![]() Spray with a fungicide the day before pruning and again immediately after pruning. Four to six applications are usually sufficient. Begin spraying in the spring when the new secondary needles are 1 to 2 inches long. Seedlings should be sprayed wit a foliar fungicide at 10- to 30-day intervals - depending upon the amount of rainfall - from the beginning of April through October. Root prune seedlings to a depth of 7 inches from 6 to 12 weeks before lifting.Ĭhemical - Spray with Bordeaux mixture, maneb, or chlorothalonil, which are effective and registered for use on brown spot. Avoid pruning when it is raining or at any time when the seedlings are wet. Remove clipped needles from nursery bed areas. If necessary, inoculate beds with the mycorrhizal fungus Pisolithus tinctorius.Ĭlip needles periodically during the growing season to prevent toppling and to expedite spraying and lifting. Promote growth of existing ectomycorrhizal fungi by controlling soil pH (less than 6.0 is optimal) and avoiding excess levels of phosphorus. Use mulch to reduce mortality from sand splash, but do not use pine needles as mulch. Remove and destroy all infected seedlings and infected pines growing in and around the nursery.Ĭultural - In the spring, plant seed in rows at low densities of about 15 seedlings per square foot. Prevention - Use superior seed that is resistant to the disease. Ascospores are produced on seedlings 2 to 3 months after the seedlings are infected.īoth spore forms overwinter in dead and infected needle tissue. Conidia are disseminated short distances by rain splash and cause local buildup of the disease. See chapter 4 for a more detailed comparison of these two diseases and their causal organisms.Īscospores, discharged during periods of rain, dew, and fog, are the principal means by which the brown spot fungus invades nursery beds.Īscospores are disseminated by the wind and initiate light, scattered infections, sometimes at great distances from the source.Ĭonidia are produced in acervuli on the lesions resulting from ascospore infection. ![]() 1-7).īrown spot needle blight can be mistaken for Dothistroma needle blight: the two diseases have similar symptoms and fruiting bodies. They are hyaline, oblong - cuneate, unequally two-celled, and 15-19 x 3.5-4.5 microns, with two prominent oil drops in each cell (fig. Ascospores are produced in pseudothecia embedded in dead leaf tissue. These spores are cylindrical, curved, 1-4 septate, olive green to brown, and 19-35 x 3.5-4 microns (fig. Conidia are exuded in sticky masses up to 1mm long that split the epidermis of the leaf. Conidia are produced in acervuli, which appear on lesions as small black dots visible to the naked eye (fig. Two types of fruiting bodies are produced. When this happens, entire beds may appear scorched (fig. The fungus can also infect the cut ends of pruned longleaf pine seedlings. Infected needles have three distinct zones: a green basal portion, a mottled middle portion, and a dead apical portion (fig. Needles with multiple lesions appear mottIed. Spots coalesce, and the needle tissue dies beyond and between groups of spots. Look for small, grayish-green spots, which become a straw-yellow color and then light brown with chestnut-brown margins (fig. Distribution of brown spot.Īlthough lesions may develop on secondary needles at any time, they most commonly appear from May to October.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |