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Lawn, Garden & Landscaping

2001-07-01 12:31:00

Trees need love too

Answer:  Most homeowners don't realize what can happen to their landscape investment if they don't take care of it.  In taking care of your trees and landscape there our four very important areas of maintenance to insure a healthy and colorful garden or landscape. 1. Water management. 2. Proper fertilization program. 3. Identification & control of insects and disease. 4. Proper pruning maintenance. To answer your question about knowing what to do or what to look for, will be difficult to explain properly.  Every tree and shrub has many different types of problems we look for or try to prevent.  Since your question did not explain the types of trees and shrubs in your landscape, I'm going to answer your questions explaining what the possible diseases and insects are, and why they're so harmful to your landscape investment.  I will also explain what to look for as well as preventive measures.Many different kinds of insects and mites feed on trees and shrubs.  Generally, the greater the variety of plants in the landscape, the more insect and mite species you will encounter.  The mere presence of an insect or mite on a tree or shrub does not necessarily mean you have to control that problems with insecticides or miticides.Predators such as wasps, ladybugs, and other biological forces play an important part in keeping many insects and mites under control during most years.  These forces may break down during some seasons and require the use of chemical and other control measures.  Some insects and mites thrive under Kansas climatic conditions so natural forces seem to exert little pressure on them.Some plants require constant attention while others are relatively free of insects and mites.  Use non-chemical methods of control whenever possible.  Practices, such as sanitation, pruning, use of tolerant species and varieties and the direct removal of pests by hand, are an important part of any control program.Sanitation is the removal and destruction of whole plants.  For example, it is a common practice to remove dead and dying elm trees to control Dutch elm disease. This may include removing large branches that are, or may become heavily infested.  It may sound wasteful to remove a healthy plant, but if a plant is a potential host or breeding site, you can avoid a heavy infestation to surrounding plants by removing these potential host plants.  Pruning is the selective removal of twigs and branches because they are heavily infested with scale.  Dormant oil helps control some scale insects and mites and is probably less environmentally polluting than some of the pesticides that are applied during the growing season. WATERING SCHEDULE:Watering your trees and landscape properly will be crucial to your success in maintaining a healthy and beautiful landscape.  There's only one problem.  Due to so many different conditions in each landscape, there is no correct answer for properly watering your landscape (i.e. sandy soil, clay soil, full sun, partial shade, shade).  All these conditions must be considered during your planning for your water schedule.  The first step in preparing your water schedule would be to water your trees and landscape, then wait two days before checking the soil.  Is it too dry or too wet?If your soil was too dry, water more often.  If your soil was too wet, try watering every third day.  The sooner you start watering properly, the sooner your trees and landscape will show you your reward.  Don't forget, your water schedule will need to be figured for every changing season (spring, summer, fall, winter).  Most important of all, too much water is just as bad as no water at all.Common insect and disease problems to look for:Scale - Scale insects have a shell-like, waxy covering on their bodies.  Scale insects feed by sucking sap from trees and shrubs and are capable of killing entire plants or parts of the plant.  Scale insect feeding can also reduce the plant's vigor, making it more susceptible to injury caused by drought, severe winters, and attacks by other insects and diseases.  Plants are often covered by a sooty mold.  The sooty mold gives the plant a blackish appearance.  Most species of trees and shrubs are subject to scale insects.Fireblight - Certain varieties of apple, flowering crab, pear, pyracantha, cherry and quince are highly susceptible to fireblight.  Hawthorns, cotoneaster and spirea are affected less seriously.  Signs of the fireblight are blossoms and leaves that suddenly wilt, turn dark brown, shrivel and die, but remain attached.  The bacteria overwinters in canker on the plants.  They are spread by wind-blowing rain, insects and pruning tools.Powder Mildew - Common hosts are roses, crabapple and lilac.  Powder mildew may produce a white powdery coating on the leaves, buds or stems of highly susceptible plants.  New growth is stunted and curled on roses.  The leaves may dry and drop.  The flower buds are often deformed and may fail to open properly.Leaf Spot - Fungal leaf spot occurs on most kinds of ornamental plants.  They usually appear first on the lower leaves.  They may begin as dark brown, pinhead-sized spots, which sometimes have a yellow halo.  Spots may cover an entire leaf. As the spots become more abundant, leaves may yellow, die and drop.  Leaf spot is most common in the early spring and fall.  Wet conditions usually are necessary for infection.  Healthy plants become infected when the fungi spores are slashed onto the infected leaves on the ground, blown to them by wind, or carried by garden tools.Scab - Apples, crabapple and pyracantha are susceptible to the scab fungus. Symptoms include spots on leaves and fruit and premature defoliation.  Scab first appears as olive-green spots on the underside of new leaves.  These spots become brown and velvety, then turn yellow and drop prematurely.  Fruit may become infected at any time with circular, olive-green spots that later become brown or black.  The fungi overwinters in infected leaves and produces spores in the spring.Mites - Several species of mites attack trees and causes the plant to take on an off green color as a result of these sap-sucking pests.  Severely infested plants lose their vigor, become unsightly, and may even be killed.  