Comparing different methods for trapping mated queens of weaver ants (Oecophylla longinoda; Hymenoptera: Formicidae)

The predatory efficiency of African weaver ants Oecophylla longinoda and their utilisation in protein production is a function of ant abundance. Reliable control of insect pests in tropical crops is achieved when ant populations are constantly high. Transplanted populations of weaver ant colonies containing egg-laying queens are more stable than those without. Achieving such stability through collection of colonies established in the wild is usually difficult because of uncertainty in locating the nest containing the egg-laying queen. In this study, we investigated four methods that may be used to collect mated queens that subsequently can be used to stock ant nurseries. The catch efficiencies of (1) leaf traps, (2) paper traps (both types providing a refuge for founding queens), (3) random search for queens and (4) light trapping were compared. Light trapping was the most efficient way to collect queens followed by leaf traps, random search and, last, paper traps. Light trapping and random search, though, required the presence of a person throughout the ant's mating season (several months), whereas this was not required when using leaf and paper traps.     

Using insect traps to increase weaver ant (Oecophylla longinoda) prey capture

Weaver ants (Oecophylla spp.) are managed in plantations to control insect pests and are sometimes harvested as a protein‐rich food source. In both cases, the amount of insect prey caught by the ants is imperative for returns, as more prey leads to more effective biocontrol and to a higher production of ants. Malaise‐like traps placed in trees may catch flying insects without catching ants, as ants may use pheromone trails to navigate in and out of the traps. Thus, ants may increase their prey intake if they are able to extract insects caught in traps. In a mango plantation in Tanzania, we estimated the amount of insects caught by simple traps (cost per trap = 3.9 USD), and whether Oecophylla longinoda was able to collect insects from them. On average, a trap caught 110 insects per month without catching any weaver ants. The number of insects found in traps with ant access was 25% lower than in control traps (ants excluded), showing that ants were able to gather prey from the traps. Ant activity in traps increased over time, showing that prey extraction efficiency may increase as ants customize to the traps. The prey removed from traps by ants constituted 5% of the number of prey items collected by O. longinoda under natural conditions (without traps), potentially increasing to 14% if ants learn to extract all insects. Thus, prey intake may be increased with 5–14% per 3.9 USD invested in traps. These numbers increased to 38 and 78%, respectively, when light was used to attract insects during night time. Combining ant predation with insect trapping is a new approach potentially building increased returns to ant biocontrol and to ant entomophagy.     

Efficacy of African weaver ant,Oecophylla longinoda (Hymenoptera: Formicidae) in reducing losses due to frugivorous fruit flies (Diptera: Tephritidae) in smallholder mango production systems in Eastern Tanzania

Fruit flies (Diptera: Tephritidae) are dipteran insects that cause high losses of fruits and vegetables in the tropical and subtropical regions of the world. As quarantine pests, fruit flies affect export markets because trade regulations hamper export of fruits from areas with occurrence of fruit flies. We compared the effectiveness of Oecophylla longinoda with the insecticide; imidacloprid for the control of Bactrocera dorsalis in a 6-year-old orchard of mango cultivar ‘Apple’. Mango samples at different developmental stages were collected between September and November in 2012 and between November 2013 and January 2014 at a three-week interval between sampling dates. Every fruit was cultured in a separate individual plastic container containing approximately 500?g sieved sterilised sand. Three weeks later, larvae and pupae were sieved from sand and counted. In both years, significantly higher (P?<?.0001) incidences and infestation rates were recorded in the control plots when compared to the trees protected with insecticides and O. longinoda. Incidences and infestation rates did not differ significantly (P?>?.05) between insecticide and weaver ants protected fruits, implying that O. longinoda was as effective as imidacloprid in suppressing the population of fruit flies. Peak fruit fly incidences and infestation rates coincided with the ripening stage of mango fruits. Our results have shown that the incidences and infestation rates on incubated mango fruits were lowest in the O. longinoda and the imidacloprid protected trees. Thus, O. longinoda is an effective bio-control agent that could be exploited to serve as a vital Integrated Pest Management component on mango orchards.     

Seasonality and host utilization of the invasive fruit fly, Bactrocera invadens (Dipt., Tephritidae) in central Tanzania

Abstract:  The temporal occurrence of the invasive and economically important pest fruit fly, Bactrocera invadens was studied in three agro-ecological areas of Morogoro Region, central Tanzania, during 2004–2005. Weekly and monthly trappings were carried out with methyl eugenol, protein bait and synthetic food attractant. Bactrocera invadens was permanently present at low and mid-altitudes (380–520 m a.s.l.) with peak periods coinciding with the fruiting season of mango ( Mangifera indica ) and guava ( Psidium guajava ). At high altitude (1650 m a.s.l.) its incidence was only temporal and apparently the result of dispersal from lower altitudes after the mango fruiting season. Rearing results showed mango, loquat ( Eriobotrya japonica ), guava and grapefruit ( Citrus  ×  paradisi ) to be the favoured commercial host fruits. Other Citrus species, cucurbits, papaya ( Carica papaya ) and avocado ( Persea americana ) were less favoured.     

An integrative approach to unravel the Ceratitis FAR (Diptera,Tephritidae) cryptic species complex: a review

This paper reviews all information gathered from different disciplines and studies to resolve the species status within the Ceratitis FAR (Ceratitis fasciventris, Ceratitis anonae, Ceratitis rosa) complex, a group of polyphagous fruit fly pest species (Diptera, Tephritidae) from Africa. It includes information on larval and adult morphology, wing morphometrics, cuticular hydrocarbons, pheromones, microsatellites, developmental physiology and geographic distribution. The general consensus is that the FAR complex comprises Ceratitis anonae, two species within Ceratitis rosa (so-called R1 and R2) and two putatitve species under Ceratitis fasciventris. The information regarding the latter is, however, too limited to draw final conclusions on specific status. Evidence for this recognition is discussed with reference to publications providing further details.     

