| Yield loss of lentil caused by Uromyces viciae-fabae | Pretorius, Z.A. | 2008 |
KeywordsLens culinaris, loss assessment, rust AbstractYield loss in lentil (Lens culinaris Medik.) due to rust (Uromyces viciae-fabae [Pers.] J. Schröt) was determined by assessing crop and disease parameters at different growth stages and leaf canopy layers in field epidemics at Akaki, Ethiopia. The epidemics were created by inoculation of the rust-susceptible cultivar EL-142 with U. viciae-fabae and spraying plots with tebuconazole at different frequencies. The epidemics produced disease progress curves that varied significantly in the rate (rL ) of temporal progression and area under the disease progress curve (AUDPC). The rust epidemic, in particular between early flowering and early pod formation, had a significant influence on seed yield, pods per plant and seed mass. Mean seed yield losses up to 41.6% were recorded. The number of seeds per pod remained unaffected by the disease. The effect of rust on seed yield of lentil can be predicted with AUDPC and critical-point models using disease severity assessed on the upper canopy layer in the early flowering stage. Every 1% increase in rust severity reduced seed yield by 8.4%. Rust severity ≥ 4.7% at the critical early flowering stage significantly reduced seed yield, and hence, any measure that keeps severity below this threshold level would be advisable. AuthorsPretorius, Z.A. and Negussie, T.G. Year Published2008 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2008.10639892 This article contributed by:
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| Yield retention of resistant wheat cultivars, severely infested with Russian wheat aphid, Diuraphis noxia (Kurdjumov), in South Africa | Tolmay, Vicki L. | 2005 |
KeywordsDamage, Diuraphis noxia, host plant resistance, Triticum aestivum, Yield AbstractRussian wheat aphid, Diuraphis noxia (Kurdjumov), has been a serious pest of wheat in South Africa since 1978. Wheat producers observed that resistant cultivars, developed for control of this aphid, differed in resistance and questioned whether insecticide treatment would be economically justifiable. This study was undertaken to confirm and quantify the observed differences in sixteen resistant cultivars under field conditions. A split-plot field trial with four replicates was planted near Bethlehem, South Africa. The yield of each aphid- infested plot was expressed as a percentage of the yield of the corresponding aphid-free plot giving percentage yield retained after infestation for each cultivar. The percentage yield retained varied in 2000 from 33.0% to 119%; in 2001 from 28.3% to 150.0% and in 2003 from 28.4% to 109.2 %. Cultivars were ranked and classified into more resistant and less resistant groups for each year and an AMMI analysis was conducted. Some cultivars compensated for D. noxia infestation with infested plots giving higher yield than aphid-free plots. It was shown that the level of resistance was not the same in all resistant cultivars and varied dramatically between cultivars and years when measured under severe D. noxia infestation. AuthorsTolmay, Vicki L. and van Deventer, CS Year Published2005 PublicationSouth African Journal of Plant and Soil LocationsDOI10.1080/02571862.2005.10634715 This article contributed by:
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