Dieffenbachia Production Guide

CFREC-A Foliage Plant Research Note RH-91-13

R.J. Henny, 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

DIEFFENBACHIA

Dieffenbachias, native from Costa Rica to Columbia, are found in many homes and offices. They are sturdy, thick-stemmed plants with colorful, oblong, pointed, glabrous leaves which are generally green and cream colored. There are 23 cultivars of Dieffenbachias listed in the 1989-1990 Foliage Plant Locator Table 1:

Table 1: Dieffenbachia cultivars listed in the 1990-1991 Florida Foliage Plant Locator.

D. amoena `Morlof'	  		 D. amoena `Topic Alix'TM 
D. amoena `Tropic Snow' (Pat #2869)	 D. maculata `Anne'
D. maculata `Camille'	  		 D. maculata `Exotica Compacta'
D. maculata `Exotica'	  		 D. maculata `Perfection'
D. maculata `Forest'	  		 D. maculata `Lancifolia'
D. maculata `Perfection Compacta'	 D. maculata `Rebecca's Jewel'
D. maculata `Silver'	   		 D. memoria-Corsii 
D. `Angustior'	  			 D. `Bali Hai'TM (Pat #6872)
D. `Bausei'	   			 D. `Golden Sunset'
D. `Hilo'TM	  			 D. `Nelly'TM
D. `Paradise'TM (Pat #6854)	  	 D. `Rebecca'
D. `Starry Nights'TM	  		 D. `Triumph'TM
D. `Tropic Star'			 D. `Victory'TM	
D. `Wilson's Delight'

Plants are normally produced commercially under 1,500 to 3,000 foot-candles (approximately 80% shade), and should be fertilized with a 3-1-2 (N-P2O5-K2O) ratio at a rate of 2.5 pounds of nitrogen per 1000 ft2 per month. Excellent Dieffenbachias can be grown in a variety of potting media, but the medium should be well aerated and have low soluble salts to avoid root damage.

PHYSIOLOGICAL PROBLEMS

1) Excess soil moisture or soluble salts

Symptoms -

Leaves are frequently curved downward, are small and sometimes have necrotic (burned) edges. Severe root loss can also occur in the absence of foliar symptoms when plants in a greenhouse are watered frequently. Plants with poor root systems will not endure either shipping or adverse interior conditions as well as those with good roots.

Control -

Fertilizer additions should be monitored, and excess soluble salts avoided. Leach to remove excess salts. Reduce irrigation frequency if rooting medium stays too wet. Dieffenbachias with a vigorous root system do not need frequent irrigations when grown in a good potting mix.

2) Foliage water-soaking

Symptoms -

Young leaves have a watery transparent appearance, generally found during winter months.

Control -

This problem is usually temporary, developing when plants are grown in high air temperatures and relatively low soil temperatures. Roots do not absorb enough water to maintain proper water balance in the leaves. Increasing soil temperature or reducing air temperature will alleviate the situation.

3) Foliar chlorosis (yellowing)

Symptoms -

The lower leaves of plants are yellow. This occurs more often in the propagation area than in stock areas.

Control -

Yellow leaves are often the result of excess moisture loss. When plants with poor root systems are kept in a warm atmosphere, the water balance is sometimes deficient and leaf chlorosis occurs. Increase the humidity, especially in the propagating area, to control this problem.

4) Cold temperature damage

Symptoms -

Areas between main veins become chlorotic or light brown as a result of cold temperatures.

Control -

Prevent exposure to low temperatures. Avoid extreme or abrupt changes in temperature. Although some Dieffenbachias can be exposed to 45°F without apparent leaf damage, plants grown in high temperatures (70-95°F) can be damaged if the temperature drops to 50°F or below.

5) Leaf notching

Symptoms -

A small notch appears, usually on lower edge of leaf.

Control -

The exact cause is unknown, but notching seems to occur when plants have been exposed to stress conditions, e.g., drought, high temperature, possibly improper pesticide application; thus, these conditions should be avoided.

