Faculty of Agriculture and Environmental Studies (FAES)

Permanent URI for this communityhttps://repository.chuka.ac.ke/handle/chuka/234

Browse

Now showing 1 - 6 of 6

INTEGRATED APPLICATION OF NAPHTHALENE ACETIC ACID, STAKING AND MINERAL NUTRIENT ON GROWTH, YIELD, AND SEED QUALITY OF CLIMBING BEANS (Phaseolus vulgaris L.)
(Chuka University, 2020-12) KIRAGU, PAULINE WANJIRU
Abstract Common bean (Phaseolus vulgaris L.) is an important grain legume in attaining food security and income. Amongst the common beans are the climbing beans that have indeterminate growth habit and require staking for support. Despite the importance of climbing bean in alleviating food insecurity, its production per unit area in Kenya has declined over the years. The decline is attributed to insufficient knowledge by farmers on the growth habit of climbing beans that is influenced by endogenous auxin activity, staking and mineral nutrient management. The study aimed to determine the effect of integrating naphthalene acetic acid (NAA), staking and mineral nutrient application on growth, yield, nutrient use efficiency and seed quality of climbing beans. The experiment was carried out in split – split plot experiment and laid down in Randomised Complete Block Design and replicated three times. This was done in three growing seasons at Kaguru Agricultural Training Centre. The treatments included three levels of NAA concentrations (0 ppm, 200 ppm and 400 ppm) which were randomly assigned to the main plot. The NAA was applied twice during the growth period through spraying at two weeks after crop emergence and at the onset of flowering for each concentration. Three levels of staking (no staking, staking with stakes and use of maize plants as support) were randomly assigned to the subplot. Four levels of DAP (18-46-0) fertiliser; 0, 200, 250 and 300 kg DAP per ha (equivalent to 0, 0; 36, 92; 45, 115 and 58 kg N per ha; 138 kg P per ha) were assigned to the sub-sub plot. Soil sampling and analysis were done before planting in order to determine the soil nutrient status in the study site. The Data was collected on growth and yield traits (Germination percentage, Number of leaves, Leaf chlorophyll content, Plant height, Root length, Total biomass, Number of branches, Days to physiological maturity, Yield per plant, Weight of one hundred seeds, Plant tissue N and P nutrient content, and Seed tissue N and P nutrient content growth vigour of the resultant plants). Data on growth and yield was used to determine Nutrient Use Efficiency, Harvest Index and Net Economic Benefit. The Data collected was subjected to ANOVA using statistical analysis software (SAS) version 9.3. The means that were significantly different were separated using LSD at a 5% level of significance. The integration of different levels of Naphthalene Acetic Acid, staking and mineral nutrient N and P affected the various parameters in climbing bean production. The germination % ranged from 52.78 % for 300 kg DAP per ha to 96.89 % for 0 kg DAP per ha, the number of leaves from 19.22 leaves for A3S3F1 (400 ppm NAA, maize plants as support and 0 kg DAP per ha) to 74.20 leaves for A3S2F4 (400 ppm NAA, staking by use of stakes and 300 kg DAP per ha), the plant height from 176.33 cm high for A3S1F1 (400 ppm NAA, unstaked climbing bean plants and 0 kg DAP per ha) to 388.89 cm for A3S2F4, the