International Centre Of Insect Physiology And Ecology Research Articles

Reviews on the Strategies Employed in Implementing the 'Push-Pull' Approach to Integrated Pest Management

Abstract: For small-holder maize farmers in Africa, the push-pull strategy is outlined as an alternate ecological management technique to traditional insecticide-based integrated pest management for the control of the spotted stem borer Chilo partellus and the autumn armyworm Spodoptera frugiperda. Push-Pull Technology (abbreviated PPT) is a unique integrated pest management method developed by the International Centre of Insect Physiology and Ecology (ICIPE) and its partners. This tactic involves influencing the behavior of natural enemies and insect pests by strategically deploying stimuli that make the resource under protection unappealing or inappropriate for the pests (the "push"). Additionally, the pests are drawn to an alluring source the pull, from which they are then eliminated

Bridging the gap in agricultural innovation research: a systematic review of push–pull biocontrol technology in sub-Saharan Africa

ABSTRACTBiological control for sustainable plant protection in sub-Saharan Africa (SSA) is gaining attention due to low crop productivity caused by pests, increasing costs of agrochemicals, and their harmful impact on health and the environment. A valuable case is the Push–pull technology (PPT) developed by the International Centre of Insect Physiology and Ecology (ICIPE). However, evidence for the success of PPT in reducing pest prevalence has not translated from experimentation and demonstration to wider-scale on-farm uptake. A systematic review was conducted to explore the research gaps, benefits of PPT, adoption determinants, barriers to uptake, and how farmers choose to adopt and adapt the technology. The study found a large body of evidence on the biophysical benefits of PPT, which comes from a relatively narrow set of ICIPE-led or managed experiments in Western Kenya. Besides, evidence of its social and economic benefits is less robust. Documented barriers to adoption include initial establishment costs, labour intensiveness, risk averseness of farmers, socio-cultural rigidity, and inadequate access to information and inputs. The review highlights the need for qualitative research, an in-depth examination of the social dynamics of innovation and decision-making processes on farms, and institutions’ role in shaping innovation for sustainable agricultural development.

Agro-Dealers’ Knowledge, Perception, and Willingness to Stock a Fungal-Based Biopesticide (ICIPE 20) for Management of Tuta absoluta in Kenya

In sub-Saharan Africa (SSA), tomato is an economically important crop that contributes not only to employment and income, but also food security. Like the rest of the SSA countries, tomato production in Kenya is constrained mainly by pests and diseases, key among them being the tomato leaf miner (Tuta absoluta), which can cause 80–100% losses if not properly managed. To suppress this pest, the International Centre of Insect Physiology and Ecology (ICIPE) and partners are introducing a fungal-based biopesticide (ICIPE 20) in an Integrated Pest Management (IPM) approach as a sustainable alternative to the sole use of synthetic pesticides. This study was carried out before the introduction of the biopesticide to assess its commercial feasibility among agro-dealers, using Kirinyaga County in Kenya where tomato production is predominant, as the study area. Specifically, the study assessed the knowledge, perception, and willingness to stock biopesticide using a market survey involving 141 agro-dealers. Successful commercialization of a new product is assumed to be the cumulative result of traders’ and buyers’ knowledge and perceptions about the product. The results show that a higher proportion of agro-dealers were willing to pay for ICIPE 20 at a higher price than Coragen®, the most popular insecticide for management of T. absoluta. The regression analysis revealed that individual characteristics such as age, education, access to social networks and credit facilities, and information are correlated to the agro-dealer’s knowledge, perception, and willingness to stock the biopesticide. Training agro-dealers may promote greater uptake of the biopesticides through enhancing their knowledge and perception towards the effectiveness of the product.

Effect of Technological Innovation on Gender Roles: The Case of Fruit Fly IPM Adoption on Women’s Decision-Making in Mango Production and Marketing in Kenya

An increase in returns from agriculture as a result of new or improved technology is often perceived to escalate women's loss of control over agricultural production and ability to make marketing decision due to persistent gender disparities in access to production resources. The International Centre of Insect Physiology and Ecology (ICIPE) and partners have developed integrated pest management (IPM) technology to suppress mango fruit flies on smallholder mango farm in sub-Saharan Africa. Despite the impressive direct economic impacts of the technology, no study has been conducted to determine whether it has any impact on intra-household gender roles in mango production and marketing decision-making. Using a sample of 470 mango-growing households from Machakos County, we employed a two-limit Tobit difference-in-differences model on the women’s decision-making index to examine the impact of IPM technology adoption on intra-household decision-making in mango production and marketing activities. The results showed a decrease of 21.2% in the women's decision-making index due to the adoption of IPM technology. The index can be enhanced through women's access to training by extension officers, increased formal education, and direct intervention for women to increase their investment in mango production.

