Arizona Vegetable & Fruit Gardening For The Arizona Desert Environment.
Pictures, Photos, Images
Descriptions, Information, & Reviews.
Vegetable Garden Diseases In Arizona.

Hey! What Is Growing Under This Perfectly Healthy Looking Eggplant Leaf?
At Least It Looked Healthy On The Top Of The Leaf!
See Next Image Below.

Health Eggplant?
At Least The Top Part Looks Healthy!
Wingless Potato Aphid , Macrosiphum euphorbiae.
Hiding In Eggplant Flower & Under The Leaf In Above Photo!

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Fruit Tree Diseases In Arizona.

Here Are Our Descriptions Of Some Of The More Common Vegetable Garden Diseases In Arizona.
No Attempt Here Is Made To Show All Of Them!!
Photos & Descriptions Courtesy Of: Wikipedia, the free encyclopedia.
Wikipedia Also Uses Our Material At No Charge.


-- Crown Gall, Caused By: Agrobacterium tumefaciens or Rhizobium radiobacter ---

Crown Gall, Agrobacterium tumefaciens Agrobacterium tumefaciens (updated scientific name: Rhizobium radiobacter) is the causal agent of crown gall disease (the formation of tumours), which is commonly associated with the roots of plants, marked by abnormal enlargement of the stem near the root crown, in over 140 species of dicot plants. Rhizobium radiobacter is a rod shaped, Gram negative soil bacterium.

The disease results from infection of wounds by the free-living soil bacterium Agrobacterium tumefaciens. The first step in the infection process is the site-specific attachment of the bacteria to the plant host. Up to half of the bacteria become attached to host cells after 2 h. At 1 or 2 weeks after infection, swellings and overgrowths take place in tissue surrounding the site of infection, and with time these tissues proliferate into large tumors. If infection takes place around the main stem or trunk of woody hosts, continued tumor proliferation will cause girdling and may eventually kill the host. Crown gall is therefore economically important, particularly in nurseries where plant material for commercial use is propagated and disseminated.

Mant plant species are susceptible, including especially rose, grape, pome, and stone fruits (e.g., apples, peaches), shade and nut trees, shrubs and vines, and many perennial garden plants.

Symptoms include roundish, rough-surfaced galls, several inches or more in diameter. At first cream-coloured or greenish, they later turn brown or black. As the disease progresses, the affected plants lose vigour and may eventually die.

Galls can disrupt food and water-conducting tissues, resulting in poor growth of young trees. In addition, the stems can break at the galls, and decay.

A non-gall-forming strain of the bacterium A. radiobacter has been successful used in some commercial fruit orchards.



-- Downy & Powdery Mildew ---------- Downy Mildew ---------- On Underside Of Leaf

Downy Mildew refers to any of several types of oomycete microbes that are obligate parasites of plants. Downy Mildews belong to the family Peronosporaceae.

They are a particular problem for growers of crucifers, grapes, cucurbits and other vegetables that grow upon vines. The prime example is Peronospora farinosa.

The initial symptoms of Downy Mildew appear on plant leaves as light green to yellow spots.

Cucurbit Downy Mildew (caused by Pseudoperonospora cubensis) is of concern to most home gardeners since it is specific to cucurbits (e.g., cantaloupe, cucumber, pumpkin, squash, watermelon and other members of the Cucurbitaceae/gourd family). This disease is one of the most important diseases of cucurbits worldwide.



------------ Fire Blight ------------------------- Fire Blight --------- Fire Blight On Gala Apple Tree-

Fire Blight, also written fireblight, is a contagious disease affecting apples, pears, and some other members of the Rosaceae family. It is a very serious concern to both home & commercial producers of apples, and pears. Under optimal conditions, it can destroy an entire orchard in a single growing season.

The term "fireblight" describes the appearance of the disease, which can make affected areas appear blackened, shrunken and cracked, as though scorched by fire.

Erwinia amylovora, a Gram-negative bacterium in the family Enterobacteriaceae, is the cause of the disease. The disease is believed to be indigenous to North America, from where it spread to most of the rest of the world.

Pears are the fruit trees most susceptible to Fire Blight, but apples, loquat, crabapples, quinces, hawthorn, cotoneaster, pyracantha, raspberry, and some other rosaceous family plants are also vulnerable.

Primary infections are established in open blossoms and tender new shoots and leaves in the spring when blossoms are open. Honeybees and other insects, birds, rain and wind can transmit the bacterium to susceptible tissue. Injured tissue is also highly susceptible to infection, including punctures and tears caused by plant-sucking or biting insects. Hailstorms can infect an entire orchard in a few minutes, and growers do not wait until symptoms appear, normally beginning control measures within a few hours.

Once deposited, the bacterium enters the plant through open stomata and causes blackened, necrotic lesions, which may also produce a viscous exudate. This bacteria-laden exudate can be distributed to other parts of the same plant or to susceptible areas of different plants by rain, birds or insects, causing secondary infections. The disease spreads most quickly during hot, wet weather and is dormant in the winter when temperatures drop. Infected plant tissue contains viable bacteria, however, and will resume production of exudate upon the return of warm weather in the following spring. This exudate is then the source for new rounds of primary infections.

