Suresh K. Raina

A scientific note on Varroa destructor found in East Africa; threat or opportunity?

In many areas of the world where it is managed, the honeybee, Apis mellifera, has been plagued by diseases, pests and parasites. Of these, the parasitic mite, Varroa destructor Anderson and Truman (Acari:Varroidae), is considered by many as the most devastating. We found this mite in honeybee colonies throughout Kenya and in Tanzania for the first time in early 2009. Beekeepers surveyed were neither aware of the mite’s presence nor had they observed any negative impact on the survival and/or productivity of their bees. In March of 2009, we sampled 38 honeybee colonies (likely A. m. scutellata, and possibly A. m. scutellata hybrids) in seven locations in Central and Eastern Kenya. We employed a common sampling technique to determine mite presence/absence that utilizes powdered sugar to dislodge mites from adult bees (Macedo et al., 2002). An average of 717 ± 43 bees per colony were sampled and Varroa mites were found in all 38 colonies examined with numbers ranging from 3–108 per sample and averaging 26.3 ± 25.9 per colony. In a further similar survey (April–May, 2009) of 125 additional colonies located in the eastern, western and coastal regions of Kenya (69 colonies in 18 locations), coastal Tanzania (18 colonies in 4 locations) including Ugunja and Pemba Islands, collectively referred to as Zanzibar (likely A.m. litorea), and Western Uganda (14 colonies in 4 locations), 87% of the

Forest Habitat Conservation in Africa Using Commercially Important Insects

African forests, which host some of the worlds richest biodiversity, are rapidly diminishing. The loss of flora and fauna includes economically and socially important insects. Honey bees and silk moths, grouped under commercial insects, are the source for insect-based enterprises that provide income to forest-edge communities to manage the ecosystem. However, to date, research output does not adequately quantify the impact of such enterprises on buffering forest ecosystems and communities from climate change effects. Although diseases/pests of honey bees and silk moths in Africa have risen to epidemic levels, there is a dearth of practical research that can be utilized in developing effective control mechanisms that support the proliferation of these commercial insects as pollinators of agricultural and forest ecosystems. This review highlights the critical role of commercial insects within the environmental complexity of African forest ecosystems, in modern agroindustry, and with respect to its potential contribution to poverty alleviation and pollination services. It identifies significant research gaps that exist in understanding how insects can be utilized as ecosystem health indicators and nurtured as integral tools for important socioeconomic and industrial gains.

Semi-captive rearing of the African wild silkmoth Gonometa postica (Lepidoptera: Lasiocampidae) on an indigenous and a non-indigenous host plant in Kenya.

The life cycle of the African wild silkmoth Gonometa postica Walker was studied between September 2000 and September 2001 in the Uasin Gishu District of western Kenya with Acacia mearnsii de Wild and Acacia hockii de Wild as host plants. The initial population of G. postica was set up from healthy live pupae in cocoons collected from host plants in the study area. Oviposition was carried out in net sleeves and small plastic cages. Moth emergence and oviposition were bimodal, occurring between September and October 2000 and between March and April 2001, respectively. Larvae were reared in semi-captivity by using net sleeves on the branches of the two host plants. Larvae passed through six developmental instars. The pupal stage lasted from December to February during the short rains and from June to September during the long rains. Moth fecundity in the net sleeves was higher than that of those kept in plastic cages and fewer eggs hatched in the plastic cages compared with the net sleeves. Larvae reared on A. mearnsii had a shorter developmental period compared with those reared on A. hockii. Male larvae spun cocoons earlier than females but moths of both sexes emerged simultaneously. Sexual dimorphism was exhibited in both pupal and adult stages, females being larger and heavier than males. The importance of the semi-captive rearing technique for sustainable utilization of wild silkmoths for mass production of cocoons is discussed.

