F Olubayo

Evaluation of companion crops for thrips (Thysanoptera: Thripidae) management on French bean Phaseolus vulgaris (Fabaceae)

Six companion crops, i.e. Tagetes erecta, Daucus carota L., Coriandrum sativum L., Brassica oleraceae L. var. acephala, Capsicum annuum L. and Zea mays L., were evaluated for their efficacy in suppressing field populations of Frankliniella occidentalis (Pergande) and Megalurothrips sjostedti Trybom on French bean Phaseolus vulgaris L. Each companion crop was interplanted with French beans in a 3 × 10 m plot and replicated three times in a completely randomized block design. Fhe thrips populations on French bean flowers in experimental plots were compared with those on beans treated with two insecticides: l-cyhalothrin (Karate 1.75% EC) and methiocarb (Mesurol 500 SC) or untreated (control). Coriandrum sativum, Z. mays and T. erecta are recommended as companion crops for intercropping with French beans to reduce populations of thrips and hence minimize the use of chemical insecticides on this crop.RésuméSix plantes associées, i.e. Tagetes erecta, Daucus carota L., Coriandrum sativum L., Brassica oleraceae L. var. acephala, Capsicum annuum L. et Zea mays L., ont été évaluées pour leur capacité à contrôler les populations naturelles de Frankliniella occidentalis (Pergande) et Megalurothrips sjostedti Trybom sur le haricots vert Phaseolus vugaris L. Chaque plante a été plantée en alternance avec des haricots verts dans des parcelles de 3 × 10 m, á raison de trois répétitions par plante dans un bloc complétement aléatoire. Les populations de trips présentes sur les fleurs de haricots verts dans les différentes parcelles expérimentales ont été comparées a celles de haricots verts traités avec deux insecticides L-cyhalothrin (Karate 1,75% EC) et methiocarb (Mesurol 500 SC) et, un témoin. Les résultats montrent que C. Sativum, Z. mays et T. erecta sont les meilleures plantes associées pour réduire l’utilisation des insecticides.

Analysis of Kenyan isolates of Fusarium solani f. sp. phaseoli from common bean using colony characteristics, pathogenicity and microsatellite DNA

Fusarium solani (Mart) f.sp. phaseoli (Burk) Synd. and Hans., is a plant pathogenic fungus that causes root rot in garden bean (Phaseolus vulgaris L.). To evaluate methods used in classifying strains of this pathogen, 52 Fusarium solani f.sp. phaseoli isolates from infected bean plants grown on different farms in Taita hills of Coast province, Kenya, were cultured and characterized using morphology, pathogenicity and microsatellite DNA. All the isolates showed high variability in aerial mycelial growth, mycelia texture, pigmentation (mycelia colour) when cultured on potato dextrose agar medium, and conidial measurements on Spezieller Nahrstoffarmer agar medium. Colonies were grouped into luxuriant, moderately luxuriant and scanty on aerial mycelial growth; fluffy and fibrous based on mycelial texture; purple, pink and white based on mycelia colour; aid long, medium and short macroconidial length. All the isolates were pathogenic on GLP-2 (Rosecoco), a susceptible bean variety commonly grown in Kenya. DNA analysis showed that the isolates carried a high genetic diversity (gene diversity = 0.686; mean number of alleles = 9). Neighbour-Joining phylogenetic clusters reconstructed using microsatellite variation showed three major clusters. However, the microsatellite groupings were independent of the altitude, colony characteristics and virulence of the isolates.

Laboratory and field investigations using indigenous entomopathogenic nematodes for biological control of Plutella xylostella in Kenya

This study was undertaken to determine the potential utility of entomopathogenic nematodes for management of diamondback moth (DBM) larvae in Kenya. Five Kenyan EPN isolates, Heterorhabditis indica, Steinernema karii, Steinernema weiseri, Steinernema sp. and Heterorhabditis taysearae were tested for their ability to penetrate DBM and their speed of kill (LT50). Heterorhabditis indica and S. weiseri were found to have the quickest rate of kill and S. weiseri was found to have the largest proportion of nematodes penetrating. Three of the isolates, Steinernema sp. (95), S. weiseri and H. indica, were used in a field experiment to test their ability to reduce DBM populations and damage to kale. All three nematodes caused significant reductions in populations of DBM and DBM damage, with the population reductions being similar to those caused by application of Bacillus thuringiensis ssp. kurstaki. This study shows that EPNs have great potential that should be exploited in the management of DBM in Kenya.

