Aphelandra Production Guide

CFREC-A Foliage Plant Research Note RH-91-4
This publication is a revision of AREC-A Foliage Plant Research Note 85-D.

R.T. Poole, A.R. Chase and L.S. Osborne
Professor, Environmental Horticulture, Professor, Plant Pathology, and
Associate Professor, Entomology, respectively.

University of Florida, IFAS Central Florida Research and Education Center-Apopka 2807 Binion Road., Apopka, FL 32703-8504

APHELANDRA

Aphelandra squarrosa cultivars, members of the family Acanthaceae, are valued for their shiny emerald green foliage with conspicuous white veins. These natives of the American tropics are commonly called zebra plants due to the characteristic striped foliage. Aphelandras have a compact growth habit consisting of elliptic, entire leaves and can reach 8 to 12 inches tall. Bright yellow flowers are borne on fleshly terminal spikes and are long lasting yellow or light green bracts. `Dania', the most commonly produced commercial variety has dark green foliage with white stripes. The white venation of `Apollo' foliage covers much of the leaf surface, coloring the leaves more white than green. `Red Apollo', with dark red to violet stems and underside of leaves, is also produced by a few growers.

Aphelandra cuttings are sold as: (1) 2-4 inch, 4-6 inch and 6-8 inch unrooted tip cuttings, (2) unrooted stem cuttings of various lengths, (3) 6-8 inch rooted liners and (4) tissue cultured liners or cuttings.

PRODUCTION

Research has shown that incorporation of 8 lb/yard3 of Osmocote 19-6-12 applied to the propagation medium at three month intervals or 1 lb of 9-3-6 soluble fertilizer (per 100 gal applied weekly to 100 ft2) improved quality of cuttings being rooted. Dolomite added to peat to raise the pH to 5.5 also improved rooting. Use of rooting promoters such as Hormodin 2 (0.3% IBA) and Patio is beneficial.

Fertilizer rates for rooted plants of approximately 1 lb nitrogen/100 square feet weekly, 5 grams 19-6-12/6 inch, pot per 3 months or 200 ppm nitrogen, 75 ppm phosphorus and 150 ppm potassium with each watering produced good growth, although aphelandras grow well over a wide range of fertilization. Potting mixes with electrical conductivity of 4000 to 7000 mhos/cm determined by the pour-through method produced excellent aphelandras. Aphelandra responded equally to urea, ammonia, nitrate N or various combinations of the N sources. Aphelandras responded equally to liquid or slow-release fertilizer (Nutricote or Osmocote) when N rates were equal. Plants grown in a mix of Florida sedge peat: cypress shavings: pine bark (2:1:1 by volume) exhibited chlorosis when 3/4 lb of FTE-503 was added to the mix. Tests with additional media indicated MicroMax, 1-3 pounds per yard, was beneficial. Aphelandra was tolerant of fluoride in the medium or the atmosphere. The tissue composition of good quality aphelandra was found to be between 1.5-2.5% dry weight of N, 0.2-0.4% P, 1.0-2.0% K, 0.2-0.4% Ca and 0.5-1.0% Mg.

Aphelandras grown on capillary mats were better than plants hand watered 3 times weekly. Satisfactory mixes are some commercial mixes, peat: builder's sand (3:1 by volume) and peat. Best growth is obtained when soil temperatures are between 70 and 80°F with daytime air temperatures up to 90°F and a minimum night temperature of 65°F.

Ancymidol (A-REST) at 0.50 mg active ingredient in one liter of medium was shown to retard growth. No other information is available regarding growth regulator effects on aphelandras.

Aphelandras can be shipped for 1 week at 55°F without loss of quality and for 3 weeks with only slight loss of quality.

Grower experience in central Florida indicates that best flowering occurs when plants receive about 1000 ft-c during long summer days and 2500 ft-c during shorter winter days. The higher light levels needed during the winter may result in some leaf deformity which will be discussed below. To maintain attractive appearance indoors place plants under 100-150 ft-c.

PHYSIOLOGICAL PROBLEMS

1) Crinkle leaf

Symptoms -

Leaves crinkled, size reduced, internodes shortened with axillary bud proliferation.

