Diseases

Calibrachoa - Tobacco mosaic virus (TMV)

Tobacco mosaic virus (TMV) has a wide host range but is of special concern on solanaceous plants. Symptoms include yellow and green mottling, upward curling, necrotic leaf spots, leaf distortion, and overall stunting. Symptoms on plants in this photo are very subtle and could be mistaken for nutrient deficiency such as iron.

TMV is not transmitted by insects, but is transmitted mechanically in sap, by contact with contaminated equipment, by vegetative propagation, and it can be carried in seed. Once a plant is infected with a virus, it cannot be cured.

Botrytis on Spring Crops

Cloudy, rainy weather, cool nights and greenhouses full of plants provide an ideal environment for Botrytis. Botrytis symptoms may include leaf spots, flower blights, bud rots, stem cankers, and stem and crown rots and can be mistaken for other causes.

Calibrachoa - Calibrachoa Mottle Virus (CbMV)

Symptoms of Calibrachoa mottle virus (CbMV) include leaf yellowing, leaf spots and dieback. Plants that show yellowing can be mistaken for iron deficiency. Symptoms of Calibrachoa mottle virus develop when plants are stressed.  
CbMV is transmitted mechanically in sap and by propagation. No insect vectors have been found to date.

Once a plant is infected with a virus, it cannot be cured. Management includes discarding and destroying infected plants, including roots.

Crown Gall - Agrobacterium tumefaciens

The bacterium Agrobacterium tumefaciens is a soil borne pathogen that causes crown gall on many types of plants. In greenhouse crops, Crown Gall has been diagnosed in recent years on mums, argyranthemum and osteospermum and this year it has been found in some of Selecta's lobelia production. Selecta found symptomatic plants in four varieties of Magadi Lobelia: Blue, Compact Dark Blue, White and Basket White. Selecta sent information out to their customers and is discontinuing shipments of Lobelia for this spring.

Poinsettia - Pythium root rot

This poinsettia was diagnosed with Pythium root rot and excess soluble salts. Plants had full root system that turned brown and collapsed. After being diagnosed, plants were watered with clear water to leach excess fertilizer from the roots and a fungicide was applied. These are the roots one week after watering with clear water. Notice the new white roots beginning to re-grow.

The close-up photo shows decayed roots. The outer root easily sloughs off when pulled with finger tips, leaving the inside strand of root (rat tail).

Pepper - Tobacco Mosaic Virus (TMV)

Tobacco Mosaic Virus (TMV) has a very wide host range including tobacco, vegetables (especially in the Solanaceous family), and many ornamental species. Unlike many plant viruses, it is not vectored by aphids, thrips, or leafhoppers; TMV spreads very efficiently in plant sap. This virus is transmitted by tools and workers as well as plant to plant contact where there wounds caused by handling or insects. TMV can also persist in tobacco products and workers should wash their hands after using tobacco products. There is no cure or treatment for TMV.

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