Home › Nursery Stock › Article

Detailed Guide to the Prevention and Control of Leaf Spot Disease in Dendrobium Orchids

Nursery Stock 0 views
Symptoms: The disease occurs on the leaves. Small brown spots first appear, then enlarge, with the center becoming necrotic and grayish-brown, measuring 5-10 mm in diameter. Small black dots appear on the surface of old lesions. Affected leaves turn yellow and drop, though there are differences among varieties; the nobile dendrobium group tends to shed leaves more heavily, and its growth and development are significantly stunted. Pathogen: Selenophoma dendrobii Abiko. It belongs to the fungi imperfecti (Deuteromycetes). Conidia are colorless, single-celled, crescent-shaped, measuring 5-8 * 1-2 micrometers.

Symptoms: The disease occurs on the leaves. Small brown spots first appear, then enlarge, with the center becoming necrotic and grayish-brown, measuring 5-10 mm in diameter. Small black dots appear on the surface of old lesions. Affected leaves turn yellow and drop, though there are differences among varieties; the nobile dendrobium group tends to shed leaves more heavily, and its growth and development are significantly stunted. Pathogen: Selenophoma dendrobii Abiko. It belongs to the fungi imperfecti (Deuteromycetes). Conidia are colorless, single-celled, crescent-shaped, measuring 5-8 * 1-2 micrometers. The hyphae are brown and septate. The growth and development temperature range is 5-30 degC, with around 25 degC being the optimum temperature for growth.

Transmission route: Mainly through airborne conidia. It occurs more frequently from autumn to spring, and generally affects the middle and lower leaves.

Prevention and control methods: 1. Promptly remove diseased leaves and dispose of them. 2. Chemical control: In the early stages of the disease, spray 75% chlorothalonil wettable powder at 600 times dilution, or 50% iprodione wettable powder at 1500 times dilution, 40% captan wettable powder at 400 times dilution, or 70% fosetyl-aluminum plus mancozeb wettable powder at 500 times dilution, or 50% thiophanate-methyl wettable powder at 500 times dilution, once every 10 days or so, for 2-3 consecutive sprays.

Related Articles