Fittonia Production Guide

CFREC- Foliage Plant Research Note, RH-91-17

R.T. Poole, A.R. Chase and L.S. Osborne University of Florida, IFAS Central Florida Research and Education Center - Apopka 2807 Binion Road., Apopka, FL 32703-8504

FITTONIA

Fittonias are hairy, low or creeping herbs, native to the moist forests of the South American Andes. The leaves are opposite and entire with white or colored veins. Small flowers appear on slender spikes. They are frequently called Silver-Nerve plant in the commercial trade. The variety `Verschaffeltii' has dark green leaves with rose colored veins, `Argyroneura' has light green leaves with a white midrib. Many other varieties are available including miniature forms of both white and rose-veined plants (`Miniature Variegated' and `Argyroneura minima') and standard forms with dark leaves (`Argyroneura Black Emerald') or red veins (`Rubrovenosa Pink'). Fittonias are readily employed in dish gardens and sometimes hanging baskets since they vine when larger.

PRODUCTION

Fittonias are easily rooted from tip cuttings with roots appearing in 1-2 weeks and cuttings well rooted by 3-4 weeks. Some benefit from use of 0.3% indolebutyric acid (IBA) has been noted in some reports. Plants are grown under 1500 to 2500 ft-c. light and fertilized with 2.5 pounds of 9-3-6 per 100 square feet per month or 17 grams of 19-6-12 per square foot per 3 months. If plants are grown in a 6" pot, 4 g 19-6-12 per pot can be applied every 3 months. Indoors, fittonias should be kept in light above 100 ft-c or they will decline rapidly.

Plants exposed to levels of ethylene at or greater than 5 l/liter air for 2-4 days abscised 50% or more of their leaves, although plants exposed to 1-10 l/liter air for 1 day were not injured.

BACTERIAL PROBLEM

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1) Xanthomonas leaf spot (Xanthomonas campestris)

Symptoms -

Fittonias are commonly infected with this bacterium although most producers do not recognize the symptoms as a disease problem. Marginal necrosis and veinal necrosis are the most common symptoms. These are sometimes confused with irrigation, phytotoxicity, or temperature problems. All types of fittonias have been found susceptible to this pathogen as well as some related plants such as Aphelandra squarrosa (zebra plant).

Control -

Both streptomycin sulfate and copper compounds cause phytotoxicity on fittonias and can actually increase severity of Xanthomonas leaf spot due to the bacteria invading the wounds. The only way to control this disease is to establish plants that are free of the disease for cuttings. All symptomatic plants should be collected and destroyed. Minimizing overhead irrigation will also reduce disease development and spread.

FUNGAL PROBLEMS

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1) Rhizoctonia aerial blight (Rhizoctonia solani AG4)

Symptoms -

A mass of brownish mycelia covers the foliage of infected plants. Growth of mycelia from the potting medium onto the plant foliage can escape notice and give the appearance that plants have been infected from an aerial source. Close examination generally reveals the presence of the mycelia on plants stems prior to development of the aerial blight phase. Rhizoctonia mycelia are usually reddish-brown and have the consistency of a spiderweb.

Control -

Good chemical control of Rhizoctonia aerial blight for most foliage plants may be achieved with weekly sprays. This disease is most severe during the summer months or at any time when the air temperatures are typically 80 - 90°F. Avoid applications of excess water the minimize conditions for disease development.

2) Southern blight (Sclerotium rolfsii)

Symptoms -

The pathogen attacks all portions of the plants but is easiest seen on the leaves and stems. Initially, symptoms on stems are confined to water-soaked areas near the soil-line. White, relatively coarse mycelia grown in a fanlike pattern on the surface of leaves or the potting medium. The sclerotia of the fungus form in this mycelia. They are white but turn dark brown when mature and are the size of a mustard seed. A cutting rot can develop on contaminated plant material especially during warm months.

Control -

All infected plants and the pots they are in should be removed from the growing area and destroyed as soon as they are found. There are not chemicals which are safe, effective and labeled for this disease on fittonias.

VIRAL PROBLEM

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1) Bidens mottle (Bidens Mottle Virus)

Symptoms -

Distortion of the normally symmetrical leaves are the most obvious symptoms of this viral disease. Interveinal chlorosis and stunting of severely infected plants can occur as well. The disease appears to be most severe during the cooler periods of the year. This disease has rarely been seen on fittonias during the past five years.

Control -

This virus is transmitted from common weed hosts to the fittonia via aphid vectors. Remove weeds from around greenhouses as much as feasible and keep aphid populations under control. Once plants are infected they should be removed and destroyed since they will not recover from the infection even if they don't show symptoms all year round.

INSECT AND RELATED PROBLEMS

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The major arthropod pests of this plant species include aphids, moths (worms), fungus gnats, mealybugs, mites, snails, slugs and thrips. Mealybug, and mite infestations are typically the result of bringing infested plant material into the greenhouse. Aphids, moths, fungus gnats and thrips have the ability to fly and thus invade the greenhouse from weeds and other infested plants outside. In the control section for each pest, a few of the many registered and effective pesticides may be listed. For a complete listing please consult the references at the end of this report.

1) Aphids

Symptoms -

Aphids are pear-shaped, soft-bodied insects which vary in color from light green to dark brown. Infestations may go undetected until honeydew or sooty mold is observed. Aphids can cause distortion of new growth or, in extreme cases, infested plants can be stunted.

Control -

Aphids are relatively easy to control with many registered materials. Phytotoxicity to this plant has been caused by many different chemicals. Please conduct your own tests to see what is safe under your conditions. Root aphids have been controlled with soil drenches.

