As the spots increase in size the foliage is killed and hangs down. Yellow streaks are often associated with these spots. Spot color varies with leaf texture and the lily species affected, but usually the center is a different color and slightly sunken. Symptoms Typical initial symptoms are water-soaked (wet-looking), teardrop- or boat-shape brown spots that occur anywhere on the leaf. Cultivars are known to differ in susceptibility. The disease can reduce bulb growth as well as making cut flowers or pot grown plants unmarketable. Injuries due to hail can also favor disease development. Colonized flower parts that fall onto leaves or stems can be the source of mycelium that directly infects healthy tissues. Under optimal conditions many spots may occur at once throughout the planting. Spore production in diseased tissue spreads the fungus during the growing season. elliptica is through stomata on the underside of leaves. Infection is most likely in wet foggy weather where plants are wet for 6 to 12 hours and when temperatures range from 50☏ to 65☏ during day or night. Conidia are windblown to healthy foliage. In spring, sclerotia on or near the soil surface produce conidia that infect leaves. Botrytis overwinters as sclerotia in the debris of plant shoots that mature and decay in fall. The former has been reported on crocus, daylily, and gladiolus but is primarily on lily while the latter has a huge host range. Use effective fungicides in rotation for optimum Botrytis management that will slow the development of resistance.Cause Botrytis elliptica and B. The fungus is commonly resistant to thiophanate-methyl (3336, 6672 and Fungo) and is often partially resistant to dicarboximides (Chipco 26019, Vorlan). Fungicide resistance is reported for Botrytis. Chemical Controlįungicides may be required under some greenhouse conditions, especially with highly susceptible crops such as exacum, geranium, poinsettia, and fuchsia. All old blossoms and dead leaves should be removed, and all fallen leaves and plant debris on or under the benches should be gathered and burned. Because the fungus readily attacks old or dead tissues and produces tremendous quantities of airborne spores, the importance of strict sanitation cannot be overemphasized. Bioenvironmental Controlīecause high humidity is required for spore production and actual condensation is necessary for spore germination and infection, Botrytis can usually be controlled under glass by avoiding splashing and by heating and ventilating to prevent any condensation on the plant surfaces. Petals shed from crops in hanging baskets may encourage Botrytis leaf infections on the crops listed below. Active, healthy tissues, other than petals, are seldom invaded. Only tender tissues (seedlings, petals), weakened tissues (stubs left in taking cuttings, tissues infected by powdery mildew), injured tissues (bases of cuttings), or old and dead tissues are attacked on most crops. The spores will not germinate and produce new infections, however, except when in contact with water, whether from splashing, condensation, or exudation. Spores of Botrytis are produced on distinctive dark-colored, hairlike sporophores and are readily dislodged and carried by air currents to new plant surfaces. The fungus is usually identified by the development of fuzzy grayish spore masses over the surface of the rotted tissues, although such sporulation will not develop under dry conditions. As a result of Botrytis infection, very small seedlings can be rotted stems of poinsettia, snapdragon, zinnia, exacum, or lisianthus can be girdled and petal tissues of many plants, including carnations, chrysanthemums, roses, azaleas, and geraniums, can be spotted and ruined. It commonly attacks the stems of geranium stock plants and wounds on cuttings. The fungus causes a brown rotting and blighting of affected tissues. The common gray mold fungus, Botrytis cinerea, attacks a wide variety of ornamental plants, probably causing more losses than any other single pathogen.
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