Infestation Reactions and Management of Helopeltis theivora(Waterhouse) (Miridae:Hemiptera) in Cocoa Clones
By: Beena Nair.
Contributor(s): Baby P Skaria(Guide).
Material type:
BookPublisher: Vellanikkara Department of Entomology, College of Horticulture 1998DDC classification: 632.6 Online resources: Click here to access online | Click here to access online Dissertation note: MSc Abstract: Investigations were carried out at the College of Horticulture,
Vellanikkara to identity sources of resistance to the cocoa mirid bug He/ope/lis
theivora (Waterhouse) among the various high yielding cocoa clones and also to
develop an effective and safer management strategy against the pest using
insecticides. In the field trial, seven hybrids and eight parental clones were
evaluated for their tolerance to the mirids at different developmental stages of the
pods and on flushes. The pod damage intensity was moderate to low, the range
being 0.25 to 5.84 per cent and in this situation the resistance traits could not be
properly quantified. However, the parental trees 01-5.9 and GYl-68 and the hybrids
involving these trees showed a moderate level of resistance. The clones M-l3.12
and GI-15.5 were found to be relatively more susceptible to the pest. The correlation
studies have established the positive correlation between the yield of pods on the
one hand and the intensity of damage to the pods and the vegetative flushes on the
other. The various pod characters such as length, width, weight, pericarp thickness,
wet bean weight and number of beans per pod did not show any influence on the
intensity of pod infestation.
'The performance of the various clones in respect of the yield of pods and
beans have been discussed in the light of variations in the intensity of damage to the
pods and vegetative flushes.
The susceptibility of clones with higher number of pods was detected in
the correlation studies. The hybrid GI-S.9 x GVI-68 which produced 23 pods per
tree on an average showed lower levels of damage by the mirid bug on the pods and
also on flushes indicating a moderate level of resistance coupled with high pod
number in this clone. The pod number was also found correlated with total wet bean
yield per tree, height and spread of the tree. With respect to higher wet bean yield
the parental clone GYI-68 ranked first with 1937.47 g followed by M-13.12,
GVI-64, GVI-6I, M-13.J2 x GJ-S.9 and GI-S.9 x GVI-68. The crosses GJ-IO.3 x
GVI-61 and 01-5.9 x GVl-54 recorded very low bean yields. However, the high
yielding and low yielding clones showed varied reactions to the infestation by
H. theivora.
With regard to the management of H. theivora using insecticides the
spray application of carbaryl at 1.25 kg ai/ha and monocrotophos at 0.5 kg ai/ha was
most effective. However, considering the higher persistent toxicity of
monocrotophos, carbaryl is recommended for field applications.
| Item type | Current location | Call number | Status | Date due | Barcode |
|---|---|---|---|---|---|
Theses
|
KAU Central Library, Thrissur Theses | 632.6 BEE/IN (Browse shelf) | Available | 171412 |
MSc
Investigations were carried out at the College of Horticulture,
Vellanikkara to identity sources of resistance to the cocoa mirid bug He/ope/lis
theivora (Waterhouse) among the various high yielding cocoa clones and also to
develop an effective and safer management strategy against the pest using
insecticides. In the field trial, seven hybrids and eight parental clones were
evaluated for their tolerance to the mirids at different developmental stages of the
pods and on flushes. The pod damage intensity was moderate to low, the range
being 0.25 to 5.84 per cent and in this situation the resistance traits could not be
properly quantified. However, the parental trees 01-5.9 and GYl-68 and the hybrids
involving these trees showed a moderate level of resistance. The clones M-l3.12
and GI-15.5 were found to be relatively more susceptible to the pest. The correlation
studies have established the positive correlation between the yield of pods on the
one hand and the intensity of damage to the pods and the vegetative flushes on the
other. The various pod characters such as length, width, weight, pericarp thickness,
wet bean weight and number of beans per pod did not show any influence on the
intensity of pod infestation.
'The performance of the various clones in respect of the yield of pods and
beans have been discussed in the light of variations in the intensity of damage to the
pods and vegetative flushes.
The susceptibility of clones with higher number of pods was detected in
the correlation studies. The hybrid GI-S.9 x GVI-68 which produced 23 pods per
tree on an average showed lower levels of damage by the mirid bug on the pods and
also on flushes indicating a moderate level of resistance coupled with high pod
number in this clone. The pod number was also found correlated with total wet bean
yield per tree, height and spread of the tree. With respect to higher wet bean yield
the parental clone GYI-68 ranked first with 1937.47 g followed by M-13.12,
GVI-64, GVI-6I, M-13.J2 x GJ-S.9 and GI-S.9 x GVI-68. The crosses GJ-IO.3 x
GVI-61 and 01-5.9 x GVl-54 recorded very low bean yields. However, the high
yielding and low yielding clones showed varied reactions to the infestation by
H. theivora.
With regard to the management of H. theivora using insecticides the
spray application of carbaryl at 1.25 kg ai/ha and monocrotophos at 0.5 kg ai/ha was
most effective. However, considering the higher persistent toxicity of
monocrotophos, carbaryl is recommended for field applications.
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