What are the control methods for bacterial wilt in eucalyptus?
How do you control bacterial wilt in eucalyptus? Please give an introduction. Eucalyptus bacterial wilt is a bacterial wilt disease. In recent years, with the continuous increase in eucalyptus varieties (lines) in South China and the rapid increase in plantation area, the occurrence of eucalyptus bacterial wilt has become increasingly serious, becoming an important obstacle in eucalyptus production. In eucalyptus bacterial wilt...
How do you control bacterial wilt in eucalyptus? Please give an introduction
Eucalyptus bacterial wilt is a bacterial wilt disease. In recent years, with the continuous increase in eucalyptus varieties (lines) in South China and the rapid increase in plantation area, the occurrence of eucalyptus bacterial wilt has become increasingly serious, becoming an important obstacle in eucalyptus production. In years when eucalyptus bacterial wilt is epidemic, the incidence of disease in newly planted young forests of susceptible eucalyptus varieties (lines) reaches 20%-40%, and for highly susceptible eucalyptus varieties (lines) it is as high as more than 60%, causing serious economic losses to eucalyptus growers and threatening the sustainable development of the eucalyptus industry.
1. Eucalyptus bacterial wilt
The pathogen of eucalyptus bacterial wilt is Ralstonia solanacearum (Smith) Yabuuchi, belonging to race 1, biovar III, and is identical to the bacterial wilt of Casuarina equisetifolia, tomato and sweet potato in morphological characteristics, staining reactions and physicochemical properties; the virulence of bacterial wilt strains isolated from different eucalyptus varieties and geographical provenances is basically the same. Ralstonia solanacearum is a soil-inhabiting bacterium that can usually survive in soil for several years. As soil temperature rises and humidity increases, the pathogen becomes more active and is very likely to invade the plant directly through the root surface or wounds, then multiply in large numbers in the vascular bundles, causing the diseased parts of the eucalyptus to turn brown and necrotic, the leaves to lose water and wilt, the root system to rot and turn black, the necrotic rhizome to have a fermenting odor, and after cross-sectioning and keeping moist, pale yellow or milky white bacterial ooze appears within a few minutes. In severe cases, brown necrosis appears from the rhizome of the diseased plant to the phloem of the trunk, and finally the whole plant wilts and dies. Acute bacterial wilt generally takes only a few weeks from infection to death of the plant; chronic bacterial wilt takes a longer time from infection to death, generally 3-6 months. The bacterial wilt pathogen can be spread through many routes such as seedlings, soil, water sources, root contact and agricultural operations.
2. Distribution and occurrence characteristics of eucalyptus bacterial wilt
2.1 Distribution of eucalyptus bacterial wilt
The eucalyptus bacterial wilt pathogen is distributed in many countries around the world. Brazil, Australia, South Africa, Congo, Uganda and other countries have all reported the occurrence of bacterial wilt. However, in South China it is particularly serious. Eucalyptus bacterial wilt was first discovered in Guangxi, and since then it has occurred and become epidemic to varying degrees in Guangdong, Hainan, Fujian, Taiwan, China, Yunnan and other provinces and regions of South China.
2.2 Main reasons for the epidemic of eucalyptus bacterial wilt in China
(1) South China has a southern subtropical climate. Influenced by the Pacific monsoon maritime climate, there are many typhoons, sufficient rainfall, and it is warm and humid, with an average annual temperature between 25-35°C. This creates favorable conditions for the bacterial wilt pathogen, which is suited to growing and reproducing in high-temperature, high-humidity and acidic soils.
(2) The epidemic of bacterial wilt in South China is because most coastal areas once planted susceptible Casuarina equisetifolia or cultivated tobacco, tomato, peanut and other crops easily infected by the bacterial wilt pathogen, resulting in an increased accumulation of the pathogen and enhanced pathogenicity, and it survives for a long time in soil, plant residues and garbage fertilizer.
(3) In recent years, various regions have promoted the large-scale planting of fast-growing and high-yielding eucalyptus varieties without considering the geographical distribution and the environmental conditions of matching tree species to sites, blindly planting large quantities of susceptible eucalyptus varieties, and rarely or never carrying out fungal testing and quarantine of seedlings, resulting in the large-scale epidemic of eucalyptus bacterial wilt.
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