• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 10
  • 5
  • 1
  • 1
  • 1
  • Tagged with
  • 19
  • 19
  • 19
  • 8
  • 5
  • 5
  • 4
  • 4
  • 4
  • 3
  • 3
  • 3
  • 3
  • 3
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Responses of Tylenchulus Semipenetrans to crude extracts of indiginous cucumis fruits with and without effective micro-organisms in citrus production

Maile, Kgahliso Desmond January 2013 (has links)
Thesis (M.Agric. (Horiticulture)) --Unversity of Limpopo, 2013 / The ground leaching technology (GLT) system, using crude extracts of wild cucumber (Cucumis myriocarpus) and wild watermelon (Cucumis africanus) fruits, had been widely researched and developed in management of the root-knot (Meloidogyne species) nematodes in tomato (Solanum lycopersicon) production. In the GLT system, experiments were harvested at 56 days after inoculation with nematodes, which was approximately three generations of Meloidogyne species. Also, studies in GLT systems demonstrated that effective micro-organisms (EM) were not essential in the release of chemicals from crude extracts for nematode suppression, with suggestions that the system exclusively relied upon irrigation or rainwater for leaching out chemicals. However, the system had hardly been tested on other nematode species with longer life cycles and crops. The objective of this study was to investigate the influence of crude extracts of C. myriocarpus (cucurbitacin A-containing phytonematicide) and C. africanus (cucurbitacin B-containing phytonematicide) with and without EM on suppression of population densities of the citrus nematode (Tylenchulus semipenetrans) on rough lemon (Citrus jambhiri) over three generations of the nematode. Two studies, one on C. myriocarpus and the other on C. africanus, with and without EM, were conducted separately using the GLT system under greenhouse conditions with three generations of T. semipenetrans as the standard of application interval of the materials. Citrus seedlings were transplanted in 7-L plastic pots contain 6.5-L pasteurised river sand and Hygromix (3:1 v/v) and inoculated with approximately 25 000 second-stage juveniles (J2s) in 2 × 2 × 2 factorial experiment, where treatments were arranged in a randomised complete block design (RCBD), with six replications. At 150 days after treatment, nematode and plant variables were collected and subjected to factorial analysis of variance. Under C. myriocarpus (Cm), EM × Cm interaction was not significant for nematodes (juveniles + eggs) in roots and juveniles in soil, while under C. africanus (Ca), EM × Ca interaction was highly significant for nematodes, but not for juveniles. Crude extracts of C. myriocarpus and C. africanus fruits contributed 21-36% and 38-59% to total treatment variation in nematodes, respectively. Relative to untreated control, crude extracts of C. myriocarpus fruit reduced nematodes by 22% in roots, but increased juveniles in soil by 93%. Similarly, C. africanus fruit reduced nematodes in roots by 80%, but increased juveniles in soil by 178%. The increase of juveniles in the soil was explained on the basis of opposing forces on nematode population densities under crude extracts of Cucumis and untreated control, along with the inherent nature of cyclic population growth in plant-parasitic nematodes. In plant variables, certain significant (P ≤ 0.05) interactions consistently occurred under both Cucumis species. However, effects of the interactions were not consistent under the two Cucumis species. In most of the variables, the non-significant effects of EM × Cm interactions supported the view that the GLT systems were independent of microbial activities, while significant (P ≤ 0.05) EM × Ca interactions suggested that the systems under C. africanus fruit could be viewed as being dependent upon microbial degradation activities. Growth of rough lemon rootstock was, to a certain extent, suppressed by application of crude extracts from Cucumis fruits, suggesting that the material were phytotoxic to this citrus rootstock. Under low nematode population densities, T. semipenetrans infection supported the view that nematode numbers below the damage threshold levels have stimulatory effects on growth of plants as observed in plant height under conditions of this study. In conclusion, the approximately three nematode-generation-application interval of 150 days for crude extracts of fruits in Cucumis species was rather too long for the efficacies of the materials on suppression of the population densities of T. semipenetrans in rough lemon seedlings. Consequently, shorter application intervals, as demonstrated for Meloidogyne species would be appropriate, although caution has to be taken to ensure that phytotoxicity to the rootstock was avoided.
12

Development of mean concentration stimulation point for fermented Lantana Camara Phytonematicide on tomato production

Malatji, Kgashane Philip January 2017 (has links)
Thesis (M.Sc. (Agriculture)) --University of Limpopo, 2017 / Root-knot nematodes (Meloidogyne species) are the major soil-borne pests of tomato (Solanum lycorpesicum) plants. Due to the global withdrawal of effective chemical nematicides from the agrochemical markets, nematodes are difficult to control under the production systems. Currently, botanicals are being researched and developed as alternative to chemical nematicides with promising results, although they have challenge of phytotoxicity. The objective of this study was to determine the Mean Concentration Stimulation Point (MCSP) of Tickberry (Lantana camara) extracts for tomato plant-infected with M. javanica. Treatments consisted of six levels of L. camara extracts, namely, 0, 2, 4, 6, 8 and 10% per pot, which were arranged in a randomised complete block design, with ten replicates. Tomato seedlings were inoculated with 2500 second-stage juveniles (J2S) of M. javanica at five days after transplanting, with treatments applied at seven days after inoculation. At 56 days after inoculation, L. camara extracts had positive effects on plant height, stem diameter, number of leaves, number of fruits and fruit mass, contributing 65, 74, 61, 25 and 61% in total treatment variation (TTV), respectively, under greenhouse conditions. Under microplot conditions, treatments contributed 55, 85, 61, 36 and 85% in TTV of the respective plant variables. Under greenhouse it contributed 60, 35 and 77% and 29, 79 and 70% under microplot on dry shoot mass, dry root mass and galling index respectively. Treatments did not have any effects on soil pH and electrical conductivity (EC). Under greenhouse conditions, treatments contributed 88, 94 and 92% in TTV of nematode in roots, soil and final population, respectively, whereas under microplot conditions 94, 97 and 95% in xvii TTV of the respective nematode stages. The derived mean concentration of L. camara extracts for tomato was 5.76 and 5.31% under microplot and greenhouse conditions, respectively. The overall sensitivity of tomato plants to L. camara extracts under microplot and greenhouse were 3 and 0, respectively. In conclusion Meloidogyne species can be managed using L. camara extracts 5.31 and 5.76% under glasshouse production and field production system respectively.
13

