Optimizing pesticide spraying in high density apple orchards in South Africa, using Venturia inaequalis as model pathogen.
| dc.contributor.advisor | McLeod, Adele | en_ZA |
| dc.contributor.advisor | Van Zyl, Gideon J. | en_ZA |
| dc.contributor.advisor | Wessels, Bekker J. P. | en_ZA |
| dc.contributor.author | Rebel, Philip | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Plant Pathology. | en_ZA |
| dc.date.accessioned | 2019-02-21T07:14:42Z | |
| dc.date.accessioned | 2019-04-17T08:04:22Z | |
| dc.date.available | 2021-07-01T03:00:10Z | |
| dc.date.issued | 2019-04 | |
| dc.description | Thesis (MScAgric)--Stellenbosch University, 2019. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Calculating pesticide dose rates, and the use of dosing models, are important for ensuring that pesticide spray applications yield effective disease control in tree crops. A dosing model that has been used for many years is South African apple orchards, is the tree row volume (TRV) pesticide dosing model. In recent years, the change to high density apple orchards has brought into question the efficacy of the model. A dosing system that is known to be suitable for use in high density apple orchards, is the Marktgemeinschaft Bodenseeobst (MABO) dosing model. Photo-macrophotography combined with image analyses and the use of a yellow fluorescent pigment is known to be accurate for assessing spray deposition parameters (quantity, uniformity and quality). The fluorescent particle coverage (FPC%) of the pigment is an effective tracer of mancozeb, the main fungicide used for controlling apple scab in South Africa. It is currently unknown what spray deposition quantities are required for controlling the destructive apple scab pathogen Venturia inaequalis. Benchmark models can be used to determine spray deposition quantities required for disease control. The current study showed that the MABO model resulted in spray deposition parameters (quantity, uniformity and quality) that were comparable to those of the TRV model in high density apple orchards (4m and 3.5m-row-width) in South Africa, by using image analyses and a fluorescent pigment. In the 4m-row-width orchards the MABO model did not differ significantly from the TRV model. The use of two different volumetric airflow rates (VAR, 28000 m³/h [low] and 36000 m³/h [high]) in the orchards (4m- and 3.5m-row width) furthermore yielded similar deposition parameters for both models. In the 3.5 m-row-width orchards, the MABO model yielded a significantly higher deposition quantity than the TRV model; either in canopy tops or for the whole canopy. No clear trends were seen in model performance with regards to deposition uniformity and quality. The MABO model on average resulted in a 40 to 28.5% spray cost saving relative to TRV, depending on the spray volume used. The deposition quantities achieved with the MABO and TRV models in apple orchards were above (0.70- 4.7 FPC%) those required for controlling apple scab with mancozeb, based on a benchmark laboratory model developed in the current study. The benchmark model, developed using thermal infrared imaging (TIRI) disease quantification, showed that 0.40 %, 0.79 % and 1.35 FPC% corresponded to 50, 75 and 90% control respectively. However, when the model was developed using quantitative real-time PCR (qPCR) for disease quantification, lower benchmarks were obtained (0.10, 0.20 and 0.34 FPC% respectively). Both benchmark models showed that mancozeb yielded high levels of disease control at very low concentrations; the FPC% values of the FPC90 (90% control) corresponded to 0.3 to 0.45 times that of the registered mancozeb concentration in South Africa. To conclude, the MABO model can be used as a cost effective and grower friendly dosing model in high density apple orchards in South Africa. The model uses a constant water delivery rate and pesticide concentration to treat multiple orchards differing in size by only adjusting forward speed. The more conservative TIRI benchmark model is recommended for evaluating mancozeb depositions, rather than the qPCR benchmark model, since apple scab is such a high risk and destructive disease. The mancozeb deposition benchmark values established in this study will be valuable for assessing the efficacy of spray applications made in future research trials and grower applications. Due to the low benchmark values identified for mancozeb, future studies should also investigate benchmark values for other contact fungicides as well as for mesosystemic and systemic fungicides used for controlling apple scab world-wide. