The Horticultural Site by Betrock Information Systems

A.R. Chase is a Plant Pathologist and President of Chase Research Gardens, Inc.
C.R.G. is a private research and consulting corporation specializing in ornamental plants.
Both hourly and contract services are available.
You can reach C.R.G. at P.O. Box 168, Mt. Aukum, CA 95656 Phone and Fax: 916-620-1624 - E-mail: MTAUKUM@AOL.COM

	BOTRYTIS BLIGHT OF LIPSTICK VINE Pathogen - Botrytis cinerea Symptoms - Botrytis blight usually appears on lower leaves of cuttings in contact with the potting medium. The water-soaked area may enlarge rapidly to encompass a large portion of the leaf blade or even the entire cutting. The area turns necrotic and dark brown to black with age. When night temperatures are cool, day temperatures warm, and moisture conditions high, the pathogen readily sporulates on both leaves and flowers, covering them with grayish-green, dusty masses of spores. Cuttings rooted during the winter are especially susceptible to Botrytis blight since the environment is ideal for the disease and very poor for rapid growth of the plant. Episcia, Sinningia, and African violets are also commonly affected by Botrytis blight. Control - Controlling Botrytis blight is particularly important during the winter months. Cultural methods which improve foliage drying and reduce moisture condensation on foliage during the night reduce Botrytis blight. Iprodione (Chipco 26019) reduces the severity of this disease and is labeled for lipstick vine.
	COLD WATER SPOTS IN NEMATANTHUS Pathogen-Cold irrigation water Symptoms-Round spots which are light yellow or green appear on the upper surfaces of leaves. Spots can appear on margins or blades and are sometimes irregular or donut-shaped and white. Control - Water that is colder than the leaf surface will cause spotting and is most common in Florida during winter. Deep well water is usually near 70°F and rarely causes problems, except when it is stored in outdoor tanks. Be sure temperatures of overhead water applications are near leaf-surface temperatures.
	CORYNESPORA LEAF SPOT OF LIPSTICK VINE Pathogen-Corynespora cassiicola Symptoms-Spots on lipstick vine appear first as tiny sunken areas which are slightly brown. These areas enlarge to about 1/2 inch in diameter and darken with age. A bright purple or red margin and a yellow halo about 1/16 inch wide are usually present on lipstick vine but not other gesneriads. Leaf drop may also occur. Similar symptoms are seen on other gesneriads such as Episcias, Streptocarpus, Nematanthus, Columnea, and Saintpaulia ionantha (African violet). Control - Use the same cultural controls as mentioned for Botrytis blight. Chemical control trials have indicated that both mancozeb (Protect T & O) and chlorothalonil (Daconil 2787) provided excellent disease control.
	FUSARIUM STEM ROT OF EPISCIA Pathogen - Fusarium spp. Symptoms - Fusarium stem rot and blight typically appears as a soft, mushy rot at the base of a cutting or rooted plant. The pathogen sometimes forms tiny, bright red, fruiting bodies or dusty tan masses of spores at the stem bases of severely infected plants. Control - Remove infected plants from stock areas as soon as they are detected. Since Fusarium stem rot appears similar to other diseases, accurate disease diagnosis is very important prior to fungicide application. Always use pathogen-free cuttings and new or sterilized pots and potting media, and grow plants on raised benches with adequate spacing to allow rapid leaf drying following irrigation. The fungicides listed for Rhizoctonia control should be effective for Fusarium control as well. Be sure to check labels for legal uses.
	MYROTHECIUM LEAF SPOT OF LIPSTICK VINE Pathogen - Myrothecium roridum Symptoms - Spots appear at edges, tips, and broken leaf veins. Dead areas are dark brown and initially appear water-soaked. Examination of the bottom leaf surface generally reveals black sporodochia (fruiting bodies) which are irregularly shaped and have a white fringe of mycelium. Sporodochia form in concentric rings within the necrotic areas. Most gesneriads are susceptible to M. roridum. Control - Using fungicides when temperatures are between 70 and 85° F, minimizing wounding, and fertilizing at recommended levels contribute to the control of Myrothecium leaf spot. Chlorothalonil (Daconil 2787) and iprodione (Chipco 26019) have been effective for Myrothecium control on other foliage plants.
	RHIZOCTONIA AERIAL BLIGHT ON LIPSTICK VINE AND EPISCIA Pathogen - Rhizoctonia solani Symptoms - Rooting cuttings may be completely covered by a mass of brownish mycelia (spider-web consistency). Growth of mycelia from the potting medium onto stems and leaves can escape notice and give the appearance that plants have been infected from an aerial source of inoculum. Close examination, however, generally reveals the presence of mycelia on stems prior to the development of obvious foliar symptoms. This disease is most common during the hottest times of the year when the plant foliage remains wet for long periods of time or when the relative humidity is high. Most gesneriads can be attacked by Rhizoctonia spp. Control - Use pathogen-free cuttings, new pots and potting media, and avoid extremes in soil moisture. Chemical control of diseases Pathogend by Rhizoctonia has been investigated on many plants using a variety of fungicides. The fungicide most widely used for soil-drench control of Rhizoctonia diseases is thiophanate methyl (Domain or Cleary 3336). Foliar applications of chlorothalonil (Daconil 2787) may be effective in protecting leaves from Rhizoctonia infection, but remember that the potting medium or soil is the most common source of this soil-borne plant pathogen.
	WEED SEEDS ON LIPSTICK VINE Pathogen - Sticky weed seeds such as those of Oxalis Symptoms - Small black bodies can be found on leaves, stems, and pots. These bodies are easily scraped away with a fingernail leaving no apparent damage to the plant surface. Sometimes weed seeds can be confused with scale insects. Control - Control weeds both within pots and under benches.