Plant Health Problems
Diseases caused by Fungi:
Damping-off, Rhizoctonia solani, Pythium spp.
Seedlings either rot and do not germinate or germinate and collapse. The disease frequently attacks the base of the seedling and leaves a shriveled, dried-up stem at the base of the seedling.
Control can be achieved by using sterile potting media and fungicide-treated seed. If seedlings become symptomatic, rogue and discard all of the seedlings since asymptomatic seedlings may also be infected.
Root and crown rot, Rhizoctonia solani, Pythium spp., Fusarium spp.
Symptoms appear as wilting and a slow or rapid collapse of the plant. The roots can appear brown and water-soaked instead of white. A water-soaked lesion can often appear at the base of the stem.
Control can be achieved by using sterile potting media, clean pots, fungicide-treated seed and using a two-year rotation with nonsusceptible plants, such as corn, to prevent the buildup of pathogenic organisms. Affected plants should be rogued out and discarded.
Stem rot, Sclerotinia sclerotiorum.
Individual stalks begin to collapse and wilt. The interior of dead stems frequently reveals small, irregularly-shaped black structures called sclerotia.
Since the fungus lives in the soil, a two-year rotation with nonsusceptible plants, such as corn, to prevent the buildup of pathogenic organisms rotation can reduce the incidence of disease.
Botrytis blight, Botrytis cinerea.
Botrytis blight occurs on many different kinds of herbs. The disease appears when plants are grown under conditions of high humidity, such as in a terrarium. The disease appears as tan to brown spots on leaves that can be associated with a grayish mold colonizing the damaged area. Senescing flowers are particularly susceptible and frequently have papery spots on them.
Botrytis blight can be suppressed by avoiding overhead irrigation and watering in the morning to allow time for leaves and flowers to dry. Proper plant spacing can improve air drainage and rapid leaf drying. Control can also be achieved with the use of fungicide sprays applied as soon as symptoms are visible. Among the compounds registered for use in Connecticut is iprodione. Consult the label for dosage rates, safety precautions, and indoor use.