2) Caterpillars (worms)

Symptoms -

Infestations are easy to detect because worms, their excrement and the damage they cause, are usually quite visible to the unaided eye. Damage appears as holes in the center or along the edges of leaves. Damage by worms is often confused with slug or snail damage. The only way to determine which pest is involved is to find a specimen. Old damage can be distinguished from new by the calloused appearance of the older damaged areas (worms are usually gone by this time).

Control -

2) Fungus gnats

Symptoms -

Fungus gnats are small black flies (1/8 inch long) and are frequently observed running around the soil surface or on leaves and are often confused for Shore flies (see later section). The adults have long bead-like antennae and their legs hang down as they fly. These insects are very weak fliers and appear to "flit" around randomly. The larvae are small legless "worms" with black heads and clear bodies that inhabit the soil. The larvae spin webs on the soil surface which resemble spider webs. Damage is caused by larvae feeding on roots, root hairs, leaves in contact with the soil and lower stem tissues. Feeding damage may predispose plants to disease and they are often found in close association with diseased plants or cuttings. Adults do not cause any direct damage, but are responsible for many consumer complaints to growers. Adults emerge and fly around in retail shops, homes, or offices and are therefore a nuisance. For further information please consult Extension Entomology Report #74 (Management of fungus gnats in greenhouse ornamentals).

Control -

Reduce the amount of water applied to each pot where possible. Avoid algae growth where possible. Soil drenches or soil-surface sprays are effective at controlling the larvae. Nematodes that seek out insects in the soil are sold commercially and have been shown to control these pests without causing any negative effects to the host plants. Adults are very sensitive to most chemicals.

3) Mealybugs

Symptoms -

Mealybugs appear as white, cottony masses in leaf axils, on the lower surfaces of leaves and on the roots. Honeydew and sooty mold are often present and infested plants become stunted, and with severe infestations, plant parts begin to die.

Control -

Systemic materials are preferred. Control of root mealybugs is accomplished with soil drenches with an insecticide. When pesticides are applied to the soil, care must be taken to assure that the pots have good drainage and that no saucers are attached, or phytotoxicity may result.

4) Mites (Broad mite)

Symptoms -

Mites are very small and go unnoticed until plants become severely damaged. Broad mites cause foliar necrosis of the vegetative shoot apex. Initial symptoms of injury show new leaves cupped downward, puckered, stunted and have serrated margins. Broad mite eggs are covered with many tubercles which give them the appearance of being jeweled.

Control -

The critical point in any control program is thorough coverage with the pesticide. The best control program is to minimize the possibility of introducing mites into the growing area on infested plant material.

5) Snails and Slugs

Symptoms -

Snail, slug and caterpillar damage are similar and determining which pest is present can be difficult. Snails and slugs are voracious feeders, with small stages feeding on surface tissue and larger ones eating irregular holes in foliage. Generally, the culprit can be found on close examination of the plant. Slugs often live under benches or in dark, moist protected places close to the damage. These pests are nocturnal and can be found feeding at night.

Control -

Sprays or baits applied to moistened soil around plants are effective. Repetitive applications are necessary. Good sanitation with removal of extraneous plant material and debris which might shelter these pests aids in control.

6) Thrips

Symptoms -

Thrips are small (less than 1/20), thin insects. Adult thrips can be identified by a long fringe of hair around the margins of both pairs of wings. Color varies between species with western and other flower thrips being yellow to light brown and banded greenhouse thrips and a few other thrips that feed mainly on leaves being dark brown to black. Feeding takes place with rasping type mouth parts. Infested leaves become curled or distorted, with silver-gray scars or calloused areas where feeding has occurred. Thrips can transmit the tomato spotted wilt virus to many different ornamentals. Any unusual symptoms should be investigated.

Control -

Many materials are registered and effective at controlling thrips.

Pesticides should be applied according to label directions.

Regardless of the pesticide or mixture of pesticides used, it is
strongly recommended that the effects be evaluated on a few
plants, under your particular conditions before treating all plants.

Mention of a commercial or proprietary product in this paper
does not constitute a recommendation by the authors,
nor does it imply registration under FIFRA as amended.

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REFERENCES

1. Chase, A.R. 1990. Phytotoxicity of bactericides and fungicides on some ornamentals. Nursery Digest 24(5):11.

2. Conover, C.A. and R.T. Poole. 1990. Light and fertilizer recommendations for production of acclimatized potted foliage plants. CFREC-Apopka Research Report RH-90-1.

3. Marousky, F.J. 1979. Effects of ethylene in combination with light, temperature and carbon dioxide on leaf abscission in Fittonia verschaffeltii (Lem.) Coem. var. argyroneura (Coem.) Nichols. Proc. Fla. State Hort. Soc. 92:320-321.

4. Price, J., D.E. Short and L.S. Osborne. 1989. Management of fungus gnats in greenhouse ornamentals. Extension Entomology Report #74.

5. Short, D.E., L.S. Osborne and R.W. Henley. 1984. Phytotoxicity of insecticides and miticides to foliage and woody ornamental plants. Extension Entomology Report #57.

6. Short, D.E., L.S. Osborne and R.W. Henley. 1991. 1991-1992 Insect and related arthropod management guide for commercial foliage plants in Florida. Extension Entomology Report #52. 13 pp.

7. Simone, G.W. and A.R. Chase. 1989. Disease control pesticides for foliage production (Revision #4). Plant Protection Pointer. Extension Plant Pathology Report #30. [also in Foliage Digest 12(9):1-8]

8. Son, K.H. and D.Y. Yeam. 1987. Effects of light intensities and temperatures in various indoor situations on growth of some foliage plants. J. Korean Soc. Hort Sci. 28(2):173-184.