Leaves disease damage

Fruit with faded or gray-white, sunken patches or pits. Causes Sunscald cold injury. Green or ripe fruit can be sunscalded. Damage shows up as a large, sunken patch on the exposed side. Patches turn dry and may develop black mold. Control leaf diseases to prevent defoliation, so fruit will be shaded and protected from direct sun. Stake plants. 

Iron toxicity is a syndrome of disorders associated with large concentrations of Fe + in the soil solution. It is only found in flooded soils. A wide range of concentrations produce the symptoms, from 1000 to only 10mgL in soils with poor nutrient status—especially of P or K—or with respiration inhibitors such as H2S. There are large differences in tolerance between rice varieties. The effects include internal damage of tissues due to excessive uptake of Fe + impaired nutrient uptake, especially of P, K, Ca and Mg and increased diseases associated with imbalanced nutrition, such as brown leaf spot (caused by Helminthospo-rium oryzae), sheath blight (caused by Rhizoctonia solani) and blast (caused by Pyricularia oryzae). 

Cause Cercospora leaf spot. Destroy spotted leaves. Spray plants with copper if this fungal disease is severe to prevent further spread, or before symptoms develop if it has been a problem in the past. To prevent problems, soak seed in 122°F water for 25 minutes before planting. (Be aware that this treatment can damage seed viability for complete instructions, see page 422.) Eliminate weeds that can harbor the disease. Plant cultivars, such as Big Red Hybrid and Red Ace , that are tolerant of this disease. 

Causes Diseases poor pollination nutrient deficiency. Many diseases cause misshapen fruit use leaf symptoms to determine the disease causing the problem. If leaves are healthy, high temperatures may have damaged pollen, or bees ma not ha e been active. Early in the season. wait for better conditions, or pollinate the flouers ourself by dusting pollen from male flowe -s onto female flowers (see page 214 for an .llustra n of male and female... 

Leaf undersides with powdery orange pustules. Cause Rust. In the western United States, rust causes reddish orange bubbles to appear on the undersides of the leaves. Later, they spread to the upper surfaces. See page 204 for an illustration of the damage. Pick off and destroy infected leaves in areas where the disease is common, start a spraying program early in the spring with weekly applications of sulfur. 

Symptoms Leaf damage starts as small yellow spots that gradually turn brown they are often surrounded by a ring of yellow or brownish black tissue. Whole leaves may turn yellow and drop, exposing fruit to sun, which may result in sunscald. This disease usually starts on lower leaves and progresses upward. 

High concentrations of ozone in the atmosphere may cause early fall color and leaf drop. This damage can be difficult to diagnose because symptoms mimic many other disease conditions. Check for similar damage on other ozone-susceptible plants growing in the same area. 

Prevention and Control Bright light or excessively high temperatures can cause sunscald. On tomatoes this problem commonly occurs when a disease such as leaf spot causes leaves to fall, suddenly exposing once-shaded fruit to full sunlight. Plant cultivars that are resistant to major foliage diseases. Once damage occurs, there is no control. 

Fungi also cause a number of plant and animal diseases. Because fungi are more chemically and genetically similar to animals than other organisms, fungal diseases are very difficult to treat. Plant diseases caused by fungi include rusts, smuts, and leaf, root, and stem rots, and may cause severe damage... 

Rubber trees are affected by a number of diseases involving roots, stems, and leaves. However, effective control measures have been evolved for all these diseases, except the South American Leaf BUght, caused by the fungus Microcyclus ulei, which has caused extensive damage to rubber plantations in South America. Fortunately Asia and Africa are free from this disease... 

In contrast to case reports of liver disease, no evidence of liver damage was found in regular consumers (1 to 10 years of regular use) of comfrey (species not identified) leaf (Anderson and McLean 1989). 

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