Bacterial pathogens are single-celled organisms that require warmth and moisture to survive and reproduce. Bacteria are not capable of penetrating host plants and enter through wounds or natural plant openings. Bacterial pathogens can enter host plants through splashed water, insects, contaminated tools and equipment, or contact with diseased plants. Symptoms associated with bacteria include leaf spots, soft rots, scabs, wilts, and galls.
Fungal pathogens can grow on living or dead host plants. Fungi grow over host tissue by means of hyphae--a fine, threadlike structure. Many fungi are able to penetrate host tissue using enzymes. Fungi grow wherever environmental conditions are favorable. Fungi reproduce by producing spores that can be either sexual or asexual in nature. Many fungi require high humidity or free water for germination of spores. Many fungal spores are able to survive long periods of unfavorable conditions and will germinate once conditions become favorable. Wind, splashed water, tools, machinery, and insects are ways in which fungal pathogens can come into contact with host plants. Symptoms associated with fungal pathogens include soft rots, stunting, curling of leaves, leafspots, wilts, mildews, and blights.
General differences between diseases caused by fungal and bacterial pathogens are outlined below.
Viral pathogens are minute organisms that cannot be seen unless highly magnified. Viruses must have a living host to survive and replicate. Viruses are most often spread by plant-feeding insects with piercing/sucking mouthparts, such as aphids, leafhoppers, and whiteflies. However, they can also be spread by grafting, insect pollination, pruning, and the growing together of infected roots. Common symptoms of viruses include stunting, mottling or mosaic patterns on leaves, or abnormal growth, such as leaf deformation.
For Further Information on Plant Diseases Consult:
Sinclair, W.A. , H.H. Lyon, and W.T. Johnson. 1987. Diseases of Trees & Shrubs. Cornell Univ. Press, Ithaca, NY. 573 pps.
Agrios, George. 1988. Plant Pathology (3rd Ed.) Academic Press, Inc., San Diego, CA. 803 pps.
|Diseases That Affect A Wide Range Of Ornamental Plants In North Carolina||Nematodes||Preparing Disease Specimens For Diagnosis|
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