number of branches from 2.89 branches for A1S3F1 (0 ppm NAA, maize plants as support and 0 kg DAP per ha) to7.89 branches A1S1F4 (0 ppm NAA, unstaked climbing bean plants and 0 kg DAP per ha), the number of days to physiological maturity from 78.67 days for A1S1F1 (0 ppm NAA, unstaked climbing bean plants and 0 kg DAP per ha) to 92 for A1S2F3 (0 ppm NAA, staking by use of stakes and 250 kg DAP per ha), the root length from viii 12.89 cm for A3S3F1to 30.00 cm for A3S2F3 (400 ppm NAA, staking by use of stakes and 250 kg DAP per ha), the chlorophyll content of leaves from 37.67 spads for A1S3F2 (0 ppm NAA, maize plants as support and 200 kg DAP per ha) to 62.53 spads for A1S2F4 (0 ppm NAA, staking by use of stakes and 300 kg DAP per ha), the number of pods per plant from 15.00 pods for A1S3F1to 44.33 pods for A2S2F4 (200 ppm NAA, staking by use of stakes and 300 kg DAP per ha), the number of seeds per pod from 4.00 seeds for A2S1F1 (200 pmm NAA, unstaked climbing bean plants and 0 kg DAP per ha) to 7.33 seeds for A2S2F4, the yield per plant from 6.50 g for A1S3F1 to 52.70 g for A2S2F3 (200 ppm NAA, staking by use of stakes and 250 kg DAP per ha), the weight of 100 seeds from 57.21 g for A3S2F4 to 75.37 g for A1S3F1, the total yield from 630.77 kg per ha ha -1 for A1S3F1to 3137.09 kg per ha for A2S2F3 (200 ppm NAA, staking by use of stakes and 250 kg DAP per ha), the seed P content from 0.1567 % for A1S1F1 to 0.6240 % for A3S2F4, the seed N content from 2.0733 % for A1S1F1 to 4.8867 % N for A3S3F4 (400 ppm NAA, maize plants as support and 300 kg DAP per ha), the crude protein of the seed ranged from 12.96 % for AISIF1 to 30.54 % for A3S3F4, the plant tissue P and N ranged from 0.158 % P and 2.692 % N for A1S1F1 to 0.3990 % P and 3.2732 % N for A3S2F4, the total biomass from 35.73 g for A2S3F1 (200 pmm NAA, maize plants for support and 0 kg DAP per ha) to 127.70 g for A2S2F4, the harvest index from 8.98 % for A1S3F1 to 20.20 % for A2S2F4, the nitrogen use efficiency ranged from 19.80 kg per kg for A1S3F4 (0 ppm NAA, maize plants for support and 300 kg DAP per ha) to 66.99 kg per kg for A2S2F3, the phosphorus use efficiency ranged from 8.32 kg per kg for A1S3F4 to 25.65 kg per kg for A2S2F3, the plant height for the resultant plants ranged from 148.331 cm for A3S2F2 (400 ppm NAA concentration, staking by use of stakes and 200 kg DAP per ha) to 186.20 cm for A2S3F4 (200ppm NAA concentration, bean plants supported by maize plants and 300 kg DAP per ha), the number of leaves for the resultant plants ranged from 25 leaves for A2S1F1 to 35 leaves for A3S3F1, the number of branches for the resultant plants ranged from 3 branches for A3S1F1 to 4 branches for A1S2F3, the net economic benefit ranged from Ksh. 28,520 for A1S2F1 (0 ppm NAA, staking by use of stakes and 0 kg DAP per ha) to Ksh. 198,009 for A2S2F3. Generally, the performance of integrating 200 ppm, staking by use of stakes and 300 kg DAP per ha significantly increased many growths and yield related parameters while integrating 400 ppm NAA, staking by use of stakes and 300 kg DAP per ha increased a number of growth parameters but not mainly the yield and yield related parameters. For high nutrient use efficiency and of net economic benefit of climbing beans the farmers would be recommended to use 200 ppm NAA, staking by use of stakes and 250 kg DAP per ha.