Control -

The disorder is most severe under high light and high temperature. No bacteria, fungi or viruses have been found associated with this disorder and pesticides have no effect. Plants do not respond to micronutrients or proper environmental conditions. Eliminate stock plants with this problem and maintain proper light levels and temperatures.

2) Ripple leaf

Symptoms -

Difficult to distinguish from crinkle leaf, but a change of environment will cause plants to produce healthy leaves.

Control -

Reduce light to less than 1500 ft-c, 1000 ft-c may be necessary in some situations. Plants grown in low light will have flat leaves and as light intensity increases, leaves assume more curvature. High temperature also contributes to ripple leaf.

3) Flowering in propagation bed

Symptoms -

Tip cuttings produce flower spikes.

Control -

Maintain a maximum of 500 ft-c in propagating area and/or production area.

4) Moisture stress

Symptoms -

Leaf collapse and occasionally tip collapse.

Control -

Aphelandras are more susceptible to moisture stress than most foliage plants. Water more frequently or reduce fertilizer levels and avoid high temperatures.

5) Leaf drop

Symptoms -

Lower leaves abscise.

Control -

Maintain proper moisture level, avoid dry air and close spacing of plants as well as excessive fertilizer applications.

FUNGAL PROBLEMS

Reference Pest Control Guides Here

1) Botrytis blight (Botrytis cinerea)

Symptoms -

Botrytis blight appears as large dark green to gray areas found primarily on leaf edges, especially those in contact with the potting medium. The dusty gray-tan spores of the fungus form readily on damaged tissue and can be seen with a hand lens. Affected leaves generally collapse.

Control -

Botrytis blight occurs during the cooler, low light months of winter and sometimes during the spring or fall. More attention to disease control will be necessary during these times.

2) Corynespora leaf spot (Corynespora cassiicola)

Symptoms -

Leaf spots start on leaf edges, tips and sometimes centers near pot edges, the potting medium and at wound sites. They are dark brown to black and often appear wet. This disease can be a serious problem on cuttings rooted under mist and on bottom leaves of potted plants.

Control -

Elimination of overhead water can control this disease.

3) Myrothecium leaf spot (Myrothecium roridum)

Symptoms -

Leaf spots caused by this pathogen appear similar to those caused by C. cassiicola when viewed from the upper leaf surface. Leaf undersides generally reveal the presence of the fungal fruiting bodies which are formed in concentric rings within the dead spots. These fruiting bodies are irregularly shaped black bodies with a white fringe and are about the size of a pin head.

Control -

The same chemical controls apply to Myrothecium leaf spot as Corynespora leaf spot. Myrothecium leaf spot is most severe when temperatures are between 70 and 85°F but can be a problem throughout the year in Florida. Temperatures above 90°F greatly inhibit Myrothecium and make chemical application less important.

4) Phytophthora stem rot (Phytophthora parasitica)

Symptoms -

Stem rot usually starts at the soil line and causes a blistering of the stem surface. The lesions are black and slightly mushy and can extend from the base of the stem up into the petioles of lower leaves. Complete collapse of the plant is common.

Control -

Control should be based on use of pathogen-free cuttings, pots and potting media since the pathogen is easily introduced in any of these ways.

5) Pythium root rot (Pythium spp.)

Symptoms -

Pythium root rot is typified by wilting and/or yellowing of the upper portions of infected plants. Root systems are generally stunted and have many black mushy roots. The outer portion of these roots can be easily removed from the inner core. Always obtain an accurate diagnosis of a root rot disease since it is vital in selection of the appropriate fungicide for control.

Control -

Control of Pythium root rot is the same as for Phytophthora stem rot.

INSECT AND RELATED PROBLEMS

Reference Pest Control Guides Here

The major arthropod pests of Aphelandra include aphids, mealybugs, mites, scales and thrips. Mealybug, mite and scale infestations are typically the result of bringing infested plant material into the greenhouse. Aphids 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 will be listed. For a complete listing, please consult the references at the end of this report.

1) Aphids (Green peach and cotton 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 -

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 -

3) 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 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 (See Shore flies). 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 on walkways, benches, and cooling pads. 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.