BACTERIAL PROBLEMS

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1) Erwinia blight and stem rot (Erwinia carotovora pv. carotovora and E. chrysanthemi)

Symptoms -

Stem rot caused by Erwinia spp. appears very much the same as Fusarium stem rot and Phytophthora stem rot. Rotted areas are usually watery and mushy and have a rotten fishy odor in many cases. The bacteria sometimes form a slimy, gelatinous mass at the base of infected cuttings and infected plants generally have yellow lower leaves. Leaf spots caused by Erwinia spp. enlarge rapidly and centers may become so watery that they fall out.

Control -

The only successful control of this disease is eradication of symptomatic plants. This should be done during the hot months when Erwinia blight is most likely to appear. Use of infected plants that are not showing symptoms (asymptomatic) generally results in cutting loss since the bacterium is found inside the plant stem (systemic) and becomes active during rooting. Antibiotic and copper compounds may provide limited control of the leaf spot symptom. Keep plant foliage dry to minimize new infections. Most other foliage plants are susceptible to this bacterium and must be considered as potential sources of infection for Dieffenbachia.

2) Xanthomonas leaf spot (Xanthomonas campestris pv. dieffenbachiae)

Symptoms -

Foliar infections on Dieffenbachia start as tiny pin point water-soaked areas which can rapidly enlarge to 1/4 inch or more. They tend to form on leaf margins where the bacterium can enter the leaf through hydathodes. When they invade a main vein in the leaf, the infection rapidly spreads throughout the leaf. These necrotic areas are frequently very black and surrounded by a bright yellow halo. Some cultivars are more resistant than others (see table below). Most other plants in the Aroid family such as Aglaonema, Anthurium and Syngonium are also hosts of this pathogen.

Control -

Eliminate all stock plants which have Xanthomonas leaf spot. The disease is very difficult to control unless plants are produced without overhead watering or exposure to rainfall. Bactericides such as copper containing compounds may be somewhat effective if used on a preventative and regular basis. Nutritional studies on dieffenbachias have shown that applications of greater than the recommended rates of fertilizer result in decreased susceptibility to X. campestris pv. dieffenbachiae.

FUNGAL PROBLEMS

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1) Anthracnose and brown leaf spot (Colletotrichum or Leptosphaeria)

Symptoms -

Symptoms of these two leaf spots are very similar, with both occurring primarily during the cooler, winter months. Leaf spots are initially tan and water-soaked and may have a bright yellow halo. Fruiting bodies of the causal organism (Glomerella or Colletotrichum spp. [anthracnose]) or Leptosphaeria sp. (brown leaf spot) appear in concentric rings of tiny black specks within the leaf spot.

Control -

Keep foliage dry, and protect from cold water drips due to condensation on overhead structures.

2) Fusarium stem rot (Fusarium solani)

Symptoms -

Fusarium stem rot typically appears as a soft, mushy rot at the base of a cutting or rooted plant. The rotten area frequently has a purplish or reddish margin. Infection of leaves under very wet conditions results in tan, papery leaf spots with concentric rings of light and dark tissue. Fusarium solani forms tiny, bright red, globular structures (fruiting bodies) at stem bases on severely infected plants.

Control -

Remove infected plants from stock areas as soon as they are detected. Since Fusarium stem rot appears similar to Erwinia stem rot, accurate disease diagnosis is very important prior to choice and application of pesticides.

3) Myrothecium leaf spot and petiole rot (Myrothecium roridum)

Symptoms -

Myrothecium leaf spot most frequently appears on wounded areas of leaves such as tips and breaks in the main vein which occur during handling. The leaf spots are watery and nearly always contain the black and white fungal fruiting bodies in concentric rings near the outer edge of the spot. They are seen on the leaf undersides. The presence of these bodies is good evidence that the cause is Myrothecium. Newly planted, tissue-cultured explants are especially susceptible to this disease. The primary symptom on these explants is petiole rot starting with the oldest leaves although leafspot can occur as well.