The pathogen spreads through the tree from the point of infection via the plant's vascular system, eventually reaching the roots and/or graft junction of the plant. Once the plant's roots are affected, the death of the plant often results. Over pruning and over fertilization (especially with nitrogen) can lead to watersprouts and other midsummer growth that leave the tree more susceptible.

Sprays of the antibiotics streptomycin or terramycin can prevent new infections. However, the use of such sprays has led to streptomycin-resistant bacteria in some areas, such as in the states of California and Washington. Certain biological controls consisting of beneficial bacteria can also prevent fireblight from infecting new trees.

The only effective treatment for plants already infected is to prune off the affected branches and remove them from the area. The rest of the tree can only be saved if the blighted wood is removed before the infection spreads to the roots.

Plants or trees should be inspected routinely for the appearance or new infections.

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Texas Root Rot or Phymatotrichopsis Root Rot, (Phymatotrichopsis omnivora and Phymatotrichum omnivorum fungi)

Texas Root Rot or Phymatotrichopsis Root Rot (also known as cotton root rot, or, in the older literature, Ozonium root rot) is a pathogen fairly common in Mexico and the southwestern United States that causes sudden wilt and death of affected plants, usually during the warmer months. It is a soil-borne fungus of the species Phymatotrichopsis omnivora that attacks the roots of susceptible plants. Because the damaged roots are unable to take up enough water to maintain the plant in warm weather, the leaves wilt and the plant dies. The dead leaves usually remain attached to the plant.

Texas Root Rot is one of the most destructive fungal plant diseases. A multitude ( more than 1,700 ) of dicotyledonous tree, shrub and herbaceous plants are susceptible to Texas root rot, including figs, pomegranates, elms, grapes, cotton, alfalfa, oleander, and roses. Some monocot plants are tolerant while others are immune.

Phymatotrichopsis omnivora and Phymatotrichum omnivorum fungi are known to thrive in moist and alkaline soils. They can survive for long periods in the soil, sometimes lying dormant for decades, and they can penetrate to depths of up to twelve feet. Increasing the organic content of the soil with compost and green manure may help to reduce growth of the fungi.

Eradication or control of Texas root rot is almost impossible!



--------- Powdery Mildew --------------- Powdery Mildew --------- Downy & Powdery Mildew -

Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of fungi in the order Erysiphales.

Powdery Mildew is one of the easier diseases to spot, as its symptoms are quite distinctive.

Infected plants display white powdery spots on the leaves and stems. The lower leaves are the most affected, but the mildew can appear on any above-ground part of the plant.

As the disease progresses, the spots get larger and denser as large numbers of asexual spores are formed, and the mildew may spread up and down the length of the plant.

Erysiphe necator (or Uncinula necator) causes powdery mildew of grapes.

The fungus causing powdery mildew of onions is Leveillula taurica (also known by its anamorph name, Oidiopsis taurica). It also infects the artichoke.

Podosphaera leucotricha is a fungus that can cause powdery mildew of apples and pears.

Podosphaera fusca is a fungus that can cause powdery mildew of Curcurbits: cucumbers, squashes (including pumpkins), luffas, melons and watermelons.

Podosphaera aphanis is the cause of powdery mildew in strawberries and other plants of the Rosaceae family.



Fruit Tree Diseases:

Many diseases of apple are not restricted to one part of the tree. For example, apple scab attacks the fruit, leaves, and flowers. Powdery mildew can also infect many parts of the tree. Fire blight is a tree disease infecting leaves, shoots, limbs, and trunk, but it can infect fruit and root stock. The fungal disease complex known as sooty blotch and flyspeck is, however, restricted to the fruit.

Common peach and nectarine diseases are peach leaf curl, brown rot, scab, bacterial spot and powdery mildew.

There are many sources of information about fruit pests and diseases. For Arizona, we often refer to Diseases of Urban Plants, from the Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona; for more information and control recommendations.

There are many other sources of information about fruit pests and diseases. We also refer to GreenShare Factsheets from the Cooperative Extension Education Center, College of the Environment and Life Sciences University of Rhode Island, Kingston, Rhode Island on these specific pests and diseases for more information and control recommendations.

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Beneficial Insects:

Not all insects found in an apple orchard are pests. Many organisms benefit the grower by eating or parasitizing pests in the orchard. These organisms are known as beneficials, natural enemies, or biological control agents. They may be native or introduced from other areas.

Beneficial natural enemies (insects and mites) that may occur in an apple orchard could be classified as predators or parasitoids. Predators are those that attack, kill, and feed directly on a pest (prey). Examples of common orchard predators are ladybeetles, flies, lacewings, wasps, bugs, ants, spiders, and predator mites. Parasitoids are insects that lay eggs on or in a pest (host). The developing larva lives and feeds on the host, parasitizing and eventually killing it. Examples include parasitic wasps such as the egg parasite, Trichogramma sp.

Bees are a different class of beneficial insects in the orchard in that they benefit the grower by aiding pollination.

It is important that growers are able to recognize, identify, and conserve beneficials in their orchard. Conservation of beneficial organisms is a basic tenet of an ecologically sound pest management strategy. Conservation or enhancement of beneficials can be achieved through judicious use of pesticides such as spraying only when and where needed, accurate timing of sprays, and selecting pesticides that are least toxic to beneficials.

For Example: Many growers now place colonies of the Blue Orchard Mason bees in their orchards to pollinate their crops for maximum production.


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