Nest Architecture as a Tool for Species Discrimination of Hypotrigona Species (Hymenoptera: Apidae: Meliponini)

Hypotrigona species are difficult to identify morphologically. Here, we show that nest sites and nest architecture can be used to discriminate three Hypotrigona species found in Kenya. Hypotrigona gribodoi, H. araujoi and H. ruspolii colonies from Kakamega forest and H. gribodoi from Mwingi, were collected and placed in a meliponiary at the International Centre of Insect Physiology and Ecology (ICIPE). The following parameters were recorded: nest sites, internal nest entrances, external nest entrance colour and size, sizes (in terms of volume) of brood cells, honey and pollen pots, arrangement of brood cells and presence or absence of involucrum (cerumen covering brood). It was found that nest sites are specific to species. Hypotrigona gribodoi nests mostly in crevices in mud walls while H. ruspolii and H. araujoi nest in cavities in specific tree species, mainly in indigenous forests. The colour of external nest entrances varies between the species. H. araujoi’s is yellowish brown, H. gribodoi’s is white or cream while that of H. ruspolii is dark brown. There is an internal nest entrance in H. gribodoi, which is absent in the other two Hypotrigona species. Brood cells are clustered in H. gribodoi and H. ruspolii whereas H. araujo's form vertical semi comb-like layers. The area of the apical opening of the entrance tube and volumes of brood cells, honey and pollen pots differ significantly between the three Hypotrigona species. Therefore, nest sites and nest architecture can be used to discriminate three Hypotrigona species. Furthermore, the study indicates that conservation of indigenous forests, the main habitat for H. araujoi and H. ruspolii is important for their conservation.

Interaction betweenPhaedrotoma scabriventrisNixon andOpius dissitusMuesebeck (Hymenoptera: Braconidae): Endoparasitoids ofLiriomyzaLeafminer

The exotic parasitoid, Phaedrotoma scabriventris Nixon, was imported from Peru for the biological control of invasive Liriomyza species in vegetable and ornamental crops in Kenya where Opius dissitus Muesebeck is the most abundant indigenous Liriomyza parasitoid. Both species are solitary larva-pupal endoparasioids attacking the same larval stage. In order to assess whether these two species compete or co-exist, an interaction study involving sole, sequential and simultaneous releases of the two species on polyphagous Liriomyza huidobrensis (Blanchard) was conducted in the laboratory at the International Centre of Insect Physiology and Ecology (ICIPE), Nairobi, Kenya. Simultaneous releases of 50 individuals each of the two parasitoids resulted in significantly higher total parasitism rate (61.96±4.60) than in the single release of P. scabriventris (34.94±8.50). Simultaneous release of 25 individuals of each species resulted in a parasitism rate (44.52 ± 2.75) similar to that obtained for single releases o...

Delivering resistance to a major constraint for rain‐fed rice production

Delivering resistance to a major constraint for rain‐fed rice production

Virulence of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae to sweet potato weevil Cylas puncticollis and effects on fecundity and egg viability

