11/30/2023 0 Comments Needle blight 5sImplementation of genomic selection in this test population of Pinus radiata resulted in a relatively high prediction accuracy of needle loss due to Dothistroma septosporum compared with a pedigree-based approach. Caution should therefore be taken with the interpretation of results in poorly phenotyped traits. However, this was likely caused by the fact that both were clustered around the population mean, while deviations from the population mean caused by genetic effects did not appear to be well described. Surprisingly, poorly phenotyped disease traits also showed very high accuracy in terms of correlation of predicted genomic breeding values with pedigree-based counterparts. This compared well with pedigree-based accuracies of up to 0.746. We found high accuracy in the prediction of genomic breeding values in the disease-related traits that were well characterized, reaching 0.975 for genotyped individuals and 0.587 for non-genotyped individuals. Genomic selection is, therefore, a promising strategy to overcome the constraints of needle disease phenotyping. The development of next generation sequencing platforms has also enabled implementation of genomic approaches in species lacking robust reference genomes. Phenotyping of traits related to resistance has many biological and temporal constraints that can often confound the ability to achieve reliable phenotypes and consequently, reliable genetic progress. Keep in mind that these products are toxic to fish and other aquatic creatures! Do not apply to run-off, or apply directly to water, or to areas where surface water is present.įor confirmation of the specific needle blight fungus present on your conifers, submission of a physical sample of infected needles on symptomatic branches is necessary.Many conifer breeding programs are paying increasing attention to breeding for resistance to needle disease due to the increasing importance of climate change. It is important to make sure that all needles are thoroughly covered with the fungicide spray. During wet years, additional later applications may be needed. For nursery or Christmas tree growers, Kocide 3000 is also labeled for control of this disease. Janna Beckerman, Purdue Ornamental Plant Disease Extension Specialist notes that labeled, protective fungicides sprays are limited to copper-based compounds such as Junction, and Camelot O in the landscape, and should be applied twice in the spring after new growth appears, and again 4-6 weeks later when new needles are expanded. As these fungicides aren’t curative, they will do nothing for last year’s infected needles so the tree may appear to get worse before it gets better.ĭr. Diseased needles will continue to deteriorate and fungicides must be applied every year for several years before improvement is actually seen. Fungicides prevent new infections–they do not cure existing ones. This may slow the spread but will not provide full control.įungicide sprays may be practical on smaller trees for management of this disease. Sanitation is the recommended cultural management: remove any dead branches, and rake up and destroy fallen needles which harbor the fungus. Watering during especially dry periods and mulching to help maintain a more consistent moisture level within the feeder root zones of trees will assist in reducing overall stress. Improving the vigor of trees is important with regard to overall tree health. Stressful site and environmental growing conditions, such as occur on berms, may predispose susceptible conifers to infection by needle blights. Spruce is thought to be of low susceptibility, only becoming infected under high inoculum pressure. It is reported that a number of coniferous hosts are affected but two-needled pines are particularly susceptible. In areas where Dothistroma needle blight is severe, you may want to consider planting another species of tree other than susceptible pines. Repeated severe infections over several years will result in decreased vigor and growth of the tree, ultimately causing death. Needles that become infected the year they emerge are often not shed until late summer the following year. For example, infected second-year needles are often cast (dropped) before the infected current-year (first-year) needles. Infected needles may develop extensive browning 2-3 weeks after the first appearance of symptoms and drop prematurely rather than remain on the tree for their normal two to three years (Fig 8). Fig 8 Extensive browning and premature needle drop due to Dothistroma infection on Scotts Pine
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