Non-phytotoxic concentration and application interval of nemarioc-al phytonematicide in management of meloidogyne javanica on potato cultivar 'mondial G3'

Kobe, Selaelo Patrisia January 2019 (has links)
Thesis (M. A. Agriculture (Plant Protection)) -- University of Limpopo, 2019 / Potato (Solanum tuberosum L.) is highly susceptible to root-knot (Meloidogyne species) nematodes, with no known nematode resistant genotypes. In Limpopo Province, two cucurbitacin-containing phytonematicides had been researched and developed. The active ingredients of the cucurbitacin-containing phytonematicides are cucurbitacins, which are allelochemicals that could induce phytotoxicity on crops being protected against nematode damage. The objectives of this study were to determine: (1) mean concentration stimulation point (MCSP) of Nemarioc-AL phytonematicide on potato cultivar ꞌMondial G3ꞌ for managing M. javanica and (2) application interval of Nemarioc AL phytonematicide on potato cultivar ꞌMondial G3ꞌ. Sprouted tubers were planted in 10 cm deep/pot with each pot filled with steam-pasteurised soil and Hygromix at 3:1 (v/v) ratio in the field under microplot conditions. After 100% emergence (2 weeks), each plant was inoculated with 5 000 M. javanica eggs and second-stage juveniles (J2). Seven treatments, namely, 0, 2, 4, 8, 16, 32 and 64% Nemarioc-AL phytonematicide were arranged in a randomised complete block design, with 11 replications. In Objective 2, four treatments, namely, 1, 2, 3 and 4 weeks were arranged in randomised complete block design, with 15 replications. Plant variables and nutrient elements were subjected to the Curve-fitting Allelochemical Response Data (CARD) model to generate biological indices used to compute MCSP using the relation MCSP = Dm + Rh/2 and the overall sensitivity value (∑k). The MCSP for plant variables and nutrient elements, were empirically derived as 4.31% and 1.33%, with the ∑k of 18 and 4 units, respectively. Nematode variables and increasing concentrations of Nemarioc-AL phytonematicide exhibited negative quadratic relations where eggs, J2 in soil and roots and total population (Pf) were optimised at xv 14.43, 28.23, 23.30 and 13.55%. To conduct Objective 2 which is application interval, empirically derived MCSP value of 4.31% from Objective 1 was used. Application interval was optimised using the concept of 1, 2, 3, and 4 weeks in weeks-per-month-of-30-days. The application interval of 4.31% was established at 2.43 weeks which translated to 18 days [(2.43 weeks/4 weeks) × 30 days]. All nematode variables in Objective 2 were not significantly different at all intervals. In, conclusion Nemarioc-AL phytonematicide can be used at 4.31% concentration to control nematodes population densities without being phytotoxic to crops at 18 days application interval. / National Research Foundation (NRF) , Agricultural Research Council (ARC) and the Flemish Interuniversity Council of Belgium
14

Potential cucurbitacin chemical residues and non-phytotoxic concentration of two phytonematicide formulations in nightshade