AbstractThe virulence of eight isolates of Metarhizium anisopliae and four isolates of Beauveria bassiana (Ascomycota: Hypocreales) to adult Cylas puncticollis (Coleoptera: Curculionidae) was tested in the laboratory. Insects were sprayed with a standard concentration of 1.0 × 107 conidia mL−1 using Burgerjon’s spray tower. All the isolates tested were pathogenic to C. puncticollis. Mortality varied between 77.5% and 84.2% with isolates of B. bassiana and between 62.5% and 89.2% with isolates of M. anisopliae, 26 days post‐treatment. The lethal time to 50% mortality for the 12 isolates varied between 9.7 and 18.5 days. Four isolates, M. anisopliae International Centre of Insect Physiology and Ecology (ICIPE) 18 and ICIPE 62 and B. bassiana ICIPE 275 and ICIPE 114 were selected for dose–response mortality [lethal concentration to 50% mortality (LC50)] bioassays. Five concentrations (1.0 × 106, 3.0 × 106, 1.0 × 107, 3.0 × 107 and 1.0 × 108 conidia mL−1) of both fungal species were used. B. bassiana ICIPE 275 was the most active isolate with LC50 value of 0.7 × 106 conidia mL−1. The effect of fungal infection on feeding, fecundity and egg viability of C. puncticollis adult females was also investigated under laboratory conditions. M. anisopliae isolate ICIPE 18 and B. bassiana isolate ICIPE 114 were tested for feeding experiment using six concentrations (0, 1.0 × 106, 3.0 × 106, 1.0 × 107, 3.0 × 107 and 1.0 × 108 conidia mL−1). For reproduction potential (fecundity and egg viability) bioassays, five concentrations (0, 1.0 × 106, 3.0 × 106, 1.0 × 107 and 3.0 × 107 conidia mL−1) of M. anisopliae isolate ICIPE 18 were used. Adult sweet potato weevils (SPWs) treated with M. anisopliae at the concentrations of 3.0 × 107 and 1.0 × 108 conidia mL−1 consumed significantly less food than weevils in the control and B. bassiana treatments at all the concentrations, except at the higher concentration of 1.0 × 108 conidia mL−1, 14 days post‐treatment. Female weevils in the control treatments laid more eggs than fungus‐treated females. Percentage egg viability differences between controls and fungus treatments were significant at all the concentrations tested, 10 days post‐treatment. These results show that B. bassiana and M. anisopliae are pathogenic to SPWs and infection can reduce feeding, fecundity and egg viability.

Farmers’ perceptions of a ‘push–pull’ technology for control of cereal stemborers and Striga weed in western Kenya

Striga and cereal stemborers are major constraints to cereal production in sub-Saharan Africa causing serious food security concerns. The International Centre of Insect Physiology and Ecology (ICIPE) and partners have developed a novel integrated management system called the ‘push–pull’ technology (PPT) in mitigation. This involves inter-cropping maize with a stemborer moth-repellent forage legume, silverleaf desmodium (push), and planting an attractive trap crop, Napier grass (pull), around the intercrop. Additionally, chemicals produced from desmodium roots inhibit Striga. We evaluated farmers’ perceptions of the pests, PPT attributes and factors influencing the likelihood of its adoption in 15 districts in western Kenya. A random sample of 923 farmers, with 478 having adopted the technology (practicing) and 445 not yet adopted but attending PPT field days (visiting) were interviewed. The practicing farmers cited both Striga and stemborers as major maize production constraints, alongside other constraints, as the main motivations for adoption of PPT. Reduced infestation by the pests, improvement in soil fertility, increase in maize grain yields, improved fodder and milk productivity were cited as main benefits of PPT. Similarly, the field day visiting farmers rated PPT as a more superior technology compared to their own maize production practices. Farmer's age, household headship by female farmers, technology attributes and exposure to a variety of extension methods significantly influenced likelihood of PPT adoption. Effective dissemination pathways are needed to provide farmers with appropriate information for evaluating potential benefits and tradeoffs of such a management-intensive technology. Further research is needed to understand how PPT contributes to farmers’ livelihood improvement and how the efficacy of different dissemination pathways in PPT technology transfer influences its adoption.

Biological control of cereal stem borers in Kenya: A cost benefit approach

Lepidopteran stem borers are the key pests of maize in Sub-Saharan Africa. In the lowland tropics, dry mid-altitude, dry transitional and the moist mid-altitude zones of Kenya, the invasive crambid Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) causes up to 73% yield loss. The International Centre of Insect Physiology and Ecology (ICIPE) started a biological control (BC) program in 1991 to control stem borers in subsistence agriculture in Africa with emphasis on classical BC of C. partellus. The project released the braconid larval parasitoid Cotesia flavipes Cameron (Hymenoptera: Braconidae) in 1993 in coastal Kenya, where it got established and spread to other regions. This study assesses the economic impact of the introduced parasitoid. Temporal data on percentage parasitism by the introduced parasitoid and on stem borer density were collected between 1995 and 2004. Socio-economic data was collected through administration of questionnaires to 300 farmers. Economic impact of the project was calculated as the value of the yield loss abated by the parasitoid based on a model of expected stem borer density and parasitism level. Average annual parasitism increased linearly from the time of introduction to reach 20% parasitism by 2004. The net reduction in total stem borer density over the last 10 years was 33.7%, thus abating 47.3% of yield loss. The region will accumulate a net present value of US $ 183 million in economic benefits in 20 years since release of the parasitoid. Introduction of other parasitoid species targeting the egg and pupal stages of the stem borer life cycle stages would be required for biological control to push yield loss by stem borers to an insignificant level.

