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

Table 4.5. Area under each ofthe outbreak frequency class during the years 1992-
94.
Frequency Area infested (ha)
class 1992 1993 1994
0 596.6 179.1 310.8
1 286.6 523.9 359.7
2 85.4 242.0 299.4
3 11.6 35.9 12.2
4 1.7 0.7 -
5 0.2 0.5 -
Total 385.5 803.0 671.3
In 1992, the outbreaks were confined to small patches, which left more
than half of the area uninfested. It can also be noticed that the sites of maximum
infestation during all the three years were in close proximity to each other.
Eventhough there were a large number of outbreaks in all the three years (8,6 and
4 during 1992,1993 and 1994, respectively), there were still places where no
infestation occurred. The results of spatial autocorrelation analysis are given in
Table 4.6.
Table 4.6. Spatial autocorrelation indices for the years 1992-94.
Year Geary index Moran index
1992 0.039960 0.95514
1993 0.033901 0.95600
1994 0.038924 0.95603
In all the years, the Geary index had a value between zero and one and the
Moran index was greater than zero. This shows that the defoliator outbreaks are
regionalized, smooth and clustered (Table 4.1). The sites with the same outbreak
frequency were adjacent to each other.
4.3.5. Correlation between outbreak incidence and topographic features
The elevation ofthe entire study area ranged from 35.9 m to 283.4 m. (Table 4.7.).
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