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Root-of-the-Problem
Rose Chart |
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A rose problem is
almost always a reflection of the plant's environment.
Bad drainage, too little water, poor soil preparation,
insects, disease - all are environmental conditions that can
either be remedied or prevented from the start.
This chart,
prepared by Jackson & Perkins, will help you diagnose and
treat problems. Your local nursery staff or county
agricultural agent will be helpful in identifying a pest or
disease or in recommending a treatment.
The first line of
defense against any rose problem is a strong, healthy
plant. A little advance preparation such as the addition
of peat or well-composted organic material to the soil before
planting will provide a blooming environment. |
|
Regional Tips
|
| Northwest |
Plant
roses in late February, early March in coastal areas.
spring rains will promote and spread blackspot.
Cleanup of plant debris is a must. Winter lime-sulfur
sprays of dormant plants will help stop blackspot before it
begins. Powdery mildew is a problem in
mid-season. To help prevent, plant in an area where
there's good air circulation and avoid wetting rose foliage. |
| Southwest |
Prune
annually in December and January. Cut back about 1/2
the height of the plant. Irrigation is a
paramount concern when planning a rose garden. Hot,
dry summers are not difficult to grow in with efficient
watering and fertilizing techniques. Mulching
helps cool roots and retain moisture. |
| Northern
Areas |
Winter
protection needed. Mulch up over the grafted part of
the rose plant. (Some gardeners prefer planting the
graft about 1 inch below the surface.) |
| Midwest |
Mulch
for winter protection. Hot summers will promote insect
problems such as spider mite and thrips. |
| South |
Plant
roses in December, January. Nematodes can be a problem
in some areas because there is no winter-kill. Downy
mildew can cause roses to drop leaves on still and humid or
wet nights when the temperature is 55%F to 65%F. |
Insect Problems
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|
|
| Masses
of bugs on the buds and leaves. |
| Aphids
- red, green or black soft bugs, about 1/8"
long, found mostly on new growth. They
appear early and can stay around or come back all
summer. |
| Most
insecticide sprays, including insecticidal soap,
are effective. Aerosol insecticides
labeled for plant pests will also work: spray
up-wind and allow the mist to drift through the
plant. Later, was off the insects with hose
water. |
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| Blooms
are shredded, discolored or buds distorted. |
| Thrips
- light brown insects, very slender, about
1/8" long. Squeeze and open bloom and
watch the inside of the petals for movement.
Thrips move quickly. They are definitely
spread by wind. |
| Apply
insecticides containing acephate when the buds are
pea-sized, then again at two week
intervals. Follow instruction on the
label for mixing and spray intervals. |
|
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|
| Leaves
appear fuzzy yellow on surface; underside has
small red specks, webbing, or spiderlike insects
moving about. (Best seen with a magnifying
glass.) |
Spider-mite
(red spider or 2-spotted mite)
Microscopic in size, but visible to the naked
eye. Hot weather is prime spider-mite
season. Activity increases or decreases with
temperature changes. |
| Sprays:
Insecticidal soap; miticides, high pressure hose
water. All treatments must be applied from
the bottom up in order to contact the insect,
which is always on the leaf underside. |
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| Leaves
have been eaten leaving either skeleton structure
or mid-ribs. Unopened flower buds chewed and
open buds damaged. |
| Beetles;
most notorious is the Japanese beetle, metallic
brown with green head. (Caterpillars can
also cause the same symptoms. |
Sprays,
dust, and "shaking." Sprays of Carbaryl
(Sevin), or Diazinon are
somewhat effective. Apply Bp (Bacillus
papilliae) or 'milky spore' when the grubs are
first detected in spring or late summer.
Neem oil, a new natural insecticide, or its
derivative.
Azadirachtin, has shown some limited
control. Practical, yet effective, is to
spread cloth or plastic on the ground and shake
the beetles off the plants. Traps can also
be effective if placed away from your roses. |
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|
|
| Leaves
stuck together, unopened buds with holes bored
into them. |
| Omnivorous
leaf roller - This a moth larvae that makes a
cocoon-like structure with leaves. |
| B.t.
