China Doll Production Guide

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CFREC-A Foliage Plant Research Note RH-91-11
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

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CHINA DOLL

China Doll, Radermachera sinica, also called Radermachera and Radar Plant, is an evergreen tree with binnate leaves having numerous green leaflets originating in southeast Asia. Since this plant is relatively new to the foliage industry little research has been conducted to determine optimal production conditions.

The plant grows best under 2,000 to 3,000 foot-candles (ft-c). It grows quickly within a wide fertilization range. Fertilization with 4 grams of 9-3-6 per 6" pot per month or 25 grams of 19-6-12per square foot per 3 months should produce optimum growth. Leachate conductivities of 1,000 to 4,000 mhos/cm obtained from media growing excellent China Doll plants. Tissue content of high quality China Doll was found to be: N (nitrogen), 2.4-4.3% dry weight; P (phosphorus), 0.26-0.35%;K (potassium), 1.3-2.6%; S (sulfur), 0.16-0.24%; Ca (calcium), 0.50-0.54%; Mg (magnesium), 0.40-0.45%; B (boron), 22-30 parts per million (ppm); Cu (copper), 6.4-9.8 ppm; Fe (iron), 39-56 ppm; Mn (manganese), 80-176 ppm and Zn (zinc), 103-145 ppm. China Doll is very sensitive to ethylene. Leaves exposed to 2 milliliters of ethylene lost all leaflets within 22 hours.


FUNGAL PROBLEMS

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1)Corynespora leaf spot (Corynespora cassiicola)

Symptoms -
Symptoms of Corynespora leaf spot vary depending upon the host. Lesions start on lower leaves, especially those in contact with the potting medium or those which are wounded. Lesions expand rapidly and are black and may encompass the entire leaflet and cause abscission when conditions are favorable. There is rarely any halo surrounding lesions on China Doll.
Control -
Keep plants as free of excess water as possible and avoid crowding to promote rapid drying of foliage. Mixed results in controlling this disease have been seen with the fungicides available.

2)Myrothecium stem rot (Myrothecium roridum)

Symptoms -
Infection of small plantlets occurs all over the plantlet and results in crown or petiole rot. Lesions also appear at edges, tips and at broken leaf veins on zebra plants. Spots are dark-brown to black and initially appear water-soaked. Examination of the lower leaf surface generally reveals sporodochia which are irregularly shaped, black and have a white fringe of mycelia.
Control -
Avoid temperatures between 60 and 85F when possible, minimize wounding, and fertilize plants at recommended levels.

3)Phytophthora crown and root rot (Phytophthora parasitica)

 

Symptoms -
Damping-off of China Doll seedlings is a common symptom when Phytophthora is present. Root and stem tissues become water-soaked necrotic and collapse. On larger plants wilting, yellowing and stunting can be signs of Phytophthora crown and root rot.

Control -
Always use seeds from pathogen-free plants and germinate in clean potting media on raised benches. Overwatering will make Phytophthora crown and root rot more severe and use of appropriate fertilizer levels is critical.

4)Rhizoctonia stem rot (Rhizoctonia solani)

Symptoms -
Rhizoctonia stem rot is typified by lesions at the soil-line on stems of small seedlings. Lesions are tan to black, dry and shrunken. When lesions encompass the entire stem the seedling wilts and dies. Larger plants rarely seem affected by this disease and apparently can outgrow an early infection.
Control -
Chemical control of diseases caused by Rhizoctonia has been investigated on many plants using a wide variety of fungicides.
 

INSECT AND RELATED PROBLEMS

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The major arthropod pests of this plant species include aphids, moths (worms), fungus gnats, mealybugs, mites, scales, and thrips. Mealybug, mite, and scale 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 will 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.

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 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.

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)

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.

6) Scales

Symptoms -
Infested plants become weakened or stunted and begin to die. Scales can be found 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 2mm 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 antennas. These insects very strong fliers and exhibit 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 may be responsible for spreading plant pathogens, 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. 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.


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. Chase, A.R. and R.T. Poole. 1989. Nutrition of Radermachera sinica. CFREC-Apopka Research Report RH-89-10.

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

4. 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.

5. 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.

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

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. Wang, Yin-Tung and J.R. Dunlap. 1990. Leaf abscission in Radermachera sinica in response to ethylene and silver thiosulfate. HortScience 25(2):233.