Fathiya M. Khamis

First record of Tuta absoluta (Lepidoptera: Gelechiidae) in Uganda

An invasive pest, Tuta absoluta (Meyrick) has been observed infesting tomato Solanum lycopersicum L. (Solanales: Solanaceae) in Central Uganda. The affected farmer made the report, and upon visiting the farm, we observed tiny larvae, green to cream in colour with a black head feeding on tomato leaves, fruit, as well as tender stems. Also, we saw several tiny moths resting on screen house linings. Delta traps baited with TUA-Optima® (Russell IPM) were set in and around the affected farm. Dozens of moths were attracted and trapped on the sticky surface of the traps. The team tentatively identified the insect as T. absoluta. Scientists at the International Centre of Insect Physiology and Ecology (icipe) in Nairobi, Kenya identified the insect using morphological features and molecular techniques.

Risk assessment and spread of the potentially invasive Ceratitis rosa Karsch and Ceratitis quilicii De Meyer, Mwatawala & Virgilio sp. Nov. using life-cycle simulation models: Implications for phytosanitary measures and management

Integrative taxonomy has resolved the species status of the potentially invasive Ceratitis rosa Karsch into two separate species with distinct ecological requirements: C. rosa “lowland type” and the newly described species Ceratitis quilicii De Meyer, Mwatawala & Virgilio sp. nov. “highland type”. Both species are tephritid pests threatening the production of horticultural crops in Africa and beyond. Studies were carried out by constructing thermal reaction norms for each life stage of both species at constant and fluctuating temperatures. Non-linear functions were fitted to continuously model species development, mortality, longevity and oviposition to establish phenology models that were stochastically simulated to estimate the life table parameters of each species. For spatial analysis of pest risk, three generic risk indices were visualized using the advanced Insect Life Cycle Modeling software. The study revealed that the highest fecundity, intrinsic rate of natural increase and net reproductive rate for C. rosa and C. quilicii was at 25 and 30°C, respectively. The resulting model successfully fits the known distribution of C. rosa and C. quilicii in Africa and the two Indian Ocean islands of La Réunion and Mauritius. Globally, the model highlights the substantial invasion risk posed by C. rosa and C. quilicii to cropping regions in the Americas, Australia, India, China, Southeast Asia, Europe, and West and Central Africa. However, the proportion of the regions predicted to be climatically suitable for both pests is narrower for C. rosa in comparison with C. quilicii, suggesting that C. quilicii will be more tolerant to a wider range of climatic conditions than C. rosa. This implies that these pests are of significant concern to biosecurity agencies in the uninvaded regions. Therefore, these findings provide important information to enhance monitoring/surveillance and designing pest management strategies to limit the spread and reduce their impact in the invaded range.

DNA Barcode Reference Library for the African Citrus Triozid, Trioza erytreae (Hemiptera: Triozidae): Vector of African Citrus Greening

Abstract Citrus (Citrus spp.) production continues to decline in East Africa, particularly in Kenya andTanzania, the two major producers in the region. This decline is attributed to pests and diseases including infestation by the African citrus triozid, Trioza erytreae (Del Guercio) (Hemiptera:Triozidae). Besides direct feeding damage by adults and immature stages, T. erytreae is the main vector of ‘Candidatus Liberibacter africanus’, the causative agent of Greening disease in Africa, closely related to Huanglongbing. This study aimed to generate a novel barcode reference library for T. erytreae in order to use DNA barcoding as a rapid tool for accurate identification of the pest to aid phytosanitary measures. Triozid samples were collected from citrus orchards in Kenya, Tanzania, and South Africa and from alternative host plants. Sequences generated from populations in the study showed very low variability within acceptable ranges of species. All samples analyzed were linked to T. erytreae of GenBank accession number KU517195. Phylogeny of samples in this study and other Trioza reference species was inferred using the Maximum Likelihood method. The phylogenetic tree was paraphyletic with two distinct branches. The first branch had two clusters: 1) cluster of all populations analyzed with GenBank accession of T. erytreae and 2) cluster of all the other GenBank accession of Trioza species analyzed except T. incrustata Percy, 2016 (KT588307.1), T. eugeniae Froggatt (KY294637.1), and T. grallata Percy, 2016 (KT588308.1) that occupied the second branch as outgroups forming sister clade relationships.These results were further substantiated with genetic distance values and principal component analyses.

A new edible cricket species from Africa of the genus Scapsipedus

A new cricket of the genus Scapsipedus is described from Kenya. The distribution, acoustic behavior, including call and courtship song, mitochondrial sequences, and data on the biology of that new species are given. This edible cricket is a very promising species for mass production for food and feed.

