Azalea CareParts of the information taken from- & University of Kentucky Entomology EXPOSUREAzaleas prefer cool, partially shaded sites, such SOILAzaleas are shallow-rooted plants that are easily damaged by excessive soil moisture. They grow best in acid
(4.5 to 6.0 pH), well-drained, organic soils. Before planting, have the soil tested and adjust the pH according to soil
test results. MULCHINGA 2- to 3-inch layer of organic mulch is very important. It conserves soil moisture, maintains soil temperature and helps discourage weeds. There are many materials available suitable for mulching. Pine straw, composted pine bark and leaves work very well, enriching the soil with organic matter as they decompose. Keep the mulch a couple of inches away from the main stem to keep the bark dry and extend it beyond the outermost branches. WATERINGAzaleas are shallow-rooted plants and require irrigation during dry periods. This is especially true of those planted
in the spring. Azaleas planted in warm weather in sandy soils may require watering of the root mass twice a week during the
first year. FERTILIZINGAzaleas have low nutritional requirements compared to other shrubs. A soil amended with organic matter prior to planting
followed by a mulch of compost, shredded leaves, pine straw or other organic material will usually provide sufficient
nutrients for adequate growth.
Assuming you have a 12-4-8 fertilizer, the equation for this example would look like this:
Since the root zone is 300 square feet, the actual amount of fertilizer to apply is calculated as follows:
Apply 2½ pounds or 5 cups of 12-4-8 evenly over the mulched bed. Azaleas do not have to be routinely fertilized during the growing season. Any fertilizer application should be based on their appearance, such as leaf color, growth rate, soil test results and your objectives, such as encouraging growth or correcting a mineral deficiency. The best time to apply fertilizer is when it will be readily absorbed by the roots of the plant and when the soil is moist, which can be any time from late spring (after new growth emerges) up to early fall. Avoid fertilizing plants stressed by drought during the summer months. Without water, plants are unable to absorb nutrients, so it is best not to fertilize if water is unavailable. PRUNINGThere are two pruning techniques used for azaleas: thinning and heading. Thinning refers to the removal of
branches back to the main trunk or another branch. This method is used to remove leggy branches that extend beyond the
canopy of the plant, remove damaged or diseased wood, or reduce the size of the plant. Thinning allows light to penetrate the
shrub, encouraging growth on interior branches. You can thin at any time of the year without causing significant impact
on flowering, growth or cold hardiness of the plant. How-ever, to reduce the impact on flowers the following year, prune
just after flowering in the spring. PROBLEMSThe most common diseases on azaleas in South Carolina include petal blight, leaf gall, leaf spots, dieback, and root
and crown rot. The most common insects are lacebug and spider mites. Good cultural practices such as careful plant location,
provision of good aeration and drainage, mulching and good watering habits will reduce the incidence of disease and insect
damage. For more information on disease and insect problems on azaleas, refer to Azalea and Rhododendron Diseases, HGIC
2050, and Azalea and Rhododendron Insects, HGIC 2051. Petal BlightThis fungal disease, caused by Ovulinia azaleae, primarily affects the flowers of azalea, but mountain laurel and rhododendron flowers can also be infected. Indian and kurume azaleas are especially susceptible. The disease starts on the flower petals as tiny, irregularly-shaped spots, giving a ''freckled'' appearance. On colored flowers the spots are white, and on white flowers the spots are brown. The spots quickly enlarge and become soft and watery. Flowers rot and stick to the leaves. Infection is easily spread from flower to flower by wind, rain and insects. The fungus survives the winter in the soil.
Mancozeb 37.0% A broad spectrum fungicide for use on a wide variety of vegetables and ornamentals. Controls leaf spot, downy mildew, blights, anthracnose, botrytis and other listed diseases. Use 2-5 teaspoons/g. Restricted in ME. Not for sale in NYS. Leaf GallLeaf gall - Left to right shows stages of development
Leaf gall (Exobasidium species) is a very common fungal disease in the early spring on azaleas and occasionally on
rhododendrons. Some of the native rhododendron species (azaleas) are more susceptible than hybrid rhododendrons. In April
and May leaves and buds of infected plants develop distorted growth. Leaves and possibly stems become thickened, curled,
fleshy and turn pale green to white. In the later stages of the disease, the galls become covered with a white powdery
substance. As the galls age, they turn brown and hard.