4) 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.

5) Mites (Broad mite and false spider mites)

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. False spider mites (Brevipalpus spp.) are red in color and sedentary. Eggs are bright red and oval-shaped and are laid on both surfaces of leaves. Initial infestations are indicated by faint brown, scruffy flecks, later becoming bronze or reddish in color. Basal leaf areas are affected, vegetative shoot apexes may be killed, and severe leaf drop may occur.

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.

6) Scales

Symptoms -

Infested plants become weakened or stunted and begin to die. Scales can befound feeding on leaves, petioles, or stems. They are usually distinct from the plant material on which they are feeding. Their shape (round to oval), size (pinpoint to 2 mm long), and color (light to dark brown) are quite variable and many scales are hard to distinguish from the plant material on which they are feeding.

Control -

See Mealybugs

7) Shore Flies

Symptoms -

Shore flies are small black flies (1/8 inch long) and are frequently observed sitting on the tips of leaves or on the soil surface feeding on algae. The adults have very short antennae. These insects are very strong fliers and exhibit very directed flight (straight between 2 points). The larvae inhabit the soil and are small legless "worms" with clear bodies and no obvious heads. No known damage is caused by larvae. This insect is believed to feed only on algae. Adults do not cause any direct damage, but are responsible spreading disease organisms, reducing value by defecating on the leaves (small black to green spots) and for many consumer complaints to growers. Adults emerge and fly around in retail shops, homes, or offices and are therefore a nuisance.

Control -

Reduce the amount of water applied to each pot where possible. Avoid algae growth on walkways, benches, and cooling pads since algae is their food. Chemicals are not believed to be very effective in the control of this pest.

8) Slugs

Symptoms -

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.

9) Thrips (Western flower thrips and Banded greenhouse thrips)

Symptoms -

Thrips are small (less than 1/20 inch long), thin insects. Adult thrips can be identified by a long fringe of hairs 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 this plant. Any unusual symptoms should be investigated.

Control -

10) Whiteflies

Symptoms -

Infested leaves often have small yellow spots where adults or immature whiteflies have fed. When populations become dense the leaves become yellowed and lower leaves are covered with black sooty mold. The immature stages of the sweetpotato whitefly are small scale-like insects and can be found on the undersides of infested leaves.

Control -

Many materials are registered and effective at controlling whiteflies. To minimize additional resistance problems, one insecticide should be applied two times per week throughout one life cycle (3 weeks) to control an established infestation. Monitor the population to determine if the particular insecticide being applied is reducing whitefly numbers. Some populations may be resistant to one or more of these insecticides. If the infestation persists, use another compound for the above list following the same schedule. Do not apply tank mixes as they may enhance resistance. If low numbers of whiteflies persist, apply one of the insecticides once per week for 3 weeks and then switch insecticides. Undersides of leaves must be covered thoroughly to achieve satisfactory control. For additional information on this pest please consult Plant Protection Pointer Report #73. (Sweetpotato whitefly on ornamental plants).

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.

Reference to University of Florida/IFAS Pest Control Guides

REFERENCES

1. Batson, F. Aphelandra, 2-way plant. Florists' Review 152(3931): 28,29.

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

3. Conover, C.A., D.W. Simpson and J.N. Joiner. 1975. Influence of micronutrient sources and levels on response and tissue content of Aphelandra, Brassaia and Philodendron. Proc. Fla. State Hort. Soc. 88: 599-602.

4. Hackett, W.P., A.M. Kofranek and C. Arnold. 1975. Aphelandra Flowering. Florida Foliage Grower 12(6): 2-3.

5. Kerbo, R. and R.N. Payne. 1978. Reducing flowering time in Aphelandra squarrosa with high pressure sodium lighting. Foliage Digest 1(9):3-4.

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

7. 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.

8. Short, D.E., L.S. Osborne and R.W. Henley. 1989. 1989-90 Insect and related arthropod management guide for commercial foliage plants in Florida. Extension Entomology Report #53.

9. Short, D.E., J.F. Price and L.S. Osborne. 1989. Sweetpotato whitefly on ornamental plants. Extension Entomology Report #73.

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