THE YARD & GARDEN CORNER

Brought To You By
Briarwood Civic Association
Beautification Committee

NOVEMBER

FLOWER OF THE MONTH

CHRYSANTHEMUM.

A little frost last night, perhaps a dusting of snow? What are those brightly colored flowers doing shining through such a cold environment....and unharmed at that.!? Most likely it's a hardy mum, or Chrysanthemum as they are formally called. Mums are indeed hardy and usually among the last flowers in your garden.

Mums are popular in in both the spring and the fall. They are "forced" into blooming in the spring inside greenhouses and sold at garden stores for Easter and Mother's Day Gifts. These same plants are then placed in flower gardens, cut back and bloom again in the fall.

There are hundreds of varieties of mums. Mums are a member of the daisy family.

POISON PLANTS.

Most people are familiar with poison ivy, but they often don't know about poison oak, poison sumac, and other toxic plants that may be growing in their yards or nearby. Learn how to spot these plants and what to do about them.

Poison Ivy, Oak, and Sumac.

Poison ivy, which grows mainly east of the Rockies, is one of the most poisonous plants. Poison oak, found mostly in the West, and sumac, found mostly in the Southeast, are less common. All three contain urushiol, an oily resin in the plant sap that causes an itchy rash.

"Leaves of three, let it be" is a common admonition for avoiding poison ivy, but it's not quite that simple. Poison ivy blooms in springtime and bears white berries in the late summer. Depending on the time of year, it may have more than three leaves, and they may be shiny or dull, red or green. In winter, when the vines have no identifying leaves, the plant is still poisonous.

Poison oak also has three leaves together, but they are lobbed at the edges, and the plant usually grows as a shrub rather than a vine.

Poison sumac is a small tree or shrub that has pairs of pointed leaves. Though it grows mainly in the South, it also thrives in freshwater wetlands in northern areas.

There is a wide range of sensitivity to urushiol; some people can handle plants that contain it without having any reaction, while others have a severe reaction at the slightest contact. Even if you haven't had problems in the past, don't assume that you're immune. Remember, too, that a reaction may occur immediately or take up to 25 days to develop.

If you suspect that you have come in contact with poison ivy, oak, or sumac, wash the affected area thoroughly with cold water and a strong soap or detergent, such as dishwashing liquid. After you have cleaned the skin in this way, apply rubbing alcohol to the area to remove any remaining sap.

You can spread urushiol to other parts of the body, not by scratching the affected area but by touching the sap on pets, clothes, garden tools, or other objects, often long after the initial exposure. Immediately after any possible contact with poison ivy, wash tools and launder clothing in hot, soapy water. Make sure children change clothes after hiking or playing in an area that might have poison ivy. Shampoo pets that may have touched the plant.

Getting Rid of Poison Ivy.

The safest way to kill poison ivy is with a systemic herbicide that contains triclopyr. It may take several days and several applications for the vine to die. Follow the directions on the package and make sure you apply it only to the poison ivy.

Even when the poison ivy plant is dormant in winter, or dead, the rash-causing urushiol persists. Whenever you remove vines that you haven't positively identified as safe, take precautions, as if they were poison ivy.

Large poison ivy vines that climb up a tree or building should be cut at the bottom and treated with a herbicide. Wear gloves when cutting the vines, and be sure to wash all tools and clothes thoroughly after you are finished.

Never burn poison ivy or any urishiol-containing plant. If you do, you may inhale poison in the smoke, which can cause a severe lung reaction. Instead, seal the plants in a plastic bag with other trash headed for a landfill.

CLEMSON TOPICS

The following article was prepared by the Clemson Extension Center:

Chrysanthemum Problems

Chrysanthemums, or garden mums, like full sun and fertile, well-drained soil. They need regular watering because their roots are very shallow. Drought will cause woody, stunted growth. Overwatering, on the other hand, causes yellowing leaves that blacken and drop. Although the list of diseases that may attack chrysanthemums is long, mums are relatively trouble-free.

LEAF SPOT

Several different kinds of fungi cause leaf spot on chrysanthemum: Septoria chrysanthemi, S. chrysanthemella, Alternaria spp., Cercospora chrysanthemi. Symptoms consist of spots on the leaves. These spots are at first yellowish, then become dark brown and black, increasing from 1/8 to 1 inch or more in diameter. Leaves may wither prematurely. The lower leaves are infected first. With a hand lens white masses of spores may be seen on the leaf spots.

