Presentation on theme: "Diseases Covered Rhizoctonia Crown Rot and Blight Botrytis Blight"— Presentation transcript:
1Diseases Covered Rhizoctonia Crown Rot and Blight Botrytis Blight Black SpotDaylily Rust
2Rhizoctonia crown and root rot. Caused by Rhizoctonia solaniRoot rot may develop either in the rooting cube or on rooted cuttings transplanted to pots as the crop is finished for retail. Infected roots become water-soaked then brown.Both root tips and sections of the root away from the tip may develop symptoms. Crown rot can develop on the stem as lesions expand from stem infections occurring during propagation.
3Rhizoctonia crown and root rot. Stem lesions may develop at a much slower pace on rooted plants, since this tissue is more hardened off and thus more resistant than stems of newly made cuttings.Foliar symptoms of crown and root rot include chlorosis, leaf necrosis, wilting, defoliation, and plant death, but often the most common symptom is stunting.Root rot infections may be initiated from lesions on stems or from inoculum introduced to the potting mix from debris surviving in the greenhouse.Generally, moist but not wet conditions in the potting mix favor development of Rhizoctonia crown and root rot on potted plants.Spacing plants with a full canopy too close together can result in moisture and soil temperatures favorable for development of disease due to shading of the container surface.
8ControlControl of stem and root rot begins with thorough removal of all crop debris from the production facility at the end of a cropping cycle.Sanitation of work area and bench surfaces with surface disinfectants is important.During propagation, misting cycles should be monitored closely to avoid over wetting foliage of cuttings once newly made cuttings become turgid.In greenhouse production facilities with a history of Rhizoctonia stem and root rot, soaking dry rooting strips in a fungicide solution can protect cuttings from diseaseGenerally one application of fungicide is sufficient to protect the crop during the propagation cycle.After transplanting, fungicide drenches may be needed at regular intervals to prevent crown and root rot
9Botrytis Blight CAUSAL ORGANISM: Botrytis cinerea Botrytis blight is common in all parts of the world. This fungus is not a specific pathogen and can take advantage of many situations to produce a blight or rot condition on many hosts.It is an opportunist on cut or pruned rose canes and will infect flowers and buds.
11Symptoms/SignsThe most common symptoms usually are seen on young flower buds which droop, turn black at the base and later produce the cottony grey-black mycelium of the fungus.Flowers can also be affected in the same way and cut ends will have the black canker like symptoms with presence of mycelium.Cool and wet conditions facilitate grey-black mycelial growth of Botrytis.
18Disease CycleThis fungus is not specific and will grow on many different plants and plant debris.Under cool wet conditions profuse sporulation results and spores are moved to roses by air currents or blowing rain.A minor wound in a bud or flower, or perhaps a pruning cut will provide the initial point of entry.As the infection progresses more sporulation results and additional sites become infected.The fungus is a low level parasite and will colonize wound sites as well as dead plant material.
19ControlPrevention is the best means of control. This can be accomplished through intense sanitation procedures.By elimination of opportunistic colonization on dead plant material the amount of sporulation can be reduced.Good ventilation is also essential in reducing disease incidence. Some sprays may give short term relief but the fungus usually becomes quickly resistant.In greenhouse conditions special covers are used to reduce the levels of ultraviolet light required by the fungus for sporulation.In most cases, removal of infected plant parts and protection of wounds by chemicals is all that can be done until warmer and dryer conditions prove too unfavorable for continuing disease.
20Black SpotCaused by the fungus Diplocarpon rosae. The disease can cause almost complete defoliation of bushes by early fall.It produces a weakened bush on which cane dieback, stem canker, and winter injury can become severe.
22SymptomsCircular black spots ranging from 1/16 inch to 1/2 inch in diameter appear generally on leaves’ upper sides.The spots are frequently surrounded by a yellow halo. Infected leaves characteristically turn yellow and fall prematurely.This leaf spot can be distinguished from others by the fringed margin and consistently black color.Cane infection produces a reddish-purple spot.In many varieties, pale flower color is indirectly caused by infection.
23Disease CycleBlack spot is spread by splashing water. Infection occurs after leaves are wet for several hours.Therefore, the disease is more serious during periods of rainfall.
24ControlA preventive program for black spot should begin with a thorough cleanup in the fall. Diseased leaves on the ground should be raked and destroyed.All diseased canes should be pruned off by cutting several inches into good wood.A fungicide program should start in the summer just before leaves become spotted. From then until frost, the leaves may require a protective fungicide coating. When the leaves are growing rapidly or during rainy weather, it may be necessary to spray the plants two times a week.However, if growth is less rapid and rains are less frequent, spraying at 7 to 10 day intervals is usually sufficient
25Daylily RustDaylily rust is caused by the fungus Puccinia hemerocallidis and affects the leaves and scapes.It is not a new disease of daylilies, having been reported previously in China, Taiwan, Korea, Japan and Russia.Unfortunately, the disease has now arrived in North America, and was first identified in the southeastern United States in August 2000. Because of widespread shipping of infected plants, by late 2001 daylily rust had been identified in approximately 30 US States, Canada and Australia. In nature, however, the main method of rust spread is by wind borne spores
26Daylily RustWhile daylily rust may kill the foliage on some cultivars, it is unlikely in the short term to actually kill the infected plant. However, it is not yet known what the effects of continuous infection will be on individual daylilies
31Disease Cycle It is not known where the rust overwinters. It has successfully overwintered in some States of USDA Hardiness Zone 7 and milder as of AprilThere are three possible ways that this rust may survive the winter.The first is as urediospores, the orange powder produced from the spots (known as pustules) on daylily leaves.Some rusts overwinter as mycelium (the strands which form the body of the fungus inside the leaf) but this can only take place where the plant tissue remains alive.The third means by which rusts can overwinter is in the form of teliospores.
32Disease CycleTeliospores are typically hardier and more durable than the urediospores and lie dormant on dead daylily leaves over winter.These new spores must be transported by the wind or other means to a plant of the alternate host, Patrinia, which is a perennial plant also of Asian origin. Thus it is possible that in climates where the rust cannot survive the winter as mycelium or urediospores, it may still be able to continue the infection in the subsequent year if there is a plant of Patrinia in the vicinity.Patrinia is not common at the moment in North America, but several species are being offered for sale both as plants and seeds. Not only does it pose a threat to daylilies as far as overwintering of the rust is concerned, but the rust life cycle stage on Patrinia is a form of sexual reproduction which may increase the chances of new races of daylily rust developing.
33Control Cultivar selection It is generally recommended to remove the foliage from all plants discovered to have rust, cutting just above the soil level.Fungicide applications mancozeb, chlorothalonil, azoxystrobin and triadimefonOverhead watering should be avoided wherever possible