Modified netting technique for capturing gazelles in Serengeti,Ngorongoro and Loliondo,Tanzania

During serological surveillance of peste des petits ruminants (PPR) disease, it required capture of randomly selected herds of gazelles as part of a study to determine the epidemiological role of these species in the circulation of peste des petits ruminants virus (PPRV). The study targeted capturing 135 Grant's gazelles (Gazella granti) from the Serengeti ecosystem, Tanzania. A modified netting technique was used aiming at providing safe, efficient and cost‐effective method for capture of gazelles. Locally available materials were used, and wildlife professionals guided the process of manufacturing supporting frame for the nets. Twenty (20) black metal pipes, 20 metal bars, four nets and three vehicles were used in the procedure. A total of 136 Grant's gazelles and nine Thomson's gazelles were captured in three missions. The Grant's gazelles were captured as per sample size calculated in all locations: Loliondo (n = 25), Serengeti National Park (n = 44) and Ngorongoro Conservation Area (NCA) (n = 67) using less time and minimum cost than estimated. Injuries of three fawns (2%) inadvertently captured with the groups of adults and sub‐adult animals were recorded. Comparing with 2014 and other studies, modified netting technique showed high animal and operator safety levels with minimal injuries. With this technique, it was possible to capture even flighty animals that behave nervously because of hunting and other human activities, including Thomson's gazelles, a species previously found to be difficult to capture by netting.     

Temporal abundance of African weaver ant,Oecophylla longinoda (Hymenoptera: Formicidae) under unimodal rainfall pattern in Tanzania

Weaver ants, Oecophylla spp., provide adequate protection to crops against insect pests when their populations are high and stable. A study was conducted in a cashew field in Tanzania from November 2012 to October 2014 to determine temporal abundance of O. longinoda. We determined (i) the number of shoots with O. longinoda in a tree (established fortnightly) monitored at four cardinal points of a tree, using 1 m² wooden quadrats, (ii) the percentage of branches with ant trails per tree per month and (iii) the number of visible ant nests within the tree canopy per month. Furthermore, we assessed the association of weather and phenology with O. longinoda populations. More weaver ant populations were recorded during reproductive and vegetative phases of cashew. We recorded significant positive associations between rainfall and temperature with the number of shoots with O. longinoda (p < .001), as well as relative humidity with the number of nests (p < .001). The percentage of shoots with O. longinoda was significantly associated with cashew growth phases. Rainfall and temperature negatively affected the number of nests. Consideration of cashew phenology and weather parameters can greatly enhance successful weaver ant augmentation strategies.     

Detection of the solanum fruit fly, Bactrocera latifrons (Hendel) in Tanzania (Dipt., Tephritidae)

Abstract:  The presence of the Solanum fruit fly, Bactrocera latifrons , in Africa is reported for the first time, based on trapped and reared specimens in Tanzania. Two new host records, Solanum aethiopicum and Solanum macrocarpon , are reported.     

Effect of mango weevil (Coleoptera: Curculionidae) damage on mango seed viability in Tanzania

Studies were conducted at the horticulture unit of Sokoine University of Agriculture, Morogoro, Tanzania, to assess the incidence and effect of mango weevil, Cryptorhynchus mangiferae (F.) (Coleoptera: Curculionidae), infestation on mango, Mangifera indica L., seed viability. Three polyembryo mango cultivars ('Sindano nyeusi', 'Sindano nyeupe', and 'Dodo') as well as three monoembryo mango cultivars ('Ex-horticulture', 'Tango', and 'Bongwa') were collected and examined for the presence of C. mangiferae. The effect of seed damage on viability was assessed for both naturally and artificially damaged seeds. However, for artificially damaged seeds, the viability was assessed by cutting away 0, 25, 50, or 75% of the cotyledon before planting. In this experiment, only monoembryo mango cultivars were used. All the examined cultivars were infested by C. mangiferae, although at varying levels. Polyembryo mango cultivars were relatively more infested than monoembryo cultivars. Bongwa and Tango were least infested, whereas Sindano nyeusi recorded the highest C. mangiferae incidence. Germination rates of damaged seeds of polyembryonic cultivars differed significantly from the uninfested control, except for Sindano nyeusi. There were no significant differences in germination percentage among the three monoembryo cultivars, and all the cultivars differed significantly from the uninfested control. The germination rates of seeds with 25% of their cotyledons removed did not differ significantly from the undamaged seeds, indicating that monoembryo cultivar seeds can withstand up to 25% damage and germinate successfully.     

Field evaluation of the relative attractiveness of enriched ginger root oil (EGO)lure and trimedlure for African Ceratitis species (Diptera: Tephritidae)

The males of some fruit flies (Diptera: Tephritidae) are known to be attracted to specific parapheromones. The trapping results between trimedlure (TML) and enriched ginger root oil (EGOlure) were compared at two experimental sites in Morogoro (Central Tanzania) for a period of 12 weeks co‐inciding with the main citrus season. Both attractants captured a comparable diversity of fruit flies, except that EGOlure also attracted fruit flies, such as Ceratitis cosyra, not normally found in TML‐baited traps. Both EGOlure and TML attracted mainly or exclusively male fruit flies, but the catches with EGOlure were equal or superior to those with TML. It is concluded that EGOlure should be considered as a suitable alternative for TML in detection, monitoring and control programs for African fruit flies of the genus Ceratitis. It has the added advantage that it combines the attractiveness with regard to species spectrum of both TML and terpinyl acetate.