Spatial dynamics of teak defoliator (Hyblaea puera Cramer) - Cochin ...

Table 4.7. The relationship between outbreak frequency and elevation.
Outbreak Elevation (m)
frequency 1992 1993 1994
0 97.1+44.1 132.1+44.3 118.3+53.4
1 108.7+46.1 104.4+48.9 103.8+44.7
2 138.5+55.3 81.2+28.9 87.0+35.8
3 71.3+19.0 57.2+15.5 51.4+9.9
4 68.7+6.2 58.4+ 1.1 -
5 68.4+2.1 44.4+2.0 -
The elevation ofsites with the highest frequency ofoutbreaks was between
40 to 77 metres above sea level. During 1992, a positive correlation was found
between the outbreak frequency and elevation. However, in 1993 and 1994, the
correlation was found to be negative. This indicates that the elevation of a site
may not be determining the susceptibility of a site to defoliation. The details of
aspect for the frequency classes are given in Table 4.8.
Table 4.8. The relationship between outbreak frequency and aspect.
Frequency Aspect (degrees)
class 1992 1993 1994
0 171.1+86.9 180.1+89.3 187.8+88.3
1 188.2±94.2 168.5±85.5 158.8+86.3
2 224.3+77.5 204.1+92.0 197.5+87.7
3 272.0+21.6 226.8+88.7 284.3+58.0
4 256.6+13.6 296.6+14.7 -
5 240.8+4.6 298.7+8.3 -
It can be seen that there is an increase in the aspect value corresponding to
an increase in outbreak frequency. It is indicated that the high frequency sites face
predominantly to the west while the low frequency sites face to the south. Sites
that were not infested during the three years faces predominantly to the south. It
was found that the aspect values were positively correlated to outbreak frequency
in all the three years.
Table 4.9. shows the elevation and aspect of the first outbreaks. The first
outbreaks are shown in landscape perspective in figures 17-19.
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