Begonia Diseases
| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Bacterial Leaf and Spot Blight |
Water-soaked areas surrounded by
yellow develop on leaves.
Plants slowly die one leaf at a time. |
Xanthomonas
campestris pv. begoniae |
Purchase plants free of the disease.
Discard infected plants; particularly Rieger-types, which are
systemically infected. Rex and tuberous types are not systemically
infected (see note for resistant cultivars). Remove infected
leaves from these types. Water in a manner that avoids splashing
and keeps the surfaces of the leaves dry. Do not propagate from
infected plants. Destroy crop debris. |
| Botrytis Blight |
Cuttings rot at their base. Tan spots
develop on leaves. Established plants rot at the crown. Infected
tissue is covered with dusty gray fungal growth. |
Botrytis
cinerea |
Maintain low humidity by spacing
plants and venting to improve air circulation. Remove dead and
dying flowers and leaves. To protect healthy plants, apply cupric
hydroxide, fludioxonil, mancozeb, copper sulfate, or chlorothalonil. |
| Foliar Nematode |
Plants are stunted. Excessive red
pigment develops in infected leaves. Bronzed or water-soaked
areas develop on leaves of some cultivars. Fibrous-rooted cultivars
have small brown leaf spots. Some cultivars exhibit no symptoms
despite heavy infection. |
Aphelenchoides
fragariae |
Purchase nematode-free plants. Avoid
overhead irrigation and splashing. Discard infected plants. |
| Powdery Mildew |
White, mealy fungal growth develops
on leaves, flowers, and stems. Tissue beneath the fungus may
die. |
Oidium |
Examine plants carefully and frequently
to detect the onset of disease. Maintain a fungicide program
to protect plants. Apply Ampelomyces,
triforine, fenarimol, piperalin, myclobutanil, or triadimefon. |
| Pythium Rot |
Seedlings die. Shiny blackened areas
develop on the stems and petioles of established plants at and
just above the soil line as plants collapse and die. |
Pythium |
Plant in pasteurized potting media.
Keep hose ends off the ground. Do not over water. To protect
healthy plants, apply etridiazole, etridiazole + thiophanate
methyl, mefenoxam, fosetyl-Al, or metalaxyl. |
| Rhizoctonia Crown Rot |
Stems rot at the soil line. Plants
collapse and die. A fine webbing of fungal growth may be seen
between the infected stems and nearby soil particles. |
Rhizoctonia |
Plant in pasteurized potting media.
To protect healthy plants, apply PCNB, thiophanate methyl, fludioxonil,
or etridiazole + thiophanate methyl. |
| Viruses |
Mosaic, malformed leaves, pale yellow
ring spots, severe chlorotic mottling of leaves, or plant stunting
may occur. |
Tomato spotted wilt, impatiens necrotic
spot, tobacco ring spot, broadbean wilt, cucumber mosaic, tobacco
necrosis virus |
Purchase plants free of symptoms.
Discard infected plants. Plant in pasteurized potting media.
Maintain good aphid control to reduce spread. |
NOTE: Rex begonia cultivars
highly susceptible to bacterial leaf spot: Dew Drop, Meteor, Mikado,
Phoenix Red; moderately susceptible: Cleopatra, Her Majesty, Red
Pride, Tiger Kitten; slightly susceptible: Duarten, Helen Teupel,
Marion Louise, Pauline, Peace, Red Dot, Vesuvius. (From:
Chase, A. R. 1992. "Resistance of some Rex begonia cultivars
to Xanthomonas campestris pv. begoniae." CFREC-Apopka
Research Report RH-92-18. University of Florida)
Fungicides mentioned above:
| COMMON NAME |
TRADE NAME |
| Ampelomyces quisqualis |
AQ-10 (biocontrol) |
| chlorothalonil |
Exotherm Termil, Daconil |
| copper sulfate |
Phyton 27 |
| cupric hydroxide |
Kocide, Nu-Cop |
| etridiazole |
Terrazole, Truban |
| etridiazole + thiophanate methyl |
Banrot |
| fenarimol |
Rubigan |
| fludioxonil |
Medallion |
| fosetyl-Al |
Aliette |
| mancozeb + thiophanate methyl |
Zyban, Duosan |
| metalaxyl |
Subdue |
| myclobutanil |
Systhane |
| PCNB |
Terraclor, Defend, PCNB |
| thiophanate methyl |
3336 |
| triadimefon |
Bayleton, Strike |
| triforine |
Triforine |
|
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