Just like people contracting bacterial disease (strep throat, TB, salmonella poisoning), plants can also be effected by bacterial disease. Bacterial diseases in plants may affect stems, leaves or roots or be carried internally. Generally, they belong to the genera
Erwinia, Pectobacterium, Pantoea, Agrobacterium, Pseudomonas, Ralstonia, Burkholderia, Acidovorax, Xanthomonas, Clavibacter, Streptomyces, Xyllella, Spiroplasma, and
Phytoplasma.
A bacterial disease may cause a variety of symptoms: blights, cankers, galls, leaf spots, overgrowths, specks, scabs, or wilts. Generally, the common name of the disease is a combination of the symptom or appearance and its location on the plant, like Bacterial Leaf Spot caused by Pseudomonas cichorii and fireblight in pears and apples, caused by Erwinia amylovora. In contrast to viruses that live inside plant cells, bacteria grow in the spaces between cells, producing toxins, special proteins or enzymes that damage the plant cells. Agrobacterium causes cells to genetically modify, producing cancer-like growths called galls.
Bacterial diseases are spread in many ways – rain, wind, birds or insects. People can also spread bacterial diseases by using infected pruning tools, by improper disposal of infected plant material, improperly managing plants in the winter, or introducing infected plants in an area. Bacteria require a wound or natural opening like stomata to get inside a plant to cause damage. Once inside, they kill host cells. Bacteria are hardy – if when spread, they find no ready host, they can go dormant until a suitable host is found.
Control of Bacterial Disease
Bacterial diseases are difficult to control; usually it is better to prevent the spread rather than cure a plant. Of course, in agricultural applications it is sometimes necessary to both prevent and treat on a large-scale basis.
- Choose plants that are resistant; use disease-free seed or plants.
- Disinfect pruning tools. Botani-Wipes are handy for this.
- Plan crop rotations to eliminate over-wintering.
- Prevent surface wounds on plants.
- Expose plant material you wish to compost to dry air, heat and sunlight to kill any disease-causing bacteria.
- After treating with any substance that kills bacteria, always replace them with good bacteria such as those in EM-1 or Compost Tea – otherwise any leftover disease causing bacteria will take over again!
- Control insects that might vector bacterial diseases.
- Water correctly; avoid wetting leaves on indoor plants. Misting may cause bacterial growth on leaves.
- Give plants plenty of room, whether in a pot or in the ground.
- Pay attention to indoor plant care in the winter because of lower light intensity.
- Isolate the diseased plant if possible and prune infected leaves. Do not prune more than 1/3 of the leaves of a plant.
- If the disease is systemic, affecting the stem as well as leaves, the plant cannot recover. Destroy it to prevent the spread of the disease to other plants.
- Make sure the soil is healthy with plenty of organic nutrients and beneficial microorganisms.
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