Malebe, Agreement Leago January 2019 (has links)
Thesis (M. A. Agriculture (Plant Protection)) -- University of Limpopo, 2019 / The successful cultivation of nightshade (Solanum retroflexum) as a leafy vegetable with the nutritional potential of contributing to food security in marginalised communities of Limpopo Province could be limited by high population densities of root-knot (Meloidogyne species) nematodes. However, the use of Nemarioc-AL/AG and Nemafric-BL/BG phytonematicides in suppressing nematodes and not being phytotoxic requires the empirically-developed non-phytotoxic concentration, technically referred to as Mean Concentration Stimulation Point (MCSP). The MCSP, developed using the Curve-fitting Allelochemical Response Data (CARD) computer-based model, is crop-specific, hence it should be developed for every crop. The objective of this study was to investigate the influence of Nemarioc-AL/AG and Nemafric-BL/BG phytonematicides on growth of nightshade, accumulation of essential nutrient elements and cucurbitacin residues in nightshade leaves. Microplots were established by inserting 20-cm-diameter plastic pots into 10-cm-deep holes at 0.6 m intra-row and 0.6 m inter-row spacing. Each pot was filled with 10 000 cm3 steam-pasteurised river sand and Hygromix at 3:1. After establishment, Nemarioc-AL and Nemafric-BL phytonematicides were applied at 7-day interval, whereas, Nemarioc-AG and Nemafric-BG phytonematicides were only applied at planting. Two separate experiments for Nemarioc-AL and Nemafric-BL phytonematicides were conducted in summer (November-January) 2017/2018 under microplot conditions with each comprising treatments namely; 0, 2, 4, 8, 16, 32 and 64%, similarly, two separate experiments for the following phytonematicides, Nemarioc-AG and Nemafric-BG comprised treatments namely; 0, 2, 4, 6, 8, 10 and 12 g arranged in a randomised complete block design (RCBD), with 12 replications. The nutrient elements in leaf tissues of nightshade were analysed using the inductively coupled plasma optical emission spectrometry (ICPE-9000) while, cucurbitacin A and B were xii each quantified using the isocratic elution Shimadzu HPLC Prominence with Shimadzu CTO-20A diode array detector. Plant growth and nutrient elements variables were subjected to the CARD computer-based model to generate biological indices to generate the curves, quadratic equations and the related biological indices (Dm, Rh, k) (Liu et al., 2003). The MCSP values were calculated using the biological indices of plant or nutrient element variables which, along with increasing concentration of Nemarioc-AL, Nemafric BL, Nemarioc-AG and Nemafric-BG phytonematicides, exhibited positive quadratic relations, with R2 ≥ 25. Using cucurbitacin A and B standards, residues of Nemarioc AL/AG and Nemafric-BL/BG phytonematicides, were not detected in nightshade leaves, respectively. Dry root mass and dry shoot mass of nightshade over increasing concentration of Nemarioc-AL phytonematicide each exhibited a quadratic relationship, with the models explained by 93 and 61%, respectively. Dry root mass, dry shoot mass, plant height, chlorophyll content and stem diameter against increasing concentration of Nemafric-BL phytonematicide each exhibited positive quadratic relationships with the models explained by 95, 72, 65, 78 and 62%, respectively. Plant height, stem diameter and dry root mass against increasing concentration of Nemarioc-AG phytonematicide each exhibited positive quadratic relationships with their models explained by 93, 88 and 91%, respectively. Dry shoot mass and stem diameter against increasing concentration of Nemafric-BG phytonematicide each exhibited positive quadratic relationships with their models explained by 94 and 84%, respectively. Na, Fe and K over increasing concentration of Nemarioc-AL phytonematicide each exhibited positive quadratic relationships with their associations explained by 96, 91 and 95%, respectively. Zn over increasing concentration of Nemafric-BL phytonematicide exhibited positive quadratic relationship with the model explained by 98%. Fe over increasing concentration of Nemarioc-AG phytonematicide exhibited positive quadratic xiii relationship with the association explained by 91%. Fe, Na, K and Zn over increasing concentration of Nemafric-BG phytonematicide each exhibited positive quadratic relationships with their associations explained by 81, 90, 80 and 89%, respectively, whereas, on the contrary, Zn over increasing concentration of Nemarioc-AG phytonematicide exhibited negative quadratic relationship with the association explained by 96%. Significant (P ≤ 0.05) plant variables were subjected to CARD, to generate biological indices which were used to compute the MCSP using the relation: MCSP = Dm + Rh/2 and the overall sensitivity value (∑k). In Nemarioc-AL phytonematicide trial, MCSP = 3.02% and ∑k = 1 for plant variables, whereas, MCSP and ∑k for nutrient elements were 12.09% and 1, respectively. In Nemafric-BL phytonematicide trial, MCSP = 3.08% and ∑k = 0 for plant variables, while MCSP = 2484.14% and ∑k = 0 for nutrient elements. In Nemarioc-AG phytonematicide trial, MCSP = 3.47 g and ∑k = 0 for plant variables, whereas, for nutrient elements MCSP = 8.49 g and ∑k = 1. In Nemafric-BG phytonematicide trial, MCSP = 4.70 g and ∑k = 0 for plant variables, whereas, MCSP =723.75 g and ∑k = 1 for nutrient elements. In conclusion, the application of Nemarioc-AL/AG and Nemafric-BL/BG phytonematicides had the ability to stimulate the growth of nightshade and enhance the accumulation of the selected nutrient elements without leaving cucurbitacin chemical residues in leaf tissues of nightshade. / National Research Foundation (NRF) and the Land Bank Chair of Agriculture