Size and shape analysis of Trioza erytreae Del Guercio (Hemiptera: Triozidae), vector of citrus huanglongbing disease: Size and shape analysis of Trioza erytreae Del Guercio (Hemiptera: Triozidae)

BACKGROUND The African citrus triozid (ACT) Trioza erytreae Del Guercio (Hemiptera: Triozidae) is one of the most devastating pests of citrus with a well-known role as a vector of the phloem-limited bacteria (Candidatus Liberibacter africanus) associated with huanglongbing (citrus greening disease), currently considered the worlds most serious disease of citrus. Although the pest can successfully develop and reproduce on non-citrus host plants, there is no documented information on the geometric morphometry of ACT. We determine the effect of host plants on ACT morphometry under controlled laboratory conditions using traditional and geometric analysis. RESULTS ACT reared on C. limon and Citroncirus spp. was significantly larger than when reared on the other host plant species. ACT reared on C. anisata and C. tangelo was consistently smaller than that reared on M. koenigii and C. sinensis. Based on warped outline drawings, ACT reared on Citroncirus spp. and Murraya koenigii had narrower wings than when reared on C. anisata, C. limon, and C. sinensis with slightly broader wing patterns. CONCLUSION This study clearly demonstrates that host plant species affect morphometric variation in ACT, which might have a direct impact on fitness parameters of the pest as well as its potential for dispersion. Wing shape and size appear to be useful in separating populations of ACT into different groups.

Spatial Distribution of Bactrocera dorsalis and Thaumatotibia leucotreta in Smallholder Avocado Orchards along Altitudinal Gradient of Taita Hills and Mount Kilimanjaro

Avocado (Persea americana) fruits are an important source of income and a nutritious food for small-scale growers and other stakeholders involved in farming along the Afrotropical highlands of Taita Hills and Mount Kilimanjaro in Kenya and Tanzania, respectively. Avocado fruits are infested by several insect pests, namely the Asian invasive fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), and the false codling moth, Thaumatotibia leucotreta Meyrick (Lepidoptera: Tortricidae). However, there is inadequate information on the distribution patterns of these pests in small-scale avocado cropping systems in the East African highlands. This study was initiated to generate a spatial distribution map of B. dorsalis and T. leucotreta in avocado orchards at Taita Hills and Mount Kilimanjaro in Kenya and Tanzania, respectively. The two pests were monitored by using their respective parapheromone lures for two years between August 2012 and July 2014. Fruit damage was assessed by computing the proportion of infested fruits for B. dorsalis, whereas the damage score was used for T. leucotreta. Our results indicated that the mean number of B. dorsalis per trap per day differed significantly across elevation, being highest in lowland zone for both Taita Hills (15.90) and Mount Kilimanjaro (24.45). Similarly, the percentage infestation of ground collected fruits by B. dorsalis varied with altitude, being lowest at highlands above 1500 m.a.s.l. (0.66% and 0.83% for Taita Hills and Mount Kilimanjaro, respectively). Conversely, the mean number of T. leucotreta did not vary with altitude in either study area. However, the damage score for T. leucotreta infestation was significantly lower in the highlands of both transects (7.0% and11.1% for Taita Hills and Mount Kilimanjaro, respectively). These findings describe spatial trends that are important in formulating strategies aimed at suppressing the populations of B. dorsalis and T. leucotreta in East African avocado cropping systems.

Fruit Fly Nutrition, Rearing and Quality Control

Tephritid fruit flies are recognized worldwide as an important threat to the horticultural industry. Most of the species belonging to this group are highly polyphagous attacking several important fruits and vegetables. They cause direct damage through larval feeding and indirect losses are associated with quarantine restrictions. The increasing awareness of the damage caused by these fruit flies to the horticultural industry has created a demand for the development of control measures based on integrated pest management (IPM) strategies and the sterile insect technique (SIT). However, success of the majority of these control methods largely depends on the ability to establish cost effective rearing methods of the fruit flies as a pre-requisite to understanding their biology, response to attractants and susceptibility to various biological control agents. In the past decades, considerable advances have been made with regard to formulations of diet for rearing fruit flies and nutritional analyses for both adults and larvae. In general, insects require a diet containing a source of energy, a protein source, vitamins and certain mineral salts. Deficiency in some of these nutrients can influence the quality control parameters of the flies such as body size, survival, pupal weight, adult emergence, longevity, flight ability, fecundity, fertility and mating ability. In this chapter, the role played by nutrition in relation to different quality control parameters is discussed.