A broad spectrum fungicide for use on a wide variety of vegetables and ornamentals. Controls leaf spot, downy mildew, blights, anthracnose, botrytis and other listed diseases. Use 2-5 teaspoons/g. Restricted in ME. Not for sale in NYS. Leaf SpotsSeptoria leaf spot
Throughout the year, fungal spots (Cercospora species, Septoria species, Phyllosticta species and Colletotrichum
species) of various colors appear on azalea and rhododendron leaves. The diseases caused are usually minor, only affecting
the aesthetic value of the plant. Cases of severe infection may result in early leaf drop, reducing the general health of
the plant. Mancozeb 37.0% A broad spectrum fungicide for use on a wide variety of vegetables and ornamentals. Controls leaf spot, downy mildew, blights, anthracnose, botrytis and other listed diseases. Use 2-5 teaspoons/g. Restricted in ME. Not for sale in NYS. Daconil(Chlorothalonil) Dieback
Dieback is an important disease of hybrid rhododendrons in the landscape and is caused by the fungus
Botryosphaeria dothidea. Azaleas with similar symptoms are more likely to be infected by the
fungus Phomopsis species. Typically, dying branches (stem dieback) begin to appear on an
otherwise healthy plant. The leaves die and can remain attached to the plant until late summer.
Usually a single branch on an established plant is affected. Scraping under the bark with a
knife reveals a reddish-brown discoloration under the bark on dying branches of rhododendron.
On azaleas the discolored wood under the bark appears chocolate brown. Mancozeb 37.0% A broad spectrum fungicide for use on a wide variety of vegetables and ornamentals. Controls leaf spot, downy mildew, blights, anthracnose, botrytis and other listed diseases. Use 2-5 teaspoons/g. Restricted in ME. Not for sale in NYS. Root and Crown Rot.Phytophthora root rotThe fungus Phytophthora species causes one of the most common disease problems in the landscape for rhododendron and
azalea. This fungus is a ''water mold,'' and thrives in poorly drained or wet conditions. A wilted plant is usually the first
sign of trouble. Rhododendron leaves will curl inward and droop. Drought can cause similar symptoms. Roots of affected
plants appear soggy or blackened, and the outer portion of the root easily pulls away from the inner portion.
AzaleasResistant: R. sanctum, R. simsii (Indian azalea), R. yedoense var. poukhanense (Korean azalea),
‘Corrine,’ ‘Fakir,’ ‘Fred Cochran,’ ‘Glacier,’ ‘Hampton Beauty,’ ‘Higasa,’ ‘Merlin,’ ‘Polar Sea,’ ‘Rose Greeley’
RhododendronsResistant: ‘Caroline,’ ‘Martha Isaacson,’ ‘Pink Trumpet,’ ‘Prof. Hugo de Vries,’ ‘Red Head,’ R. davidsonianum,
R. delavayi, R. glomerulatum, R. hyperythrum, R. lapponicum, R. occidentale, R. poukhanense, R. pseudochrysanthum, R.
quinquefolium and R. websterianum Whiteflies
Little white bugs that fly around the azalea or whiteflies. After blooming, spray with insecticidal soap or pyrethrins. Repeat the spray again in 3 days and again in 3 days, being sure to target the bottom of all the leaves. Click here to go to White Fly pageAzalea Lacebug - ControlYou may have seen the damage lace bugs do to azaleas without knowing who did the dirty deed. Lace bugs suck the juice out of individual leaf cells. Since they hide underneath azalea leaves, you’ll never notice the bugs but it’s easy to see their damage. Since the bugs slurp out the chlorophyl in a leaf cell, the top of the leaf has hundreds of yellow speckles. Thousands of hungry lace bugs can make an azalea appear yellow all over. Since azalea lace bugs have an active sex life, just a few can produce thousands of offspring in the course of a summer. Dr. Kris Braman says that she has seen adult lace bugs on her research azaleas even during the winter. Inspect your azaleas for speckled yellow leaves. Examine the backside of the leaves too. If you see tiny black spots scattered across the leaf and concentrated along the mid-vein, you will have a population explosion of the creatures before many weeks pass. The adult lacebug is barely one fourth inch long, with transparent wings. It feeds on the underside of azalea leaves, sucking juice from the leaf cells. Mid-spring is a great time to control the first few generations of lacebug larvae and adults. Insecticidal soap, horticultural oil, neem oil and most synthetic insecticides will kill the insects. The key to good control, though, is thorough coverage. Use a garden sprayer and pump it up vigorously. When spraying, point the spray wand up from beneath so the undersides of the leaves are covered with spray. Another pesticide option is to use a systemic insecticide that poisons the sap of the azalea. Imidacloprid (Bayer Tree and Shrub Insecticide) can be poured around the roots of azaleas in spring, when growth begins, to achieve season-long control. It is easier to manage azalea lacebugs in spring or summer than it is in August!
