|Control of coconut black-headed caterpillar (Opisina arenosella
Walker) by systemic application of Soluneem A new water-soluble neem
Shivashankar*, R. S. Annadurai, M. Srinivas, G. Preethi, T. B. Sharada, R. Paramashivappa,
A. Srinivasa Rao, K. S. Prabhu**, C. S. Ramadoss, G. K. Veeresh and P. V. Subba Rao
Vittal Mallya Scientific Research Foundation, P.O.
K. R. Road, Bangalore 560 004, India
*Agricultural Research Station, Arsikere 573 103,
**Present address: Center for Molecular Toxicology,
226 Fenske Laboratory, Pennsylvania State University, University Park, PA 16802, USA
The coconut black-headed caterpillar (bhc) Opisina
arenosella is one of the major pests of coconut palms causing considerable damage to
coconut industry. As effective control has so far been elusive, the discovery of a
successful method of control of this pest by systemic application of Soluneem,
the first water soluble, non-toxic neem pesticide is reported. A single dose of systemic
administration of the formulation containing 3000 ppm of azadirachtin A in aqueous
solution at the base of the trunk translocated the biopesticide to the crown within
24 h. A highly significant reduction in the larval population, moult inhibition,
reduction in adult emergence and malformation in the emerged adults was recorded in
Soluneem-treated trees. The protection lasted for more than 120 days with no
phytotoxic symptoms to the treated palms and Soluneem was safe for natural enemies.
COCONUT black-headed caterpillar (bhc) Opisina arenosella Walker (Lepidoptera:
Oecophoridae) is one of the major pests of coconut causing considerable dam-
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age to coconut industry and according to a recent
survey, about 1.6 million palms are affected in Karnataka alone. Available control
measures include mainly topical sprays and systemic application (root administration) of
synthetic pesticides1. The latter method has been shown to leave persistent
pesticide residues2. Consumption of tender coconuts from trees applied with
synthetic pesticides may pose health hazards. In spite of several concerted efforts made
for the past two decades to control the pest by synthetic insecticide application, the
anticipated results have never been achieved. In this communication, we report the
effectiveness and superiority of Soluneem over other neem formulations for the management
of this notorious pest by systemic application.
Neem seed kernel extract is known to have potent
insecticidal properties3. The insolubility of the active constituent
azadirachtin in water and its poor stability limited the use of neem as a safe and
effective insecticide for systemic application. Recently, we have developed the first
water soluble eco-friendly neem pesticide formulation in a powder form (Soluneem)
containing azadirachtin and other limonoids, which are otherwise very sparingly soluble in
aqueous solutions4. Soluneem was found to be very safe
(LD50 > 5 g/kg body wt), highly stable and effective in the control of a
number of pests of economically important crops such as paddy, vegetables and ornamentals
by foliar spray.
Soluneem along with three commercially available
neem-based formulations, viz. Neemark, Nimbecidine and Neemazal F were selected to study
their systemic absorption by coconut palms and effectiveness in the control of bhc
infestation in a private farm at Chaluvanahally, Arsikere taluk, Karnataka, a heavily
infested site with bhc since December 1995. The syringe method5 was
used to systemically deliver the insecticidal formulations. Randomly selected coconut
trees were used to study the effect of absorption rate of the formulations and their
phytotoxic effects. For each of the formulations, four trees were selected for
administration of the test chemicals. Fifteen hundred ppm of all the four formulations
suspended/dissolved in 10 ml of mineral water were uniformly administered using 20 ml
syringes between 8 and 9 am during July 1999. Observations were made on the absorption
rate at 6 h intervals over a 24 h period. The treated trees were monitored for
14 weeks to record phytotoxic effects including any abnormal development like button
shedding, yellowing, drooping or drying of leaves.
Two Soluneem-treated trees were sacrificed after a
week of treatment to check for phytotoxicity at the administration site, adjoining
tissues, and in the xylem bundles. To monitor the movement of the insecticide, a mixture
of methylene blue (3 g) and Soluneem (1500 ppm) dissolved in 20 ml of
mineral water was also administered to two more palms and after 24 h they were cut
open to trace the movement of the dye. Appearance of blue colour in the xylem vessels in
the trunk at different heights was used as an indicator for the upward translocation of
Soluneem5. The absorption of Nimbecidine, Neemark and Neemazal F in 24 h
duration was 1, 0.5 and 2 ml, respectively. The unabsorbed emulsion of these
formulations was clearly visible in the syringe as two layers. Since the absorption was
very poor, no further observations were made with these commercial formulations. The
absorption of Soluneem (10 ml) on the other hand, was complete within 18 h. Two
of the Soluneem-treated trees when cut open appeared normal and histological examination
did not show any symptoms of phytotoxicity. Methylene blue dye mixed with Soluneem was
traced in the xylem vessel up to a height of 6.3 m within 24 h. In an earlier
study, an aqueous solution of methylene blue reached a height of 7.0 m in 48 h
(ref. 5). During the entire study period, neither button shedding nor yellowing, drooping
or drying of leaves was observed in Soluneem-treated trees.