15

Integrated control of gastrointestinal nematodes of sheep using plant extracts. and bicontrol agents.

Ahmed, Mawahib Alhag Ali. 29 November 2013 (has links)
Infection of small ruminants by gastrointestinal nematodes (GIN) is a major health concern because they cause substantial economic losses, especially in the tropics and sub-tropics. For many years, control of GIN has been based upon use of anthelmintics. However, there is now a global challange because mutant GIN individuals can tolerate most of the widely used anthelmintics. Therefore, alternative control measures are needed. The objective of the study was to screen a number of plant species for their anthelmintic effects, and to evaluate selected strains of Bacillus thuringiensis (Berliner) and Clonostachys rosea (Schroers) for activity against sheep GIN. Subsequently, the combined treatments would test a dual control strategy for nematodes by using a combination of plant extracts with biocontrol agents. Ethanol extracts of 25 plant species were screened for their anthelmintic effects against Haemonchus contortus (Rudolphi 1803). Extracts of each plant were used in vitro at various concentrations (10, 20 and 30%) to treat 10 day faecal cultures. Five plants with high efficacies (Ananas comosus L. Merr., Aloe ferox Mill., Allium sativum Linn., Lespedeza cuneata Dum. Cours. and Warburgia salutaris Bertol.f. Chiov) were selected for further investigation, using ethanol, dichloromethane and water extracts at four concentrations (2.5, 5, 10 and 20%). Ethanol was the most effective solvent. Larval counts decreased as a result of increasing extract concentrations. An ethanolic extract of Lespedeza cuneata caused more than 70% mortality at all concentrations. In an in vivo study, the five plants A. comosus, A. ferox, A. sativum, L. cuneata and W. salutaris extracts were compared to a positive Control (Equimax®, a modern anthelmintic based on abamectin and praziquantel). Gender, eggs count (EPG₀) and initial body weights were used in assigning sheep (24 females and 24 males) to six groups. Each group was randomly assigned a treatment. Plant extracts were applied as an oral dose (100 mg kg⁻¹ BW), one dose per week per animal for 42 days (Phase 1). Subsequently, the same sheep were dosed for three consecutive days with the same treatments, keeping them in the same groups (Phase 2). Rectal faecal samples were taken for counting of eggs per gram of faeces (EPG) and L₃ larvae per gram (LPG) in faecal cultures. With application of plant extracts, the EPG count decreased with time (P<0.001), and the impact of the plant extracts increased (P<0.001) with time. Two extracts, from A. comosus and L. cuneata, were the most effective in Phase 1 (58% and 61% reduction of EPG, respectively,), and in Phase 2 (77% and 81% reduction of EPG, respectively). In a study on potential biocontrol agents, two strains of Bacillus thuringiensis (Bt) and one of Clonostachys rosea f. rosea (C. rosea), and compared with a diatomaceous earth (DE) product for their anthelmintic activity in sheep. Bacillus thuringiensis and C. rosea were fed to sheep at a rate of 1g kg⁻¹ BW, and DE was fed at 2% of sheep diet. The biocontrol treatments had no effect on EPG (P>0.05), but reduced GIN larvae per gram (LPG) (P<0.001) in faecal culture. Efficacy varied with time (P<0.001). By Day 7 Bt, C. rosea and DE had caused mortalities of GIN of 75.7, 86.9 and 60.6%, respectively. In addition, the efficacy of feeding 1g kg⁻¹ BW of C. rosea chlamydospores to sheep every day, every second day and every third day was tested. Daily feeding of fungal chlamydospores reduced LPG (a count of 12±1.67 GIN larvae) (P<0.001) more than feeding them the biocontrol agent every second day (39±0.77) or third day (58±1.77). By Day 12, feeding the biocontrol agent to sheep every day, every second day, or every third day caused mortality of GIN larvae of 90, 63 and 49%, respectively. Four dietary levels (treatments) of C. rosea (0.25g (F1), 0.5g (F2), 1g (F3) and control (C) of C. rosea product kg-1 BW) were tested. Treatments were each mixed with a complete diet and fed to sheep once daily for 10 weeks, according to body weights. Increased doses of the biocontrol agent reduced LPG (P<0.001), larval development (LD) (P<0.001), and increased efficacy (P<0.001). On Day 70, F1, F2, F3 and the Control controlled LD by 33.3, 72.3, 89.4 and 2.6%, respectively. Clonostachys rosea was effective in reducing third stage larvae (L₃) on pastures significantly (P<0.001) by Day 63 and Day 70. Ethanolic extracts of A. comosus, A. ferox, A. sativum, L. cuneata and W. salutaris all reduced egg production by GIN parasites of sheep. Feeding sheep cultured chlamydospores of a biocontrol fungus, Clonostachys rosea, reduced counts of nematode larvae in sheep; and 1g C. rosea chlamydospores kg⁻¹ BW daily was enough to reduce nematode infective larvae, therefore reducing the degree of pasture contamination. An initial trial showed that the combination of the two treatments of an A. comosus extract and C. rosea chlamydospores was more effective than either treatment on its own in controlling gastrointestinal nematodes in sheep. A long-term trial is being undertaken currently to confirm this finding. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.
16