Again, the most important thing to remember is to READ and FOLLOW the directions on the label of the product that you purchase. Most horticultural oils will come with summer and winter directions. Don't mix stronger than the directions say. And these products don't clog up your sprayer. They are combined with emulsifiers that turn the oils into a pure solution. Horticulture and Dormant Spray Oil Leaf-Mining InsectLeaves develop little white trails due to leaf mining insects. Parts of the informationBy Michael F. Potter, Urban Extension EntomologistSpider MitesSPIDER MITES ON LANDSCAPE PLANTSSpider mites are common pests in the urban landscape and can inflict serious damage to trees, shrubs and flowers. Both evergreen and deciduous plants may be attacked. Spider mites are not insects but are more closely related to ticks and spiders. Their common name is derived from their ability to produce silk, which most species spin on host plants. Mites are tiny—about the size of the period at the end of this sentence. They can also be very prolific, which is why infestations often go unnoticed until plants exhibit significant damage. General CharacteristicsSpider mites (family: Tetranychidae) have a simple, oval-shaped body and no wings or antennae. All species pass through
an egg stage, a six-legged larval stage, and two eight-legged nymphal stages (protonymph and deutonymph) before
transforming into an eight-legged adult. Immature stages resemble the adults except in size. An adult female may live
for several weeks and lay many dozens of eggs during her lifetime. Under optimum conditions, spider mites can complete
their development from egg to adult in less than one week, so there may be many overlapping generations in a single season.
Therefore, populations can increase rapidly and cause extensive plant damage in a very short time. Spider mites have
needle-like mouthparts and feed by piercing the leaves of host plants and sucking out the fluids from individual plant
cells. This causes the leaves to have a stippled or flecked appearance, with pale dots where the cellular contents have
been removed. Prolonged, heavy infestations cause yellowing or bronzing of the foliage and premature leaf drop similar to
drought stress. Severely-infested plants may be stunted or even killed. Most of the mites feed from the undersides of
leaves, although the damage is most evident from the upper surface. Damaging Species In KentuckySeveral species of spider mites live on plants. Fortunately, a rather small number routinely damage landscape plants in Kentucky. Some, such as the twospotted spider mite, have very broad host preferences, wheras with others (e.g., European red mite, spruce spider mite, southern red mite) the number of susceptible landscape plants is more limited. The twospotted spider mite and European red mite thrive under hot, dry summer conditions, whereas the spruce spider mite and southern red mite prefer cooler temperatures in the spring and fall. Being familiar with the following four mite species will help you to determine which landscape plants are most susceptible, and the time of year they are most vulnerable to attack. Two Spotted Spider Mite(Tetranychus urticae)
This is the most common and destructive mite on deciduous ornamentals. It has an extremely wide host range and will feed on many varieties of trees, shrubs, flowers, weeds, fruits, greenhouse and field crops. Immatures and adults are yellowish to greenish with two dark spots on either side of the body. Eggs are spherical and translucent. Strands of webbing are spun by the mites on the undersides of infested leaves and between branches. Twospotted spider mites overwinter as adult females in the soil or under the bark of host plants. They become active during the spring and may feed and reproduce throughout the summer and into fall provided conditions remain favorable for plant growth. It is considered a “warm season” mite which thrives under hot, dry summer conditions. Damaging populations seldom during wet, cool weather. The mites are especially destructive to winged euonymous (burning bush) in landscapes. European Red Mite(Panonychus ulmi)Another “warm season” species, this mite attacks deciduous trees and shrubs. It is especially common on flowering fruit trees such as apple/crabapple, cherry, pear, plum, hawthorn, and serviceberry. European red mites overwinter as bright red eggs laid in clusters on branches, limbs and trunk, often in such great number that the bark seems to be covered with red brick dust. Eggs of subsequent generations are laid on the foliage, usually on the lower leaf surface. Following spring egg hatch, there may be several generations per year. Development from egg to adult varies from about 3 weeks at 55 degrees F to less than 1 week at 77 degrees F. All life stages (eggs, immatures, and adults) are brick red. The presence of the overwintering eggs on the bark makes the use of dormant oils an effective control measure (see “Controlling Infestations” section below). Spruce Spider Mite (Oligonychus ununguis)Despite its common name, this mite feeds on more than 40 species of conifers. Most often attacked are spruce
(especially Alberta spruce), pine, juniper, fir, arborvitae, hemlock, taxus and false cypress. The mites have a similar
appearance to those already discussed. Coloration varies from green to deep olive to brownish red. Close inspection of
the needles will reveal tiny white flecks and speckles where the mites have fed. Prolonged feeding causes yellowing,
browning, and premature needle drop, often originating from the canopy interior. Infested foliage may also display
