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during daylight hours in moist and shady spots. On sunny days they
can be found in leaf and weed litter beneath the plant. On cloudy/
rainy days, they may be found on the plant itself. Spray early in the
morning or late in the day, to minimize the affect on the birds
and bees.Foliar insecticides registered for controlling black vine
weevil and strawberry root weevil, include Orthene, Talstar (liquid &
granular), and Mavrik. The last two have a longer residual property
and hence greater control.
Biological & Ecological Controls - Increased interest is developing
for controlling insects with materials from nature. Lady bugs, as an
example, prey upon aphids, mites and scale; spiders prey upon flying
insects; and the ground beetle (Vedalia Lady) preys upon aphids,
scale, mealy buds and caterpillars. Toads, snakes and birds prey upon
many garden pests. There are also natural chemicals such as nicotine
from tobacco, pyrethrum from chrysanthemums and Dimboa from
corn. Researchers are working on microorganisms that feed on
insects. A commercial insect called nematodes (Steinernema
Carpocapsae) is a tool for some control of weevil larvae, as long as
soil temperatures remain about 60°F., plus an application of water.
This fall application must be repeated yearly.
Organic Controls - There are several other measures that can be
used to reduce the weevil population without sprays. Tangle-foot,
Stik-Em or Tack Trap can be applied to the trunk of the plant just
above the ground level. The sticky band acts as a barrier and entrapment.
Make a pitfall trap by placing a sizable plastic drinking cup into the
soil near the base of the plant so that the lip of the cup is at soil level.
Coat the inside of this cup with 30W motor oil or WD 40 to discourage
the adult weevil from climbing out. To keep rainfall and/or irrigation
water out of this cup, invert a coffee can or plastic pot over the
pitfall traps, making legs, etc. Check daily and destroy weevils.
Fold a burlap bag into 4” accordion folds, holding one end against
the plant and rotating the burlap around the stem, creating a good
daytime environment for the adult weevil. After a day or two, cautiously
unwind the burlap from beneath the plant and shake over a
white sheet or clear surface. Collect and destroy the weevil. Repeat.
Cultural Control - Many varieties of rhododendrons and azaleas
demonstrate considerable weevil resistance. Selecting resistant varieties
will reduce required maintenance and damage.
Other Chemical Controls - Some of the minor pests to the genus
rhododendron are aphid, loopers, cutworms, caterpillars, azalea leaf
miners, rhododendron lacebugs, and whitefly, which can all be controlled
by the use of insecticides. Along with the chemical formulation,
use 1T. per gallon of a sticker or liquid detergent. This helps
to retain the chemical on the leaf longer.
Control for Slugs - Slugs and snails are usually controlled with slug
bait - metaldehyde formulated with cereal grains and molasses
placed under raised boards. Another method is to use wooden planks.
The slug attaches to the underside of the plank and by turning over
the plank, removal is possible. Placing beer or yeast in a shallow
container attracts slugs and they drown in the container. Ducks,
snakes and toads will prey upon slugs as natural predators.
Control for Moles - In the Pacific Northwest; there are several mole
traps that are recommended. Poison baits should be odorless and
tasteless. Baits containing chlorophacinone have been effective,
although more than a single feeding may be necessary to do the job.
Traps and poison bait must be placed carefully in a main underground
tunnel, which is usually 6”-10” below the surface. The other
remedy is to destroy the food chain of the mole.
Control for Deer - Deer do not like rhododendrons, but love to eat
azaleas, dogwood blooms, new growth on evergreen trees and
shrubs. A product called ‘Hinder’ is 80% effective, as long as you
continue to spray. The uses of certain hand soaps, human hair, blood
meal, etc. all have questionable effectiveness.
Control for Algae, Lichen and Moss on Plants - The cool, moist
and cloudy weather in western Washington is ideal for these organ-
isms. They do not directly injure the plants on which they grow. The
growth is somewhat objectionable and unsightly. Control with copper
fungicides such as Microcop or lime sulfur. Best applied during
the dormant season. Remember, that birds use much of this material
to build their nests. Next time, look at a Hummingbirds’ nest.
Control of Powdery Mildew - Leaves are covered with a grayish/
white powdery fungus growth. It usually affects plants located in
more shade. At the first sign of the fungus, spray with a registered
fungicide as Bayleton, Benomyl; also rake up and destroy all fallen
leaves.
Control for Rust - To date no fungicides are registered for control
of this disease. The symptoms are light green to yellow spots randomly
distributed on the leaf. Yellow to orange powdery spores on
the underside of the leaf are also associated.
Caring for Rhododendrons - Rhododendrons should be pruned to
reduce their stature, to rejuvenate them, to make them more compact
and to cut away diseased or injured branches. There are two ways of
controlling the shape, density and size of a rhododendron - pruning
and pinching (removing growth buds).
Pruning - Rhododendrons can be cut back early in the spring. By
using pruning shears and/or saws, cut at an angle just above the termination
of a growth period. If, however, you want to save the
bloom, prune after blooming. Big old limbs should be cut at random
and then after the side shoots have appeared, the stub above that
point can be removed.
Pinching (Removing Growth Buds) - Pinching is the removal of a
single growth bud at the tip of a branch. Any branch tip that shows
two or more developing shoots is passed by. Pinching can be done in
the fall; however, if done about blooming time, pinch when growth
is less than 1” long. Pinching encourages increased foliage density,
compact growth habit and a greater floral display for the coming
years.
Deheading (Removing Faded Flowers) - The best practice is to
remove by carefully snapping or cutting off all faded trusses soon
after the flower wilts. Some plants produce a greater abundance
ofseed, so deheading has a greater importance. Deheading gives the
plant an immediate well-groomed look and reduces the problem of
disease as the faded blooms decay, and hopefully, encourages blooms
for the next year.
Winter Protection - The aim is to give a plant a ventilated enclosure
in which temperature fluctuations are more moderate. 1) Wooden
frame covered with burlap leaving the top open. 2) Other plants or
trees, lath barriers or fencing. 3) Evergreen trees branches thrust into
the ground at an angle. 4) A wooden teepee covered with burlap,
allowing a vented space on top for snow protection. 5) Leaf mulch
added to the base of the plant in the fall (not to cover foliage, and
removed in spring) keeps the trunk from splitting and the earth from
freezing deeply.
Why plants fail to bloom - It is usually difficult to determine the
exact cause a particular plant fails to bloom, but in most cases the
problem is attributed to environmental factors. 1) There is a direct
correlation between adequate light and bloom. Too much shade
decreases the bud set. 2) Competition for moisture and nutrients by
adjacent trees and shrubs also reduces and discourages blooms. 3) If
you plant your shrub too deep or in a wet area, it reduces the amount
of oxygen to the roots and again bud set is compromised as well as
the health of the plant. 4) Pruning at the wrong time of the year. 5)
Too much nitrogen encourages vegetative growth at the expense of
bud development.
Hardiness - A newly planted shrub is hardier after the first year, as
it establishes itself in its new, healthy and enriched environment. A
plant is considered totally matured for hardiness at five years of
age. There are many aspects, which play an important role in hardiness,
as the amount of water and fertilizer, and when applied; also the
exposure to wind, sun and freeze and the duration thereof, and the
amount of snow cover and mulch on the roots, etc. In general, the
degree of dormancy, the age, the health, the exposure and the
environment provide the total answer to plant hardiness.
Website: www.whitneygardens.com. • Brinnon, WA 98320 • Ph: (800) 952-2404 • Fx: (360) 796-3556
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