Control -

Preventive treatments to newly transplanted tissue-cultured plants is recommended. Avoid wounding leaves and keep the foliage as dry as possible. Many other plants are hosts of M. roridum such as Aglaonema, Aphelandra, Begonia, Calathea, Spathiphyllum and Syngonium and these plants must be included in control programs.

4) Phytophthora stem rot and leaf spot

Symptoms -

This disease occurs primarily on plants grown in or on the ground in south Florida. Leaf spots are initially small and water-soaked, with irregular margins. They may become tan and papery if conditions are dry or their centers may fall out if conditions are wet. Stem rot usually begins at the soil line where the stem becomes soft and watery and lower leaves turn yellow. Eventually, the area becomes sunken and a cavity may form and result in lodging of the stem.

Control -

Growing plants on raised benches, away from the natural source of infection (the soil), is the best way to avoid this disease. Due to similarities between this and several other diseases, diagnosis must be confirmed by a diagnostic laboratory before optimum control strategies can be chosen.

VIRAL PROBLEMS

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1) Dasheen mosaic virus (DMV)

Symptoms -

Dasheen mosaic virus is most severe on `Perfection' and related cultivars of Dieffenbachia. Symptoms which include mosaic, leaf distortion and stunting, appear periodically during the year. See the table below for symptom differences among some cultivars.

Control -

DMV is spread by both aphids and man although the latter is the more common vector. It is very important to use pathogen-free stock since the symptoms of DMVare not always noticeable. No chemicals have any known effects on this virus disease. Other hosts such as Aglaonema, Philodendron and Spathiphyllum must be monitored for symptoms, since they can act as a reservoir for the virus.

Table 2. Susceptibility of some dieffenbachias to Xanthomonas campestris pv. dieffenbachiae and Dasheen Mosaic Virus.

CULTIVAR		XANTHOMONAS		DASHEEN MOSAIC VIRUS
Amoena			not tested		slight
Bausei 			slight			hypersensitive, dies
Camille			slight			chronic, severe
Compacta		slight			chronic, severe
Maculata		not tested		moderate
Memoria-corsii		slight			hypersensitive, dies
Perfection		slight			chronic, severe
Rudolph Roehrs		not tested		moderate
Star White		slight			not tested
Starry Nights		slight			not tested
Triumph			moderate		not tested
Tropic Star		resistant		not tested
Victory			moderate		not tested

INSECT AND RELATED PROBLEMS

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The most serious pest which attacks Dieffenbachia spp. is the two-spotted spider mite. Plants can become infested with this pest at any time during the year. Multiple applications of pesticides are needed if quality plants are to be grown. There are other less serious pests which require control butonly when they are observed. In the control section for each pest, some of the many registered and effective pesticides are listed. For a complete listing please consult the references listed 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. The root systems of Dieffenbachia spp. are sometimes infested with a small reddish aphid. This aphid (rice root aphid) can be found by removing the plant from its container and inspecting the roots with a hand lens.

Control -

Aphids are relatively easy to control with many registered materials.

2) Mealybugs

Symptoms -

Mealybug eggs appear as white, cottony masses in leaf axils, on lower leaf surfaces and on roots. Honeydew and sooty mold are often present and infested plants become stunted. With severe infestations, plant parts die.

Control -

Mealybugs are difficult to control especially when they are mature. Control measures should be aimed at killing this pest when it is in the crawler stage. Systemic materials are preferred.

3) Mites

Symptoms -

Two-spotted spider mites are very small and go unnoticed until plants begin to turn yellow or become speckled due to the feeding of this pest. Webbing, loss of leaves and plant death can occur when mite populations reach high levels.

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. Biological control programs have worked in small scale studies but remain unproven in commercial greenhouses.

4) Scales

Symptoms -

Infested plants become weakened or stunted and begin to die. Scales can be found feeding on leaves, petioles, or stems. Their shapes, sizes and colors are variable.