Performance of Nile Tilapia (Oreochromis Niloticus) Fed on Oilseed meals with Crude Papain Enzyme
(Chuka University, 2019-09) Kirimi, James Gitonga
The greatest challenge to increased aquaculture production in Kenya is the high cost of fish feed. The objective of this study was to determine the effect of replacing fish meal with oilseed meals and improving the availability of nutrients using crude papain enzyme in Nile tilapia diets. A control diet (D1) of 30% crude protein and 2900Kcal DE/kg was formulated using fishmeal (FM), soybean meal (SBM), canola meal (CM) and sunflower meal (SFM). The test diets were formulated by replacing 10% CP of FM by SBM (D2), CM (D3) and SFM (D4), respectively. The diets were analysed for proximate, fatty acid and amino acid composition. The level of inclusion of crude papain enzyme was tested at 0.02%, 0.04%, 0.06% and 0.08% by the in vitro enzyme assay using pH drop method. One hundred and one days feeding trial was conducted in a 4x2 factorial design on 4 diets (D1, D2, D3 & D4) with (0.06%) and without (0%) the enzyme using seven hundred and twenty Nile tilapia fingerlings (7±3g). The fingerlings were randomly distributed into eight groups of three replicates of 30 fingerlings per net hapa (2x1x1m). Fish were fed twice daily at 5% of their biomass at 10am and 4pm in two equal meals. They were weighed fortnightly and slaughtered at the end of feeding trial for carcass quality analysis and sensory evaluation. Apparent nutrient digestibility was done at the end of feeding trial using chromic oxide as an external marker. Substituting FM with SBM, CM and SFM significantly increased the levels of crude fibre (P<0.05) but reduced ash level. The diet based on SFM recorded highest (16.03%) crude fibre content (P<0.05), while CM based diet recorded highest ether extract content (10.75%). Substituting 10% CP of FM with SBM, CM and SFM, reduced the levels of isoleucine, leucine, arginine, lysine, phenylalanine, histidine and threonine (P<0.05) and increased levels of methionine in diet with SBM. In all the diets, methionine was the 1st limiting amino acid and isoleucine 2nd limiting. Though the diet containing FM exhibited higher (P<0.05) essential amino acid index (EAAI) (0.97), it was not satisfactory because it was limiting in methionine. EAAI reduced (P<0.05) with replacement of fishmeal; SBM (0.78), CM (0.77) and SFM (0.76). Crude papain extract contained (crude protein 66.61%, ash 6.89%, crude fat 7.69%, crude fiber 1.56%, dry matter 93.55% and nitrogen free extract 16.98%). Addition of crude papain at 0.06% had highest (P<0.05) protein digestibility (39.16%). Apparent Digestibility Coefficients (ADC‟s) increased (P<0.05) for all the nutrients tested upon crude papain enzyme supplementation. Growth performance showed that there was no significant different (P>0.05) on final body weight (47.32g) on 0.06% enzyme and (46.17g) on 0% papain enzyme. However, fish fed FM based diet were larger (56.89g) (P<0.05) than those fed SBM (45.59g) CM (43.89g) and SFM (40.59g). The profit index was highest (2.41) in 0% enzyme and lower in 0.06% enzyme (2.19) (P<0.05). Although 10% CP replacement of FM with SBM, CM and SFM was associated with reduced growth, the economic returns were higher. Final carcass proximate composition increased on enzyme supplementation. Crude papain enzyme supplementation led to increase in saturated and mono saturated fatty acid and decrease in polyunsaturated fatty acid. The overall acceptability of fish decreased (3.87) with 0.06% enzyme. The present results indicates that enzyme supplementation led to increased digestibility and growth of fish but carcass fatty acid, sensory attributes and profit index reduced. Based on this, more research is needed on crude papain enzyme supplementation in Nile tilapia diets.
