MSc

The bionomics and ecological management of coconut eriophyid mite,
Aceria guerreronis (Keifer) was studied under the Department of Entomology,
College of Horticulture, Vellanikkara. The preference of mites to bunches of different
maturity, symptoms of damage, population dynamics, relationship of mite population
with weather factors and the distribution pattern of mites based on plant morphology
were considered for the study. Some ecological management practices were also tried
along with this. The experiment was laid out as completely randomised design.
Mites were absent in male and female flowers and also on buttons of first
bunch. Initiation of infestation starts from buttons of second bunch and population
increases further and maximum population is noticed in buttons of third and fourth
bunches and thereafter it decreases. This is because after fourth bunch, the
meristematic tissue becomes necrotic due to feeding of mites and hence mites cannot
feed further easily. Traces of population were noticed even on nuts of ninth bunch.
Predatory mites were also seen along with eriophyid mites even though they are very
negligible.
Symptoms of damage were seen outside from second bunch onwards. The
symptom initially appears as whitish streak or triangular patch and it increases further
in length and breadth and becomes brownish and later necrotic. In some cases, cracks,
cuts and gummosis can be seen on the husk. The relationship between surface damage
and mite population was worked out. Maximum mite population was noticed when
the surface damage was 1-3 and 3-6 cm2 before and after the removal of perianth
respectively and the percentage of damage was 1-3 per cent.
Mite population was found to vary with different weather parameters.
Minimum temperature of current week, current, -1 and -2 fortnights and maximum

temperature of -2 fortnight were positively related with mite population. Morning
humidity is also positively related with mite population. Mite population was
negatively related with wind speed of zero current, current, -I and -2 fortnights. There
is no direct relation between mite population and rainfall, number of rainy days,
evening humidity and sunshine hours.
Mite infestation was irrespective of the height of the palm, crown shape and
perianth arrangement. The intensity of infestation varies between each inner tepals.
Maximum infestation was under fourth tepal followed by fifth and sixth tepa\. The
preference of mites to different portions under each tepal also varies with maximum
entry through the 'outer edge' of fourth tepal followed by 'outer edge' of fifth tepal,
'middle' portion of sixth tepal, 'middle' portion of fifth and fourth tepal, and 'inner
edge' of sixth and fifth tepa\. Infestation was found to be less in round shaped nuts
compared to oval and oblong nuts. Maximum incidence was in green coloured nuts
followed by greenish yellow and orange coloured nuts.
There was no reduction in mite damage by different water regimes (rainfed,
channel and drip irrigated) fertilizer regimes (0.34:0.17:0.68 kg NPK/palm,
0.5:0.32:1.2 kg NPKlpalm and 0.25:0.32:1.2 kg NPKlpalm) micronutrients (MgS04,
ZnS04, MnS04, Borax and Micronutrient mixture) and crown cleaning (once and
twice in an year).