Niche partitioning among two Ceratitis rosa morphotypes and other Ceratitis pest species (Diptera,Tephritidae) along an altitudinal transect in Central Tanzania

Two standard parapheromones, trimedlure (routinely used for monitoring Ceratitis rosa and Ceratitis capitata) and terpinyl acetate (routinely used for monitoring Ceratitis cosyra) were compared with enriched ginger root oil (EGO) lure for detecting and monitoring the presence and relative population abundance of these particular pest species. Standard yellow fruit fly traps were used for the comparison, which was conducted at 10 sites along an altitudinal transect ranging from 540 to 1650 masl on the Uluguru mountains, in Morogoro Region (Central Tanzania). A gradual change of relative occurrence of the two Ceratitis rosa morphotypes was clear from the EGO lure trapping. The morphotype R1 was predominant at lower altitudes while morphotype R2 was predominant at higher altitudes. Further experiments are needed to confirm the consistency of the observed pattern across regions, seasons and years as well as possible differences in the developmental physiology of both morphotypes. The mango fruit fly, Ceratitis cosyra, showed a distinct predominance at altitudes below 800 masl as shown in both the EGO lure and the terpinyl acetate trapping. The catches of all three target species were higher in traps with the EGO lure compared to the conventional lures trimedlure and terpinyl acetate. It is argued that for these species EGO lure can act as a suitable and more effective alternative for trimedlure and terpinyl acetate parapheromones. In addition, EGO lure has the added advantage that it combines the taxon spectrum for the two latter substances, thus requiring the use of only a single attractant.     

Population structure and cryptic genetic variation in the mango fruit fly,Ceratitis cosyra (Diptera,Tephritidae)

The fruit fly Ceratitis cosyra is an important agricultural pest negatively affecting the mango crop production throughout Africa and also feeding on a variety of other wild and cultivated hosts. The occurrence of deeply divergent haplotypes, as well as extensive morphological variability, previously suggested possible cryptic speciation within Ceratitis cosyra. Here we provide the first large-scale characterisation of the population structure of Ceratitis cosyra with the main objective of verifying cryptic genetic variation. A total of 348 specimens from 13 populations were genotyped at 16 polymorphic microsatellite loci. Hardy-Weinberg equilibrium (HWE) deviations were observed in 40.4% of locus-population combinations and suggested the occurrence of genetic substructuring within populations. Discriminant Analysis of Principal Components (DAPC) showed genetic divergence between the vast majority of vouchers from Burundi and Tanzania (plus a few outliers from other African countries) and all other specimens sampled. Individual Bayesian assignments confirmed the existence of two main genotypic groups also occurring in sympatry. These data provided further support to the hypothesis that Ceratitis cosyra might include cryptic species. However, additional integrative taxonomy, possibly combining morphological, ecological and physiological approaches, is required to provide the necessary experimental support to this model.     

A review of the current knowledge on Zeugodacus cucurbitae (Coquillett) (Diptera,Tephritidae) in Africa,with a list of species included in Zeugodacus

This paper reviews all available information regarding the occurrence and biology of the melon fly, Zeugodacus cucurbitae (Coquillett), in the Afrotropical Region, including data on invasion history, distribution patterns, population genetics, host range, and interspecific competition. Although limited intraspecific variability has been observed within the region regarding the above mentioned aspects, there seems to be no indication that Zeugodacus cucurbitae represents a species complex. A checklist of all of the species included in Zeugodacus as recently proposed by Virgilio et al. (2015) is provided.     

Dynamics of infestation and losses of stored maize due to the larger grain borer (Prostephanus truncatus Horn) and maize weevils (Sitophilus zeamais Motschulsky)

The dynamics of infestation and losses of stored maize due to the larger grain borer (Prostephanus truncatus Horn) and maize weevils (Sitophilus zeamais Motschulsky) were investigated in Tanzania. In single species populations, significantly higher maize damage (P ≤ 0.05) was caused by P. truncatus (23.3%) compared to S. zeamais (6.4%). Weight losses caused by P. truncatus were higher (12.7%) than for S. zeamais (6.7%) under similar conditions. A higher proportion of P. truncatus in the initial infestation population led to significantly higher (≤0.05) maize damage compared to equal or higher proportions of S. zeamais. Irrespective of the initial number of S. zeamais, population size increased to levels higher than for P. truncatus. Maize losses in unimproved storage structures were >80% compared to <2.5% in improved structures under natural infestation. Inter-specific competition appeared to influence the dynamics of infestation, damage levels and weight losses. The first two months of storage were critical for damaging insect populations to build up.     

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

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.     

Control of mango seed weevils (Sternochetus mangiferae) using the African Weaver Ant (Oecophylla longinoda Latreille) (Hymenoptera: Formicidae)

The mango seed weevil, Sternochetus mangiferae (Fabricius), is among the major threats to mango production in Tanzania. Sternochetus mangiferae is primarily a quarantine pest whose presence inside the fruits restricts access to new foreign markets and leads to rejections of fruits destined for export. Management options for the pest have largely been dependent on field sanitation and application of synthetic insecticides with some success. Thus, more sustainable methods are needed to substitute insecticides, as this may also open up opportunities for organic markets. We conducted field experiments for two fruiting seasons in a mango plantation at Mlandizi, Kibaha district, along the coastal belt of Tanzania to evaluate and compare the effectiveness of the predaceous ant Oecophylla longinoda Latreille with foliar insecticidal sprays of Dudumida (70 WDG Imidacloprid) in controlling S. mangiferae. Mango seed weevil infestation was assessed fortnightly based on infestation marks on developing fruits starting eight weeks after fruit set to early ripening phase. Between 50 and 64 fruits were sampled, well labelled in jute bags, secured and transported to the laboratory at Kibaha Biological Control Unit (KBCU) for incubation at room temperature using rearing transparent containers. Two weeks later, the fruits were dissected and inspected for the presence of S. mangiferae developmental stages. Field and laboratory results indicated that fruits from trees that were occupied by O. longinoda and from those treated with insecticide showed significantly (P < 0.0001) lower incidences and infestation rates by S. mangiferae than from untreated trees. Furthermore, there were no significant differences between the insecticide and the weaver ant treatments. We conclude that in our experiments, O. longinoda is an efficient biological control agent for a long‐term control programme and is comparable to insecticide (Dudumida) in suppressing S. mangiferae and may be used in Tanzanian mango plantations.