Plant Protection 3 : Selected Ornamentals, Fruit and Vegetables

Calendula
English marigold, pot marigold
Calendula officinalis
Family Asteraceae (daisy family)
PESTS AND DISEASES
Parasitic
Virus and virus-like diseases
Fungal diseases
Grey mould
Powdery mildew
Root, stem and collar rots
Rust
Smut
Nematode diseases
Root knot nematode
Insects and allied pests
Aphids
Caterpillars
Non-parasitic
PESTS AND DISEASES
Parasitic
VIRUS AND VIRUS-LIKE DISEASES
Several viruses have been recorded on calendula
but none appear to be serious.
Cucumber mosaic virus
Lettuce necrotic yellows virus
Tomato big bud mycoplasma (greening)
Tomato spotted wilt virus
Some are spread by insects and are seedborne.
See Annuals A 4.
FUNGAL DISEASES
Grey mould, Botrytis, flower blight (Botrytis
cinerea) may occur sporadically during moist
weather. See Greenhouses N 22.
Powdery mildew (Oidium spp.) is common.
Whitish mycelium covers leaves of plants grown
under excessively moist conditions. Circular spots
2-5 mm across first appear irregularly scattered
over leaves. Later the whole plant is affected and
may finally wither and die. See Annuals A 6.
Root, stem and collar rots
Ashy stem blight, charcoal rot, base rot
(Macrophomina phaseolina)
Rhizoctonia (Rhizoctonia solani)
Sclerotium (Sclerotium rolfsii)
Sclerotinia rot (Sclerotinia sclerotiorum)
See Annuals A 6, Vegetables M 7.
Rust (Puccinia lagenophorae) is a native rust and
a serious disease of Asteraceae, ie native plants,
eg Lagenophorae spp., Senecio spp., Erichtites
spp., exotic plants, eg calendula, cineraria,
English daisy (Bellis perennis), exotic weeds, eg
groundsel (Senecio vulgaris), and self-sown plants.
Pale yellow-green spots may develop on leaves,
stems and flower stalks (Fig. 22) during warm
humid weather. Clusters of minute orange cup-like
structures (aecia) later develop on these spots (Fig.
23). Masses of black spores (teliospores) may be
produced amongst the aecia. Both leaf surfaces
look as if they are covered with a yellow dust (rust
spores) and may shrivel up. See Annuals A 7.
Smut, fungal leaf spot (Entyloma calendulae,
Ustilaginales, Basidiomycetes) causes pale yellow
leaf spots about 5 mm across, which later turn
brown to black. Occasionally other fungi may also
cause leaf spots on calendula. See Annuals A 5,
Dahlia C 24.
NEMATODE DISEASES
Root knot nematode (Meloidogyne spp.) has
been recorded on C. officinalis and other
Calendula spp. See Vegetables M 10.
INSECTS AND ALLIED PESTS
Aphids (Aphididae, Hemiptera)
Green peach aphid (Myzus persicae)
Marigold aphid (Neotoxoptera oliveri)
These aphids infest new growth of calendula and a
range of other plants. They may damage calendula
during humid conditions in spring and autumn.
See Roses J 4.
Caterpillars (Lepidoptera)
Cabbage white butterfly (Pieris rapae)
Cluster caterpillar (Spodoptera litura)
Cutworms (Agrotis spp.) attack seedlings
Native budworm (Helicoverpa punctigera)
See Annuals A 8.
Others: Earth mites (Penthaleidae) may feed on
leaves, greenhouse whitefly (Trialeurodes
vaporariorum) may infest leaf undersurfaces,
leafhoppers (Cicadellidae) may feed on leaves.
Mealybugs (Pseudococcus sp.) feed on stems and
leaves. Plague thrips (Thrips imaginis) infests
flowers, vegetable weevil (Listroderes difficilis)
and other weevil larvae may feed on foliage.
Non-parasitic
Hen and chickens marigold (C. officinalis
prolifera) has an unusual form (Fig. 24). Nectar
scarabs (Phyllotocus spp.) and the mottled flower
scarab (Protaetia fusca) may damage petals with
their spiny legs. See Roses J 8.
SELECTED REFERENCES
Nowak, J. and Rudnicki, R. M. 1990. Postharvest
Handling & Storage of Cut Flowers, Florist Greens,
& Potted Plants. Timber Press, Portland, Oregon.
Pirone, P. P. 1978. Diseases & Pests of Ornamental
Plants. 5th edn. John Wiley & Sons, NY.
State/Territory Departments of Agriculture/Primary
Industry eg
Rust of Calendula, Cineraria and English Daisy
(NSW Agfact, Vic Agnote)
See Annuals and herbaceous perennials A 10
A 14
ANNUALS AND HERBACEOUS PERENNIALS
Remember, always check
for recent references