List of Plant Diseases that you might find in your Garden
Blossom End Rot of Tomato
Blossom end rot is a troublesome disease, familiar to most gardeners who have grown tomatoes. The disease is often prevalent in commercial as well as home garden tomatoes, and severe losses may occur if preventive control measures are not undertaken.
Symptoms may occur at any stage in the development of the fruit, but, most commonly, are first seen when the fruit is one-third to one-half full size. As the name of the disease implies, symptoms appear only at the blossom end of the fruit. Initially a small, water-soaked spot appears, which enlarges and darkens rapidly as the fruits develop. The spot may enlarge until it covers as much as onethird to one-half of the entire fruit surface, or the spot may remain small and superficial. Large lesions soon dry out and become flattened, black, and leathery in appearance and texture.
This disease does not spread from plant to plant in the field, nor from fruit to fruit in transit. Since it is of a physiological nature, fungicides and insecticides are useless as control measures. The occurrence of the disease is dependent upon a number of environmental conditions, especially those that affect the supply of water and calcium in the developing fruits. Factors that influence the uptake of water and calcium by the plant have an effect on the incidence and severity of blossom end rot. The disease is especially prevalent when rapidly growing, succulent plants are exposed suddenly to a period of drought. When the roots fail to obtain sufficient water and calcium to be transported up to the rapidly developing fruits, the latter become rotted on their basal ends. Another common predisposing factor is cultivation too close to the plant; this practice destroys valuable roots, which take up water and minerals. Tomatoes planted in cold, heavy soils often have poorly developed root systems. Since they are unable to supply adequate amounts of water and nutrients to plants during times of stress, blossom end rot may result. Soils that contain excessive amounts of soluble salts may predispose tomatoes to the disease, for the availability of calcium to the plants decreases rapidly as total salts in the soil increase.
Control of blossom end rot is dependent upon maintaining adequate supplies of moisture and calcium to the developing fruits. Tomatoes should not be excessively hardened nor too succulent when set in the field. They should be planted in welldrained, adequately aerated soils. Tomatoes planted early in cold soil are likely to develop blossom end rot on the first fruits, with the severity of the disease often subsiding on fruits set later. Thus, planting tomatoes in warmer soils helps to alleviate the problem. Irrigation must be sufficient to maintain a steady even growth rate of the plants. Mulching of the soil is often helpful in maintaining adequate supplies of soil water in times of moisture stress. When cultivation is necessary, it should not be too near the plants nor too deep, so that valuable feeder roots remain uninjured and viable. In home gardens, shading the plants is often helpful when hot, dry winds are blowing, and soil moisture is low. Use of fertilizer low in nitrogen, but high in superphosphate, such as 4-12-4 or 5-20-5, will do much to alleviate the problem of blossom end rot. In emergency situations, foliage can be sprayed with calcium chloride solutions. However, extreme caution must be exercised since calcium chloride can be phytotoxic if applied too frequently or in excessive amounts. Foliar treatment is not a substitute for proper treatment of the soil to maintain adequate supplies of water and calcium
Leaf symptoms are roundish, black spots with fringed margins that can be up to ½” in diameter. The spots form on the upper sides of leaves. The tissue surrounding the spots turns yellow. Infected leaves may prematurely drop from the plant. Usually lower leaves are infected first. Excessive leaf drop weakens the plant, predisposing it to other forms of injury such as those caused by temperature extremes. Cane symptoms are blister-like, reddish-purple blotches that later turn black.
plants with dark brown to black Ascochyta leaf spots develop a stem canker that leads to plant wilting and dieback.The most devastating disease to attack clematis. It is a fungal disease. The disease appears as a sudden stem collapse just as the flowers begin to open.
One or several stems on the plant may discolor and collapse.
Powdery mildew first appears as white, powdery spots that may form on both surfaces of leaves, on shoots, and sometimes on flowers and fruit. These spots gradually spread over a large area of the leaves and stems. An exception is one of the powdery mildews that affects artichokes, onions, peppers, and tomatoes: it produces yellow patches on leaves but little powdery growth.
Leaves infected with powdery mildew may gradually turn completely yellow, die, and fall off, which may expose fruit to sunburn. On some plants, powdery mildew may cause the leaves to twist, buckle, or otherwise distort. Powdery mildew fungal growth does not usually grow on vegetable fruits, although pea pods may get brownish spots. Severely infected plants may have reduced yields, shortened production times, and fruit that has little flavor.
Dollar Spot on Turf Grass
On putting green turf, dollar spot appears as small spots, approximately the size of a dollar coin, that are bleached-white or light tan in color. On turf mowed at heights greater than 0.5”, the spots may expand in size up to 6” or more in diameter. The affected leaves typically remain upright and are characterized by having white or light-tan lesions with light reddish-brown margins. As the lesions expand, the leaves are girdled and the upper part of the leaves dies slowly. Distinct lesions are sometimes not evident on close-cut turfgrasses; instead, the leaves die back from the tip and turn white or light tan in color. The grass in the spots may be killed to the soil surface if the disease continues to develop, and many spots may merge to produce large blighted areas
Downy mildew colonies often appear first on the underside of leaves, and they sometimes have a bluish tinge (1; 3). In many cases, they can grow systemically throughout the plant. If growing abundantly on a leaf, downy mildew colonies can be confused with gray mold (Botrytis) or with powdery mildew. Microscopically, they are very easy to tell apart from powdery mildew and Botrytis. On the foliage, small yellow spots develop on the upper sides of the leaf while white to bluish-white fluffy growth forms on the underside of the leaf. As the leaf spot dies, the fluffy growth darkens to gray in color. Infected leaves and branches may be distorted and die.
This is a fungal disease that usually attacks ornamentals and fruit trees. Dry, reddish orange, spores are usually found on the under side of leaves. Moderate amounts will usually not harm plants. Severely infected plants can die from rust.
The first evidence of damping-off or seed piece decay (as in potatoes) is the failure of some plants to emerge. If seeds are attacked before they germinate, they become soft and mushy, turn dark brown, and decay. They may have a layer of soil clinging to them when they are dug up because the soil is interwoven with fine, threadlike fungus growth. Germinating seedlings shrivel and may darken. If seedlings are attacked after they emerge, stem tissue near the soil line is decayed and weakened, usually causing plants to topple and die. When only roots are decayed, plants may continue standing but remain stunted, wilt and eventually die. As seedlings get older, they become less susceptible to damping-off pathogens.
Nuisance and Detrimental Molds.
Organic mulches are a valuable asset to the gardener. They control weeds and retain moisture. They add valuable beneficial microorganisms to the soil.
However every now and then undesirable microorganisms find their way into our soil. The result is molds and fungi. The fungal growth is caused by a lack of oxygen.
Fire Blight on Ornamentals.
Fire blight is a disease that can cause blight of blossoms and shoots, dieback of branches from cankers and when severe, death of the entire tree. Flowers and flower clusters appear water-soaked then droop and shrivel turning brown or black. Young leaves and shoots wilt, turn gray-green, and bend downward forming the characteristic shepherd’s crook.Leaves and tips of infected shoots turn brown or black
Common Plant Diseases in the Landscape and Garden
Frequently Asked Questions