Orchid doctor

LEAF-SPOT NECROSIS: Control by Various Compost Techniques

Ailments Orchid Doctor

by Robert M. Hamilton (Compiler)

Originally published in The Orchid Doctor in 1980 and 1988

Posted by Sys Admin about 3 years ago.

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A build-up of undissolved solutes in water cause the leaves to die at the tip; it also causes punctate areas of necrosis of tender leaves of species such as stanhopeas, pescatoreas, lyxastes, etc.; good drainage and much leaching helps; the "wet growing" system is described, emphasizing use of Palco wool and plastic chips medium; refer to OD68-8
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Leaf-spot Comments
LEAF-SPOT: Cercospora angraeci Fungus found in Florida in 1964; tiny tan or light brown spots become dark purple-brown; may occur in a circular pattern or on a whole leaf; spray with benomyl 50WP at 1 ttpg. fortnightly three times and use a wetting agent; or, with Daconyl 2787; destroy leaves; space plants out. BU24 This has been reported on various angraecums, dendrobiums and odontoglossums. AH86-77 0
LEAF-SPOT: Cercospora dendrobii Infects dendrobiums as light yellow area under leaves; circular enlargement; spots become sunken, purple-black, yellow margined; corresponding yellow-green areas follow on top; spreads to other plants; spray with benomyl 50WP at 1 ttpg. fortnightly, or with Ferbam, or Zineb. B21; BU20 0
LEAF-SPOT: Cercospora dendrobii and Others Control is a spray with benomyl or Benlate 20 at 1 ttpg. AH86-76 0
LEAF-SPOT: Cercospora dendrobii, C. epipactis, C. peristeriae Plus Six Other Cercospora Sp. Usually shows as yellowish or brown spots on underside of leaves; sometimes join together to form larger spots; all are controlled by spraying with Benlate at 1 ttpg. with a wetting agent, and repeat at 15 day intervals three times to eliminate it from the greenhouse; illus. AH23+ 0
LEAF-SPOT: Cercospora epipactidis On Phaius grandifolius, etc.; tiny sunken, yellow spots under leaves, later on top also; enlarge in a few days and become sunken, purple-black; about 1/2 inch or larger; on old lesions center falls out; spray with benomyl at 1 ttpg., or with Ferbam or Zineb. B18; BU19 0
LEAF-SPOT: Cercospora odontoglossi Control by spraying with benomyl (Benlate 50W) at 1 ttpg plus wetting agent, three times at 15 day intervals. AH86-80 0
LEAF-SPOT: Diplodia Laeliocatleyae Small yellow areas on top and bottom of leaf turn brown, become black and greasy; spray with fungicide such as Fore/ Dithane; Benlate is not effective in this case. AH86-70 0
LEAF-SPOT: Phyllosticta pyriformis It is infrequent in Florida; it blemishes the leaves; starts as tiny slightly yellow spots, sunken, which enlarge and turn tan to dark brown or red with black margins; control with benomyl (Benlate 50W) A86-814 0
LEAF-SPOT: Septoria selenophomoides Usually found on imported plants; starts as tiny yellow lesions, enlarges and turns dark, the spots coalesce; leaves soon fall and promote more infective spores; spray with benomyl (Benlate 50W) at 1 ttpg. three times fortnightly. AH86-69 0
LEAF-SPOT: Soft Spots Slowly Cover the Whole Leaf The condition should be treated early with Truban, 1 to 1.5 tpg. thoroughly even to the point of drenching, after removing the blackening leaves; if Truban is unavailable use Lesan (Dexon). A81-688 0

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