Prevalence and Characterization of Foliar Fungal Diseases of Tomato and Their Biocontrol Using Rhizospheric Streptomyces in Kirinyanga County, Kenya
(Chuka University, 2022-09) Ogolla, Fredrick
Global tomato production is characterized by inconsistent quality and yields partly emanating from biotic constraints attributed to fungal foliar diseases. In Kirinyaga County, where tomato production is a major source of livelihoods, there exists knowledge gaps on prevalence fungal foliar diseases such as early blight, late blight and Septoria spot, and the susceptibility of locally grown tomato varieties to the infection. The objective of this study was to assess the prevalence of three fungal foliar diseases, isolate and characterize the pathogens, assess varietal susceptibility of some locally grown tomatoes to the pathogens under control conditions, and determine the biocontrol potential of some rhizospheric Streptomyces sp. Incidence and severity was assessed using a cross sectional survey design on established macro plots within tomato farms. Pathogen characterization was carried out using morphological and molecular techniques. Susceptibility of tomato varieties to the fungal pathogens was evaluated by artificial inoculation in a greenhouse arranged in a completely randomised design (CRD). Antifungal activity of Streptomyces was determined in-vitro in co-plate culture and in vivo under artificial inoculation using CRD in the greenhouse. Molecular characterization for fungal pathogen and Streptomyces involved BLASTIN analysis of DNA amplicon Sanger sequenced nucleotides and use of NCBI databases. Percentages data of disease incidences and severity were subjected to analysis of variance (ANOVA) using Kruskal Wallis H test at α = 0.05. Median comparison was performed using Steel Dwass Critchlow Fligner (SDCF) with bonferroni adjustment in Statistical Analysis Software (SAS) version 9.4. Conidia lengths (µm) was subjected to ANOVA and significant means separated by Least significance difference (LSD) at α = 0.05. Susceptibility data (%) was subjected to ANOVA and significance means separated using LSD at α = 0.05. Zones of inhibitions for the antifungal activity of Streptomyces isolates in co-plate culture were analysed using ANOVA and significance means separated using LSD at α = 0.05. Disease reduction data on antifungal activity of Streptomyces were analysis by Kruskal Wallis H test and medians of significant means compared by SDCF α = 0.05 in SAS. Incidences and severity of early blight, late blight and Septoria leaf spot in tomato farms differed significantly (p < 0.05) among the villages and agro-ecological zones. Incidence of early blight ranged from 35.7% to 76.65% with severity ranging from17.15% to 50.87%. The incidence of Septoria leaf spot ranged from 23.56% to 93.42% with severity ranging from 16.67% to 44.44%. The incidence of late blight ranged from 33.33% to 86.63% with severity ranging from 16.67% to 33.33%. The incidence of early blight was significantly higher in AEZ UM3 (Median= 75%), the incidence of Septoria leaf spot was significantly higher in AEZ LM4 (Median = 83.33%) while the incidence of late blight was significantly higher in AEZ UM3 (Median= 50%). The severity of early blight was significantly higher in AEZ UM3 (Median = 38.89%), Septoria leaf spot was significantly severe in AEZ LM4 (Median = 40.28%) while late blight was significantly higher in AEZ UM4 (Median = 32.72%). Morphologies of pathogens differed significantly (p < 0.05) with conidia lengths from 52.8 and 204.20µm (Early blight pathogen), 37.20 and 102.30 µm (Septoria leaf spot pathogen) and 26.4 µm to 49.3 µm (Late blight pathogen). Molecular characterization of some selected culture implicated Alternaria solani and A. alternate involvement in causing early blight. Tomato varieties differed in their susceptibility to foliar fungal pathogens (p < 0.05). Kilele F1 was the most susceptible variety (73.84%) while Terminator F1 was least susceptible (56.48%) to late blight pathogens. Kilele F1 was the most susceptible variety (57.99%) while Terminator F1 was least susceptible (37.73%) to Septoria leaf spot pathogens. Riotinto F1 was the most susceptible variety (72.11%) while Terminator F1 was least susceptible (56.48%) to late blight pathogens. Streptomyces assessed differed in their antifunal activity significantly (p < 0.05). Tomato inoculated with Streptomyces isolate Strep6
RESISTANCE TO THE SPOTTED STEM BORER AND AFRICAN MAIZE STEM BORER IN TROPICAL MAIZE
(Chuka University, 2014-05) MUNYIRI SHELMITH WANJA
