Effects of Planting Density and the Composition of Wheat Cultivar Mixtures on Stripe Rust: An Analysis Taking into Account Limits to the Replication of Controls

Garrett, Karen A.; Mundt, Christopher C.

doi:10.1094/phyto.2000.90.12.1313

Cited by 27 publications

(19 citation statements)

References 27 publications

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“…But, in this experiment, there was no evidence for an influence of planting density on hostdiversity effects, as might be expected because of the small density effects in single-genotype stands. This is in contrast to wheat stripe rust, for which there was a large influence of planting density on host-diversity effects (12). Differences in the influence of density in these two systems may be due in part to differences in plant architecture and pathogen dispersal, but it would be useful to consider lower potato densities than were included in this experiment to clarify the comparison.…”

Section: Discussionmentioning

confidence: 98%

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The Effects of Host Diversity and Other Management Components on Epidemics of Potato Late Blight in the Humid Highland Tropics

Garrett¹,

Nelson²,

Mundt³

et al. 2001

Phytopathology®

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A field study at three highland sites near Quito, Ecuador, was conducted to determine whether host-diversity effects on potato late blight would be as important as recently found in studies conducted in temperate areas. We compared three potato mixtures and use of mixtures in combination with different planting densities and two fungicide regimes. Treatment comparisons were made by absolute and relative measures of host-diversity effects and incorporating a truncated area under the disease progress curve as a means of standardizing comparisons across sites. Potato-faba intercrops consisting of only 10% potato provided an estimate of the effects of dilution of susceptible host tissue. Host-diversity effects were very different across study sites, with a large host-diversity effect for reduced disease only at the site most distant from commercial potato production. Planting density had little influence on host-diversity effects or on late blight in single-genotype stands. Fungicide use in combination with potato mixtures enhanced a host-diversity effect for reduced late blight. Potato-faba intercrops produced only a small decrease in potato late blight. Effects of host diversity on yield were variable, with the greatest increase in yield for mixtures treated with fungicides at the site most distant from commercial potato production. The effects of host diversity on late blight severity may be less consistent in the tropical highlands than in the temperate zone, but can contribute to integrated disease management.

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Section: Discussionmentioning

confidence: 98%

“…However, several recent studies have found either no effect of density or a negative association between planting density and disease severity (5,7,12,20). One reason that disease may show little response to density changes is that the realized density of foliage may be similar over planting densities (20).…”

Section: Discussionmentioning

confidence: 99%

The Effects of Host Diversity and Other Management Components on Epidemics of Potato Late Blight in the Humid Highland Tropics

Garrett¹,

Nelson²,

Mundt³

et al. 2001

Phytopathology®

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“…The second step in the analysis of disease severity was to compare the linear responses of the two different diseases to the proportion of susceptible genotype in mixture (11,15). For each experimental unit (plot), we estimated the difference between the slopes of the curves for the two diseases using data from the third sampling date.…”

Section: Fieldmentioning

confidence: 99%

Cultivar Mixtures for the Simultaneous Management of Multiple Diseases: Tan Spot and Leaf Rust of Wheat

Cox¹,

Garrett²,

Bowden³

et al. 2004

Phytopathology®

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Because of differences in life histories between Puccinia triticina, a highly specialized, polycyclic, windborne pathogen with a shallow dispersal gradient, and Pyrenophora tritici-repentis, a residue-borne pathogen with a steep dispersal gradient, wheat mixtures are expected to be more effective at controlling leaf rust than tan spot. The objectives of this research were to determine the effect of two-cultivar mixtures with varying proportions and different pathogen resistance profiles on the severity of tan spot and leaf rust, to evaluate yield of the mixtures in the presence or absence of disease, and to directly compare the relative effectiveness of cultivar mixing for tan spot versus leaf rust. In a field experiment at two sites in Kansas over two growing seasons, winter wheat cvs. Jagger and 2145, which have differential resistance reactions to leaf rust and tan spot, each were planted in proportions of 0.25, 0.50, 0.75, and 1.00. Plots were inoculated with each pathogen alone, both pathogens, treated with a fungicide, or exposed to ambient conditions. For both diseases for all siteyears, severity decreased substantially on the susceptible cultivar as the proportion of that cultivar decreased in mixture. Mixtures were significantly more effective at reducing leaf rust than tan spot in three of four site-years. Mixtures generally yielded the same as the weighted mean of components in monoculture although, in two of three site-years, at least one fungicide-treated and one diseased mixture each yielded higher than expected values. Although this particular mixture produced only modest yield benefits, the potential for simultaneous reductions in tan spot and leaf rust was demonstrated.

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“…Practices such as deployment of crops in mixtures, intercrops, or polycultures may be an important component in perennial grain agriculture (4,7,8,17,18,30,46). But whether perennials are mixed within polycultures or uniform in monocultures, resistance to a set of locally important cereal diseases will be an essential managerial component (3,7).…”

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Reactions of Perennial Grain Accessions to Four Major Cereal Pathogens of the Great Plains

et al. 2005

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Methods of disease management used in annual grain crops, especially cultural practices designed to disrupt the disease cycle of a particular pathogen, will not necessarily be applicable to perennial grain crops. Resistance to multiple pathogens, therefore, will clearly be important in disease management. The objective of this research was to evaluate disease resistance in 10 perennial grain accessions (one to two accessions of each: perennial wheat (Thinopyrum sp. × Triticum aestivum), intermediate wheatgrass (Thinopyrum intermedium), perennial rye (Secale montanum), hexaploid triticale (Triticum turgidum × S. montanum), octoploid triticale (Triticum aestivum × S. montanum), tetraploid perennial rye (Secale cereale × S. montanum), and tall wheat-grass (Thinopyrum ponticum)) to tan spot (caused by Pyrenophora tritici-repentis), take-all (caused by Gaeumannomyces graminis var. tritici), wheat streak mosaic, and barley yellow dwarf, four important diseases of the Great Plains. Several of the grasses were resistant to tan spot, barley yellow dwarf, and wheat streak mosaic. Indeed, the wild grasses and perennial donors T. intermedium (including BFPMC1), T. ponticum, and S. montanum, in addition to Permontra, a tetraploid perennial rye, were highly resistant to all three diseases. Additionally, the remaining grasses tested were also more resistant to tan spot than the susceptible wheat control. However, none of the 10 grass accessions appeared highly resistant to take-all, and substantial losses in biomass were observed, although such effects may be moderated under field conditions due to the potential for take-all decline in perennial plantings.

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Effects of Planting Density and the Composition of Wheat Cultivar Mixtures on Stripe Rust: An Analysis Taking into Account Limits to the Replication of Controls

Cited by 27 publications

References 27 publications

The Effects of Host Diversity and Other Management Components on Epidemics of Potato Late Blight in the Humid Highland Tropics

The Effects of Host Diversity and Other Management Components on Epidemics of Potato Late Blight in the Humid Highland Tropics

Cultivar Mixtures for the Simultaneous Management of Multiple Diseases: Tan Spot and Leaf Rust of Wheat

Reactions of Perennial Grain Accessions to Four Major Cereal Pathogens of the Great Plains

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