Use of Sleeve Nets to Improve Survival of the Boisduval Silkworm, Anaphe panda, in the Kakamega Forest of Western Kenya

Abstract Prospects for development of a wild silk industry in Africa would be improved if silkworm survival during mass production could be improved. A study on the survival of the Boisduval silkworm, Anaphe panda (Boisduval) (Lepidoptera: Thaumetopoeidae) was conducted with and without protection by net sleeves in two different forest habitats (natural and modified) in the Kakamega forest of western Kenya. Overall, cohort survival was significantly higher (P < 0.001) in the natural than in the modified forest, but larval survival was improved over three-fold by protection with net sleeves in both habitat types. In the modified forest, only 16.8% of unprotected larvae survived to the pupal stage and formed cocoons, whereas 62.3% survived in the same environment when they were protected with net sleeves. In the natural forest, 20.4% of unprotected larvae survived, whereas 67.7% survived in net sleeves. There was also a significant effect of season; cohorts of larvae that eclosed in the wet season had significantly lower survival than those eclosing in the dry season (P = 0.02). Sources of mortality appeared to be natural enemies (parasites, predators and diseases) and climatic factors.

Evaluation of various mulberry Morus spp. (Moraceae) cultivars for the rearing of the bivoltine hybrid race Shaanshi BV-333 of the silkworm Bombyx mori (Lepidoptera: Bombycidae)

The performance of the Bombyx mori Linnaeus bivoltine hybrid, Shaanshi BV-333, was evaluated on six mulberry cultivars of Morus spp. based on economic characters in rearing and mulberry leaf quality. The growth rate and morphological characteristics for all the cultivars were studied using several parameters. Specific characters such as disease resistance, survival percentage, cocoon weight, cocoon shell weight and single cocoon filament length were recorded during the rearing of silkworm larvae. Tested cultivars significantly differed in all parameters. Cultivars Kanva-2/M5, Thailand, Thika and S-36 exhibited superiority in rearing performance over other tested cultivars. Silkworms fed with cv. Thailand had the highest survival percentage of larvae in the short (S1) and long (S2) rainy seasons as compared with other cultivars. However, cv. Embu produced the lowest mortality during the dry season (S3), while S-41 produced the lowest survival rate in all seasons. Embu had significantly higher filament length and cocoon yield compared with the other cultivars during S3. However, S-41 performed poorly in survival percentage, cocoon yield, silk reeling and cocoon shell weight.

Variations in races of the honeybee Apis mellifera (Hymenoptera: Apidae) in Kenya

The three races of the honeybee Apis mellifera Linnaeus in Kenya (A. m. scutellata, A. m. monticola and A. m. litorea) differ from each other with respect to size, cubital index and abdominal colour banding pattern. These differences were used to assess the extent of interbreeding and hybridization between the races. This was verified on the basis of selected morphometric traits. Bee samples were collected from traditional log hives in seven geographical locations throughout Kenya ranging from lowland Mombasa in the coastal region to the highland Kinangop ranges. The length and width of the right forewing, length of proboscis, right antenna and right hindleg were measured, and the cubital index was computed for each specimen. The bees were classified according to size and colour banding pattern. Data analysis indicated there was hybridization among the three races of A. mellifera in Kenya due to swarming and migration under seasonal pressure.RésuméLes trois races kényannes de l’abeille domestique Apis mellifera Linnaeus (Hymenoptera: Apidae) (A. m. scutellata, A. m. monticola et A. m. litorea) diffèrent l’une de l’autre par la taille, l’index cubital et le patron de couleur des bandes abdominales. Ces différences ont été utilisées pour évaluer le niveau de croisement et d’hybridation entre les races à l’aide de caractéristiques morphométriques. Les échantillons d’abeilles ont été récoltés dans des ruches traditionnelles aménagées dans des bû ches dans sept localités géographiques du Kenya, du niveau de la mer à Mombasa jusque dans les hautes terres du Mt Kinangop. La longueur et la largeur de l’aile antérieure droite, les longueurs de la trompe, de l’antenne droite et de la patte postérieure ont été mesurées, et l’index cubital calculé, pour chaque spécimen. Les abeilles ont été classées en fonction de leur taille et du patron de couleur des bandes abdominales. L’analyse des données indique qu’il y a une hybridation entre les trois races d’A. mellifera du Kenya par suite d’essaimages et de migrations résultant de conditions saisonnières.