The International Centre of Insect Physiology and Ecology (ICIPE)

Hans Herren and Bernard Lhr describe the work of ICIPE in the area of IPM in horticultural crops.

Phenotypic stability of sorghum hybrids for resistance to the spotted stemborer, Chilo partellus (Swinhoe)

The phenotypic stability of resistance to the stemborer, Chilo partellus and grain yield in 10 newly developed sorghum hybrids namely HYD-1, HYD-2, HYD-3, HYD-4, HYD-5, HYD-6, HYD-7, HYD-8, HYD-9 and HYD-10, and two local checks, Serena (tolerant) and IS-1044 (resistant), were evaluated for seven seasons at the International Centre of Insect Physiology and Ecology (ICIPE) Mbita Point Field Station and Ungoye Field Site in western Kenya. Two stability parameters were determined: (1) The linear regression (b1) of an entry mean on an environmental index, and (2) the deviation from regression (S2d). The significance found for the linear component of environment implies that the variation over the different environments is adequate to test for cultivar stability. Hybrids HYD-1, HYD-5, HYD-8 and HYD-10 were identified as the most suitable genotypes for future commercial production.

The Effect of Intercropping on Relative Resistance and Susceptibility of Cowpea Cultivars to Maruca Testulalis Geyer when in mono and when Intercropped with Maize

Field studies to investigate the effect of intercropping on the relative resistance and susceptibility of cow pea cultivars to Maruca testulalis impure stands and intercropped with maize, were conducted at the International Centre of Insect Physiology and Ecology (ICIPE). It was clearly indicated that intercropping affected the relative resistance and susceptibility of cowpea cultivars. The resistance of TVU 946 to Maruca was reduced when the cultivar was under maize. This was attributed to the phenological changes observed, i.e. when planted with maize there was a significant (P=0.05) increase in length of the pods and peduncles and significant (P=0.05) reduction in the number of branches. Weekly mean temperatures and relative humidities indicated that there were significant differences between cropping patterns. Similarly there was a significant reduction in the photosynthetic active radiation incident on cowpea canopy in all the intercropped plots. This suggested that both intercropping and microenvironmental differences observed, reduced resistance in cultivar TVU 946 by probably acting directly on the crop, thus rendering it more susceptible.

The role of host plant resistance and intercropping in integrated pest management (IPM) with specific reference to the Oyugis project

Abstract Intercropping studies conducted at the International Centre of Insect Physiology and Ecology (ICIPE) for 10 years identified sorghum and cowpea as the best crop combination in terms of minimizing crop borer population, stabilizing productivity and reducing yield loss due to crop borers. The maize and cowpea dicrop and the sorghum, cowpea and maize intercrop were also found to be effective. The worst crop combination was found to be an intercrop between maize and sorghum. It was also indicated that incorporation of resistant and tolerant cultivars in an intercropping system offers an added advantage (by reducing the pest attack) to farmers who for some very good reasons had to plant the maize and sorghum dicrop (the worst combination). The use of resistant and tolerant cultivars therefore offers an alternative. In the study further observations were noted from three combinations, viz. resistant/resistant; resistant/susceptible; and susceptible/susceptible. Results showed that there were no signifi...

Managing drought and locust invasions in Africa

The two most critical African natural disasters, drought and locust outbreaks, are least understood in terms of the four activities considered essential to long-term disaster reduction: hazard prediction, risk assessment, disaster preparedness and disaster management. In finding a solution to the drought and desertification that plague Africa's Sudano-Sahelian belt, planners would do well to study indigenous adaptations to the unpredictable Sahelian ecosystem. The key to solving the problem of locust swarms may lie in the work being done by the International Centre of Insect Physiology and Ecology (ICIPE) which hopes to find a way to dampen the locusts' swarming cycle and intensify their solitary cycle so that locust populations can maintain a relatively sedentary, grasshopper-like lifestyle.

Trypanosome diversity in Lambwe Valley, Kenya-Sex or selection?

