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Plant Library

Sooty Molds

Sooty molds

Sooty molds are Ascomycete fungi which grow on plant exudates and the sugary honeydew secreted by insects such as aphids, scales, the whitefly, and other insects which suck sap from their host plants. The name itself is descriptive, as sooty mold is a black, powdery coating adhering to the leaves of ornamental plants such as azaleas, gardenias, camellias,crepe myrtles, and laurels.

 

 

Leaf Spot

Leaf Spot

Pathogen-caused leaf spot diseases, particularly those of stone fruit trees and such vegetables as tomatoes, peppers, and lettuce are of two types, those caused by bacteria and those caused by fungus. Leaf spotting of either kind is generally similar in appearance and effect. Prevention and treatment of both kinds often involve the same practices.

 

 

Mite

Mite

Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.

 

 

Whitefly

Whitefly

Whiteflies are small hemipterans that typically feed on the undersides of plant leaves. They comprise the family Aleyrodidae, the only member of the superfamily Aleyrodoidea. More than 1550 species have been described.

 


Slug

Slug

Slug is a common name for an apparently shell-less terrestrial gastropod mollusc. The word “slug” is also often used as part of the common name of any gastropod mollusc that has no shell, has a very reduced shell, or has only a small internal shell.

 

 

Scale Insect

Scale insect

The scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. They comprise the superfamily Coccoidea, previously placed in the now obsolete group called “Homoptera”. There are about 8,000 described species of scale insects.

 

 

Club Root

Club Root

A serious problem in home gardens, club root can be managed using these organic methods.

Symptoms

Affecting members of the cabbage family, club root is a serious plant disease in North America. It is caused by the soil-borne fungus, Plasmodiophora brassicae, which infects susceptible plants through root hairs. Diseased roots become misshapen and deformed (clubbed), often cracking and rotting. As a result, plants have difficulty absorbing water and nutrients properly.

 

 

Downy Mildew

DOWNY MILDEW

A fungal disease, downy mildew (Plasmopara viticola) affects many plants and appears as yellow to white patches on the upper surfaces of older leaves. On the undersides, these areas are covered with white to grayish, cotton-like fungi. These “downy” masses are most often noticed after rain or heavy dew and disappear soon after sunny weather resumes. As the disease progresses leaves may eventually turn crisp and brown and fall off even though the plant has ample water.

 

 

Gray Mold

Gray Mold

Found on a wide range of plants (too many to mention), gray mold (Botrytis cinerea) is a fungal disease that travels quickly through gardens, especially during damp, cool to mild weather. It can be identified as grayish colored soft, mushy spots on leaves, stems, flowers and on produce. Spots may become covered with a coating of gray fungus spores, especially if humidity is high. Fruit or plants shrivel and rot and often develop black, stone-like sclerotia under rotted parts.

 

 

Leaf Curl

Leaf Curl

A fungal disease that affects peaches and nectarines, leaf curl (Taphrina deformans) is one of the most common disease problems found in backyard orchards. It appears in spring as reddish areas on developing leaves. These areas become thickened and puckered, causing leaves to curl and distort. When severe, leaf curl can substantially reduce fruit production.

 

 

Brown Rot

Brown Rot

The most common fungal disease affecting the blossoms and fruit of almonds, apricots, cherries, peaches and plums. Brown rot (Monilinia fructicola) overwinters in mummified fruit (on the tree and on the ground) and infected twigs.

 

 

Mosaic Virus

Mosaic Virus

Affecting a wide variety of plants, including roses, beans, tobacco, tomatoes, potatoes and peppers, mosaic is a viral diseases found throughout the United States.

Plant viruses can be difficult to detect as symptoms look similar to several nutrient deficiencies. Look for:

  • Yellow stripes or spots on foliage
  • Wrinkled or curled leaves
  • Stunted growth and reduced yields
  • Infected fruit appears mottled and develops raised “warty” areas

 

 

Early Blight

Early Blight

Symptoms. All aboveground parts of the plant can have symptoms of this disease. The fungus can kill seedlings before or after they break the soil surface. It can also cause collar rot in young plants, in which a dark, slightly sunken spot develops on one side of the stem. This spot will either grow completely around the stem or weaken the stem, causing the plant to fall over and die.

 

 

Septoria Leaf Spot

 

 

Leaf rusts

Leaf rusts

Symptoms of leaf rusts include bright yellow, orange or red leaf spots. These leaf spots often produce an abundance of yellow, orange, red, or brown powdery spores that can be easily rubbed off and seen on a white tissue or paper towel. Spores may be produced in little blisters within leaf spots or may emerge from tiny cups or tubes on the lower surface of the leaf. In some hosts, leaf rust fungi also infect petioles, young green stems, and fruit.

 

 

Roses

Roses: Diseases and Abiotic Disorders

A variety of plant pathogens can attack roses. The most common problem in California is powdery mildew, but a number of other diseases including rust, black spot, botrytis, downy mildew, and anthracnose may cause problems where moist conditions prevail.

 

 

Snails and Slugs

Snails and Slugs

Snails and slugs are among the most bothersome pests in many gardens and landscapes. The brown garden snail, Cornu aspersum (formerly Helix aspersa), is the most common snail causing problems in California gardens. It was introduced from France during the 1850s for use as food. Another troublesome snail is the white garden snail, Theba pisana. It currently is established only in San Diego County but has been found in Los Angeles and Orange counties as well.

 

 

Aphids

Aphids

Aphids are small, soft-bodied insects with long slender mouthparts that they use to pierce stems, leaves, and other tender plant parts and suck out fluids. Almost every plant has one or more aphid species that occasionally feed on it. Many aphid species are difficult to distinguish from one another; however, management of most aphid species is similar.

 

 

Thrips

Thrips

Thrips, order Thysanoptera, are tiny, slender insects with fringed wings. They feed by puncturing the epidermal (outer) layer of host tissue and sucking out the cell contents, which results in stippling, discolored flecking, or silvering of the leaf surface. Thrips feeding is usually accompanied by black varnishlike flecks of frass (excrement).

 

 

Earwigs

Earwigs

Earwigs are among the most readily recognized insect pests in home gardens. Although earwigs can devastate seedling vegetables or annual flowers and often seriously damage maturing soft fruit or corn silks, they also have a beneficial role in the landscape and have been shown to be important predators of aphids.

 

 

Mealybug

Mealybug

Mealybugs are part of the insect families collectively known as scale insects. They are soft-bodied, without the outer shell associated with insects in the other scale insect families. Instead, mealybugs are usually covered with a white waxy powder

 

 

Fungus

Fungus

Disease fungi take their energy from the plants on which they live. They are responsible for a great deal of damage and are characterized by wilting, scabs, moldy coatings, rusts, blotches and rotted tissue.