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Black Sooty Mold

Description

Sooty mold is caused by saprophytic fungal organisms that feed and grow on honeydew excreted by piercing-sucking insects such as aphids, whiteflies, mealybugs, psyllids, and scale insects. This plant disease is characterized by black patches or coatings on leaves, stems, and fruits.

Damage

Black sooty mold causes superficial black or dark brown marks or patches on leaves and fruits. This fungus is not parasitic, but it blocks sunlight to reach the leaves and reduces the leaf’s photosynthesis which can stunt plant growth and cause premature leaf drop.

Control

Control of sooty mold requires suppression of insects creating the honeydew.

Advice
  • Spray sooty mold on the plant by adding one tsp of mild liquid soap to one gallon of water. Some types of soap can damage sensitive plants, so test the solution on a few leaves before spraying the entire plant.

Mosaic Virus

Description

Mosaic virus in plants is contagious and can be transmitted by piercing-sucking insect pests such as aphids from the infected plant to the healthy plant. Virus-carrying aphids can spread the virus within minutes to a few hours in a field resulting in high rates of infection.

Damage

This disease is characterized by leaf deformities, yellowing, mosaic, or mottling patterns. In other words, it makes a pattern of irregular marks, spots, streaks, and blotches of yellow colours. Plants often distorted or stunted growth, and fruits and flowers are deformed and reduced.

Control

There is no cure for plant virus diseases. To control the Mosaic Virus, suppress aphids that transmit the virus.

Advice
  • Remove all infected plants and destroy them.
  • Disinfect pruning tools between each cut.

Fire blight of apple and pear

Description

Fire blight is a plant disease caused by a bacterium -Erwinia- which is spread passively by insects with piercing-sucking mouthparts such as aphids. This bacterium infects hosts in the Rosaceae family such as apples, pears, and quince.

Damage

Fire blight is a very destructive bacterial disease that causes considerable damage and economic losses. Symptoms may appear on the blossoms, shoots, branches, and trunk of apples and pears. Infected blossoms produce a typical blighted, wilted, shriveled, and brown appearance and in infected leaves complete chlorosis, browning, and withering occurs. Fruitlets also appear water-soaked, off-colour, and shrivel up. This bacterium can kill young trees in a single season, while older trees can survive several years, even with continuous dieback.

Control

Control of fire blight requires suppression of the insects with piercing-sucking mouthparts such as aphids that transmit the virus.

Advice
  • Monitor trees regularly, remove, and destroy fire blight infections.
  • Disinfect pruning tools between each cut.

Citrus canker

Description

Citrus canker is a devastating disease of citrus caused by Xanthomonas citri bacterium. The bacterium that causes citrus canker enters leaves through stomata, or wounds caused by weather damage or insects such as the citrus leaf miner. Citrus leaf miners damage the leaf through mining activity and create wounds in the leaf tissue, increasing the risk of Xanthomonas bacterium infection.

Damage

Citrus canker bacterium causes lesions usually surrounded by a yellow halo on leaves, branches, stems, and fruits of plants including citrus and other plants in the citrus family. The disease leads to defoliation, twig dieback, blemished fruit, and fruit drop prematurely. In severe cases, it significantly affects the vitality of citrus trees. Generally, young plants and seedlings are more susceptible to citrus canker.

Control

Control of citrus cankers requires insect pest management such as controlling leaf miners.

Advice
  • Pruning and burning twigs infected by citrus canker
  • Disinfect pruning tools between each cut.