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Berekening van plaagdoder dosis per eenheid area, en die gebruik van dosering modelle, is belangrik om te verseker dat plaagdoder spuit toedienings effektiewe siektebeheer verseker in boom gewasse. ‘n Dosering model wat al vir baie jare in Suid-Afrikaanse appel boorde gebruik is, is die boom-ry-volume (BRV) plaagdoder dosering model. Vernuwing van appel boorde na hoë digtheid aanplantings het gelei tot die bevraagtekening van die doeltreffendheid van die BRV plaagdoder dosering model. Die Marktgemeinschaft Bodenseeobst (MABO) dosering model is n dosering model wat daarvoor bekend is om geskik te wees vir die gebruik in hoë digtheid appel boorde. Foto-makrofotografie en die gebruik van digitale beeld-analise is ‘n bekende en akkurate metode vir die kwantifisering van spuit deposisie (kwantiteit, eenvormigheid en kwaliteit) op die blaar oppervlakte. Die metode word gebruik om ‘n fluoresserende pigment (SARDI yellow fluorescent pigment 40% EC), te kwantifiseer wat dien as aanwyser van spuit deposisie. Die fluoresserende partikel bedekking (FPC%) van die pigment is 'n doeltreffende aanwyser van mancozeb spuit deposisie, die hoof swamdoder wat gebruik word in Suid-Afrika vir die beheer van appel skurf siekte. Dit is tans onbekend hoeveel spuit bedekking op appel blare benodig word vir die beheer van die vernietigende appel skurf patogeen Venturia inaequalis. Maatstaf deposisie modelle kan gebruik word om spuit bedekking hoeveelhede wat nodig is vir siektebeheer te bepaal. Die huidige studie het getoon dat die MABO model tot spuit deposisie (kwantiteit, eenvormigheid en kwaliteit) gelei het wat vergelykbaar was aan dié van die BRV model in hoë digtheid appelboorde (4m en 3.5 m-ry-wydte) in Suid-Afrika, deur die gebruik foto- makrofotografie, digitale beeld-analise en 'n fluoresserende pigment. In die 4m-ry-wydte boorde het die spuit deposisie van die MABO model nie statisties betekenisvol verskil van die BRV model nie. Die gebruik van twee verskillende volumetriese lugvloei hoeveelhede (VAR, 28000 m3 / h [lae] en 36000 m3 / h [hoë]) in die boorde (4m- en 3.5 m-ry-wydte) het ook soortgelyke spuit bedekking vir beide modelle te weë gebring. In die 3.5 m-ry-wydte boorde, het die MABO model statisties betekenisvol hoër spuit deposisie kwantiteit as die BRV model opgelewer; hierdie was waar óf in boom toppe óf oor die hele boom struktuur. Geen duidelike tendense was waargeneem in model werking ten opsigte van eenvormigheid en kwaliteit van deposisie. Die MABO model het glei tot spuit kostebesparings van 40 tot 28,5% in ‘n vergelyking van spuit koste teenoor die BRV model, afhangende van die spuit volume wat gebruik is vir die berekeninge. Die deposisie kwantiteit wat deur die MABO en BRV modelle in appel boorde behaal was, was bo (0.70- 4.7 FPC%) die deposisie kwantiteit wat genoegsaam is vir die beheer van appel skurf siekte met mancozeb, gebaseer op 'n laboratorium-maatstaf deposisie model wat ontwikkel was in die hierdie studie. Die maatstaf model, wat ontwikkel was deur die gebruik van ‘n termiese infrarooi fotografie (TIRI) siekte kwantifisering metode, het getoon dat 0,40%, 0,79% en 1,35 FPC% ooreengestem met 50, 75 en 90% beheer van appel skurf siekte onderskeidelik. Wanneer ‘n kwantitatiewe werklike-tyd (real-time) polimerase ketting reaksie (qPCR) metode vir siekte kwantifisering gebruik was om die model te ontwikkel, was laer maatstaaf deposisie kwantiteit vlakke verkry (0.10, 0.20 en 0.34 FPC% - 50, 75 en 90% beheer onderskeidelik). Beide maatstaf modelle het getoon dat mancozeb hoë vlakke van siektebeheer opgelewer het teen baie lae konsentrasies in die spuit oplossing; die FPC% waardes van die FPC90 (90% beheer) het ooreengestem met ‘n spuit oplossing konsentrasie van 0,3-0,45 keer dié van die geregistreerde mancozeb konsentrasie in Suid-Afrika. Om af te sluit, die Mabo model kan gebruik word as 'n koste-effektiewe en gebruiker vriendelike dosering model in hoë digtheid appel boorde in Suid-Afrika. Die model maak gebruik van 'n konstante water lewering en spuit tenk konsentrasie van ‘n plaagdoder om verskeie boorde wat verskil in grootte te behandel deur net trekker ryspoed aan te pas. Die meer konserwatiewe TIRI maatstaf model word aanbeveel vir die evaluering van mancozeb deposisie in boorde, eerder as die qPCR maatstaf model, aangesien appel skurf siekte 'n hoë risiko en vernietigende siekte is. Die mancozeb maatstaaf deposisie vlakke wat in hierdie studie geïdentifiseer was sal waardevol wees om die effektiwiteit van spuit toedienings wat in toekomstige navorsing proewe en produsent spuit toedienings te evalueer. As gevolg van die lae maatstaf waardes wat geïdentifiseer was vir mancozeb, moet toekomstige studies ook ondersoek wat die maatstaf waardes ook bepaal word vir ander kontak, meso-sistemiese en sistemiese swamdoders wat wêreldwyd gebruik word vir die beheer van appel skurf siekte. | af_ZA |
| dc.description.version | Masters | en_ZA |
| dc.embargo.terms | 2021-07-01 | |
| dc.format.extent | 100 pages : illustrations (some color) | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/105604 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Apple orchards -- South Africa | en_ZA |
| dc.subject | Apples -- Breeding | en_ZA |
| dc.subject | Apples -- Disease and pest resistance -- Genetic aspects | en_ZA |
| dc.subject | Venturia inaequalis | en_ZA |
| dc.subject | Apple scab -- Control | en_ZA |
| dc.subject | Spraying and dusting in agriculture | en_ZA |
| dc.subject | UCTD | en_ZA |
| dc.title | Optimizing pesticide spraying in high density apple orchards in South Africa, using Venturia inaequalis as model pathogen. | en_ZA |
| dc.type | Thesis | en_ZA |