Chrysantus M. Tanga

Antagonistic Interactions between the African Weaver Ant Oecophylla longinoda and the Parasitoid Anagyrus pseudococci Potentially Limits Suppression of the Invasive Mealybug Rastrococcus iceryoides

The ant Oecophylla longinoda Latreille forms a trophobiotic relationship with the invasive mealybug Rastrococus iceryoides Green and promotes the latter’s infestations to unacceptable levels in the presence of their natural enemies. In this regard, the antagonistic interactions between the ant and the parasitoid Anagyrus pseudococci Girault were assessed under laboratory conditions. The percentage of parasitism of R. iceryoides by A. pseudococci was significantly higher on “ant-excluded” treatments (86.6% ± 1.27%) compared to “ant-tended” treatments (51.4% ± 4.13%). The low female-biased sex-ratio observed in the “ant-tended” treatment can be attributed to ants’ interference during the oviposition phase, which disrupted parasitoids’ ability to fertilize eggs. The mean foraging time, host handling time and number of successful oviposition in “ant-excluded” treatment were significantly higher compared to “ant-tended” treatments. When ant workers were allowed access to sterilized sand grains, mummified and unmummified R. iceryoides, they selectively removed the mummified mealybugs, indicating that they recognized the mummies as potential foods (1.2 ± 0.46 to 7.8 ± 1.17 mummies at 10 min intervals for 2 h). Percentage emergence from mummified R. iceryoides removed by the ants was significantly lower compared to emergence from mummies not exposed to ants. Although, host seeking parasitoids frequently evaded attacks, some were killed by the foraging ant workers (2.0 ± 0.38 to 6.0 ± 0.88 at 10 min intervals for 2 h). These results suggest for the first time that the presence of O. longinoda has a detrimental effect on the abundance, reproductive success and possibly oviposition strategy of female parasitoids, which might be a delimiting factor in field conditions if both natural enemies are to be recommended for use within the same agro-ecosystem.

Comparative analysis of development and survival of two Natal fruit fly Ceratitis rosa Karsch (Diptera, Tephritidae) populations from Kenya and South Africa

Abstract Comparative analysis of development and survivorship of two geographically divergent populations of the Natal fruit fly Ceratitis rosa Karsch designated as Ceratitis rosa R1 and Ceratitis rosa R2 from Kenya and South Africa were studied at seven constant temperatures (10, 15, 20, 25, 30, 33, 35 °C). Temperature range for development and survival of both populations was 15–35 °C. The developmental duration was found to significantly decrease with increasing temperature for Ceratitis rosa R1 and Ceratitis rosa R2 from both countries. Survivorship of all the immature stages of Ceratitis rosa R1 and Ceratitis rosa R2 from Kenya was highest over the range of 20–30 °C (87–95%) and lowest at 15 and 35 °C (61–76%). Survivorship of larvae of Ceratitis rosa R1 and Ceratitis rosa R2 from South Africa was lowest at 35 °C (22%) and 33 °C (0.33%), respectively. Results from temperature summation models showed that Ceratitis rosa R2 (egg, larva and pupa) from both countries were better adapted to low temperatures than R1, based on lower developmental threshold. Minimum larval temperature threshold for Kenyan populations were 11.27 °C and 6.34 °C (R1 and R2, respectively) compared to 8.99 °C and 7.74 °C (R1 and R2, respectively) for the South African populations. Total degree-day (DD) accumulation for the Kenyan populations were estimated at 302.75 (Ceratitis rosa R1) and 413.53 (Ceratitis rosa R2) compared to 287.35 (Ceratitis rosa R1) and 344.3 (Ceratitis rosa R2) for the South African populations. These results demonstrate that Ceratitis rosa R1 and Ceratitis rosa R2 from both countries were physiologically distinct in their response to different temperature regimes and support the existence of two genetically distinct populations of Ceratitis rosa. It also suggests the need for taxonomic revision of Ceratitis rosa, however, additional information on morphological characterization of Ceratitis rosa R1 and Ceratitis rosa R2 is needed.

