Common diseases and disorders of Bromelias

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


Pathogen - Low soil moisture or low humidity
Symptoms - Plants may wilt, although this is unusual for most bromeliads due to their rigid leaves. Sometimes the leaves will curl. Patches of tan or dead tissue form on the leaf edges and tips.
Control - Make sure plants receive adequate irrigation. Keep humidities high to reduce development of the leaf burn even when soil moisture is high. Reducing the light level and temperature can also reduce desiccation damage when humidities cannot be maintained at sufficiently high levels.

Erwinia blight
Pathogen - Erwinia spp.
Symptoms - A blackened, wet, slimy spot generally starts at the base of the plant. Plants wilt, collapse and usually die. A rotten, fishy odor may be present on severely rooted plants.
Control - Remove and destroy infected plants as soon as they are found. Keep watering to a minimum and avoid splashing since this can spread the bacterium to other plants. Irrigate early in the day to allow rapid drying of the foliage which reduces the ability of the bacterium to infect. Be sure to obtain an accurate diagnosis of the problem since several of the diseases caused by fungi appear similar. Do not use bactericides for control of Erwinia on bromeliads since they are not effective.

Helminthosporium leaf spot
Pathogen - Exserohilum rostratum
Symptoms - Initial spots are pinpoint, water-soaked and yellow. They are circular (1/16 to 1/8 inch diameter) to elliptical. Individual spots become sunken with brown centers and often have a yellow border. Under optimal conditions, spots merge to form large dead areas causing affected leaves to collapse and hang limply on the plant. This disease can be very serious on small plants when they are transplanted, since wounding creates more infection sites.
Control - The cultural controls listed for Erwinia blight are also effective for Helminthosporium leaf spot. Fungicides which control this leaf disease included chlorothalonil (Daconil 2787), mancozeb (Dithane T & O) and zineb (Ortho Zineb 75WP). Check fungicide labels for legal uses on bromeliads.

Fusarium rot
Pathogen - Fusarium sp.
Symptoms - Dieback, root and leaf rot may occur as a result of the Fusarium infection. Spots are generally tan and may be dry at times and appear sunken. The orange or tan colored spores of the pathogen form in these areas, and they spread easily by water or air since the spores are light weight. A water-soaked rot at the soil line is common as well as 1/16 to 1/8 inch roughly circular spots on the stem.
Control - Use the same cultural controls as listed for Erwinia blight. Thiophanate methyl (Domain or Cleary 3336) and mancozeb (Dithane T & O) are effective in controlling Fusarium diseases. Reduction of water applications greatly reduces spread of the pathogen to aerial portions of the plants, thus reducing disease severity. The majority of bromeliads are susceptible to this disease with infections occurring with or without obvious wounding.

Pythium root rot
Pathogen - Pythium spp.
Symptoms - Bromeliads infected with Pythium spp. turn a dull gray-green and may wilt. Stems become rotted at the soil line and upper portions of the plant collapse. Roots are darkened and mushy and generally sparse.
Control - Use pathogen-free pots and potting media and grow plants on raised benches. Over-watering plants may predispose them to attack by root-rotting fungi. Soil drenches with the combination of etridiazol and thiophanate methyl (Banrot), etridiazol (Truban and Terrazole formulations) or metalaxyl (Subdue 2E) each aid in control of stem and root rots caused by Pythium spp.

Rhizoctonia aerial blight (Rhizoctonia solani)
Symptoms - A mass of brownish mycelia can cover infected plants. Growth of mycelia from the potting medium onto the plant 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 development of obvious symptoms. Rhizoctonia mycelia are usually reddish-brown in color and have the consistency of a spider web. Under wet conditions, Rhizoctonia spots are gray or black and mushy.
Control - Chemical control of diseases caused by Rhizoctonia has been investigated on many plants using a variety of fungicides. The fungicide most widely for soil drenches control of Rhizoctonia diseases is thiophanate methyl (Domain or Cleary 3336). Cultural controls are the same as those listed for Pythium root rot.

Pathogen - Puccinia tillandsia
Symptoms - Rust disease is easily recognized because of the reddish-brown or yellowish-brown pustules which occur on leaf undersides. The spots first appear white or light yellow when viewed from the upper surface. Most rust pustules form on the undersides of leaves but some can be found on leaf upper sides.
Control - Rust diseases are inhibited by frequent rainfall or irrigation and high temperatures. Fungicides for rust control on some ornamentals include chlorothalonil (Daconil 2787), ferbam (Carbamate), triadimefon (Bayleton) and mancozeb (Dithane T & O). Few fungicides are labelled for use on bromeliads so be careful to check labels for legal uses on your plants.

Slime mold
Pathogen - one of many genera of myxomycetes
Symptoms - Small tan or creamy colored structures sometimes similar in appearance to rust diseases found anywhere on the plant surface. They are easy to scrape off the leaf surface. The cause of this problem is slime mold which is a saprophytic fungus that can grow on any surface including the potting medium, pots and the plant leaves.
Control - Fungicides have not been found effective in controlling slime molds. Keep pots as dry as feasible for good plant growth and grow on raised benches only.


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