A survey of farmers’ perceptions and management strategies of the sweet potato weevil in Homa bay county, Kenya

Sweet potato (Ipomoea batatas L.) is one of the most widely grown root cropsworldwide. In Africa, it is grown in small plots by poorer farmers. Production of thecrop is extremely low in Kenya as compared to other African countries due to theexistence of common insect pests. Sweet potato weevil (Cylas spp.) is known as thebiggest pit fall for production and productivity of the crop in the country. This studysought to determine the opinion of sweet potato farmers concerning sweet potatoresistance to Cylas spp. and determine control strategies employed by sweet potatofarmers in managing the pest. The study also sought to determine the sweet potatoproduction constraints faced by the farmers in Homa Bay County, Kenya. The studywas conducted using a Participatory Rural Appraisal approach in which 269 farmers inthe County were interviewed on the sweet potato varieties with field resistance to Cylasspp., the crops’ production constraints (with emphasis on damage by Cylas spp.) andfarmers’ control strategies in regard to the weevil. Data were also collected from thefarmers whose sample size was determined using the table on sample size selection andstandardization equation. Data were analysed using descriptive statistical techniquesthat were frequencies, percentages and standard errors. The study established thatmajority of the farmers from Rachuonyo (89.7%) and Ndhiwa (91.9%) were not awareof any variety that had field resistance to Cylas spp. However, 10.5% of the farmers inRachuonyo and 8.1% of the farmers in Ndhiwa identified nine varieties which haveshown relative field resistance to root damage by Cylas spp. The varieties that wereidentified to be resistant to Cylas spp. by farmers in Rachuonyo were Kalamb Nyerere,Tombra, Sinia, Odinga, Kemb 10, Wera and Zapallo. However, the varieties that wereidentified to be resistant to Cylas spp. by farmers in Ndhiwa were Amina, Mugandeand Ndege Oyiejo. Further, the findings revealed that Cylas spp. was the mostproblematic pest by 90.3% and 96.8% of households in Rachuonyo and Ndhiwa,respectively. Majority (64.5%) of the farmers in Ndhiwa did not use any methods tomanage Cylas spp. However, farmers in Rachuonyo (26.2%) and Ndhiwa (15.3%)preferred re-ridging during weeding as a management strategy in regard to Cylas spp.These findings reiterate the importance of the sweet potato weevil in rural sweet potatofarming systems and thus innovative management strategies are necessary.Key words: Sweet potato, control strategies, Cylas spp., resistance, pest, variety,constraint

Analysis of the genetic diversity of selected East African sweet potato (Ipomea batatas [L.] Lam.) accessions using microsatellite markers

Sweet potato (Ipomea batatas [L.] Lam.) is an economically important crop in East Africa chiefly grown by small holder farmers. Sharing of vines for planting is a very common occurrence among these farmers and eventually varieties are given local names, making it hard to trace the original pedigree. It is therefore important to characterise the sweet potato germplasm for purposes of breeding and germplasm conservation. In this study, 68 sweet potato accessions were evaluated for diversity using 12 microsatellite markers. The genetic relationship of the germplasm was evaluated using the Jaccard’s coefficient for dissimilarity analysis, unweighted pair group method with arithmetic means (UPGMA) tree and principal component analysis (PCoA) on DARwin software, while summary statistics was done using PowerMarker and Popgene softwares. The polymorphic information content of the markers ranged from 0.1046 for markers J67b and J67 to 0.3671 for marker J1809a, with a mean value of 0.2723. The total number of alleles amplified was 21. The major allele frequency ranged from 0.5882 for marker JB1809a to 0.9412 for markers J67b and J67c. Cluster analysis divided the accessions into four major clusters. Principle component analysis divided the accession into four groups which were different from those by cluster analysis. This study was able to identify several distinct accessions as well as a few possible duplicate accessions that overlapped on the cluster analysis.Key words: Sweet potato, cluster analysis, genetic diversity, principal component analysis, Simple SequenceRepeats

Botanical pesticide production, trade and regulatory mechanisms in sub-Saharan Africa: making a case for plant-based pesticidal products

Pesticides are the major technology used in the management of field and postharvest losses due to pests. There is growing demand for effective alternatives that present low health risks and conserve ecosystems and biological diversity. Pesticidal plants are increasingly used as alternatives where synthetic products are unaffordable, have limited availability or are ineffective. Plant materials, however, are often used inefficiently and their effective use requires optimisation. In Africa wide-scale uptake of pesticidal plants remains limited despite the success of pyrethrum in some countries and other pesticidal plant products in China and India. This is mainly due to lack of data on efficacy and safety, inconsistent efficacy of plant products, the prohibitive cost of registration, and an inadequately developed conventional pesticides sector. Globally, the demand for botanicals is poised to grow due to an increasing shift in consumer demand for safe food, increasing organic farming, lobbying by environmentalists and the increasing pressure from new regulations on internationally traded foods in Europe. These demands can only be met by formalising production, marketing and use of pesticidal plants. This has to be supported by friendly registration procedures, sustainable forest management, propagation and cultivation of pesticidal plants. This paper presents a critical review of the enabling environment required for wide-scale adoption and commercialisation of botanical pesticides in sub-Saharan Africa. We conclude that regulations and protocols for production, marketing and trade need to be reviewed to facilitate the development of the botanicals sector in Africa

Visual, vibratory, and olfactory cues affect interactions between the red spider mite Tetranychus evansi and its predator Phytoseiulus longipes

Phytoseiulus longipes Evans (Mesostigmata: Phytoseiidae) is an exotic predator widely used in biological control programs for the red spider mite Tetranychus evansi Baker & Pritchard (Acari: Tetranychidae) in East Africa. However, little is known about the cues mediating this prey/predator interaction. Here, we performed behavioral assays to test the involvement of visual, vibratory, and olfactory cues using a combination of dead/living insects enclosed in either perforated or non-perforated transparent/opaque capsules. We monitored insect responses with a video tracking system and analyzed the data with Ethovision software. Our results showed avoidance behavior of T. evansi in the presence of live P. longipes through visual, vibratory, and olfactory cues. P. longipes was attracted by vibratory and olfactory cues emitted by T. evansi. The composition of volatiles from T. evansi was identified by GC/MS as methyl salicylate (MeSA), linalool, beta-caryophyllene, octanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid. Our behavioral assays with predatory mites in a Y-tube olfactometer revealed that among the identified volatiles, only MeSA, linalool, and MeSA + linalool attracted P. longipes. The implications of these findings for the control of T. evansi are discussed