webbing, eggs and cast skins. Heavy attacks can cause branch dieback or death of the plant. This is the most common and destructive spider mite on broad-leaved evergreens, especially Japanese and American hollies, azaleas, viburnum, roses and rhododendron. Feeding on the undersides of leaves causes stippling, browning, occasional distortion, and premature leaf drop. Southern red mites overwinter in the egg stage on the undersides of leaves. Like the spruce spider mite, its numbers are greatest during cooler periods of the spring and fall. Diagnosing InfestationsTimely inspection of susceptible landscape plants — especially during periods favoring mite outbreaks — is key to
preventing serious damage. When scouting for spider mites, pay particular attention to plants having a history of mite
problems. Spider mites often re-infest the same plants year after year. Controlling InfestationsSpider mites are one of the more difficult groups of landscape pests to control. Infestations are easiest to control when detected early, before the mite populations have reached very high levels. Twospotted spider mite infestations can often be traced to the purchase of infested plant material, especially bedding and houseplants. When buying new plants, it pays to inspect the lower leaf surfaces for evidence of mites. Spraying plants with a strong stream of water from a garden hose or faucet can dislodge many mites from leaf surfaces. The approach is generally more effective on smaller plants (e.g., houseplants), with non-dense foliage and low mite populations. Water sprays should be directed upward against the lower leaf surfaces, and the technique will need to be repeated on regular intervals. Low populations of spider mites may be held in check by naturally occurring predatory mites which feed on both eggs and active stages. PesticidesRemember azaleas sprayed with leafshine or strong insecticides can causes black specks on the leaves and blooms?
Horticultural oils can be used on landscape plants during the warmer months of the year when green foliage is present and the plants (and mites) are actively growing. Horticultural oils are applied at rates of 1.0 to 2.0 %. Dormant oils are applied in winter or early spring prior to bud break, or in the fall after the leaves have dropped and there have been several light frosts. They are useful for killing overwintering mite eggs and, therefore, can help to suppress infestations of spruce spider mites, European red mites and southern red mites which overwinter as eggs on infested plants. A dormant oil spray will not guarantee mite-free plants the following year, but will delay mite buildup the following spring. Dormant oils are either specially-formulated petroleum-based products or horticultural oils applied at higher rates (3.0 to 4.0%). When using any type of oil, be aware that these sprays will discolor many conifers that have a bluish, waxy coating on their needles. Mapes, hickories, black walnut, smoketree and azaleas also tend to be oil sensitive. (Refer to the product label for a complete list of plants which may be sensitive to these products.) Horticulture and Dormant Spray Oil Insecticidal/miticidal soaps are also widely available to homeowners. These products are useful in the warmer months when plants are actively growing, and may also be used to control cool season mites. Thorough coverage is essential. Trade names are used as examples. No endorsement is intended, nor criticism implied of similar products not namedProducts Labeled for Mite Control on Landscape Plants
Issued: 4/98 Revised: 4/98 Soaps (fatty acid salts) Talstar You can also use Generic brand Bifen and save money. It has the same ingredient as Talstar One.
Horticulture and Dormant Spray Oil Organic Insect ControlKelthane CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication. Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE! Check ListJanuarySpray azaleas, to control scale, spider mites, lace bug, leaf minor and other over-wintering insect pests. When applying the oil, the ambient temperature must be at least 40° F but 50° F is preferred. MarchCool, humid March weather is unfortunately ideal for the regeneration and spread of many fungal diseases. Check for petal blight on azaleas. AprilDo not do general trimming on spring flowering shrubs like azalea at this time. Dead branches may be removed but
otherwise wait until after flowering to prune. MayLace bug infestation is easy to recognize. Turn over the leaf of your evergreen plant and look for black specks.
If your leaf looks dirty on the underside, you have lace bug. Left untreated the little eggs under the black smudges
will hatch and sucking insects will drain each leaf of all nutrients. Milky coffee colored azalea leaves are a sure
sign of lace bug activity. Unfortunately, when you see that color it is too late. Treat infected plants with a good
systemic insecticide. AugustDO NOT PRUNE spring flowering trees and shrubs after August 1st. The flowering buds for next year's display are now forming within the plants. Pruning now will remove these buds. If the weather is dry in August and September, water these trees and shrubs twice a week, deeply, to promote lush spring bloom. Do you remember those years when the only azalea blooms were at the very bottom of the plant? This was caused by lack of water in August and September of the previous year! OctoberDo NOT prune spring blooming plants such as azalea, rhododendron, and camellias because they have already set their flower buds for next spring. It is best to prune them immediately after they bloom. For more information go to Clemson University or University of Kentucky Entomology |
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