Abstract:
Many ant species (Hymenoptera, Formicidae) have the potential to control herbivore
abundance, reducing the plant damage while increasing plant growth, reproduction
and yield in agro-ecosystems. Ant assemblages on six cashew trees in Delgoda,
Gampaha District were recorded throughout three phenological phases by visiting
the field six times from March to June in 2015. Seven to 15 baited traps were set 25
cm apart on the branches of each small, medium and large tree and collected after
three hours. Worker ants seen on the main trunk and four major branches of each tree
during a five minute period were hand-collected 5 to 9 times from small to large trees
on each occasion. Collected ants were preserved in 70% ethanol, identified and
listed. Number of Oecophylla smaragdina (Fabricius) nests observed on the same
trees was recorded from April to June in 2015. The materials carried by O.
smaragdina workers on cashew tree branches were also collected, preserved in 70%
ethanol and identified to the possible levels using a Low Power Stereo-microscope.
Fourteen ant species in five subfamilies were recorded. Species richness observed on
each occasion ranged from 7 – 11 while O. smaragdina was the only species on all
cashew trees. Nests of the species of O. smaragdina were observed only on one or
two large and medium-sized trees. Various plant and animal materials carried by O.
smaragdina workers confirmed that the species is an omnivore and a generalist
predator. Presence of ant assemblages on cashew trees in the absence of any
insecticide application in the current cashew field may have contributed to an
observed absence of serious damage by cashew insect pests elsewhere.
