PhD

Experiments were conducted to study the influence of alternate hosts on the
population dynamics of the coreid bug, Paradasynus rostratus Dist. and consequent
damage to coconut and to evolve an eco-friendly management strategy to the pest. An
abstract of the work done and the results are given below.
A survey conducted in Thiruvananthapuram district to study the incidence and
intensity of coreid bug infestation on coconut revealed that the infestation was the
highest in the coastal region. The incidence was lower in the upland and midland
regions. Among the variety of crops seen in the coconut based homesteads, guava,
cashew, cocoa and neem were recorded as potential hosts of the pest.
Studies on the influence of alternate hosts on the population build up of coreid
bug revealed that the alternate hosts were a major determinant in the extent of
infestation of coreid bug on coconut. The pest multiplied on the alternate hosts
during flushing, flowering and fruit formation stages of the crops and subsequently
shifted to the base crop, coconut in multiple cropping systems.
The changes in size and yield parameters of nut due to the infestation of
P.rostratus were assessed. Nuts with negligible damage (category II) did not show
any significant difference in nut shape, nut characters, copra and oil content.
Significant reduction in copra and oil was observed in moderately (category IV) and
,
heavily (category V) damaged nuts. The endosperm was not at all formed in severely
damaged (category VI) nuts.
The changes in the biochemical constituents of coconut buttons due to feeding
of coreid bug were studied. The phenol content in young infested nuts recorded an
increase compared to healthy nuts. A progressive reduction in starch and fibre content
of young nuts was obtained with increase in degree of infestation
The study on the effect of infestation of P.rostratus on germination and
vigour of seedlings revealed that though all the nuts in damage category II (negligible

damage) to IV (moderate damage) germinated within six months, only seedlings from
nuts with negligible damage (category II) had the qualities of good seedlings.
The antifeedant effect of neem based botanicals and efficacy of synthetic
chemical pesticides were evaluated against coreid bug. Among the botanical and
chemical pesticides, neem seed oil- garlic emulsion 2 per cent and profenophos 0.05
per cent proved most effective against the coreid bug.
A field experiment was conducted to evaluate the effect of selected treatments
on alternate hosts for control of coreid bug in coconut. The study revealed that the
combined application of neem seed oil- garlic emulsion 2 per cent + profenophos
0.025 per cent was the most effective in reducing the extent of coreid bug infestation
in the surrounding coconut palms.
The present study could establish the role of alternate hosts on the population
buildup of coreid bug. Plant protection operations in alternate hosts against coreid
bug are more effective, economical and viable options compared to those in coconut.
Based on the results of the study, a package involving regular monitoring of the
alternate hosts in the homesteads, removal and destruction of the egg masses and
early instars of the pest and giving a need based spray with an insecticide formulation
like neem oil- garlic emulsion 2 per cent + profenophos 0.025 per cent on the
alternate host would be a practical and cost effective approach for reducing the
damage of P.rostratus on coconut in the homesteads.