NURSERY/GREENHOUSE DISEASES

Diseases of Greenhouse Ornamental Crops
Authors: Mike Arnold, Larry Barnes, Bart Drees, Dan Lineberger, Don Wilkerson, Priscilla Files

Plant Pathology Update
Author: Larry W. Barnes

Watch for Pythium & Phytophthora Problems
Each year during the spring months, there are a significant number of plant disease problems submitted to the Texas Plant Disease Diagnostic Laboratory (TPDDL) resulting from infection by the water-mold pathogens,Pythium and Phytophthora. These specimens range from pot crops and color (bedding plants) to woody ornamentals.
Author: Larry W. Barnes

Aerial Blight
Most susceptible plants: vinca.
This fungal pathogen causes a major disease in vinca in the landscape but it can also be a serious disease of greenhouse-grown vinca.

Bacterial Blight
Most susceptible plants: begonia, geranium, zinnia.
This disease can be devastating, causing loss of an entire crop. The pathogen is systemic so watch for symptoms and take immediate action upon detection.

Bacterial Stem Rots
Most susceptible plants: kalanchoe.
Infected plants develop a black, soil-line lesion that usually results in stem weakening, lower stem breakage, plant stunting, plant wilt and plant death. The soil-line lesion is usually very soft and mushy in texture.

Black Root Rot
Most susceptible plants: pansy, vinca.
Black root rot can cause significant production losses in greenhouse crops. Although this fungal pathogen also has a very wide host range, the most serious problems occurr on pansy and vinca. Pansy and vinca plug infection has resulted in significant plant losses.

Botrytis Blight
Most susceptible plants: exacum, geranium, impatiens.
Probably the most common and troubling greenhouse pathogen is the gray mold fungus, Botrytis cinerea. Botrytis can infect any above-ground portion of the plant. Wounded or stressed tissues are much more susceptible to infection. Botrytis can cause serious problems in geranium both as a flower blight as well as a stem/cutting rot.

Crown and Root Rot
Most susceptible plants: gerbera daisy, gloxinia, pansy
This disease is second only to Impatiens Necrotic Spot virus as a serious pathogen in gloxinia. Root and crown rot can also cause serious losses in gerbera daisy production. Infection can occur at any stage of gerbera production but seems to be more common after flowering begins.

Fusarium Stem and Root Rot
Most susceptible plants: exacum
Infection by this fungal pathogen can cause rapid wilt and plant decline. This disease can easily be confused with Impatiens Necrotic Spot Virus and Botrytis stem infection.

Fusarium Wilt
Most susceptible plants: cyclamen
Infection can occur at the seedling stage, with symptoms becoming obvious in older plants following an environmental trigger such as hot greenhouse temperatures.

Impatiens Necrotic Spot Virus - Part 1
Impatiens necrotic spot virus (INSV) can be one of the most serious viral pathogens of greenhouse crops. INSV is sometimes confused with tomato spotted wilt virus (TSWV), a closely related virus that shares many similarities and characteristics with INSV.
Author: Larry W. Barnes

Impatiens Necrotic Spot Virus
Most susceptible plants: begonia, chrysanthemum, exacum, gloxinia, impatiens, vinca
This is one of the most serious diseases of greenhouse crops. INSV has a very large host range, numbering more than 648 different plant species. It is the number one disease of gloxinia and impatiens. INSV is transmitted by the thrips insect; it is not known to be routinely transmitted by any other means. One of the most frustrating features of INSV is that infection can result in a number of different symptoms.

Poinsettia Disease Primer
Poinsettia production is in full swing and growers should be aware of several disease problems that can cause at various production phases. Careful attention to sanitation, irrigation, spacing, pesticide application, and environmental conditions in the greenhouse can help minimize disease problems.
Author: Larry Barnes

Powdery Mildew
Most susceptible plants: begonia, chrysanthemum, gerbera daisy, kalanchoe, zinnia
Although most greenhouse crops can be infected by powdery mildew pathogens, each powdery mildew pathogen is specific to its host. The powdery mildew that infects gerbera daisy will not infect zinnia, etc.

Pythium Black Leg
Most susceptible plants: geranium
Symptoms:
Pythium black leg develops as a distinctive blackened deterioration of the lower stem, starting at the soil line. Infected stem tissue softens and deteriorates, damaging the plant's vascular tissue and interfering with movement of moisture to the leaves and other above-ground tissue. Plant wilt, stem collapse and plant death commonly result.