| Disease (causal agent) |
Symptoms |
Survival of pathogen and effect of environment |
Comments on control |
Cottony rot
(Sclerotinia sclerotiorum) |
Plants wilt and die. Basal stem
rot. Cottony, white mycelium present in and on stems under moist conditions. Long, black sclerotia form in and on stems. |
Fungus survives in soil as
sclerotia, which germinate after a cold‑dormancy period to produce
airborne spores. Direct infection from sclerotia may occur. Fungus has a wide host range. Favored by overhead irrigation and high humidity. |
Avoid planting in infested fields
or fumigate soil. Treat soil with PCNB before planting. Carrots, celery, and
lettuce are common hosts. Irrigate early in the day so plants dry quickly.
Spray base of plants and lower foliage with thiophanate-methyl. more info * |
Crown gall
(Agrobacterium tumefaciens) |
Spherical galls on stems most often at base of plant. Heavily infected plants are stunted. |
Soilborne bacterium with a wide host range. Survives in soil for several years. |
Plant disease‑free plants.
Propagate from clean plants. Dip or spray cuttings with Agrobacterium radiobacter 'K84' immediately if wounded. Avoid wounds,
especially when plants are wet. more
info * |
Pythium root rot
(Pythium spp.) |
Plants stunted as a result of reduced root system. Small roots rotted. |
Soilborne pathogen. Spores spread with soil and water. Favored by excess soil moisture and poor drainage. |
Avoid poorly drained soils. Plant
on raised beds. Reduce amount of irrigation water. Mefenoxam applied at
transplanting will help get plants started. more info * |
Root knot nematode
(Meloidogyne hapla) |
Plants are stunted; swellings or galls on roots. Galls have lateral roots. |
Nematodes survive in soil as eggs.
Disease is usually most severe in sandy soils. Also prevalent in cooler
climates: optimum temperature to invade roots is 59° to 68°F (15° to 20°C) and for growth and reproductions is 68° to 77°F (20° to 25°C). |
Preplant fumigate with methyl bromide‑chloropicrin mixture or solarize soil.** |
Root lesion nematode
(Pratylenchus spp.) |
Plants are stunted. Necrotic lesions on roots that involve the cortex and deeper tissues. |
Nematodes survive in soil as adults, larvae, and eggs. |
Preplant fumigate with methyl bromide‑chloropicrin mixture or solarize soil. |
Southern blight
(Sclerotium rolfsii) |
Plants wilt and collapse. Basal
stem and roots are rotted. White cottony fungus growth may be present on
infected parts and soil. Small (0.625 inch), tan or brown sclerotia form on rotted tissues and in soil. |
Sclerotia survive in soil. No
airborne spores are formed. Sclerotia germinate and infect susceptible plants. Fungus has a wide host range. |
Avoid fields where the disease has
occurred or fumigate with methyl bromide‑chloropicrin mixture. PCNB
applied to the base of plants or as a preplant treatment will help. more info * |
| Marguerite
Daisy is also susceptible to downy mildew* (Peronospora radii), powdery mildew * (Erysiphe cichoracearum), Verticillium wilt * (Verticillium dahliae),
leaf spot (Ramularia sp.), curly top (curly top virus), and aster yellows (aster yellows phytoplasma). |
| * For additional information, see section on Key Diseases. |
| ** For additional information, see section on Nematodes. |
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