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

explained as caused by progenies of earlier populations in the entire Nilambur
area. Thus percentage area infested by populations which could be caused by
earlier populations increased to 88% when the populations in the entire
Nilamur area was considered.
A comparison of temporal sequence of outbreaks which was observed
at Kariem-Muriem and at all the plantations at Nilarnbur, including the
Kariern-Muriem plantations, shows that when the larger area is considered, the
sequence of outbreaks become more explainable. The percentage of outbreaks
that could be attributed to local populations was computed for this purpose.
Only about 33% (2 out of 6) of the outbreaks could be attributed to local
populations when only Kariem-Muriem area was considered. Nevertheless,
about 70% (16 out of 23) of outbreaks could be explained when all the
plantations were taken together. This indicates that the chain of outbreaks that
occurred during a year is more self-sustained when viewed in a larger area.
Short-range migration of moths within Nilambur can explain this
phenomenon. When only Kariem-Muriem is considered, the effect of
emigration or immigration will lead to unexplainable outbreaks within
Kariem-Muriem. However, when all the plantations at Nilambur are
considered the effect ofshort-range movement is only spatial displacement but
temporally the outbreaks remain explainable.
The salient features of the spatial and temporal pattern of outbreaks
can be summarized as follows:
(a) Temporal pattern
i. The period of defoliator outbreaks at Nilambur extends
from February to September.
11. The initial outbreaks that occurred in February and March
in 1993 could theoretically cause a sequence of outbreaks
which comprised 78% of the total area under outbreak
during the year.
111. The outbreaks which occurred during the later part of the
year (August and September in 1993) could not be caused
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