Pests of Specific Crops

Pest Description
Foliar Blights (Kabatina thujae, Seiridium cardinale and
Seiridium unicorne): Foliage on individual
branches turns yellow, then brown to grey
before shattering, eventually leaving large bare
areas. Twig canker/dieback often occurs on
new growth. These fungi also cause foliar
blights on Thuja.
Insects:
Cypress Tip Moth (Argyresthia cupressella): See
description under JUNIPERUS - JUNIPER.
Juniper Scale (Carulaspis juniperi): This scale attacks
cones, twigs and needles, causing bushes to
turn greyish or yellow. Little new growth is
produced and individual branches can die.
Little honeydew is generated. The adult scale is
grey and round. Crawlers appear in June.
CLEMATIS
Diseases:
Botrytis Blight (Botrytis cinerea): Is a common cause
of leaf blight on cuttings and greenhousegrown
plants. It causes large, necrotic leaf
lesions and dieback of petioles, often in
conjunction with Ascochyta. A grey, fuzzy
mould appears on dead tissue in humid
conditions.
Powdery Mildew (Erysiphe polygoni): Leaf and flower
surfaces become covered with white powdery
patches. Often occurs or is more severe on
plants grown in shade.
Stem Rot and Leaf Spot (“Clematis Wilt”) (Ascochyta
clematidina): Attacks the roots, crown and stem
near the soil line. Individual shoots wilt
suddenly when stems are infected and girdled
at the base. Wounds and warm, wet conditions
favour infection. On leaves, small water-soaked
spots with reddish margins enlarge to form
brown circular/oval lesions. Black fungal
fruiting bodies called “pycnidia” can
sometimes be seen on infected tissue.
Chemical Control
(rate per 100 L water; or per
unit area if indicated)
COPPER SPRAY 50: 400 g
If disease occurs every year,
spray once prior to fall rains
and every 14 days in spring to
protect new growth.
Cultural Management
Avoid crowding and overhead
watering. Avoid drought
stress. Prune out affected
branches below cankers.
Sanitize pruning tools between
cuts with 10% bleach, Lysol or
other disinfectant.
If damage is slight, infected
foliage can be pruned out in
mid-summer. See under
JUNIPERUS – JUNIPER.
See General Insect and Mite Management: Scales, Chapter 11.
SENATOR 70WP: 65-85 g
ROVRAL 50WP-WDG: 100 g
Crop injury may occur. Test on a
small area first before treating
entire crop.
See General Disease
Management: Botrytis Blight
and Storage Moulds, Chapter 9
and Stem Rot and Leaf Spot
(below).
See General Disease Management: Powdery Mildew, Chapter 9.
SENATOR 70WP: 65-85 g
Use disease-free stock plants
and maintain strict sanitation
at propagation. Remove and
destroy diseased plants.
Reduce greenhouse humidity
and overhead watering as
much as possible. The disease
is usually not a problem in the
landscape, since the humidity
is often too low for infection
to occur.
In Europe, there are reports of
a similar disease (“clematis
wilt”) being caused by a
Coniothyrium fungus. This
disease is not present in North
America.
10 • Pests of Specific Crops Nursery Production Guide