Prevention and Treatment: Hand pick and destroy the infected leaves. Also, regularly clean up and destroy dead plant debris in the garden to reduce spore populations. These fungi overwinter as spores in such debris. A layer of mulch helps prevent spores from splashing from the soil onto plants. If disease is severe enough to warrant chemical control, fungicides containing chlorothalonil or copper hydroxide may be used. Follow all the directions on the label.

FOLIAR NEMATODES (Aphelenchoides ritzema-bosi)

Hardy chrysanthemums that develop yellow-brown spots starting on the lower leaves and gradually moving up the stems may be infested with foliar nematodes. Nematodes are slender, unsegmented roundworms that are barely visible to the unaided eye. Foliar nematodes overwinter in the soil, in infested plant material. They swim up the film of water on the plants, created by spring rains, and enter leaves through the stomata. Yellow-brown spots on the leaves eventually run together and cover the entire leaf, which dies, turns brittle, and falls. Severe infestations can kill entire plants. Foliar nematodes are easily confused with leaf spot (see above), but fungal leaf spots are most often black, not brown.

Prevention and Treatment: Remove infested plant material, along with the surrounding soil. Mulch plants in the spring to discourage nematodes from climbing up from the soil, and avoid spraying water on the leaves when watering. Infested soils may be treated preplanting with oxamyl (according to instructions on the product label).

RUST

This disease is caused by the fungus Puccinina chrysanthemi. Rust infection causes pale areas to appear on upper leaf surfaces, with powdery orange pustules or spots directly beneath on the undersides of the leaves. Severely infected plants are much weakened and fail to bloom properly.

Prevention and Treatment: Remove infected leaves as soon as possible. Set new plants farther apart and provide better ventilation. Water the soil without wetting the plants. If disease is severe enough to warrant chemical control, use a fungicide with mancozeb or triadimefon as active ingredient. Follow all directions on the label. Some chrysanthemum varieties, which are resistant to rust, are Achievement, Copper Bowl, Escapade, Helen Castle, Mandalay, Matador, Miss Atlanta, Orange Bowl, and Powder Puff.

WILT

This disease is caused by the fungi Verticillium albo-atrum and/or Fusarium oxysporum).

The first symptoms of wilt are yellowing and browning of the leaves, which die from the base of the plant upwards. Infected plants are stunted and often fail to produce flowers. The entire plant may wilt and die. The fungus is soil-borne, and enters the plant through the roots, later invading the vessels of the stem and cutting off the water supply.

Prevention and Treatment: Control of this wilt on plants grown in infested soil is difficult. Remove and destroy all infected plant material. Ultimate control lies with purchasing certified disease-free plants and strict sanitation locally. It is best to use resistant varieties. If Fusarium has been a problem, increase the pH of the soil to 6.5 7.0.

POWDERY MILDEW

This disease is caused by the fungus Erysiphe cichoracearum. The leaves are covered with a whitish, ash-gray powdery growth. The spores require a very moist atmosphere in which to germinate and spread the infection.

Prevention and Treatment: Remove diseased plant material. Spray with wettable sulfur or Benlate according to instructions on the product label.

RAY BLIGHT

This disease is caused by the fungus Mycosphaerella ligulicola.

The ray flowers (marginal flowers of an inflorescence) are attacked, so that the blooms are deformed and one-sided. Early infection may cause blasting of the buds.

Prevention and Treatment: Benlate is very effective as a foliar spray when applied at label rates.

RAY SPECK

This disease is caused by the fungi Stemphylium and Alternaria. These fungi cause brown or white necrotic specks surrounded by colored halos on the fully expanded ray florets when humidity and temperatures are high.

Prevention and Treatment: see Ray Blight.

GRAY MOLD

This disease is caused by the fungus Botrytis cinerea. Leaves show brown water-soaked spots. Infected parts become covered with a grayish-brown, powdery mass of spores. This disease may be confused with Ray Blight disease.

Prevention and Treatment: Space plants for free circulation of air. Apply a foliar spray of Benlate (follow instructions on the label).

BACTERIAL BLIGHT

This disease is caused by Erwinia chrysanthemi. The most pronounced symptom is a rot of the upper part of the stem, resulting in wilt and collapse of the distal portion. Infected cuttings may show a brown to black decay at their bases. Occasionally, the only symptom is a marginal leaf scorch.