Comparison of Food-Based Attractants for Bactrocera invadens (Diptera: Tephritidae) and Evaluation of Mazoferm—Spinosad Bait Spray for Field Suppression in Mango

ABSTRACT Catches of Bactrocera invadens Drew, Tsuruta, & White (Diptera: Tephritidae) in Multi-lure traps baited with six commercial food-based attractants, Mazoferm E802, Torula yeast, GF-120, Hymlure, Biolure, and Nulure were compared in mango orchards in Kenya. In 2007, Mazoferm E802 and Torula yeast were the most effective attractants and captured 2.4-2.6 times more females and 3.4-4.0 times more males than the standard Nulure. All attractants captured more females than males (ranging from 63 to 74%). In 2008, Mazoferm E802 was the most effective bait capturing 5.6 and 9.1 times more females and males, respectively, than the standard Nulure. Among all the attractants, in both years, Nulure captured the greatest proportion of females: 74% compared with 51–68% for the other attractants. In 2008, the use of Mazoferm E802 in combination with spinosad as a bait spray in mango orchards reduced B. invadens catches relative to the control by 87% within 4 wk and 90% within 8 wk. At harvest, the proportion of fruit infested was significantly lower in the treated orchards (8%) compared with the control orchards (59%). Estimated mango yield was significantly higher in orchards receiving the bait sprays (12,487 kg/ha) compared with control orchards (3,606 kg/ha). Based on bait spray costs, yield data, and monetary gains, a cost—benefit ratio of 1:9.1 was realized, which is acceptable for growers. In 2009, the experiment was repeated with similar results. We have demonstrated that Mazoferm E802, used alone for monitoring of B. invadens or in conjunction with spinosad for population suppression, shows great promise in Kenya.

Effect of Six Host Plant Species on the Life History and Population Growth Parameters of Rastrococcus iceryoides (Hemiptera: Pseudococcidae)

ABSTRACT The effect of 6 host plant species [Mangifera indica L., Cajanus cajan (L.) Millspaugh, Coffea arabica L., Cucurbita moschata Duchesne, Parkinsonia aculeata L., and Ficus benjamina Roxb.], on bionomics of the mango mealybug Rastrococcus iceryoides Green (Hemiptera: Pseudococcidae) was studied in the screenhouse. Biological and life table parameters of the mealybug differed significantly among the host plants. Developmental period (egg to adult) was shortest on M. indica (23.5 days and 25.3 days for females and males, respectively), whereas it was longest on F. benjamina (33.0 days and 37.3 days for females and males, respectively). The egg to adult female survivorship was highest on C. moschata (79.6%) and lowest on C. arabica (30.9%). Fecundity was highest on C. moschata (811.3 egg/female) followed by M. indica (716.8 egg/female). The sex ratio was female-biased on C. moschata, M. indica, C. cajan and P. aculeata. Adult mealybug longevity also varied with host plant for both mated and unmated females. Adult female body length and width were significantly higher on C. moschata, M. indica, C. cajan and P. aculeata than on F. benjamina and C. arabica. The highest intrinsic rate of natural increase (rm), finite rate of increase (&lgr;) and the shortest mean generation time (GT) and doubling time (T d) were recorded on M. indica. The highest and lowest net reproductive rate (Ro) occurred on C. moschata and C. arabica, respectively. The implication of these findings in relation to damage, population growth and management of R. iceryoides on the target crops is discussed.

Some key elements on entomophagy in Africa: culture, gender and belief

Edible insects are a natural renewable food resource and, within the context of food security could be one solution for Africa. Although, entomophagy is still being practiced in Africa, there is a degree of rejection in certain milieu due to negative images associated with insects and poor awareness efforts. In order to understand the key elementsthat govern entomophagy in Africa, we conducted an online survey on edible insects in African countries anddocumented the importance of insects, cultures and believes associated to their use. We eventually looked at genderparticipation in entomophagy. Study showed that insect consumption can be restricted to one tribe, community or toa whole region. Distinct ethnic names of edible insects and their respective host plant presented in this study implythat entomophagy constitutes an important part of community livelihood and can be easily promoted. However, insects are mainly used as complementary food, and in very few occasions, as main food. They are also used for...

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.

