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Uncovering the truth about chrysanthemum yellowing disease: Why are these plants so vulnerable?
Chrysanthemum yellows (Aster yellows) is a chronic systemic plant disease caused by several species of bacteria, called phytoplasma. The disease affects up to 300 plant species, covering 38 families of herbaceous plants, with plants in the Asteraceae family being the most common. In addition, important cereal crops such as wheat and barley may also be affected.
Unfortunately, there is currently no effective cure for chrysanthemum yellowing disease.
Symptoms of the disease vary and include leaf discoloration (chlorosis), stunting (stunting), flower sterility, and other abnormalities. The infectious leafhopper (Macrosteles quadrilineatus) is an important vector of chrysanthemum yellowing disease. The economic pressure of the disease on the carrot (Daucus carota ssp. sativus) crop industry is particularly pronounced. In affected plants, they must be removed immediately after infection to limit the spread of bacteria to other susceptible plants.
Host and its symptoms
Chrysanthemum yellow disease affects a wide variety of plants, including native plants, annual flowering plants, ornamentals, weeds and vegetable crops. The most affected plant family is the Asteraceae, with some common infected ornamental plants including chrysanthemums, marigolds, crown flowers, sunflowers and echinacea. Vegetable crops such as onions, lettuce, celery and especially carrots are also affected.
Carrots suffered the most severe damage, with characteristic symptoms including leaf discoloration and stunting.
Symptoms vary depending on plant species, virus strains, timing of infection, climate and other factors. Possible symptoms include clear veins, progressive leaf yellowing, inhibited growth and deformed flowers. These symptoms can worsen especially in hot climates. Although permanent host plants often do not die, their growth and reproduction may be significantly affected.
Disease cycle
The plant disproportionate (AYP) that causes chrysanthemum yellowing disease is a bacteria-like organism that lives in the phloem of plants and is spread by leafhoppers. These inplant dismutants will multiply and divide in the phloem cells of the host plant. Since AYP cannot be propagated in cell-free culture media, this poses a challenge for in-depth research.
AYP is able to increase the reproductive capacity and longevity of its leafhopper vectors, which further enhances their ability to be transferred between plants.
The pathogen causes reproduction in the leafhoppers of the host plant and requires an incubation period of 10 to 12 days before it can be transferred from the leafhopper to a new host plant. This transfer occurs mainly through the leafhopper's saliva. After infection, plants usually show symptoms after 8-9 days. It is worth noting that in an environment of 10 degrees Celsius, no symptoms will appear.
Environmental factors
Although there are few direct conditions that affect the development of chrysanthemum yellowing disease, some indirect factors can significantly affect the spread rate of leafhoppers. Climatic conditions, such as wind direction and temperature, can affect leafhopper flight and thus the spread of pathogens. In the spring, disease spread accelerates as leafhoppers migrate from the South to the Midwest as the wind picks them up to feed on plants.
Continued hot and dry conditions are not conducive to the spread of chrysanthemum yellowing disease, while a humid environment helps the plants flourish.
In the western United States, leafhoppers do not migrate, allowing pathogen transmission to occur year-round. This shows that the influence of geographical region on chrysanthemum yellowing disease cannot be ignored.
Management and Control
Controlling chrysanthemum yellow disease is a difficult task, especially due to its extremely broad host range. Since there is currently no effective treatment in cultivation, removal of infected plants and weeds is the only control measure available. For agriculture, certain methods for managing leafhopper populations in carrots may help reduce the spread of AYP.
AYI values affecting carrot crops can guide when to use chemical controls.
Unfortunately, cultural industries affected by chrysanthemum yellowing disease have suffered heavy losses, especially the carrot industry. The biggest challenge is that carrots cannot reach the market because of the symptoms they produce.
Importance and future prospects
Chrysanthemum yellowing disease is an economically important plant pathogen in the agricultural and nursery industries. According to reports, carrot production may be reduced by 25% as a result, and in some cases, the loss can even reach 80%. Not only that, the disease also affects the market value of production seeds and nursery plants.
Therefore, nurseries must strengthen monitoring of plants to prevent primary infection with AYP.
Finally, as climate change and agricultural practices change, the risk of chrysanthemum yellowing will continue. However, only through more in-depth research and innovative management measures can we better deal with this problem and reduce the impact on business and the environment. Do you think we can find an effective treatment for this plant disease?
