What to Do When Flowers and Plants Get Crown Gall Disease? A Detailed Guide to Prevention and Control Methods
1. Symptoms: Crown gall disease is also known as crown gall. In cherry blossoms and Chinese roses, crown gall mainly occurs at the root crown, but can also occur on the roots and aboveground parts. In the early stage of the disease, small nearly round tumor-like growths appear, which gradually enlarge and harden, with a rough, cracked surface, and the color changes from light to dark brown or black-brown, with the interior of the gall becoming lignified. The galls vary in size; large ones can be as big as a fist or larger, and their number ranges from a few to a dozen or more. Because the root system is damaged, affected plants grow slowly, and in severe cases the entire plant dies. Besides harming cherry blossoms and Chinese roses, this disease can also harm dahlias, lilacs, begonias, geraniums, roses, plum blossoms, as well as forest trees and fruit trees, affecting more than 300 species of plants.
2. Prevention and Control Methods
① Strengthen quarantine. For diseased nursery stock, soak in 500-2000 ppm streptomycin solution for 30 minutes or in 1% copper sulfate solution for 5 minutes, then rinse with clean water before planting.
② In severely affected areas, practice crop rotation for more than 2 years or disinfect the soil with chloropicrin before planting.
③ Cultivate carefully to avoid all kinds of wounds.
④ Replace cleft grafting with bud grafting, and disinfect grafting tools with 0.5% potassium permanganate.
⑤ Severely diseased plants should be dug out and removed. For lightly diseased plants, irrigate with 402 diluted 300-400 times, or after cutting off the galls, apply 500-2000 ppm streptomycin or 500-1000 ppm thiram or 5% ferrous sulfate to the wounds. It is also reported that applying methyl-iodine solution (50 parts methanol, 25 parts glacial acetic acid, 12 parts iodine flakes) to the galls has a therapeutic effect; Agrobacterium radiobacter strain 84 can be used for biological control.