Nemarioc-AL and nemafric-BL phytonematicides : bioactivities in meloidogyne incognita, tomato crop, soil type and organic matter

Dube, Zakheleni Palane January 2016 (has links)
Thesis (Ph. D. Agriculture (Plant Production)) -- University of Limpopo, 2016. / Nemarioc-AL and Nemafric-BL phytonematicides, had been researched and developed from indigenous plants at the University of Limpopo, Green Technologies Research Centre, under the auspices of the Indigenous Cucurbitaceae Technologies (ICT) Research Programme. After the international 2005 cut-off withdrawal date of the highly effective methyl bromide nematicide from the agrochemical markets, management options on nematode population densities shifted to more environment-friendly alternatives. Nemarioc-AL and Nemafric-BL phytonematicides as environment-friendly alternatives to synthetic chemical nematicides had been consistent in nematode suppression under diverse conditions. In order to avoid challenges similar to those experienced with the use of synthetic chemical nematicides, the South African Fertiliser, Farm Feeds, Agricultural Remedies and Stock Remedies Act No. 36 of 1947 (amended) require that the product to be used in agriculture must first be registered with the National Department of Agriculture, Forestry and Fisheries, after extensive efficacy and bioactivity tests. The information on bioactivity of the phytonematicides is also critical in the effective application of the product for efficient management of nematodes. Information on bioactivities of Nemarioc-AL and Nemafric-BL phytonematicides on nematodes, plant and soil was not available. This study comprised eight objectives: (1) to examine whether (i) increasing concentration of cucurbitacin A and B would have impact on second-stage juvenile (J2) hatch of M. incognita, (ii) the Curve-fitting Allelochemical Response Dosage (CARD) model would quantify the three phases of density-dependent growth (DDG) patterns on J2 hatch when exposed to increasing cucurbitacin concentrations, (iii) computed J2 hatch inhibition concentration (EHIC) and xli CARD-generated D-values would be statistically similar, (iv) the CARD model would provide information on minimum inhibition concentration (MIC) and (v) J2 hatch inhibition would be reversible when cucurbitacins were diluted, (2) to determine whether (i) increasing concentration of Nemarioc-AL and Nemafric-BL phytonematicides would have impact on J2 hatch of M. incognita, (ii) the CARD model would quantify the three phases of DDG pattern on J2 hatch when compared to increasing phytonematicide concentrations, (iii) comparison of computed EHIC and CARD-generated D-values would be statistically comparable in magnitudes, (iv) the CARD model would provide information on MIC and (v) J2 hatch inhibition would be reversible when phytonematicides were diluted, (3) to establish whether (i) increasing concentration of cucurbitacin A and B would have impact on M. incognita J2 immobility, (ii) the CARD model would quantify the three phases of DDG pattern on J2 immobility when compared to increasing cucurbitacin concentration, (iii) comparison of computed J2 immobility concentration and CARD-generated D-values would be statistically comparable in magnitudes, (iv) the CARD model would provide information on MIC and (v) juvenile immobility would be reversible when cucurbitacins were diluted, (4) to test whether (i) increasing concentration of Nemarioc-AL and Nemafric-BL phytonematicides would have impact on M. incognita J2 immobility, (ii) the CARD model would quantify the three phases of DDG pattern on J2 immobility when compared to increasing phytonematicide concentrations, (iii) comparison of computed J2 immobility concentration and CARD generated D-values would be statistically comparable in magnitudes, (iv) the CARD model would provide information on MIC and (v) juvenile immobility would be reversible when phytonematicides were diluted, (5) to determine whether (i) increasing xlii concentration of cucurbitacin A and B would have impact on M. incognita J2 mortality, (ii) the CARD model would quantify the three phases of DDG patterns on J2 mortality when compared to increasing cucurbitacin concentration, (iii) comparison of computed lethal concentration (LC) and CARD-generated D-values would be statistically comparable in magnitudes and (iv) the CARD model would provide information on minimum lethal concentration (MLC), (6) to investigate whether (i) increasing concentration of Nemarioc-AL and Nemafric-BL phytonematicides would have impact on M. incognita J2 mortality, (ii) the CARD model would quantify the three phases of DDG pattern on J2 mortality when compared to increasing phytonematicide concentrations, (iii) comparison of computed LC and CARD-generated D-values would be statistically comparable in magnitudes and (iv) the CARD model would provide information on MLC, (7) to test whether (i) increasing concentrations of Nemarioc-AL and Nemafric-BL phytonematicides would impact on M. incognita J2 infectivity of susceptible tomato plant, (ii) the CARD model would quantify the three phases of DDG pattern (iii) generated inhibition concentration (IC) and CARD-generated D-values would be statistically comparable in magnitudes and (iv) the CARD model would provide information on MIC and (8) to determine whether nematodes can serve as bioindicators of Nemarioc-AL and Nemafric-BL phytonematicides in tomato plant roots/fruits, soil types and organic matter at different depths. To achieve these objectives, reliability of measured variables was ensured by using statistical levels of significance (P ≤ 0.05) and coefficient of determination (R2), with validity ensured by conducting three independent experiments over time. In Objective 1, pure cucurbitacin A and B concentration effects on J2 hatch were significant, with both exhibiting DDG patterns. xliii The DDG patterns demonstrated that J2 hatch was inhibited at low pure cucurbitacin concentrations and slightly stimulated at higher cucurbitacin concentrations. At 24-, 48- and 72-h exposure periods, cucurbitacin A reduced J2 hatch by 40‒67, 34‒66 and 34‒45%, respectively, whereas cucurbitacin B reduced J2 hatch by 12‒57, 3‒36 and 9‒54%, respectively. CARD model quantified the concentration ranges of the two pure cucurbitacins associated with the phases of DDG patterns. The J2 hatch was highly sensitive to cucurbitacin B and highly tolerant to cucurbitacin A, as shown by sensitivities values of 0‒2 and 5‒20 units, respectively. The CARD-generated MIC values for cucurbitacin A and B were 1.75‒2.88 and 1.31‒1.88 µg.mL-1, respectively. The conventionally generated J2 hatch inhibition concentrations were higher than CARD-generated D-values at all exposure periods for both pure cucurbitacins. The J2 hatch inhibition effect was not reversible for both pure cucurbitacins. In Objective 2, Nemarioc-AL and Nemafric-BL phytonematicide concentration effects on J2 hatch were highly significant (P ≤ 0.01), with both exhibiting DDG patterns. The DDG patterns demonstrated that J2 hatch inhibition increased with increase in phytonematicide concentrations. Relative to water control, Nemarioc-AL phytonematicide significantly reduced J2 hatch at 48-, 72-h and 7-d by 22‒92, 3‒79 and 1‒42%, respectively, whereas Nemafric-BL phytonematicide reduced it by 