Role of Microsatellite Markers in Molecular Population Genetics of Fruit Flies with Emphasis on the Bactrocera dorsalis Invasion of Africa

Microsatellites, also referred to as short tandem repeats (STRs) or simple sequence repeats (SSRs) are short sequences of tandem repeats of 1–6 bp in length in clusters of less than 150 bp flanked by sections of non-repetitive unique sequences that are scattered throughout the nuclear genome. These markers are co-dominant and hypervariable, revealing many alleles per locus; they are inherited in Mendelian fashion making them useful for detecting genetic variability within species. Once isolated and characterized, microsatellites can also be used in closely related taxa. Microsatellites can be amplified, even from highly degraded DNA, and are very simple to score. More importantly, these markers are highly polymorphic due to the plethora of variations in the repeat motifs. Several studies have endorsed microsatellite markers as an effective genetic tool to determine the historical distinctiveness of populations, and hence, the designation of species. Being highly polymorphic and selectively neutral, microsatellite markers offer a powerful genetic tool for investigating population structure, colonization processes, temporal and spatial population dynamics and evolutionary trends of insect pests. Furthermore, these markers have been successfully applied to different invasive fruit fly species to infer the evolutionary aspects underlying their invasive processes. Microsatellite markers have offered an analytical tool for the study of fruit fly invasion genetics as exemplified for the Mediterranean fruit fly, Ceratitis capitata. Herein, a detailed utility of microsatellite markers in inferring invasion histories of key fruit flies of economic importance is given, with a special focus on invasion into Africa of Bactrocera dorsalis.

Host stage preference and performance of the aphid parasitoid Diaeretiella rapae (Hymenoptera: Braconidae) on Brevicoryne brassicae and Lipaphis pseudobrassicae (Hemiptera: Aphididae)

We assessed the host stage preference and performance of the aphid parasitoid Diaeretiella rapae (Mcintosh) on two aphid species, Brevicoryne brassicae (L.) and Lipaphis pseudobrassicae (Davis). Although the parasitoid parasitized all nymphal instars of both aphid species, it showed a higher oviposition preference for 2nd (48.2 ± 7.74%) and 3rd (41.0 ± 7.82%) instars of L. pseudobrassicae, and for the 3rd (40.0 ± 4.59%) instar of B. brassicae. Across the host species, there was no significant difference in parasitoid preference between the 3rd and 4th instars, while 1st and 2nd instars of L. pseudobrassicae were significantly more preferred than their counterparts (B. brassicae). Days to mummification among different instars of the same host was not significantly different when the parasitoid was reared on B. brassicae, whereas this was highest on the 2nd, 3rd and 4th instars of L. pseudobrassicae. Number of mummies was also significantly different among the nymphal instars of both host species and between the two host species for the 1st and 2nd instars. In terms of body size, female D. rapae reared on L. pseudobrassicae were significantly larger than those reared on B. brassicae. We discuss the findings in the context of laboratory mass rearing of D. rapae and its potential as a biological control agent for both aphid pest species.

Biochemical changes in developing embryos of Schistocerca gregaria (Orthoptera: Acrididae) induced by pheromone produced by ovipositing gregarious females

Trans-generational transfer of gregarious-phase traits in the desert locust Schistocerca gregaria (Forskål, 1775) is mediated by primer gregarizing pheromonal signals produced by ovipositing females that experience crowding. We monitored time-course proteomic events in eggs from solitary-reared locusts that had been exposed for 1, 3, 5, 7, 10 and 12 days to different levels of the sand-associated gregarizing signal originating from 0, 3, 5 or 10 ovipositions by crowd-reared females. Evidence for the phase transition was sought by comparing the protein patterns of embryos thus exposed with those from crowd-reared (gregarious) controls; this comparison was continued until the stage of the first instars. Expressed proteins were analysed by two-dimensional protein gel electrophoresis, and patterns from the different treatments within stages were compared by profile matching and χ2 analyses. Eggs derived from crowd- and solitary-reared females showed essentially similar protein patterns at early stages of embryogenesis; however, mature stages (particularly, days 10 and 12) and hatchlings demonstrated significantly different patterns. Protein patterns of eggs from solitary-reared females that were incubated in sand contaminated with the pheromonal signal and of the hatchlings that emerged were similar to those derived from gregarious females and dependent on the level of the pheromone to which the embryos had been exposed. The results confirm the gregarizing effect of the signal and constitute a useful basis for unravelling the mechanism of the signalling cascades associated with gene expressions triggered by the pheromone.