Optimizing a method for locating queen nests of the weaver ant Oecophylla longinoda Latreille (Hymenoptera: Formicidae) in cashew, Anacardium occidentale L. plantations in Tanzania W. Nene a, * , G.M. Rwegasira b , M. Mwatawala b a Naliendele Agricultural Research Institute, Box 509, Mtwara, Tanzania b Sokoine University of Agriculture, Department of Crop Science and Production, Box 3005, Morogoro, Tanzania article info Article history: Received 15 March 2017 Received in revised form 6 August 2017 Accepted 13 August 2017 Keywords: Weaver ants Queen nest Bio-agent Success rate Tanzania abstract The African Weaver Ant, O. longinoda Latreille is an important and successful biological control agent of numerous important pests of tree crops including cashew. There are hundreds of nests in a colony but only a single nest contains a queen with the role of laying eggs which ultimately produce viable offspring. The introduction of weaver ant colonies in a plantation is sustainable when a reproductive queen is included. Therefore, locating weaver ant colonies that contain a queen nest is essential, particularly during relocation of a mature colony in a plantation. We investigated locating queen nests in 52 colonies of O. longinoda. This study revealed that a tree with a queen nest (i) was not infested by weaver ant antagonists (ii) had more weaver ant trails with more active/aggressive workers than was the case with other trees (confirmed in 96% of cases). The queen nests was identified by aggregation of workers on or near the nest surface and the presence of workers on the exterior surface of the queen nest forming a chain/bridge like structure when queen nest is slightly disturbed. Furthermore, the queen nest is con- structed with thick silk threads tightened between the queen nest leaves. Significantly (p < 0.0001), more queen nests were of smaller size and were located at the middle or lower position inside the tree canopy. It took an average of 5.6 min with a success rate of 99.6% to locate a O. longinoda queen nest. These new findings may facilitate the application of weaver ant technology in IPM-programs. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Weaver ants, Oecophylla spp., are recognized as biological agents for the control of insect pests in multiple tree crops including cashew, citrus and mango (Way and Khoo, 1992; Peng and Christian, 2007; Abdulla et al., 2015). The two species of weaver ant, Oecophylla smaragdina Fabricius and O. longinoda Latreille (Hymenoptera: Formicidae), are effective biological control agents against more than 50 different pests in multiple tree crops and forest trees (Way and Khoo, 1992; Peng et al., 1995). Their control ability can be equal to or more effective than chemical pesticides (Peng et al., 2005; Dwomoh et al., 2009; Offenberg et al., 2013), resulting in increased crop yields and or higher fruit quality (Barzman et al., 1996; Peng and Christian, 2007). Furthermore, they may be utilized as protein food for humans (Sribandit et al., 2008; Offenberg, 2011; FAO report, 2013) or feed (C esard, 2004) and in this way, they can contribute to food security (Offenberg and Wiwatwitaya, 2009). Colonies of O. longinoda are established by a mated queen (Nene et al., 2016a). A mature colony of O. longinoda is composed of maternal queen, workers (large and small), winged males and fe- males (sexuals) (Rwegasira et al., 2014). During the rainy season, males and queens are liberated from their natal nests and perform a flight (nuptial flight). After the nuptial flight, a mated queen lands to start a new colony (Nene et al., 2016a). The queen's role in a colony is to lay eggs which ultimately produce viable offspring (larvae, pupae, imagos and mature workers). Therefore, the use of weaver ants as a bio-control agent can only be sustainable and successful when a colony contains a maternal queen (Peng et al., 1997, 2008). Colonies can be found by trapping newly mated queens, and with the use of artificial nests, which are reared in nurseries which can be introduced in a new orchard (Peng et al., 2013; Rwegasiraet al., 2015; Nene et al., 2015, 2016a). Knowledge on the weather conditions that trigger flights and time of the day of * Corresponding author. E-mail address: wilsoninene@gmail.com (W. Nene). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro http://dx.doi.org/10.1016/j.cropro.2017.08.013 0261-2194/© 2017 Elsevier Ltd. All rights reserved. Crop Protection 102 (2017) 81e87