Plant Ailments Caused by Bacteria
Bacteria, microscopic single-celled organisms, play a significant role in the health of plants. They can be beneficial or pathogenic, causing diseases that affect various crops. This article aims to shed light on common plant bacterial diseases, their symptoms, and methods for controlling their spread.
Understanding Plant Bacterial Diseases
Bacteria-free seed or propagation materials are essential in cultural practices, helping to prevent the introduction of pathogens. Integrated management measures for bacterial plant pathogens include genetic host resistance, sanitation, use of resistant planting materials, and chemical control.
Anthrax, caused by Bacillus anthracis, was the first bacterial disease discovered in 1876. Since then, numerous bacterial diseases have been identified, such as bacterial leaf spot, bacterial spot in tomatoes, angular leaf spot in strawberries, and bacterial wilt of geraniums. These diseases commonly manifest as angular or dark brown spots on leaves, stems, and fruits, leaf yellowing, wilting, and sometimes fruit scabbing or wilting of entire plants.
Identifying and Controlling Common Bacterial Diseases
- Bacterial leaf spot: Dark, angular spots on leaves, sometimes enlarging, can cause leaf yellowing and drop. This is often seen in tomatoes and peppers.
- Bacterial spot (tomatoes): Small, dark brown angular spots on leaves, stems, and fruits, with potential leaf yellowing and scabby lesions on fruit.
- Angular leaf spot (strawberry): Angular lesions on leaves, typical of Xanthomonas fragariae infection.
- Bacterial wilt: Wilting and death of plants caused by Ralstonia solanacearum, often with no foliar spots but rapid decline.
Preventative cultural practices combined with resistant cultivars and sanitation are the most effective control strategies for these diseases. Using disease-resistant plant varieties, employing crop rotation, using certified disease-free seeds and transplants, avoiding overhead irrigation, sanitizing gardening tools, removing and destroying infected plant debris promptly, maintaining good garden hygiene, and managing plant spacing and pruning to improve air circulation and reduce humidity are all crucial steps in managing bacterial diseases.
Chemical Control and Other Factors
Chemical treatments are often limited or less effective for bacterial pathogens. However, antibiotics such as streptomycin and oxytetracycline can help kill or suppress plant pathogenic bacteria prior to infection and reduce the spread of disease. Tetracycline is used to treat diseases caused by phytoplasmas and spiroplasmas, particularly pear trees with the pear decline disease. Applications of copper-containing compounds or Bordeaux mixture can also be used in chemical applications.
Bacterial diseases tend to thrive in warm, wet, and humid conditions and are spread by water splash, contaminated tools, seed, and infected plant material. Preventative cultural practices are, therefore, of utmost importance in managing these diseases.
This summary is based primarily on data about common plant bacterial diseases from tomato, strawberry, and general garden crops in North America and Florida, as well as Canadian plant disease surveillance. Fastidious vascular bacteria, difficult or impossible to culture in the laboratory, cause diseases in plants. Fireblight of pear and apple, caused by Erwinia amylovora, was discovered in 1877-1885. Phytoplasmas and spiroplasmas are bacteria that lack rigid cell walls and infect plants.
In conclusion, understanding and managing bacterial diseases in plants is crucial for maintaining healthy crops. By implementing preventative cultural practices, using resistant cultivars, and employing sanitation measures, gardeners and farmers can significantly reduce the impact of these diseases.