In sub-Saharan Africa (SSA), maize (Zea mays L.) is the staple food for about 50% of the population. However, lepidoptera stem borer poses a major threat to sustained food sufficiency in SSA causing annual yield losses of 15% and particularly in Kenya where they cause losses estimated at 13.5%. The potential to manage insect pests using host-plant resistance exists, but has not been adequately exploited. The goal of this study was to determine the resistance levels in tropical maize to the African (Busseola fusca Fuller) and the spotted stem borer (Chilo partellus Swinhoe) to support breeding efforts for improved maize productivity. Specific objectives were; i) Determine the variability in resistance to spotted and African stem borers in tropical maize; ii) Investigate the mechanisms of resistance in CIMMYT tropical maize inbred lines and; iii) Map the quantitative trait loci (QTL) associated with resistance to C. partellus and B. fusca stem borers using a tropical maize population. Two hundred and ninety five (295) germplasm which included 120 inbred lines, 75 landraces, 100 hybrids and open pollinated varieties (OPVs) were evaluated for two seasons at the Kenya Agricultural Research Institute (KARI)-Kiboko and KARI-Embu field stations. Data were recorded on leaf damage on a 1-9 scale, number of stem borer exit holes, stem tunnel length (cm) and grain yield. A selection index was computed using the damage traits leaf damage, number of stem borer exit holes and cumulative tunnel length to categorize genotypes into resistant and susceptible categories. Germplasm with selection index of below 0.8 were regarded as highly resistant, 0.8-1.00 as moderately resistant, 1.0-1.2 as moderately susceptible and above 1.2 as highly susceptible. Evaluations for mechanisms of resistance were carried out for two seasons at KARI-Kiboko on 120 inbred lines. Data were recorded on leaf toughness, stem penetrometer resistance, trichome density and pith sugar content. To map the QTL for stem borer resistance, a population of 203 F2:3 individuals were developed between 2009 and 2011. Field evaluations were carried out at six sites, three for each stem borer species. Data were recorded on leaf damage, number of stem borer exit holes and cumulative tunnel length as putative stem borer resistance traits. The mapping population was genotyped with 152 single nucleotide polymorphism (SNP) molecular markers. Phenotypic data were subjected to ANOVA using PROC GLM of SAS 2007 and means separated using Fisher’s protected LSD (P<0.05). Variability for resistance to maize stem borers was identified in the genotypes evaluated. Top ten highly resistant landraces against C. partellus were GUAT 1050, GUAT 280, GUAT 1093, GUAT 1082, GUAT 1014, CHIS 114, GUAT 1034, GUAT 1038, CAQU 321 and GUAN 34. Topmost highly resistant commercial hybrids and OPVs to C. partellus were DH01, PH1, ECA-STRIGOFF-VL-102-#-, KDV1-1-#, KDV1-2- #, and PH3253 while, KDV1-3-#, EEQPM-8-EA-#, DH02, KDV1-2-#, DKC8053, POOL15QC, KDV1-1-#, WH403, EEQPM-9-EA-#, and PH4 were highly resistant to B. fusca among others. Open pollinated varieties KDV1-1-#, KDV1-2-#, KDV1-3-#, EEQPM-8-EA-#, POOL15QC and EEQPM-9-EA exhibited high resistance to both stem borer species. Most CIMMYT MBR lines exhibited high resistance levels, with CKSBL10008, CKSBL10005, CKSBL10025, CKSPL10273 and CKSBL10027 being the top five highly resistant lines to B. fusca and CKSBL10039, CKSBL10025, CKSBL10026, CKSBL10014 and CKSBL10004 the top five highly resistant to C. partellus. Dual and high resistance to both stem borer species was found in CIMMYT MBR lines CKSBL10025, CKSBL10026, CKSBL10027, CKSBL10034, CKSBL10014 and CKSBL10039 among other inbred lines. Trichome density was the best mechanism in discriminating genotypes into resistant and susceptible categories, followed by leaf toughness and stem sugar content in that order. Number of stem borer exit holes and cumulative tunnel length were the most consistent traits in assessing resistance. A linkage map spanning 1248.01 cM on 10 chromosomes with an average 8.21cM was constructed. Several QTL for putative resistance traits were detected on chromosomes 1, 2, 3, 4, 5, 6, 7 and 9 based on data from both individual sites and different species. In the combined B. fusca sites analysis, one QTL for stem tunnelling was revealed on chromosome 4 (LOD 2.86) while in the C. partellus combined sites, one QTL for reduced stem tunnelling on chromosome 4 (LOD 2.81), and another QTL for reduced number of borer exit holes was revealed on chromosome 5 (LOD 2.53). Individual sites analyses revealed five QTL for reduced stem tunnelling, three for stem exit holes and two for leaf damage. Phenotypic variances explained by each QTL ranged from 6 to 10% suggesting a need to validate these QTL using a larger population and in different environments. Variability for resistance against maize stem borers was identified and germplasm identified as highly resistant are recommended as novel sources of resistance for stem borer resistance breeding in SSA. Information on resistant commercial hybrids and OPVs should to be disseminated to farmers in the relevant ecologies for adoption to curb grain yield losses. Trichome density, leaf toughness and stem sugar content could be adopted as satisfactory indicators of resistance mechanisms and used for pyramiding of resistance genes for high and durable resistance. Quantitative trait loci for the three putative resistance traits were detected in the CIMMYT tropical population studied. Overall, this study identified new sources of resistance to spotted and African stem borers in tropical maize germplasm that could be used as new varieties and/or used as sources of resistance in breeding for resistance to stem borers.