41‒93, 1‒80 and 12‒84%, respectively. The J2 hatch inhibition was highly sensitive to Nemarioc-AL and Nemafric BL phytonematicides, with sensitivity of 0‒1 and 0‒4 units, respectively. The conventionally generated J2 hatch inhibition concentrations at 50 and 100% were higher than CARD-generated D-values for both phytonematicides. The J2 hatch inhibition effect was not reversible for both phytonematicides. In Objective 3, pure cucurbitacin A xliv and B concentration effects on J2 immobility were significant, with both exhibiting DDG patterns. The J2 immobility over increasing concentrations of pure cucurbitacins had DDG patterns which were similar for conventional method and those from CARD model. The DDG patterns were characterised by stimulation of J2 immobility at low concentrations, followed by saturation at higher concentrations. The CARD model could not generate the D-values for comparison with JMC-values, but generated MIC-values for cucurbitacin A and B which were 0.5‒0.6 and 0.5‒0.7 µg.mL-1, respectively. The J2 immobility was moderately sensitive to both cucurbitacins with sensitivity of 4 units and the inhibition effect of the two pure cucubitacins was not reversible. In Objective 4, Nemarioc-AL and Nemafric-BL phytonematicide concentration effects on J2 immobility were highly significant (P ≤ 0.01), with both phytonematicides exhibiting DDG patterns. The DDG pattern had stimulation, saturation and inhibition effects for Nemarioc-AL phytonematicide, whereas for Nemafric-BL phytonematicide they had stimulation and saturation effects on J2 immobility as concentrations increased. The MIC-values for Nemarioc-AL and Nemafric-BL phytonematicides were 3.6‒115.2 and 0.1‒6.5%, respectively. The CARD generated D-values were comparable with computed JMC values for Nemafric-BL phytonematicide unlike for Nemarioc-AL phytonematicide. The J2 immobility was highly sensitive to the two phytonematicides with sensitivity values of 0‒4 and 0‒2 units, respectively. The effects on J2 immobility of the two phytonematicides were not reversible. In Objective 5, pure cucurbitacin A and B concentration effects on J2 mortality were highly significant (P ≤ 0.01), with both cucurbitacins exhibiting DDG patterns. The DDG pattern had stimulation, saturation and slight inhibition effects for both cucurbitacin A and B as concentrations increased. The xlv MIC-values for cucurbitacin A and B were 0.63 and 0.61 µg.mL-1, respectively. The CARD-generated D-values were higher than the computed LC-values for both cucurbitacin A and B, with J2 mortality being highly sensitive to cucurbitacin A and B, with sensitivity of 4 units for both cucurbitacins. In Objective 6, Nemarioc-AL and Nemafric-BL phytonematicide effects on J2 mortality were highly significant (P ≤ 0.01), with both phytonematicides exhibiting DDG patterns. The DDG pattern had stimulation effect at low phytonematicide concentrations and saturation effects at higher concentrations for both relative impact and CARD-generated graphs of J2 exposed to both phytonematicides. The MIC-values for Nemarioc-AL and Nemafric-BL phytonematicides were 1.12 and 0.67%, respectively. The CARD-generated D-values were higher than the computed LC-values for both phytonematicides and J2 mortalities were highly sensitive to Nemarioc-AL and Nemafric-BL phytonematicides with sensitivity value of 2 and 1 units, respectively. In Objective 7, Nemarioc-AL and Nemafric-BL phytonematicide concentrations had a highly significant effect on infectivity of M. incognita post-exposure on susceptible tomato seedlings. The relationship between infectivity and increasing concentrations of the two phytonematicides exhibited DDG patterns. The DDG patterns were characterised by stimulation effect at low Nemarioc AL phytonematicide concentrations and saturation effects at higher phytonematicide concentrations, whereas for Nemafric-BL phytonematicide slight inhibition, saturation and stimulation effects were observed. The CARD-generated inhibition concentrations for Nemarioc-AL phytonematicide were comparable with computed inhibition concentrations, whereas for Nemafric-BL phytonematicides, the values were not comparable. The MIC-values for Nemarioc-AL and Nemafric-BL phytonematicides were xlvi 0.2 and 0.7%, respectively and J2 infectivity were highly sensitive to the two phytonematicides, with sensitivity value of 2 and 0 units, respectively. In Objective 8, M. incognita was an excellent bioindicator in response to the application of two phytonematicides. The two phytonematicides significantly affected distribution of population densities of M. incognita across the tested soil types, with Nemafric-BL phytonematicide reducing population densities of M. incognita relative to Nemarioc-AL phytonematicide. The active ingredient of Nemafric-BL phytonematicide, cucurbitacin B tended to remain in the top layers of soil, where more roots accumulated, thereby reducing a relatively higher population densities of M. incognita than did active ingredient of Nemarioc-AL phytonematicide, cucurbitacin A which moved with water beyond the effective root zone. Soil type alone and phytonematicide alone had no effect on nematode numbers, whereas the interaction of soil type, phytonematicides and depth, the nematode population densities were inversely proportional to soil depth. The interaction of clay with any of the two phytonematicides, reduced M. incognita population densities compared to sand and loam interactions. More than 62% tomato root systems occurred in the top 0–25 cm depth. The interactions between organic matter levels, phytonematicides and depth had no effect on the population densities of M. incognita. The two phytonematicides were able to reduce nematode population densities throughout the soil column in all four soil types and organic matter levels. Cucurbitacin residues were not detected in all tomato fruit samples. In conclusion, Nemarioc-AL and Nemafric-BL phytonematicides have bioactivities on J2 hatch, J2 immobility, J2 mortality and J2 infectivity. The CARD model quantified the three phases of DDG patterns for most of the variables. Even though CARD-generated inhibition xlvii concentrations at 50 and 100% were not comparable with computed values for pure cucurbitacins they were for most phytonematicide variables, the model was able to generate excellent MIC-values for all variables. The inhibition effects of the two phytonematicides were irreversible. The major findings of this study were that the two phytonematicides exhibited DDG patterns for all variables tested and that the CARD model could be adopted for the in vitro evaluation of phytonematicides. Meloidogyne incognita was an excellent bioindicator on movement of two phytonematicides across soil types and organic matter levels at different depths. Nemarioc-AL and Nemafric-BL phytonematicides did not leave any cucurbitacin residues in tomato fruit. The information on bioactivities of the two phytonematicides generated in this study provides a much needed data for the registration of the products as required by the law. Proposed future research area includes, microscopy study of molecular effects of the phytonematicides on nematodes post-exposure. / National Research Foundation (NRF), Flemish Interuniversity Council (VLIR) and Land Bank Chair-University of Limpopo.
17

