Pests of Specific Crops

Pest Description
Sooty Mould: Black mould appears on leaves. It
grows on honeydew produced by aphids,
whiteflies, scales, mealy bugs and leafhoppers.
Chemical Control
(rate per 100 L water; or per
POPULUS - POPLAR AND ASPEN (COTTONWOOD)
Diseases:
Leaf Blister (Taphrina spp.): Bright, yellow-brown
blisters of various sizes occur on leaves after
long periods of cool, wet weather.
Leaf Spot (Marssonina populi, Septoria populicola and
other spp.): Brown spots or blotches appear on
leaves and small cankers form on green twigs.
Early defoliation and reduced growth may
occur especially during wet years when
symptoms are severe.
Rust (Melampsora spp.): Yellow, then brown leaf spots
occur in late summer/fall. Leaves may drop
early. Spores released from yellow pustules on
leaves cause the disease to spread. Older
pustules turn brown. Alternate hosts are Abies,
Larix, Picea, Pinus, Pseudotsuga and Tsuga.
Needles are infected in spring by spores from
fallen poplar leaves.
Shoot Blight (Venturia tremulae): Dark brown to black
lesions form on succulent leaves and new
shoots. Leaves wither and dying shoots form a
“shepherd’s crook” at the tip.
Insects:
Poplar and Willow Borer (Cryptorhynchus lapathi):
Larvae (grubs) attack limbs and trunks causing
black, swollen scars. Old damage is indicated
by death of small stems, 2-8 cm in diameter.
Current damage is indicated by splits and holes
in bark from which sap and sawdust exude.
Affected limbs may break off. The adult weevil
is greyish-brown with a wide cream-coloured
band across the mid-section of the body. It is 1
cm long and appears in mid-summer.
Satin Moth (Leucoma salicis): Larvae are defoliators of
poplars and willows. Adult moths are pure
satin white. Caterpillars are black with red and
white markings and grow up to 5 cm long.
They appear in May and late July and
skeletonize the foliage until fall.
Cultural Management
unit area if indicated)
Control insects to reduce sooty mould. Successful insect
control will prevent sooty mould. See the Ministry’s Home and
Garden Guide for landscape tree recommendations.
DACONIL 2787F: 250 mL
DACONIL Ultrex: 150 g
SENATOR 70WP: 110 g
Early spring applications at
budbreak may be justified if trees
are small enough to spray.
Control is not usually
required.
This disease rarely
requires control on larger
trees in the nursery or
landscape.
No fungicides are specifically registered for this disease.
Application of fungicides for leaf spot (above) may help to
control this disease if applied before the disease is
widespread.
Management: Collect fallen leaves and compost, burn, or
bury. This disease is very common in late summer on native
poplar and cottonwood. It usually does not damage trees,
although it can be unsightly on landscape and nursery trees.
More severe damage can occur on the alternate hosts if grown
nearby.
Fungicides applied for leaf spot
(above) should also help to
control shoot blight. Apply at
bud-break if needed.
The fungus can overwinter
on diseased shoots and
leaves. Prune out and
destroy affected shoots.
Rake up and burn, bury or
compost leaves in fall.
Remove and burn badly
infested trees and limbs.
The boring grubs cannot
be controlled. Insecticides
are directed against adults
and new, pre-boring
grubs. See General Insect
and Mite Management: Bark
Beetles and Wood Borers,
Chapter 11.
AMBUSH 500EC: 7 mL
BIOPROTEC CAF: 4 L/ha
See General Insect and Mite Management: Caterpillars and Moths,
Chapter 11.
Nursery Production Guide Pests of Specific Crops • 29