Diurnal population trends of Megalurothrips sjostedti and Frankliniella occidentalis (Thysanoptera: Thripidae) and their natural enemies on French bean Phaseolus vulgaris (Fabaceae)

A field experiment was conducted to track the daily population trends and occurrence of the flower thrips Megalurothrips sjostedti Trybom and Frankliniella occidentalis (Pergande), and their indigenous natural enemies Orius spp. and Ceranisus menes (Walker), infesting French beans. French beans in monocrop or interplanted with six companion crops (Zea mays L., Coriandrum sativum L., Tagetes erecta L., Brassica oleracea var. acephala L., Daucus carota L. and Capsicum annuum L.), and two chemical insecticides, methiocarb (Mesurol 500SC) and L-cyhalothrin (Karate 1.75% EC), were evaluated for their effects on the abundance of flower thrips, throughout the day, at 1-h intervals. The average population peak of thrips was found to occur at around 1300 h, but each species had different peak periods. Adult F. occidentalis populations peaked at midday and adult M. sjostedti populations at 1500 h, while the larvae of the two thrips species peaked at around 1300 h. Orius spp. were the most abundant natural enemies and their populations peaked at around 1400 h. Ceranisus menes population also peaked at around 1400 h.RésuméUne expérimentation de terrain a été conduite afin de déterminer la dynamique des populations des trips de fleurs Megalurothrips sjostedti Trybom et Frankliniella occidentalis (Pergande), et de leurs ennemis naturels indigènes Orius spp. et Ceranisus menes (Walker) sur haricot vert au cours de la journée. L’abondance des trips a été évaluée sur des haricots verts cultivés en monoculture ou en culture associée avec six autres plantes (Zea mays L., Coriandrum sativum L., Tagetes erecta L., Brassica oleracea var. acephala L., Daucus carota L. et Capsicum annuum L.) et avec deux insecicides methiocarb (Mesurol 500SC) et L-cyhalothrin (Karate 1.75% EC), pendant toute la journée, à 1 heure d’intervalle. Le pic d’infestation des trips a été observé vers 1300 h, avec toutefois une période différente pour chaque espèce. Le pic de population des adultes de F. occidentalis est observé à la mie journée et celui de M. sjostedti à 1500 h, alors que le pic de populations des larves des deux espèces est observé à 1300 h. Les espèces du genre Orius sont les ennemis naturels les plus abondants avec un pic de population vers 1400 h. La population de Ceranisus menes est maximum vers 1400 h.

Effect of grain moisture content and storage time on efficacy of inert and botanical dusts for the control of Sitophilus zeamais in stored maize

The effect of grain moisture content and time of storage on the efficacy of inert and botanical dusts, conventional and bacterial metabolite insectcides were evaluated in the laboratory. Maize grains at 10, 12, 14 and 16% moisture content were admixed with inert powder (diatomaceous earth Kensil Superfine®), maize cob and bean trash ashes, and botanical (neem seed cake powder) at a dose rate of 0.9% w/w. Actellic Super® and Spintor® dusts applied at the recommended rate of 50 g/90 kg grain and diatomaceous earth Dryacide® at 0.9% w/w were included as positive controls. Untreated maize grain served as the negative control. Thirty (30) unsexed two ‐week-old Sitophilus zeamais Motsch. adults were introduced in the treated maize. The treatments were replicated four times and held undisturbed for 14 days at ambient conditions (26 ± 2°C and 67 ± 3% r.h.), after which mortality was assessed. Results showed that grain moisture content significantly (p<0.05) affected efficacy of grain protectants and superior control was achieved when it did not exceed 12% for inert dusts and 14% for pesticides. For the evaluation of the effect of time of storage, 4 kg maize grain were admixed with each treatment except for Spintor® dust, maize cob ash, neem seed cake powder as described earlier and put into the 5 kg capacity hessian baglets, replicated four times. Untreated grain acted as the control. Adult S. zeamais (population of 1500) were put in the plastic Petri dish and left to infest the baglets naturally. The potency of the protectants began to wane significantly (p<0.05) after 6 months. Dryacide ® followed by Kensil Superfine® dusts performed better than Actellic Super® with the grain weight loss of 2 and 4%, respectively, over a period of 9 months. The study demonstrates that Superfine ® dust has the potential but should be further evaluated on ‐ farm, for the control of storage insect pests and serve as another stored products protectant option.

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.