A spatial multi-criteria analysis of land use, land cover and climate changes on wildlife ecosystems planning and management in Meru conservation area
(Chuka University, 2018) Kiria, Edwin Muchomba
Protected areas are recognized as among the most effective tools that have protected the wildlife species from extinction and human induced threats. However, despite the establishment and spread of these protected areas in most parts of the world, wildlife numbers and their habitats have declined drastically due to land use land cover changes (LULCs) coupled by climate variability in the past decades. Protected areas and their buffer zones have been converted to settlement areas, grazing fields and farms by people living around these parks and reserves as a coping mechanism for declining resources at the expense of wildlife populations and their ecosystems. The study was carried out at Meru National Park (MNP) and Mwingi National Reserve (MNR) to establish changes in land use, land cover and climate variability over time and their implications on wildlife ecosystems. The study specifically sought to establish changes in land use land cover, establish climate change over time, and determine the effectiveness of the existing management plan and identifying the adaptation strategies that are being used as mitigation to climate change. To achieve these objectives, the study used remotely sensing data from Landsat satellite images of 1985 to 2015 together with physical, demographic data and questionnaires were used in post classification analysis using ArchGIS to analyze the outcome of different land use practices. The results showed a rapid decline in forest and shrub land in the study area by 14.1% and 37.8%, respectively while grassland and bareland tend to have increased to 27% and 16.2% respectively over time. From the Pearson correlation test, there was significant positive correlation between grassland and bareland (r = 0.860, p=0.140), significant negative correlation between forest and bareland (r = -0.692, p=308) and between shrubland and bareland (r = -0.631,p=369). Climate variability in MNP and MNR had impacts on wildlife ecosystems as established during by the strong negative correlation observed (r = -0.766, p=0.05). Multi-criteria decision making analysis was applied as a planning tool to establish the effectiveness of the management plans. This analysis incorporated the value measurement, goal setting and outranking. In addition to guided observations, semi structured questionnaires, and interview schedule were administered to the local community and institutions respectively to acquire relevant data on establishing the adaptation strategies for climate change mitigation by the wildlife managers and local communities in the study areas. The study established that continuous increase in human wildlife conflicts, encroachment into the Protected Areas (PAs), and low support of conservation programs by community are indicators of non effectiveness in the management plan. More so, there are various adaptation strategies to mitigate changes in climate by local community and wildlife managers. These included fencing of Protected Areas (PAs), introduction of irrigation, encroachment in protected areas and amendments of laws, policies and institutional structure. Both MNP and MNR have undergone significant changes in land use land cover over the years which have over time affected the wildlife populations and their ecosystems. These changes are likely to have been brought about by inevitable climate change which has altered rainfall distribution leading to droughts that have hindered vegetation growth. On the other hand, increasing human population by 57.4% from 1980 around these protected areas has over the years contributed towards land cover from their interaction with land through activities that are meant to provide socioeconomic livelihoods such as farming and livestock keeping. In view of these findings, the study recommends an integrated planning of protected areas in view of the changing land use land cover and climatic regimes in the study areas.
