Spatial and Temporal Distribution of Dolichoderus Thoracicus Smith in a Cocoa-Coconut Agroecosystem
Cocoa, an important crop in Malaysian agriculture is subjected to infestation by a number of insect species the most important of which is the cocoa pod borer, Conopomorpha cramerella Snellen. The black cocoa ant, Dolichoderus thoracicus is found to be effective in controlling this pest. The abu...
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| Format: | Thesis |
| Language: | English English |
| Published: |
1999
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/10438/1/FP_1999_16_A.pdf |
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| Summary: | Cocoa, an important crop in Malaysian agriculture is subjected to infestation
by a number of insect species the most important of which is the cocoa pod borer,
Conopomorpha cramerella Snellen. The black cocoa ant, Dolichoderus thoracicus is
found to be effective in controlling this pest.
The abundance of nesting sites is crucial in the establishment of this ant. Coconut
palms afford a great deal of nesting sites in the crown and spadices. A large
number of ants also nests in artificial cocoa leaf-litter nests which basically comprises
of a plastic bag (3 1 x 45 cm) stuffed with dry cocoa leaves. The ants also nests
in the cocoa canopy, between two cocoa leaves that overlapped forming a leaf nest.
The population size of the ant in the three types of nests on a per hectare basis should
be compared to determined the more important nesting site. Hence the objective was
to a) study the distribution of the ants in the spadices of coconut crowns, cocoa canopy
and artificial cocoa leaf-litter nest b) study the effects of time and amount of cocoa
leaf-litter on the size of ant population in the artificial nest and c) determine the
nest site preference of D. thoracicus in the canopy of cocoa trees. A sampling technique using a pipette fitted with a modified tip was developed
to estimate the number of ants and its brood in various types of nests. The end
of the pipette tip was cut to make an opening with a diameter of 4.2 mm. Results
showed that taking seven aliquots of 3 ml per aliquot gave the best estimate for
adults and total number of individuals.
Samples of all three types of nests i.e. spadices, artificial nests and cocoa leaf
nests were obtained and the number of adults and brood on a per hectare basis estimated.
There were significantly more ants in the artificial nests compared to the
other two types of nests.
The nest site preference of the ant in relation to canopy strata was examined.
The ants prefered to live in nests placed at the top and bottom strata of the canopy.
Artificial nests were set up on the cocoa trees and the change in population
size of the ants in the nests over time was observed. The ants colonized the nests after
two months with the population reaching a maximum of about 20 x 1 04 individuals
in about five months.
In another experiment, 1 75 , 3 50, 525 and 700g of dry cocoa leaves were
placed in plastic bags measuring 3 1 x 45 cm. All four treatments were placed on a
cocoa tree. After five months, it was found that the bag with 3 50g of dry leaves had
significantly more ants compared to the other three nests.
This study shows the potential of the artificial cocoa leaf-litter nest in the
establishment of the black cocoa ant especially in a monococoa agroecosystem. In
Malaysia where the cocoa pod borer poses a serious problem, the use of the artificial
nest will help in the establishment of the ants and thus leading to the control of the
most dangerous insect pest of cocoa. |
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