cowpea. The mechanisms that may play role in the
decreasing of level of damage are lower number of egg masses, higher possibility
of cannibalism, and the effect of secondary compounds in groundnut and cowpea.
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