Pre- and post-emergent application effects of nemafric-bg phytonematicide on growth of potato cultivar 'mondial g3' and suppression of meloidogyne javanica

Huma, Tiego Isaac January 2019 (has links)
Thesis (M. A. Agriculture (Plant Protection)) -- University of Limpopo, 2019 / Available potato (Solanum tuberosum L.) cultivars do not have any genotype that is resistant to the root-knot (Meloidogyne species) nematodes. Due to the susceptibility of potato cultivars to Meloidogyne species, alternative management strategies had to be researched and developed after the withdrawal of methyl bromide from the agro-chemical markets, amongst which were the cucurbitacin-containing phytonematicides. However, of the available application methods of phytonematicides, the ground leaching technology (GLT) and botinemagation technology were not suitable for use in most high-rainfall potato-producing regions, where production is under rain-fed conditions. The objective of the study, therefore, was to determine whether pre- and post-emergent application of Nemafric-BG phytonematicide would have effects on growth of potato and suppression of M. javanica population densities. Parallel pot trials of pre- and post-emergent application of Nemafric-BL phytonematicide were conducted under greenhouse conditions in autumn (February-April: Experiment 1) 2017 and validated (Experiment 2) in 2018. Each plant was inoculated with 3000 M. javanica eggs and second-stage juveniles (J2). Five treatments, namely, 0, 2, 4, 8 and 16 g concentration of Nemafric-BG phytonematicide, arranged in randomised complete block design, were either applied mixed with seed tubers for pre-emergent or spread on the soil surface after emergence for post-emergent trials. In all cases, plant growth variables were assessed using the Curve-fitting Allelochemical Response Data (CARD) model, whereas nutrient elements (Fe, K, Na and Zn) and nematode variables were assessed using analysis of variance, with data subjected to lines of the best fit. In pre-emergent application trial, plant height (R2 = 0.98) and fresh root mass (R2 = 0.99) exhibited quadratic relations, characterised by density dependent growth patterns with increasing concentrations of Nemafric-BG xv phytonematicide in Experiment 1, similar trends were also observed on plant height (R2 = 0.99) and root mass (R2 = 0.99) in Experiment 2. In contrast, in post-emergent application trial, plant height (R2 = 0.97), fresh root mass (R2 = 0.99) and dry shoot (R2 = 0.98) exhibited quadratic relations in Experiment 1, which ascribed to DDG patterns, similar trends were also observed in Experiment 2 on plant height (R2 = 0.99), fresh root mass (R2 = 0.96) and dry shoot (R2 = 0.99) of potato cv. ꞌMondial G3ꞌ. In pre-emergent application trials, Mean Concentration Stimulation Point (MCSP) = 24.18 and 7.82 g, respectively, in Experiment 1 and Experiment 2, with ∑k being equivalent to 20 and 6 units for potato to the product, respectively, in Experiment 1 and Experiment 2. In contrast, post-emergent application trials, MCSP = 9.87 and 12.10 g, respectively, in Experiment 1 and Experiment 2, whereas the ∑k value for potato to the product was 11 and 6 units, respectively in Experiment 1 and Experiment 2. Increasing concentrations of the phytonematicide significantly (P ≤ 0.05) affected the selected nutrient elements. In pre emergent application trials, K (R2  =  0.96) Na (R2  =  0.90) and Zn (R2  =  0.83) each with increasing Nemafric-BG phytonematicide concentrations exhibited positive quadratic fashion, while Fe (R2  =  0.87) exhibited negative quadratic relations in Experiment 1. In Experiment 2, K (R2  = 0.99), Na (R2  = 0.90) and Zn (R2 =  0.97) contents each in leaf tissues against the increasing concentrations of the phytonematicide exhibited negative quadratic relations, while Fe (R2  = 0.88) exhibited positive quadratic relations. In post emergent trials, Fe (R2 = 0.91, Na (R2 = 0.90) and Zn (R2 = 0.99) contents in leaf tissues against increasing Nemafric-BG phytonematicide concentration exhibited negative quadratic relations, whereas K (R2 = 0.86) exhibited positive quadratic relation in Experiment 1. In Experiment 2, Fe (R2 = 0.93), K (R2 = 0.92), Na ( R2  = 0.79) and Zn (R2 xvi = 0.89) contents in leaf tissues of potato exhibited positive quadratic, respectively. In pre emergent trial for Experiment 1, eggs in roots (R2 = 0.78), J2 in roots (R2 = 0.85), J2 in soil (R2 = 0.97) and Pf (R2 = 0.78) of M. javanica against increasing pre-emergent application concentrations of Nemafric-BG phytonematicide exhibited negative quadratic relations, characterised by DDG patterns. Similar trends were observed on eggs in roots (R2 = 0.82), J2 in roots (R2 = 0.99), J2 in soil (R2 = 0.84) and Pf (R2 = 0.85) in Experiment 2. In contrast, in post-emergent application trial, eggs in roots (R2 = 0.87), J2 in roots (R2 = 0.99), J2 in soil (R2 = 0.91) and Pf (R2 = 0.99) of M. javanica against increasing post emergent application concentrations of Nemafric-BG phytonematicide also exhibited negative quadratic relations in Experiment 1, which ascribed to DDG patterns. Similar trends were also observed on eggs in roots (R2 = 0.72), J2 in roots (R2 = 0.68), J2 in soil (R2 = 0.85) and Pf (R2 = 0.83) in Experiment 2. Results from the study demonstrated that Nemafric-BG phytonematicide stimulated plant growth at lower concentration and the product does not have any detrimental effects in accumulation of nutrient elements in leaf tissues. Therefore, it is concluded, that the product could be applied at the recommended rates of 7.82 and 9.87 g/plant in pre and post-emergent application, respectively, for the management of root-knot nematodes, provided the active ingredient does not accumulate in potato tubers or have any detrimental effects in accumulation of nutrient elements in tubers and temper with nutritional value of potatoes.
18

Biological control of gastrointestinal nematodes of small ruminants, using Bacillus thuringiensis (Berliner) and Clonostachys rosea (Schroers).