Thirty-year-old coconut trees (n = 6)
infested with bhc were selected to study the efficacy of Soluneem in the control of bhc.
In an earlier study, aerial application of Soluneem at 10 ppm dilution was found to
be very effective in the control of pests associated with vegetables, rice and roses.
Considering the total biomass of a single coconut tree, 3 bhc-infested trees were
systemically administered each with 3000 ppm of Soluneem in 10 ml water while
similar infested trees (n = 3) were given 10 ml of water only. In
order to record the bhc population prior to treatment and at different time intervals from
each of the treated and control tree, 25 infested leaflets were clipped from the middle
portion of the leaves of 1st, 2nd and 3rd whorls of the palm6. Observations
were also made on such parameters as per cent pupation, average pupal weight, per cent
eclosion and malformation. Total leaf area fed in the damaged leaflet after pupation was
recorded from the treatments. The trees were continuously monitored for 12 weeks. Residual
analysis of the coconut water for azadirachtin A was carried out by HPLC.
Assessment of bhc population from all the treatments
at the time of Soluneem administration revealed majority of the larvae in second instar
(78%). The mean bhc population at the commencement of the experiment in both the control
and experimental groups were comparable (Table 1). Fifteen days after the treatment,
control larval groups were found larger and more active when compared with larvae in the
Soluneem group. The population assessment in terms of number of larvae per leaflet showed
a declining trend in Soluneem-treated palms from 17th day after administration compared to
the control (Table 1). Till the end of the study, the shrunken carcasses of dead larvae
were observed in treated palms. The total area fed in the untreated palm leaflets
(152 cm2) were significantly (P < 0.01)
*Numbers in parentheses indicate % adult
1. Effect of Soluneem on the larvae, pupae and adults of bhc (O.
arenosella). a, Soluneem-treated malformed (upper) and normal (lower)
5th instar larvae; b, Soluneem-treated (upper) and normal (lower) pupae; c,
normal and d, Soluneem-treated malformed adult moths (magnification
8 ´ ).
(t = 4.14) higher
than in the Soluneem-treated leaflets (57 cm2). The reduction in the
feeding efficiency of Soluneem treatment could be attributed to the presence of the
insecticide in the leaflets, which contributed to a reduction in physical fitness of the
larvae. Reduced feeding efficiency by insects has been reported in a number of instances
where a foliar application of a neem-based formulation was used7. Throughout
the study period, the organoleptic tests of tender coconut showed no change in taste. HPLC
analysis of coconut water from nuts harvested from Soluneem-treated trees did not reveal
any detectable levels of azadirachtin-A. To the best of our knowledge, this is the first
report of systemic application of an azadirachtin containing water-soluble neem
insecticide in coconut palms that contributed for reduced feeding and consequent reduction
in larval population. Another interesting observation was the delayed pupation as a
consequence of extended postembryonic development. By 69th day, only 22% of the larval
population on Soluneem-treated palms pupated when compared to 38% in the untreated group.
Such delayed post-embryonic development has been reported in several insects upon foliar
application of neem-based formulations8. A significant (P < 0.01)
reduction in the average pupal weight was also observed in Soluneem treatment (Table 2)
presumably due to reduced feeding on leaflets from Soluneem-treated palms. The most
striking observation was the drastic reduction in adult eclosion as a consequence of the
treatment (Table 1). A majority of the moths emerging from treated palms (66%) showed
malformation, while all the control group pupae emerged into normal adults (Figure 1). An
incidence of a fresh early instar larval population of the next generation was observed in
both control and Soluneem-treated palms 110 days after initial systemic application (Table
1). However, a significantly (P < 0.01) lower number of larvae were
recorded on leaflets of Soluneem-treated trees, which could be due to its extended
Preliminary observations on the systemic application
of Soluneem to coconut trees infested with the eriophyid mite, Aceria (Eriophyes)
guerreronis have shown that it drastically reduces the population of these mites,
which are spreading at an alarming rate in the southern parts of India threatening the
coconut industry. In the light of the recent ban on the application of the synthetic
pesticide, Monocrotophos, Soluneem could be a safe alternative for the control of pests
infesting not only coconut palms but also other economically important perennial trees by
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ACKNOWLEDGEMENT. We thank Mr C. N.
Puttaswamy for his kind cooperation and permitting us to carry out the studies in his
Received 17 December 1999; revised accepted 6 January 2000