(Bacillus thuringiensis) or Orthene used as
previously explained for thrips. |
|
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|
| Holes
in pruned cane ends. Circular pieces cut
from leaf margins. |
| Leaf
cutter bee - They use the circular leaf pieces for
egg partitions inside the burrowed cane. |
| Controlled
by applying white glue to the cane ends. |
|
|
|
| Drooping,
unopened buds, accompanied by a small discolored
stem slightly below the bud. |
| Rose
Midge - A small fly that pupates in the ground
below the bush, then flys up and lays eggs in the
soft upper stem. The hatched larvae eat the
stems and cause breakage. The worm then
drops to the ground to complete the last stage of
metamorphosis into a fly. |
| Spread
Diazinon granules on the ground below the bush to
control this pest. Sprays are of limited
value here because of midge lifestages in the
ground. |
|
Cultural Problems
|
| Symptom: |
| Possible
Cause: |
| Remedy: |
|
| Slow
starting Roses. |
| Dry
canes, dry roots. |
| Water
the roses heavily during first three weeks.
Spray canes during the day if
possible. After three weeks, if the
rose is not showing growth, sweat the plant by
placing wet sphagnum moss in the center of the
crown and then cover the canes with a clear
polyethylene bag or burlap to force new
growth. Be careful of excessive heat
buildup. Check daily for signs of bud
growth, then remove. |
|
|
|
| Sucker
growth - This is seen on grafted plants. It
is the rootstock trying to grow out around the
graft. This growth is usually very rapid,
producing long canes with no lower leaf
buds. Foliage is usually lighter color and
thorns are spaced differently than the rest of the
plant. |
| Wearing
gloves, grasp firmly and snap or pull off from
below ground level. |
| Be sure
the growth originates from below the graft.
Bottom or basal growth from the graft can be
confused with suckers. If in doubt, allow
the growth to continue until the difference is
visible. You may have to remove suckers
throughout the growing season. They
are not symptoms of a sick plant but of a healthy,
vigorous one. |
|
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Disease Problems
|
|
|
| Leaves
fold at mid-rib, or are distorted.
White powdery material appears on the
formaing buds and leaf tops or undersides. |
| Podery
Mildew - Fostered by cool nights, warm
days and high humidity. |
| Spray
Triforine, dust with sulphur, or spray
with baking soda and soap. |
|
|
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| Dark
black spots on the leaves. The spots
tend to be round, varying in size from pin
point to quartersized. Half of leaf
yellows or leaf drops completely from the
plant. |
| Black
Spot - This is a fungus favored by rainy
weather or improper watering. |
| Sprays-Dusts-Watering
Technnique - Begin in winter with a
dormant lime-sulphur spray.
Remove dropped leaves and other
debris. Spray with Neem oil, Daconil
2787, Triforine or a sulphur-based
fungicide. The fungus spores are on
leaf undersides so spray up from
underneath. Spray in the early
morning when weather is calm and
cool. When watering, keep
foliage dry or water in the morning so
foliage dries by midday. |
|
|
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| Brown
spots on petals, also red-pink spots on
lighter colored flower buds. Brown
dieback of cut canes; brown fuzzy mold on
debris around the plant. In severe
cases, the entire flower bud rots. |
| Botrytis
blight - High humidity nights or rainy
cool periods favor fungus growth. |
| Spray
with Daconil 2787. Clean up all
twigs on the plant and leaves and debris
below to prevent fungus from spreading.
Maintain good air circultation. |
|
|
|
| Dark
irrecular splotches on the leaves,
dropping of healthy leaves, yellowed leaf
section. |
| Downy
Mildew - A systemic fungus disease.
It is present in the soil and will begin
to cause problems when night temperatures
reach 55ºF to 65ºF, with still air
measuring 85% humidity. |
| Cut
back the defoliated plant. Clean up
debris, dust with sulfur and spray with
Daconil 2787. (Be careful to
spray Daconil 2787 only in the morning so
it will dry before hot mid-day
temperatures occur.) |
|
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| Tumor-like
growths on canes, rooots or at bud union. |
| Gall
(aerial, crown or root) - A bacterial
problem entering through a wond or
contaminated pruning tool. |
| Prune
away the affected section, if
possible. (Galls on the graft would
kill the plant if pruned off.) Be
sure to sterilize pruners and other tools
with bleach or alcohol to prevent bacteria
from spreading. Destroy seriously
weakened plants. Treat soil with
bactericide or leave fallow for two
seasons before replanting. |
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