Methods for enhancing weaver ant (Oecophylla Longinoda Latreille) (Hymenoptera; Formicidae) populations for sustainable control of insect pests of crops

A THESIS SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY OF SOKOINE UNIVERSITY OF AGRICULTURE. MOROGORO, TANZANIA.

Weaver ants (Oecophylla spp) are eusocial insects used in pest management. Studies were conducted in citrus field in Tanga and Morogoro regions to determine occurrence of sexual, efficient methods for trapping mated queens, population structure and optimizing queen rearing methods as prerequisite for transplanting weaver ants population. Result of a study conducted between 2011 to 2013 showed that sexuals occurred in nests for a prolonged period with peaks between February and April. Numerically, males were more abundant than queens (6:1). Average number of males per nest was 87 (± 54) and for the queens was 17 (± 6). Harvesting of two nests per colony per month did not affect the number of nests per colony (treatment effect, F1.31 = 1.87, P = 0.8; time effect, F11.21 = 8.96, P < 0.0001, treatment x time F11.21 = 1.18, P = 0.36). Results also showed that out of 34 collected queens 73% were from leaf traps, 24% from paper traps and 3% from search and catch. However when light trap, was included it accounted for 91% of 236 collected queens. The collected mated queens were reared in the screen house using three methods; limited access to water, Continuous direct access to 5 mls of water Continuous indirect access to 15 mls of water. Results showed that queen survival was independent of all the three tested rearing methods (χ2 = 2.0; df = 2, 48; P = 0.36). Rearing methods significantly affected the total numbers of brood (F = 4.85; df = 2, 48; P = 0.012) with higher numbers recorded on continuous direct and indirect access to water methods. Results also showed that colony size varied significantly. One colony of O. longinoda covered 3 to 30 citrus trees in an area between 27 m2 to 270 m2, Average number of nests per colony ranged from 18 (± 6 SE) to 142.5 (± 17.5 SE). The highest numbers of major and minor workers per nest was 1064.5 ± 252.9 and 2365 ± 895.9 respectively. Weather parameters had effects on the numbers of major workers, minor workers and winged queens.