If plant foliage begins to turn an off green color and you suspect mites, make a foliage check by holding a piece of white paper under a branch and striking it hard against the paper.  The mites are only about 1/50 of an inch in diameter, so you can't see them on the foliage.  If the foliage check reveals 10 mites or more, take action.Bagworms - Bagworms will attack and defoliate most evergreens and deciduous trees and shrubs.  However, they are particularly destructive to arborvides, cedar, junipers and other ornamental evergreens.  Bagworms live inside spindle-shaped bags that they construct while in the larva or caterpillar stage.  They construct them  out of silk and bits of foliage.  They drag these bags wherever they go and use them for protection against their natural enemies.  Bagworms overwinter in the egg stage inside the material bag attached to the tree or shrub.  The eggs hatch in late May or early June, and small caterpillars begin feeding and constructing the bag in which they stay.  You can handpick light infestations, particularly on shrubs and small trees, and burn the bags before the eggs hatch in June.  You can also spray half grown to nearly full-grown bagworm caterpillars, but they are difficult to kill.Cankerworms - Cankerworms are known also as measuring worms, inch worms or hoppers.  There are two species.  Both attack early in the spring just as the leaves are beginning to appear, or they sometimes attack the buds before the leaves open.Beetles - The most damaging leaf beetle in Kansas is the elm leaf beetle. The elm leaf beetle is an introduced pest from Europe, which feeds only on elm.  Although most elm species are subject to attack, the beetles usually prefer Siberian elm (commonly called Chinese elm) and hybrid elms.  Elm leaf beetle feeding damage may result in partial or complete defoliation of the tree.  Severely infested leaves will turn brown, and often drop prematurely.  In some cases, the entire tree may be defoliated by mid-summer.  The majority of the damage is caused by the larva as it feeds on the lower sides of leaves.  Trees that lose many of their leaves as a result of elm leaf beetle damage commonly put out a new flush of growth, which remaining resident insects may consume.  Feeding damage by elm leaf beetles seldom kills an elm tree.  However, severe feeding will weaken a tree, making it more susceptible to attack by other insects and diseases.Aphids - Hardly a plant exists, cultivated or wild, that is not a host to one or more aphids species.  Aphids, like scale insects and the true plant bugs, obtain their food by sucking the sap from plant tissue.  Some species feed only on foliage, others on twigs, branches, flowers of fruit, and still others on roots.  Many live on several distinct hosts, spending part of their seasonal development on one host and the remainder on another.  Aphids are small (seldom over 1/8-in. long), soft-bodied, pear-shaped insects of many colors, such as green, black, gray or red.  Most aphids prefer young shoots and leaves.  Their attacks may cause serious damage to plants by robbing them of sap, poisoning plants with the salivary secretions injected during feeding, and serving as vectors of viruses that cause galls on leaves, stems and roots. OTHER PROBLEMS THAT MAY OCCUR:Scorch - Scorch is when leaves or needles die from their margins to the center or from the tips to the base.  It occurs when transpiration water loss from leaves is faster than uptaken.  Scorch can result from drought, heat, drying wind, a poor root systems, root or trunk injuries, girdling roots, or toxic materials in soil such as gas, herbicides, high salt and excessive fertilizer.  It is impossible to tell what caused the scorch by looking only at leaf symptoms.Winterkill - Winterkill or winter injury is when trees die during the winter or spring and no other specific cause for death is found.  Exact causes for this are difficult to identify.  You can blame cold temperatures directly for the death of some winter tender trees, such as mimosa and some magnolias.  Sudden drops in temperature after warm weather are more damaging than steady declines.  Trees in active growth from warm wet autumns and late fertilizing are more easily damaged.  Low humidity accompanied by wind while roots are frozen and unable to take up moisture is especially damaging to broadleaf and coniferous evergreens. Death is often slow and does not become obvious until warm weather.  Arborvitae are especially susceptible.  This type of winter injury is often referred to as desiccation.  Freezing sometimes causes splits in the bark on trunks. Iron chlorosis - Iron deficiency results in stunted yellow leaves with veins remaining green.  Youngest leaves are most severely affected.  In terminal stages, the leaves develop brown spots and die.  Iron chlorosis is more severe in western Kansas because iron becomes less available as the soil pH increases.  Pin oaks, sweetgums, and soft maples are most severely affected but many other species also show symptoms.   Providing available iron through the soil and by trunk injections will help.  You can also plant more tolerant species in high pH soils.Herbicide damage - Many tree problems result from careless use of herbicides.  If the leaves are exposed to herbicides before they mature, they are cupped and distorted with thickened, prominent veins.  Mature leaves often yellow and drop off without obvious distortion.  Drift of volatile phenoxy herbicides is the most common problem.  But plant roots can absorb other materials, such as dicamba, and this can damage the plant.  Redbud, boxelder and hackberry are the most severely affected, but all broadleaf trees can be damaged.  Tree roots can pick up soil sterilants used in driveways, fence rows and ditches 40 to 50 feet away, causing injury or death. These are the most common insects and diseases that occur in our region, not to say these are the only problems. Identification of insects and diseases is very difficult, unless you are trained to identify problems in early stages, before major damage occurs.  Before taking a risk on losing a large investment on your landscape, I highly recommend consulting with a certified chemical applicator to monitor your landscape investment on a regular schedule.