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June/July 2003
In The Garden By Aggie Roberts
Salts In the Soil - Salts often accumulate in the soil from the use of irrigation waters. Since all irrigation waters contain some salt, salinity may build-up gradually even if low salt water is used. This is very apt to occur in soils of poor permeability. The salts added by the irrigation water will not be leached readily through such soils. If irrigations are insufficient to provide water excess, leaching will not occur in any soil and sooner or later the salt content will become high enough to cause plant injury. This can cause stunted plant growth and the leaf margins on the plant to brown. Adequate drainage is necessary to remove excess salts from the soil. Before planting any vegetation like trees or shrubs, make sure good drainage exists in the area where the vegetation will be planted because it is much easier to correct the problem before rather than after planting. Iron Chlorosis - Prevalent in our soils is iron chlorosis, which usually occurs as a result of excess calcium carbonate, which is lime. The first sign of deficiency is the yellowing of the young leaf tissues between the veins. When the deficiency becomes more severe the entire leaf turns yellow, finally progressing to a creamy white color. In severe cases growth is stunted and twigs and branches die back. Try to catch this problem in the first stages, look for yellowing of the leaves with prominent green veins. All plants need iron for proper plant development but some plants are extremely sensitive to iron deficiency. A few of these plants include roses, pyracantha and peach trees. To help correct iron deficiency symptoms in plants, iron chelate should be used. Depending on how severe the conditions are several treatments may be needed to bring back the lush color found on a normal plant. Irrigation is needed after each application to move the chemicals down to the root zone where they can be absorbed by the roots and then carried throughout the plant's vascular system. Insects - Several of the insects the gardeners have to contend with include aphids and spider mites. Both are sucking insects. Aphids - These insects are most abundant in early spring when new plant growth is very young. However, you can see them well into October. Aphids feed by inserting a needlelike beak, composed of four stylets into the stems and leaves and then sucking out plant sap. They target new growth, which is juicy and tender but victimize plants at any stage. Aphids are slow-moving oval or pear shaped, soft bodied insects ranging in length from 1/16 to 1/4 inch. Most adults have no wings, but winged forms appear at specific times. Their body colors vary from light green, rose colored, red-brown and black. You can detect an infestation of aphids if ants are present on the plants or you may find a sticky material, which is secreted, when heavy infestation is present. Ants feed on this sticky material. You can also see aphids with the naked eye. Heavily infested leaves, yellow, curl and become distorted. Control of these insects is simple. You can wash them from your plants by hosing them down with a strong spray of water, which should be done seven consecutive days. If this is not effective use an insecticidal soap. Spider Mites - Spider mites sometimes leave a fine silk over leaf surfaces but they do not weave typical spider webs because they are not spiders, merely spider relatives. Being spider relatives means that spider mites are not insects, either. Lacking true jaws with eight legs and compound eyes, they are closely related to ticks and spiders. They do not have antennae or wings. Spider mites are small, often difficult to see without a magnifying glass. These mites puncture plant tissue with piercing mouthparts to feed on plant juices. Chlorophyll is removed along with plant fluids. As a result plants infested with spider mites have a white or yellow speckled appearance. The plants look dull and unhealthy. Mites feed primarily on the undersides of leaves, out of sight and away from direct sunlight. Heavy infestations discolor leaves. If a spider mite infestation is suspected, carefully inspect individual leaves. Hold a white piece of paper beneath the branch and give the foliage a tap. Use a magnifying lens to inspect the paper for dislodged mites. They look like tiny, moving specks. You can significantly reduce mite population by hosing down infested plants with a fine hard water stream from your garden hose. Hold the hose nozzle 4 to 8 inches away from the infected leaves and wet them completely including the undersides. The mites will be killed and will cause no further damage. Water does not destroy the eggs, however, despite your best efforts, so repeat the hosing every other day for at least two weeks. If this is not effective try insecticidal soap or neem. Diseases - Vigorous, well-nourished plants have a natural ability to resist diseases. Gardening practices such as composting and improving the soil organic content tend to keep disease organisms in check by producing stronger plants. Living organisms cause plant diseases. Disease causing microorganisms include bacteria, fungus, and viruses. Several of the most prominent diseases in our valley include powdery mildew and sooty canker. Powdery Mildew - This disease is one of the most widespread and easily recognized of diseases. Mildew forms a white to grayish powdery growth, usually on the upper surfaces of leaves. Small black dots appear and produce spores that are blown by the wind to infect new plants. The white powder or spores that land on the same or other plants will germinate overnight under favorable conditions. The powder will infect the plant by sending "root like" projections through the surface cells of shoots, leaves, flower or fruit and drawing nourishment from the plant making this fungus a true parasite. If not controlled this condition will get worse and worse until mid-summer when temperatures of 105 and above usually kill mildew spores. For control try a regular routine of spraying with jets of water to wash off the fungus spores and prevent the dry conditions that encourage the fungus to spread in the wind. Sooty Canker - This wilt is a disease commonly attacking mulberry trees, oleanders and ash trees. The fungus enters the plant by a variety of wounds or openings, including pruning wounds, mechanical damage and frost injuries. By far the most common means of entry is through sunburned bark. Sooty canker can be spread from infected to healthy trees by spores carried by wind, rain, birds, insects, and on pruning tools. Trees affected by Sooty Canker generally produce smaller than normal leaves. Symptoms on limbs first appear as brownish, moist areas on the back. As the disease develops these areas ultimately crack, split and reveal a black dusty mass of fungal spores. This disease can be controlled when infections are confined to tree limbs and upper portions of the branches. Removal of the smaller infected branches should be done whenever symptoms appear. When removing infected limbs, cut back to at least one inch below the site of infection. The cut area and pruning tools should be treated with a solution of one part household bleach and nine parts of water. Good sanitation and cultural management practices aimed at preventing the occurrence of Sooty Canker are the most successful methods of controlling this disease.
Check your garden everyday
For insects and diseases along the way If there is a change that you see at any time Take care of the problem and your plants will be fine. |