Baloyi, Mahlatse Annabella. January 2011 (has links)
Gastrointestinal nematode parasites cause great losses in the production of small ruminants through reduced productivity and the cost of preventive and curative treatments. Because of the threat of anthelmintic resistance, biological control of sheep nematodes has been identified as an alternative to anthelmintic drugs. Bacillus thuringiensis (Bt) (Berliner) and Clonostachys rosea (Schroers) have been widely studied as biocontrol agents. B. thuringiensis has been used for the biocontrol of insects and C. rosea has been successfully used as biocontrol agent of Botrytis cinera (De Bary) in plants. B. thuringiensis and C. rosea strains were isolated from soil collected from the Livestock Section at Ukulinga Research Farm, University of KwaZulu Natal, Pietermaritzburg. Twenty-five strains of Bt and 10 strains of C. rosea were successfully isolated. The Bt colonies were identified by their circular, white, flat and undulate character, and the gram-positive and rod-shaped endospores. C. rosea was identified by white colonies on Potato-dextose agar and the characteristic conidiophores, which were branched and showed phialides at the tips. In vitro screening of the isolates was undertaken to select the best isolates. The isolates that caused significantly greater mortality were Bt isolate B2, B10 and B12 and C. rosea isolates P1, P3 and P8. These isolates caused substantial nematode mortality in both faeces and water bioassay. Nematode counts were reduced by 28.5% to 62% and 44% to 69.9% in faecal bioassay for Bt and C. rosea, respectively. In the water bioassay, nematode counts were reduced by 62% to 85% for Bt and by 62.7% to 89.3% for C. rosea. The best inoculum level at which the best isolates were most effective, and the optimum frequency of application were determined. The trial was conducted using bioassays with faeces and water. Inoculum levels of 10(6), 10(8), 10(10), 10(12) spores ml-1 for Bt and 10(6), 10(8) and 10(10) conidia ml-1 for C. rosea was used in the faecal bioassay. The inoculum levels tested in water bioassay were 10(6), 10(8), 10(10) and 10(12) spores ml-1 for Bt and 10(9), 10(10), 10(11), 10(12) conidia ml-1 for C. rosea. In the faecal bioassay, B2 was the most effective Bt isolate at an inoculum level of 10(10) spores ml-1. Isolate P3 was the best C. rosea isolate at 10(8) conidia ml-1. In the water bioassay, Isolate P3 caused a mortality of 85% at inoculum levels of 10(9), 10(10) and 10(11) conidia ml-1. The performance of biological control agents in the field is sometimes inconsistent. Combining different biocontrol agents may be a method of improving their reliability and performance. However, the combination of most of the isolates was antagonistic, with efficacy less than that of either individual biocontrol agent. In particular, Isolate P3 was more effective when used alone than when combined with any other isolates. Therefore, the combination of biocontrol agents does not always result in synergistic interaction. There were some additive interactions between two bacterial isolates, and with one bacterial and fungal combination. The effect of feeding the best of the biocontrol agents, or diatomaceous earth (DE), was evaluated in sheep. Two doses of Bt (1g and 2g kg-1BW) and C. rosea (1g kg-1BW) reduced the numbers of L3 nematode larvae in sheep faeces. The DE product (at 15% of feed) also reduced L3 numbers but it was less effective than either the Bt or the C. rosea products. Nematode counts were reduced by 74.6%, 75.1%, 84.6%, 68.5% and 27.5% for Bt 1g kg-1BW, Bt 2g kg-1BW, C. rosea (1g kg-1 BW), DE and control, respectively. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.
19

Biologiese beheer van plantparasitiese nematodes met die swam Paecilomyces lilacinus by aartappels, sitrus en wingerd

Neethling, Jacob van der Westhuizen 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Paecilomyces Ii/acinus, ras 251 (geregistreer in terme van wet 36 van 1947 as Suid-Afrika se eerste natuurlike nematisiede en kommersieel beskikbaar as PI Plus) is as biologiese beheer agent getoets by aartappels en in geïntegreerde beheer programme by sitrus en wingerd teen respektiewelik Me/oidogyne species, Ty/enchu/us semipenetrans en verskeie ektoparasitiese nematodes. Die swam toon belofte vir die beheer van hierdie nematodes en het terselfdertyd nie 'n nadelige effek op nie-teiken, voordelige organismes in die grond nie. Veral in kombinasie met chemiese middels, as deel van geïntegreerde programme, kan dit lei tot verminderde gebruik van hoogs toksiese middels en dus meer omgewingsvriendelike landboupraktyke. Biological control of plant parasitic nematodes on potatoes, citrus and grapevine with the fungus, Paecilomyces liIacinus. Paecilomyces liIacinus, race 251 (registered in terms of act 36 of 1947 as South Africa's first natural nematicide, commercially available as PI Plus) was tested as a biological control agent on potatoes and in integrated control programs on citrus and grapevine against Me/oidogyne species, Ty/enchu/us semipenetrans and various ectoparasitic nematodes respectively. The fungus shows promise for the control of these nematodes, without having a harmful effect on non-target, beneficial organisms in the soil. Especially in combination with chemical products, as part of integrated programs, this can lead to less use of highly toxic compounds and thus to more environmentally friendly agricultural practices. / AFRIKAANSE OPSOMMING: Sedert die ontdekking van die swam, Paeci/omyces Ii/acinus (Thom.) Samson as 'n effektiewe eierparasiet van Meloidogyne incognita acrita en Globodera pal/ida (Jatala et al., 1979) het verdere veldproewe in Peru tot die effektiewe beheer van M. incognita en Tylenchulus semipenetrans gelei. Na verskeie suksesse in Peru is die swam onder verskillende klimaat- en grondkondisies in verskeie ander lande beproef. Die sukses behaal in die Filippyne het gelei tot die kommersiële produksie van die swam onder die handelsnaam Biocon. Anders as met chemiese middels vind die werking van biologiese agente stadig oor tyd plaas. Biologiese beheer sal nie chemiese beheer sonder meer kan vervang nie. Dit behoort egter deel te vorm van geïntegreerde nematode bestuur. Inkorporering van die natuurlike organismes, die oordeelkundige gebruik van chemiese nematisiedes, moontlik in kombinasie met die biobeheer agente, weerstand, en ander kulturele praktyke moet ernstig oorweeg word as ons hoop om die steeds groeiende wêreldbevolking te voed (Jatala, 1986). Paecilomyces liIacinus, ras 251, Suid-Afrika se eerste geregistreerde natuurlike nematisiede, kommersieel beskikbaar as PI Plus, is in die Olifantsrivier besproeiingsgebied geëvalueer vir die bestuur van ekonomies belangrike plantparasitiese nematodes by aartappels, sitrus en wingerd. Hierdie gewasse is belangrike bedryfstakke van die streek en is onderhewig aan skade deur nematodes wat die opbrengs nadelig beïnvloed. Chemiese beheer bied slegs 'n korttermyn oplossing vir nematode probleme en skadelike getalle word in 'n kort tyd weer opgebou. Boonop lei dié hoogs toksiese middels tot agteruitgang van die omgewing en sy waterbronne. Die toenemende besorgdheid hieroor en die groot potensiaal van biologiese beheer agente (Jatala, 1986) was die hoofrede vir die werk waaroor hier gerapporteer word.

Page generated in 0.1064 seconds