Prevention and Treatment: Soil in which diseased plants grew should be pasteurized with heat before reuse. Use cuttings that are disease-free, or dip cuttings for 4 hours in solutions of antibiotics such as streptomycin or aureomycin.

CROWN GALL

This disease is caused by the bacterium Agrobacterium tumefaciens. Infection with these bacteria causes large swellings on the crown and nearby roots.

Prevention and Treatment: Discard infected plants. Do not wound the stems. Buy rooted cuttings, which are certified to be disease-free. Use Agrobacterium radiobacter (strain K84) as preventive treatment.

VIRUS DISEASES

Chrysanthemums are subject to a large number of virus diseases, including mosaic, chrysanthemum smut virus, tomato spotted wilt virus, and aster yellows. Virus-infected plants generally have spindly, stunted shoots and yellowed foliage. Leaves may be marked with ring spots, lines, pale areas, or mottling. Infected plants are stunted, form dense "rosettes", and have small flowers. Virus diseases are spread by sucking insects such as aphids and leafhoppers.

Prevention and Treatment: There is no cure for virus-infected plants. Remove and destroy them. To control the insects that transmit these viruses, see the insect portion of this fact sheet. Remove weeds that may harbor the viruses. Wash tools used around infected plant.

INSECTS AND RELATED PESTS

Chrysanthemum aphids (Macrosiphoniella sanborni) and other aphid species are pests on chrysanthemums. The chrysanthemum aphids are brown to black, which other species range in color from green to pink. Aphids feed by piercing plant tissue and sucking plant sap. They prefer feeding on new growth in such areas as shoots, the undersides of leaves, buds and flowers. Their feeding can result in distorted growth, stunting and sometimes death of the entire plant. As they feed on plant sap, they excrete honeydew (a sugary material). The sooty mold fungus feeds on the honeydew, resulting in unsightly, dark fungal growth. In addition to damage caused by their feeding, chrysanthemum aphids can transmit various plant viruses.

Control: Aphids can be removed from plants by applying a forceful spray of water to the plants every 2 days, especially to the undersides of leaves. Continue as needed, but at least 3 times. Several naturally occurring enemies feed on aphids. As much as possible, these predators should be allowed to reduce aphid populations. As a result of their phenomenal ability to reproduce, aphids are very difficult to control with insecticides. Leaving one aphid alive can result in the production of a new colony very quickly. In addition, the use of insecticides kills the beneficial insects that normally keep aphid populations under control.

If natural predators do not keep aphids under control and serious damage is occurring, spray with one of the following materials: insecticidal soap, horticultural oil, acephate (ORTHENE), diazinon, and malathion. As with all pesticides, read and follow all label directions and precautions.

Two-spotted spider mites (Tetranychus urticae) and other mite species are pests of chrysanthemums. Mites are not insects, but are more closely related to spiders. They tend to be more of a problem during hot, dry periods. Mites are extremely small and can barely be seen without a magnifying lens. They have piercing mouthparts with which they puncture plant tissue and suck plant sap. With a light infestation, leaves develop stipples (tiny yellow spots) and appear dusty. Early damage is often overlooked until damage is more severe. With heavier infestations, symptoms include distorted leaves, and withered and discolored blooms. In addition, fine webbing can be seen on flower buds, between stems and on the undersides of leaves.

Control: Consider destroying severely infested plants or portions of plants, as spider mites are difficult to control under these circumstances. Spider mites can be removed by spraying plants forcefully with water. Repeat as needed, but at least 3 times. Insecticidal soap, if started early in the infestation, is effective at controlling spider mites. ISOTOX INSECT KILLER FORMULA IV (a combination of acephate and hexakis) contains a miticide. Usually two or more applications at 5-7 day intervals are required. Be sure to apply the spray to all leaf surfaces. As with all pesticides, read and follow all label directions and precautions.

Chrysanthemum leafminer (Phytomyza syngenesiae) is the larva (immature form) of small (about 1/8-inch) dark-colored flies. The adult female lays eggs on the undersurfaces of leaves. The larvae hatch and penetrate the surface to enter the leaf and live between the upper and lower surfaces of the leaves. As they move through the leaf feeding, they create winding trails that are pale green to brown in color. Dots of black waste products are visible in some of the trails. Severely infested leaves may dry up and droop downward along the stems.

Control: Prune off and destroy infested leaves. Any leaves that fall to the ground should be picked up and destroyed. Remove and destroy any plant remains in the fall. If damage is severe, spray with acephate (ORTHENE).

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