Iris Bacterial Soft Rot Control Techniques
If you want to learn about the explanation of iris in the flower clinic, the control techniques for iris bacterial soft rot, let's get to know it together.
【Distribution】Bacterial soft rot is a common disease of iris, which can occur in both bulbous iris and rhizomatous iris, and is distributed in the United States, Canada, and Japan. It also occurs in cities such as Shanghai, Hangzhou, Hefei, and Qingdao in China.
【Symptoms】When the disease occurs in bulbous iris, the base of the diseased plant's roots becomes water-soaked and soft, the bulbs become slimy and腐败, emitting a foul odor. As the disease progresses in the underground parts, the new leaves on the ground turn yellow first, followed by the outer leaves. The above-ground parts are easily pulled up, and the whole plant turns yellow and withers. When other types of iris are affected, the disease spreads from the underground stem to the leaves and rhizome, the leaves start to become water-soaked and soft, turning from dirty white to dark green, the above-ground plants are easily pulled up, the base of the stem becomes soft and rots, emitting a foul odor. Before planting, if the bulbs are affected, they appear frostbite-like water-soaked spots, turn tea-brown at the bottom, emit a foul odor, and have dirty white sticky fluid. If the bulbs are slightly affected and planted, they develop water-soaked brown spots at the tip of the leaves, leaf expansion stops, and soon the whole leaf turns yellow and dies, and the entire bulb rots.
【Pathogen】The pathogen is a bacterium. There are two known pathogens of iris soft rot: Erwinia carotovora pv. Carotovora (Jones) Bergey and E. aroideae (Townsend) Holl., both belonging to the Eubacteria order and the Enterobacteriaceae family. The bacteria are short rods that move with peritrichous flagella and are Gram-negative. The former measures 0.7×2μm; E. aroideae measures 1.2-3.0μm×0.5-1.0μm. The optimal growth temperature for both is 27-30°C, with the highest temperature range being 32-40°C. They can ferment glucose and are negative for oxidase. The host range of the bacteria is very wide, affecting not only iris but also cyclamen, hyacinth, lily, and tulip, among other flowering plants.
【Disease Cycle】The pathogen overwinters in the soil and crop residues, can survive in the soil for several months, and can survive for years in the diseased plant residues in the soil. The pathogen is spread through water, insects, contact between healthy and diseased leaves, or tools used for operation, and invades through insect wounds, division wounds, transplant wounds, and other wounds. In particular, the wounds caused by the iris borer larvae on young leaves or the wounds caused by dividing roots and transplanting provide an easy entry for the bacteria; the disease is spread by rainwater, irrigation water, and insects, and commonly occurs from June to September under natural conditions. The disease is severe when the temperature is high and humidity is high, especially when the soil is moist; the bulbs are prone to disease in dense plantings and areas with high green cover; continuous cropping leads to severe disease. German iris and Austrian iris are commonly affected.
【Control Methods】
1. Choose healthy bulbs; avoid causing wounds during excavation; do not use diseased roots for propagation; when growing in greenhouses, change the soil, promptly remove diseased leaves or plants, and destroy them; completely remove decayed bulbs, and promptly remove diseased bulbs during storage. Severely diseased soil can be disinfected with 0.5%-1% formalin at 10g/m² before planting, or new soil can be used; contaminated tools should be disinfected with boiling water or 70% alcohol, or 1% copper sulfate solution before use. Tools for cutting flowers should be disinfected with 0.5% potassium permanganate.
2. In the early stages of the disease, a mixture of streptomycin or streptomycin plus terramycin (10:1) at a concentration of 100-150×0.000001 can be sprayed, with 2-3 consecutive applications for better results. After the disease occurs, spraying 1000 times the concentration of agricultural streptomycin once a month can control the spread of the disease. Spraying insecticides to control the damage caused by iris borers can reduce the occurrence of the disease.
3. When harvesting bulbs, avoid causing wounds; in autumn, remove the withered and diseased leaves from the field to prevent pests from laying eggs on them.
4. Plant healthy bulbs; the field should have good drainage; bulbs should be planted shallow rather than deep; avoid overhead watering during management.
5. During the growing season, pay attention to controlling the iris borer that causes wounds to the iris. A 50% malathion emulsion at 1000-2000 times the concentration or a 2.5% bromide emulsion at 2000-3000 times the concentration can be used for control.
These are the detailed control techniques for iris bacterial soft rot, hoping this article can bring you help in green plant management!