Effect of supplementary feeding of Oecophylla longinoda on their abundance and predatory activities against cashew insect pests

Abstract

Many studies have shown the efficiency of using weaver ants (Oecophylla species) as natural biocontrol agents against agricultural pests. Supplementary feeding could promote fast growth of this ant's population and discourage them from moving away. However, such artificial feeding might slow down ants search rates and in this way make them less efficient bio-agents. The experiments were conducted for two consecutive seasons at Naliendele Research Station. Cashew trees planted at a spacing of 12 m × 12 m in 2002 were used to investigate whether supplementary feeding could enhance foraging behaviour of Oecophylla longinoda. Fed O. longinoda colonies fed weaver ants (FWA) were supplemented with a 30% sugar solution and approximately 22 g of finely ground fish meat at two-week intervals while the unfed colonies unfed weaver ants (UWA) had access to only naturally occurring food sources. Weaver ant densities and pest damage were monitored fortnightly on newly damaged shoots, panicles and fruits and nut yields assessed after each harvest season. The results revealed that there was a significant difference (P < 0.05) with higher weaver ant densities in the FWA compared to UWA colonies and significantly lower (P < 0.05) pest damage levels were recorded on weaver ant treatments compared to plots without weaver ants. No significant differences (P > 0.05) in yields and mean damage levels were recorded between the two weaver ant treatments. Highest nut yield (4.22 ± 0.30 kg/tree and 5.37 ± 0.27 kg/tree) was recorded in the fed colonies, followed by non-fed colonies (4.20 ± 0.30 kg/tree and 4.88 ± 0.24 kg/tree) and the least (2.66 ± 0.19 kg/tree and 2.99 ± 0.19 kg/tree) was recorded from the untreated controls in 2012/2013 and 2013/2014, respectively. The studies indicated that supplementary feeding could boost weaver ants to higher population levels without reducing their effectiveness as biocontrol agents.

Keywords:

• ant feeding
• biocontrol agents
• O. longinoda
• predatory activities
• supplementary feeding

Acknowledgements

Authors would like to thank the Naliendele Agricultural Research Institute (NARI) management and staff for permission to conduct research in their cashew orchards and provision of technical assistance whenever needed. Dr. Renkang Peng is acknowledged for his technical assistance in differentiating symptoms caused by different pests. We also acknowledge the support from Messrs. Hassan Libubulu, Hamza Mawazo, Mohammed Salim and Mohammed Machunja during the field activities. Lastly, support from W. George during some stages of weaver ant transplantation is acknowledged. This study was funded by the Danish International Development Assistance (DANIDA) [grant number DFC No.10–025AU].

Disclosure statement

No potential conflict of interest was reported by the authors.