PhD. Thesis
Experiments to determine the potential of Weaver ants, Oecophylla longinoda Latreille (Hymenoptera: Formicidae) as biocontrol agents of major insect pests of cashew and mango were conducted at Naliendele Agricultural Research Institute in Mtwara and Kibaha in the Coast region, during 2012/13 and 2013/14 fruiting seasons. Cashew is attacked by Coconut bugs, Pseudotheraptus wayi Brown; Mirid bugs, Helopeltis spp. and Thrips, Selenothrips rubrocinctus Giard. Mango is threatened by several fruit fly species and the mango seed weevils, Sternochetus mangiferae (Fabricius); both being quarantine pests. Farmers use synthetic insecticides to control these pests and no alternative measures are available for organic growers. Reliance on chemical control measures has not made it possible to suppress the pests‟ populations to uneconomic levels. Similarly, dependency on insecticides for the control of S. mangiferae during flowering season has not proven very successful. In the current study, the efficiency of O. longinoda as bio-control agents was compared with Karate® (lambda-cyhalothrin) and the control plots against Cashew insect pests. On mango, the efficacy of O. longinoda was compared with Dudumida (70WDG Imidacloprid) and the control against fruit flies and the S. mangiferae. The results indicated significantly lower (P<0.0001) damages for the three cashew pests in the protected trees compared to control. For two seasons, P. wayi damage was <5% in protected trees as opposed to 29% and 25% in the unprotected plots; Helopeltis spp damage was <3% in protected trees for two seasons as opposed to >8% and >6% in unprotected, and S. rubrocinctus damage was <11% in protected trees for both seasons as opposed to >41% and >39% in the unprotected plots in 2012/13 and 2013/14 respectively. Incidences of fruit flies was <6% and <8% in protected trees as opposed to >18% and >24% in the unprotected in 2012/13 and 2013/14 respectively, whereas incidences of S. mangiferae was <7% and <8% in protected trees as opposed to >24% and >30% in unprotected trees in 2012/13 and 2013/14 respectively. Throughout the experiments O. longinoda was as effective as insecticides in controlling major cashew and mango insect pests. Thus, O. longinoda can serve as a substitute to insecticides.
DANIDA