Control -

See mealybugs.

5) Thrips

Symptoms -

Curled or distorted leaves with silver-gray scars where feeding has occurred.

Control -

Many materials are registered for thrips 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.

Reference Pest Control Guides Here

REFERENCES

1. ben-Jaacov, J., R.T. Poole and C.A. Conover. 1985. Long-term dark storage of Dieffenbachia sprayed with cytokinin. Gartenbauwissenschaft 50(1):19022.

2. Chase, A.R. 1983. Phytotoxicity of some fungicides used on tropical foliage plants. ARC-Apopka Research Report RH-83-2.

3. Conover, C.A., R.T. Poole and T.A. Nell. 1982. Influence of intensity and duration of cool white fluorescent lighting and fertilizer on growth and quality of foliage plants. J. Amer. Soc. Hort. Sci. 107(5):817-822.

4. Henny, R.J. 1986. Increasing basal shoot production in a nonbranching Dieffenbachia hybrid with BA. HortScience 21(6):1386-1388.

5. Mortensen, L.M. and S.O. Grimstad. 1990. The effect of lighting period and photon fluxdensity on growth of six foliage plants. Scientia Horticulturae 41(4):337-342.

6. Mortensen, L.M. and R. Olsen. 1987. Light acclimatization of some foliage plants. Gartenbauwissenschaft 52(4):157-161.

7. Poole, R.T., C.A. Conover and A.R. Chase. 1988. Chemical composition of good quality tropical plants. Revision. CFREC-Apopka Research Report RH-88-6.

8. Poole, R.T. and C.A. Conover. 1989. Fertilization of four indoor foliage plants with Osmocote or Nutricote. J. Environ. Hort. 7(3):102-108.

9. Poole, R.T. and C.A. Conover. 1985. Boron and fluoride toxicity of foliage plants. AREC-Apopka Research Report RH-85-19.

10. Poole, R.T. and C.A. Conover. 1986. Response of foliage plants to commercial interior paints. AREC-Apopka Research Report RH-86-15.

11. Poole, R.T. and C.A. Conover. 1989. Growth of Dieffenbachia and Gardenia in various potting ingredients. Proc. Fla. State Hort. Soc. 102:286-288.

12. Poole, R.T., C.A. Conover and A.R. Chase. 1989. Effects of sulfur application to media containing foliage plants. CFREC-Apopka Research Report RH-89-5.

13. Poole, R.T. and R.W. Henley. 1980. Fertilization and water use of Dieffenbachia maculata and Peperomia obtusifolia. Proc. Fla. State Hort. Soc. 93:162-164.

14. Semeniuk, P., H.E. Moline and J.A. Abbott. 1986. A comparison of the effects of ABA and an antitranspirant on chilling injury of coleus, cucumbers and dieffenbachia. J. Amer. Soc. Hort. Sci. 111(6):866-868.

15. Short, D.E. 1978. Phytotoxicity of insecticides and miticides to foliage and woody ornamental plants. Extension Entomology Report #57.

16. Short, D.E., L.S. Osborne and R.W. Henley. 1982. 1982-83 Insect and related arthropod management guide for commercial foliage and woody plants in Florida. Extension Entomology Report #52.

17. Simone, G.W. 1982. Disease control pesticides for foliage production-1982. Extension Plant Pathology Report #30.

18. Turner, M.A., D.L. Morgan and D.M. Reed. 1987. The effect of light quality and fertility on long term interior maintenance of selected foliage plants. J. Environ. Hort. 5(2):76-79.

19. Wang, Yin-tung. 1989. Medium and Hydrogel affect production and wilting of tropical ornamental plants. HortScience 24(6):941-944.

20. Yeager, T.H., R.D. Wright and S.J. Donahue. 1983. Comparison of pour-through and saturated pine bark extract N, P, K and pH levels. J. Amer. Soc. Hort. Sci. 108:112-114.