LEAF NECROSIS: Severe

Ailments Orchid Doctor

by Robert M. [Bert] Hamilton (Compiler)

Originally published in The Orchid Doctor in 1980 and 1988

Posted by Sys Admin almost 8 years ago.

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It is caused by Cymbidium necrotic ringspot virus; deadly but rare; new and old growths are killed; destroy plant. N323 see also Necrotic spots
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Leaf Ailments Comments
LEAF CRINKLING: On Dendrobiums Caused by inadequate watering. A79-784 0
LEAF DIE-BACK: Fungus Disease Spreads slowly from the tip through the leaf unless cut off; Glomerella cincta infects the tip and spreads backwards with a marked line between good and diseased tissue; control with Benlate. A73-811; it is caused by a water mold Pythium splendens; cut it off and use a fungicide. S204 0
LEAF DIE-BACK: Glomerella cincta Fungus starts at the leaf tip and spreads fully towards the base; areas turn brown, later dry out; cut it out; treat with Tersan. N318 0
LEAF FALL: As An Indicator It is no cause for concern as most plants shed leaves sooner or later in the natural course of events. A84-584It is usually natural; leaves fall from bulbs three or four years old; may be a cultural fault such as under- or over-watering; check the roots -- if they are brown, soggy, decayed it means over-watering; if white and dry, under-watering; no great problem. 0D66-316 0
LEAF NECROSIS: Cymbidium Mosaic Virus The initial infection is conspicuous; kills some leaves, afterwards milder symptoms show; plant becomes a reservoir of infection; brown sunken pits on underside of leaves; black and chlorotic alternate streaks,or rings of dead tissue appear on the underside; some length-wise stripes of white or gray; roughness. N323 0
LEAF ROLLERS: Characteristics and Controls The larvae of Tortricid moths can be destructive; they tie leaves together and feed on terminal growths and bore into the buds and shoots; caterpillars are yellowish or greenish, 1/2 inch long, they wriggle violently when disturbed; spray with Zectran or Sevin. RMH 0
LEAF ROT: Erwinia and Sp. of Pseudomonas Stimulated by warm, damp weather; areas are yellowish or brownish and watery; the bacteria spread quickly; cut off whole leaf; soak the plant in Anti-Damp or Natriphene. A73-815 0
LEAF SPOTS: Anthracnose Is a Common Cause Small spots occasionally run together; tissue between becomes tan and papery; fruiting bodies show as black dots sometimes as rings; sometimes caused by Circospora sp. (see Leaf-spot) with brown sunken spots or streaks; for all kinds cut off affected leaves; spray with Captan, Physan 20 or Benlate. A73-811 0
LEAF TIP BLACKENING: On Main Leaflet of Cattleyas Caused by Phytophora or Pythium diseases; best controlled by Truban (ethazole) at 1 tpg.; avoid syringing with water at adverse times. A79-1112 0
LEAF TIP BURN: Cercospora odontoglossi A fungus attacks cattleya seedlings and others; tiny raised spots dark brown in color under the leaves spread to the whole leaf; resembles spider mite injury; best control with benomyl 50% at 1 ttpg. three times fortnightly plus a wetting agent; or Ferbam, Daconil 2887, Zineb, Captan, twice a month. B22; BU25 0
LEAF TIP BURN: Cercospora peristeriae Yellowish to pale brown, oval to elongate spots appear on the under surfaces; move to the top; spray with benomyl 50WP, at 1 tpg. fortnightly to check infection. B20; BU20 0
LEAF TIP BURN: Cercospora Sp. Several fungi attack specifically cattleyas, vandaceous types, oncidiums, cymbidiums, odontoglossums; spray preferably with benomyl 50WP at 1 ttpg. fortnightly, or use ferbam or zineb; use a wetting agent. BU26+They first appear as yellowish spots; then sunken and dark; or, small brown spots which darken and become depressed or, as brown streaks; in all cases they enlarge and kill tissue; dip or soak in fungicide, such as Captan,Ferbam, Zineb, Benlate. N318 0
LEAF TIP BURN: Diplodia laeliocattleyae Sometimes found on cattleyas in Florida; small, yellow areas on top or bottom of leaf turn brown and become black, greasy areas; fruiting structures develop on older leaves; destroy all leaves; treat as for wound-infecting parasites and spray with fungicide. B27; BU35 0
LEAF TIP BURN: Fungus Invasion of Leaf Cut out the diseased parts before treating with AntiDamp or Tersan; frequently seen on cymbidiums with pendant leaf-tips which hold drops of water which attract Botrytis; use Benlate. A73-811 0
LEAF TIP BURN: Phyllostictina pyrjformis Leaf-spotting fungus infrequent in Florida and not destructive but makes plants unsightly; tiny, slightly yellow spot, sunken, becomes larger, tan to dark brown; red to purple-black margin; round singly, irregular when coalesced,on pseudobulb oval; about 1/4 inch; spray with common fungicide such as benomyl. B25+ 0
LEAF TIP BURN: Septoria selenophomoides Fungus found on many imported genera; tiny sunken yellow lesions on top or bottom surface; enlarge and become dark brown or black; spots sometimes coalesce; on older plants and fallen leaves fruiting bodies become a source of infection to other plants; destroy all fallen leaves; spray with benomyl three times fortnightly, or Daconil 2787, or ferbam; spray especially a month before regular leaf fall on dendrobiums. B24+; BU-30+ 0
LEAF TIP DIE-BACK: Cause It is caused by high soluble salt content in the water, or by fertilizer salts not flushed out. A70-55; A78-13 0
LEAF TIP DIE-BACK: Disorder of Cattleya Types Newly matured leaves show darkening of veins very close to the tip, later developing into dark, sunken spots which spread to cover three-quarters of the leaf tip ; most active in summer; many theories advanced; the conclusion: calcium deficiency. A73-227+ 0
LEAF-TIP NECROSIS: Causes It is a nutritional and compost problem and is not caused by fungal attacks as is commonly supposed; an unhealthy root system is likely at the base of it. AU84-199; it can be caused by a mix which stays too wet, or, a deficiency of magnesium and/or iron; or, possibly a buildup of sodium or sulfur. AU84-204 0

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