SYNERGISTIC QUALITIES OF SELECTED PLANT EXTRACTS ON POTENCY OF PYRETHRINS AGAINST THE MAIZE WEEVIL, SITOPHILUS ZEA-MAIS (MOTSCH.) (COLEOPTERA: CURCULIONIDAE)
(Chuka University, 2020-12) Michura, Anne Jerotich Garry
Post-harvest losses of grains are a major hindrance to attainment of food security in Kenya due to infestation of coleopteran grain pests such as weevils. Although synthetic chemical insecticides are being used in their control, overuse and misuse of these insecticides have resulted in problems of pesticide resistance, environmental contamination, pest resurgence and even consumer poisoning. Several studies have been done on utilizing plant essential extracts and oils in control of storage pests but their limitations, such as inconsistencies in efficacy, lack of persistence and residual effect have hindered their use as stand-alone products for pest management. Piperonyl butoxide (PBO) is often the synergist used to enhance efficacy of insecticides like pyrethroids and pyrethrum formulations. Synergists enable the use of an active ingredient in very small quantities by preventing detoxification within the insect thus un-synergised formulations are rarely used. This study aimed at evaluating synergistic qualities of selected plant extracts on potency of pyrethins formulations against the maize weevil, Sitophilus zea-mais (Motsch.) (Coleoptera: Curculionidae). Plants extracts (Black pepper seeds, Nutmeg seeds, Coriander leaves and roots) “synergists” used were selected on the basis of possessing a methylenedioxyphenyl (MDP) ring structure similar to that of PBO. Full dose response, dose-mortality, synergism experiments were carried out on S. zea-mais at four concentrations of synergists, each at four ratios (synergist: pyrethrins) while infestation was carried out on maize treated with plant ectracts-pyrethrins formulations. Topical application of pyrethrins/synergist/formulation on S. zea-mais was done in triplicate in a Completely Randomised Design. Experiments were conducted under controlled laboratory conditions of 27 ± 2OC and 60 ± 5% RH with normal day light hours. Probit analysis was used to determine the lethal concentration (LC) of pyrethrins to the S. zea-mais. Analysis of Variance was used to obtain the mean mortality differences of S. zea-maisat P ≤ 0.05 while Duncan’s Multiple Range Test was used to rank significant concentration means within a synergist. Results obtained found LC20 value for pyrethrins to be 2,200 ppm. To obtain LC50, 14227 ppm, 13780 ppm and 8868 ppm of pyrethrins wwere required over a 24 h, 48 h and 72 h exposure time respectively. Black pepper seed hexane extract (BPSHE) and PBO after 48 h exposure were statistically significant (P ≤ 0.05) with the average percentage mortalities of 10% and 20% at 10,000 ppm and 20,000 ppm respectively, while PBO and Coriander leaves hexane extract (CLHE) were significant P ≤ 0.05 after 72 h. PBO was the most toxic synergist (36.67 ± 3.33%) followed by CLHE (26.67 ± 3.43%) at 20,000 ppm. In the formulations of synergist: pyrethrins, CLHE, Nutmeg seed hexane extract (NMHE) and Black pepper seed methanol extract (BPSME) at ratio 1:1 were statistically significant (P ≤ 0.05) 24 h after exposure. PBO registered higher percentage (83.33 ± 12.02%) mortality followed by CLHE (46.67 ± 3.33%), BPSME (43.33 ± 6.67%) and NMHE (26.67 ± 3.33%) at ratio of 3:1 while BPSHE was most effective synergist at ratio 2:1. BPSME and NMHE co-toxicity values were below 20 and -20 respectively while in PBO, BPSHE and CLHE values were above 20. Low concentrations of pyrethrins were required to achieve higher percentage mortality of S. zea-mais when exposure time was extended to 72 h. The toxicity of plant extracts tested was low hence qualified as potential synergists to replace the standard, PBO in pyrethrins formulations. BPSHE was a better synergist than PBO at a concentration of 5,000 ppm followed CLHE while BPSME was an additive to the pyrethrins while NMHE was antagonistic to pyrethrins at 1,000 ppm. It is recommended that time of exposure of a synergist and an insecticide play a critical role in high mortality rates of S. zea-mais regardless of the ratio of synergist: pyrethrins and should be considered when formulating insecticides.

Browse

Browsing Faculty of Agriculture and Environmental Studies (FAES) by Title