Physico-chemical properties of extruded aquafeed pellets containing black soldier fly (Hermetia illucens) larvae and adult cricket (Acheta domesticus) meals

Fish farming is faced with the challenge of high cost of feeds because of the cost of high quality protein needed for formulation of the feeds. Thus, there is urgent need for alternative protein sources. The effects of substituting freshwater shrimp meal (FWSM) with black soldier fly larvae meal (BSFM) or adult cricket meal (ACM) on physico-chemical properties of hot-extruded fish feed pellets were investigated. The FWSM protein in a 26 g/100 g protein fish feed formulation was substituted at 0, 25, 50 and 75%, and moisture content of the formulated blends adjusted to 10, 20 or 30 g/100 g prior to extrusion. Floatability, expansion rate, bulk density, durability index, water absorption index, water solubility index, and water stability of extruded pellets were determined. Sinking velocity and the total suspended and dissolved solids in water were determined for the optimal pellets. Pellet floatability was not influenced by the type of insect meal but the interaction between level of inclusion and moisture...

Insects for Income Generation Through Animal Feed: Effect of Dietary Replacement of Soybean and Fish Meal With Black Soldier Fly Meal on Broiler Growth and Economic Performance

Abstract The ever-increasing animal feed costs are driving many vulnerable communities involved in animal husbandry out of business.The high cost is mainly driven by the protein source, which represents the most expensive component in animal feed. In conventional feed, protein is obtained mainly from soybean and fish meal (SFM).The present study explored potential of partially replacing this SFM with black soldier fly prepupae meal (BSFPM) in Cobb 500 broiler chicken diets. A SFM-based diet was compared to three experimental diets formulated by partially substituting SFM with BSFPM at 13.8, 27.4, and 42.0% of the crude protein (CP) in the starter feed and 11.0, 37.2, and 55.5% of the CP in the finisher feed of diets D1, D2, and D3, respectively. Dietary effects on average daily feed intake, average daily body weight gain, feed conversion ratio, carcass characteristics, breast meat sensory attributes, and the economic implication of their use in broiler production were evaluated. Replacement of SFM with BSFPM did not affect daily feed intake, daily body weight gain, feed conversion ratio, aroma or taste of cooked breast meat. A 16.0% higher Cost Benefit Ratio and 25.0% better Return on Investment was recorded when the birds were reared on the highest concentration of black soldier fly (D3) compared to the conventional diet which was 19.0% more expensive. The implication of these findings for the promotion of insect mass production enterprises for animal feed protein, and their potential for income generation and job creation particularly in developing countries is discussed.

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.

Fruit Fly Species Composition, Distribution and Host Plants with Emphasis on Mango-Infesting Species

Mango is the most widely cultivated fruit tree in tropical and sub-tropical Africa. However, the sustainability of this lucrative business is threatened by infestations of fruit flies (Diptera: Tephritidae) that annually inflict heavy economic losses on the industry. The nutritional quality of different fruit species can influence the survival and fecundity of adult fruit flies. This host-insect interaction determines the species composition, distribution and abundance of the major frugivorous tephritids. The economic impact of fruit fly pest species includes direct yield losses and the loss of export markets due to quarantine restrictions implemented to prevent the entry and establishment of exotic fruit fly species in importing countries. The economically important tephritid fruit flies attacking mango in Africa can be divided into two major categories based primarily on their origin, i.e., invasive (Bactrocera dorsalis, Bactrocera zonata and Zeugodacus cucurbitae) and indigenous species (Ceratitis anonae, Ceratitis capitata, Ceratitis catoirii, Ceratitis cosyra, Ceratitis ditissima, Ceratitis fasciventris, Ceratitis quinaria, Ceratitis rosa [recent taxonomic advances have separated C. rosa into two species; C. rosa and C. quilicii], Ceratitis silvestrii, Dacus ciliatus and some unverified records of Ceratitis punctata and Dacus bivittatus). These species are known to have a wide host range and distribution across Africa. Their distribution is also influenced by competitive interactions between native and indigenous species. The host plant status and distribution of fruit fly species is an evolving phenomenon largely due to new invasions, misidentification and identification of hitherto unknown species. For this reason this review provides the current situation but should be updated on a regular basis.