Datasets on abundance of common blossom thrips and weather variables in small-scale avocado orchards at Taita Hills and Mount Kilimanjaro

Avocado, Persea americana Miller (Lauraceae), is an important fruit crop cultivated by small-holder farmers along Afrotropical highlands of Taita Hills in South-eastern Kenya and Mount Kilimanjaro in Northern Tanzania. The small-holder farmers in these East African regions generate substantial food and cash from avocado fruits. However, the avocado crop is faced with challenges of infestation by insect pests such as the common blossom thrips (Frankliniella schultzei Trybom) which feeds on pollen and floral tissue thereby reducing productivity of the trees. Moreover, there is no information describing distribution patterns of Frankliniella schultzei and associated weather in East African avocado orchards despite the fact that small-scale farming is dependent on rainfall. This article was, therefore, initiated to provide dataset on abundance of Frankliniella schultzei from the avocado plants that relates with monthly rainfall and air temperatures at Taita Hills and Mount Kilimanjaro. Frankliniella schultzei was collected using white coloured beating tray and camel brush whereas air temperatures (°C) and rainfall (mm) was recorded daily using automatic data loggers and rain gauge, respectively. The survey at the two transects commenced during peak flowering season of avocado crop in August up to end of harvesting period in July of the following year. Temporal datasets were generated by Kruskal-Wallis Chi-square test. Current temporal datasets presents strong baseline information specifically for Kenya and Tanzania government agencies to develop further agricultural strategies aimed at improving avocado farming within Taita Hills and Mount Kilimanjaro agro-ecosystems.

Assessment of Yield Loss Caused by the African White Rice Stem Borer (Maliarpha separatella Rag (Lepidoptera: Pyralidae) at Mwea Irrigation Scheme, Kirinyaga County, Kenya

Information on losses caused by the African white rice stem borer, Maliarpha separatella rag, which is an important rice pest in Kenya is scanty. The development and implementation of effective pest management strategies relies on accurately defined Economic Injury Levels (ElL) for that pest. Investigations were, therefore, conducted to determine yield losses caused by M. separatella and economic injury level of the pest. The experiment was conducted in an insect proof screen house at Kenya Agricultural and Livestock Research Organization, Mwea station. The experiment was arranged as a (2×6) factorial design and each treatment replicated three times. First factor was time of infestation at two levels, early and late which was 3 and 6 weeks after transplant date, respectively. Second factor was infestation rate at six levels (0, 1, 2 4, 6 and 8 egg masses). Results indicated that infestation levels of 1, 2, 4, 6 and 8 M. separatella egg masses at early infestation resulted in grain yield losses of 59.8, 83.2, 84.8 90.2 and 90.9%, while losses of same infestation levels at late infestation was 34.3, 52.1, 63.4, 81.8 and 80.8%. There was a strong positive relationship between yield loss and M. separatella population levels (y = -214.29x+ 1693.4, r2 = 0.8416). On the basis of cost benefit ratio, the economic injury level was 6 and 8 egg masses per square meter in the early and late infestation, respectively. The action threshold for early infestation was 4 egg masses and 6 egg masses for late infestation.

Why Pests and Disease Regulation Should Concern Mankind

Nature, through balancing mechanisms, provides ecosystem services, comprising provisioning, regulating, cultural and supporting services for the survival of mankind (MEA, Ecosystems and human well-being: biodiversity synthesis. World Resources Institute, Washington, DC, 2005). The balance and stability is usually upset by interventions or development activities, thereby threatening survival. Maintaining the balance guarantees sustainable development. Pests and disease regulation provides one component of managing the ecosystem. This chapter highlights why pest and disease regulation is important in contributing to sustainable agricultural production and development. Continued multidisciplinary research efforts are needed to enable understanding of the biological interactions between pests, beneficial and host communities on one hand and the interactions between and among cost-effective pest management methods, soil health, climate change, food security and human well-being on the other hand. The holistic approach in developing the understanding of the role of pest and disease regulation in the ecosystem will ultimately contribute to the development of appropriate strategies for the achievement of human well-being

Comparative Susceptibility of Kenyan Improved Cowpea Varieties to Infestation by Storage Bruchids (Coleoptera: Bruchidae)

In the late 1980s, the cowpea improvement programme in Kenya released 3 improved cowpea varieties: 419, K80 and M66, to the farmers in the semi-arid areas of Kenya. These varieties are suitable for areas with rainfall below 250 mm per season and can be grown for both leaf and grain production. In the improvement of the varieties, emphasis was placed mainly on drought and heat tolerance, disease resistance and resistance to some insect pests (Ngugi et al., 1985), yet postharvest keeping quality is one of the factors that determine the acceptability of grain crops by the farmers. Cowpea varieties vary in susceptibility to bruchid beetles (Dick and Credland, 1986; Ndlovu and Giga, 1988) and while bruchid infestation on the 3 improved varieties has been observed, their relative susceptibility is not known.