Study on the microstructure of African wild silk cocoon shells and fibers

Silk fibers and cocoon shells from four African wild silkmoths Gonometa postica, Anaphe panda, Argema mimosae and Epiphora bauhiniae-were studied to gain insight into the structure-property-function relations and potential commercial application. The surface and cross-section of cocoon shells and fibers revealed the presence of prominent structural variations. Cocoon shells were multilayered and porous structures constructed from highly cross-linked fibers that are densely packed within the sericin/gum. Fibers had fibrillar sub-structures running along the fiber axis and with greater number and size of voids. The ecological significance and implication of these structures for further application are discussed.

Monitoring wild silkmoth, Gonometa postica Walker, abundance, host plant diversity and distribution in Imba and Mumoni woodlands in Mwingi, Kenya

A survey of the abundance of larvae and pupae of Gonometa postica Walker and their host plants was undertaken in the long rainy season in 2006 at six sites in the Imba and Mumoni forests of Mwingi, eastern Kenya. One hundred trees of the primary host species of G. postica were sampled at each site, in addition to minor host species with G. postica pupae. The density of each tree species was calculated and the height, canopy, diameter and number of branches were measured. In order of decreasing abundance, the host plants in Imba forest were Acacia tortilis, A. elatior and A. nilotica, and in Mumoni forest, A. tortilis, A. nilotica, A. mellifera and A. brevispica. A. elatior had significantly more larvae than the other host plants in Imba. In Mumoni, A tortilis and A. mellifera had significantly more larvae, followed by A. nilotica and A. brevispica. The minor host plants harbour significantly more pupae than the major host plants in the two forests. In general, Imba had a significantly higher abundance of larvae and pupae than Mumoni. Host plant species richness did not differ between the two forests, but their evenness was significantly higher in Imba than in Mumoni.

Spatial distribution of cocoon nests and egg clusters of the silkmoth Anaphe panda (Lepidoptera: Thaumetopoeidae) and its host plant Bridelia micrantha (Euphorbiaceae) in the Kakamega Forest of western Kenya

A study on the spatial distribution of the silkmoth Anaphe panda (Boisduval) cocoon nests, egg clusters and the host plant Bridelia micrantha (Hochst) Baill. was conducted in two different habitats of the Kakamega Forest of western Kenya: Ikuywa (indigenous forest) and Isecheno (mixed indigenous forest). Fhe mean densities of cocoon nests, egg clusters and B. micrantha were significantly different in the two blocks and were not semi-randomly distributed in the two habitats. The host plants were underdispersed in the indigenous forest, whereas they were overdispersed in the mixed indigenous forest. The cocoon nests were overdispersed and the silkmoth egg clusters were underdispersed in the two blocks of forest. This study reveals that A. panda tends to distribute its egg clusters uniformly over the lower and middle crown of B. micrantha with a preference to eastern localization and confirms the insufficient presence of populations of this silkmoth in a mixed indigenous forest compared with an indigenous forest. Consequently, indigenous forests should be managed in a sustainable way and more indigenous tree species should be used in reforestation campaigns.

Enhancement of fruit quality in Capsicum annum through pollination by Hypotrigona gribodoi in Kakamega, Western Kenya

A study was carried out in Kakamega forest, in the western region of Kenya, to evaluate the effectiveness of the stingless bee Hypotrigona gribodoi (Magretti, 1884) on the pollination of green pepper. Three treatments were applied and consisted of self‐pollination, pollination by feral pollinators in the open field and pollination by H. gribodoi in a net cage. The differences in fruit yield and seed quality were compared among treatments. Flowers pollinated by H. gribodoi produced the heaviest fruits with the highest seed numbers followed by feral pollinators and lastly self‐pollinated flowers. Moreover, seeds were significantly bigger in size in fruits resulting from flowers pollinated by H. gribodoi compared to fruits obtained from self‐pollinated flowers or flowers pollinated by feral insects. We, therefore, conclude that H. gribodoi is an efficient pollinator of green pepper in the tropical region of East Africa.