Lambwe Valley, situated close to Lake Victoria in western Kenya, is one of two remaining foci of sleeping sickness in Kenya. Ruma National Park occupies the valley floor, with a large mammal fauna including hyena, leopard, buffalo, bushpig and various species of antelope. Outside the park, the land is densely settled by subsistence farmers, mainly of the Luo tribe, who keep cattle, sheep and goats. The latter half of I980 saw a striking increase in the incidence of sleeping sickness in Lambwe Valley, with 68 cases reported by the end of the year, more than the cumulative total for the previous five years. This outbreak was curtailed by the aerial spraying of insecticide in I98 I, coupled with active case finding and treatment, and now there are only sporadic cases. At the time of the outbreak, the valley was massively infested with the tsetse fly, Glossina pallidipes; biconical trap catches of over 500 per day were not unusual. This tsetse population had been building up from reduced numbers left by the control operations of the early I97Os, and had come to infest not only the thickets in the game park itself, but also areas outside where people had settled. By the start of the 1980 outbreak most dogs had already died with ‘white eyes’, the cornea1 opacity characteristic of trypanosomiasis in the dog. Cattle were also heavily infected with trypanosomes and infection rates of over 50% with J. brucei-group trypanosomes were recorded. Clearly, the valley was undergoing a sudden upsurge of trypanosomiasis on all fronts. The most obvious explanation was that encroaching human settlement had brought humans and their livestock within range of the expanding fly population of the game park, but what other factors might have been involved? Mihok and colleagues’ have reanalysed the large data set on isoenzyme characterization of Lambwe Valley J. brucei spp isolates in an attempt to gain new insight into this question. The team from the International Centre of Insect Physiology and Ecology (ICIPE) W. Gibson

Insect pest management and socio-economic circumstances of small-scale farmers for food crop production in western kenya: A case study

Sorghum, maize and cowpea serve as staple food for people in Africa and are grown mostly by small-scale farmers. A major constraint on the production of these crops is attack by insect pests among which crop borers are most important, causing 30–80% yield losses. Use of pesticides to control these pests is hazardous and not feasible for the farmers. Alternative strategies for the integrated pest management (IPM) are being developed at the International Centre of Insect Physiology and Ecology (ICIPE) and include the following components: (1) Intercropping and other cultural practices, (2) Plant resistance to insect pests, and (3) Biological control. These IPM components have now been developed to a stage where they can be taken for on-farm trials under farmers’ management for subsequent use by them. But, adoption and diffusion of agricultural innovations requires a prior knowledge of the farming systems and the socio-economic circumstances in which the target farmers operate, and their bearing on the use of innovations. Information on these aspects has therefore been obtained through a survey of farming households in Rendu Bay and Oyugis Divisions in western Kenya during April–August 1986. The survey was conducted jointly with UNEC A and Ministry of Agriculture, Kenya, under a project funded by the Royal Government of Belgium. The survey involved interview with 150 farmers, (75 in each Division. In Kendu Bay 27 were men and 48 women whereas in Oyugis 40 were men and 35 women.) and was based on a questionnaire which comprised six sections. Five sections covered the farmers’ background, farming practices, pest problems and their control, socio-economic conditions, and accessibility/willingness of the farmers to participate in the project. The last section included field observations on the insect pests of sorghum, maize and cowpea. On the basis of the information obtained on above-mentioned aspects, criteria were defined and assigned appropriate weigh tage for selecting 25 farmers in each Division for on-farm trials. The selected farmers included 12 men and 13 women in Kendu Bay while in Oyugis 13 men and 12 women were selected. The measures that need to be taken to counter these limitations and thereby assist the farmers in increasing food production have been recommended.

(B6) Humoral immunity in TSETSE: Differences in response due to sex and age and tsetse, species and doses of immunizing agenst and the in vitro effects of temperature and bacterial factors : G.P. Kaaya and N. Darji. The International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya

(B6) Humoral immunity in TSETSE: Differences in response due to sex and age and tsetse, species and doses of immunizing agenst and the in vitro effects of temperature and bacterial factors : G.P. Kaaya and N. Darji. The International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya

Chemical Ecology: Studies from East Africa

The International Centre of Insect Physiology and Ecology (ICIPE), in Nairobi, provides a laboratory at which a multinational group of scientists pursues interdisciplinary research. In collaboration with their colleagues in biology, ICIPE chemists have characterized the sex pheromones of the tick which serves as a vector of East Coast fever and have identified a termite queen-cell-building pheromone. The structure of many anthropod defensive chemicals have been determined; most interesting of these are the trinervitenes, structurally novel diterpenoids from nasute termites. Several highly active insect antifeedants were discovered using a simple bioassay to screen selected East African plants. These antifeedants may provide leads for the development of new insect-control techniques.