A Study On Proxenus Hennia Swinhoe And Nymphula Responsalis Walker As Potential Biological Control Agents Of Water Lettuce (Pistia Stratiotes L.)
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Date
1982-07
Authors
KASNO
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Abstract
A search for arthropods attacking water lettuce
(Pistia stratiotes L.) was carried out, at some locations
on Penang Island and Kuala Kedah, Malaysia The
objective of the search was to look for appropriate
candidate biological control agents of this aquatic
weed. Several arthropods were found attacking the weed,
amongst them, were Proxenus hennia Swinhoe (Lepidoptera:
Noctuidae) ,and Nymphula responsalis Wlk. (Lepidoptera:
Pyralidae)~ both of which were selected for further
studies.
The life histories and the possible use of P. hennia
and N. responsalis as biological control agents of water
lettuce were studied under laboratory conditions. The
complete life cycle of P. hennia took 2S.53 + 1.65 days
of which 1S.S0 + 1.45 days were destructive to Pistia
stratiotes. The complete life cycle of N. responsalis
was 32.92 ~ 1.44 days of which 23.04 ~ 1.31 days were
destructive. Under controlled conditions the adult
female of P.hennia produced 620 eggs with 70 percent
survival to the pupal stage and N. respqnsalis produces
320 eggs with SO percent survival to the pupal stage.
However, under field conditions the populations of P.
hennia and N. responsalis were generally low: indicating
that natural factors have an important role, in their
respective ability to survive. Therefore, these factors
need to be studied further, e.g. predators, parasites and
climate.
Studies on damage potential of the insects to water
lettuce were carried out; two or three larvae of either
or both of the insects cause significant decrease in the
growth of water lettuce plants having a crown diameter of
8 - 10 cm.
Besides the high damage potential of the insects to
the weed, P. hennia is monophagous on water lettuce, whilst
N. responsalis is oligophagous, the larvae feeding on seeral
non-economic aquatic plants, such as Salvinia cucullata
Roxb. ex Bory, Azolla pinnata R.Br., Lemna minor Auct.,
Eichhornia crassipes (Mart.) Solms, Limnocharis flava (L.)
Buch., as well and economic terrestrial plant Colocasia
esculenta (L.) Schott.
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A Study On Proxenus Hennia Swinhoe And Nymphula Responsalis Walker , As Potential Biological Control Agents Of Water Lettuce (Pistia Stratiotes L.)