Status and Management of Three Major Insect Pests of Coconut in the Tropics and Subtropics 373
In field trapping experiments, (4 S)-ethyl 4-meth-
yloctanoate and the racemic mixture were equally
attractive and ten times more effective in attract-
ing beetles than ethyl chrysanthemumate. Ethyl
4-methylheptanoate was as attractive as ethyl
chrysanthemumate and more attractive than the
4-methyloctanoic acid, but further studies are re-
quired before it can be classified as an aggrega-
tion pheromone (Chakravarthy et al. 2014 ). Com-
pared to ethyl 4-methyloctanoate alone, combina-
tions of the three male-produced compounds did
not increase attraction, whereas addition of fresh-
ly rotting oil palm fruit bunches to pheromone-
baited traps significantly enhanced attraction.
With increasing dose, captures of O. rhinoceros
increased, but doses of 6, 9, and 18 mg/day were
competitive with 30 mg/day lures. Newly de-
signed vane traps were more effective in captur-
ing beetles than were barrier or pitfall traps. The
results of this study indicated that there is poten-
tial for using ethyl 4-methyloctanoate in opera-
tional programs to suppress O. rhinoceros in oil
palm plantations (Hallett et al. 1995 ).
The total number of RB caught in phero-
mone traps varied with concentrations. Nearly
98 and 108 beetles were caught in pheromone
traps baited with pheromone lure with 750 and
1000 mg, respectively, and were found signifi-
cantly superior to other treatments. Records of
250 and 500 mg proved inferior with only 33 and
42 beetles, respectively, in the pheromone traps
(Chakravarthy et al. 2014 ). The peak activity of
beetles was found during the 29th to 53rd week
after the installation of the traps, i.e., from July
to March. The beetles caught in the traps ranged
from 0.0 to 4.5 beetles/trap/week recorded from
the 29th to the 53rd week after the installation of
the traps in India. Beetles caught in the trap var-
ied from 0.25 to 1.75 beetles/trap/week recorded
from the 29th to the 53rd week after trap installa-
tion. Rhinolure is an aggregation pheromone ef-
fective in mass trapping both males and females
of the coconut RB (Chakravarthy et al. 2014 ).
The active compound serving as an attractant,
ethyl 4-methyloctanoate is supplied as a bubble
formulation in sachets, and the chemical is sus-
pended in lure. The trap should be installed at
about 0.8 m from the ground and is effective at 1/
ha. The septa can be suspended in the upper lid of
the bucket, taking care to avoid direct sunlight as
it would be affecting the performance of the lure.
The bucket should contain holes and rough cor-
rugations on the lateral sides just below the upper
lid so that the beetles that are attracted alight on
this rough surface before entering the holes.
Field evaluation of traps revealed that nano-
matrix-loaded pheromone (240 mg) trapped
18.0 beetles/trap/month, followed by the com-
mercial lure (containing 800 mg pheromone),
which trapped 12 beetles/trap/month. Studies on
the longevity of pheromone lures indicated that
the commercial lure was exhausted in 3 months
whereas in the nanomatrix, it remained active up
to 8 months (CPCRI 2012 ). Jayanth et al. ( 2009 )
evaluated the reproductive status of RB females
captured in aggregation pheromone traps and re-
vealed that the majority of females captured were
virgin or gravid females (Fig. 6 ). Hence, the mass
trapping of RB is particularly more effective due
to attract female beetles that had not started re-
productive activity.
The control of the RB is difficult once they in-
vade the new area; therefore, it is better to imple-
ment quarantine measures in those countries that
are found in the probable spreading zones. If new
infections are noticed, immediate control mea-
sures should be taken to stop the spreading of the
pest. Once they spread, integrated management
measures, such as mechanical and biological
use of pheromone and chemical control tactics,
should be taken to manage the pest.Fig. 6 Reproductive status of RB females in pheromone
traps (Source: Jayanth et al. 2009)