What causes onion bulb rot? Cause analysis and control methods

Onion bulb rot is relatively common in onion-growing areas and has caused serious economic losses for farmers, so farmers should strengthen their understanding of this disease and do a good job of prevention and control. So how should onion bulb rot be controlled? Follow the editor to learn about it.

1. Poor disease resistance of varieties

There are obvious differences in disease resistance among onion varieties. If a variety with weak disease resistance is chosen, bulb rot is very likely to occur, so varieties with strong disease resistance should be selected in production, such as Kamui, Sorachi Yellow, Fuxing, Dongke Apple Onion, Keshite, Daqing Yellow Skin, etc.

2. Unbalanced nutrition

Onions have a peak demand for nitrogen in the early growth stage. If nitrogen is deficient, the vegetative body will be small, bulb maturity will be low, and yield will decline. If nitrogen fertilizer is applied excessively, the onion tissues will become soft, increasing the chance of pathogen invasion. After entering the bulb expansion stage, if nitrogen fertilizer is applied in a one-sided way, calcium deficiency will occur, causing the growth and development of the root system and growing point to be hindered. This affects bulb expansion and quality and triggers bulb rot. Therefore, when cultivating onions, fully decomposed organic fertilizer should be applied, nitrogen, phosphorus, and potassium should be reasonably balanced, and nitrogen fertilizer should not be applied in a one-sided way. At the same time, the intake of trace elements such as calcium, magnesium, sulfur, copper, and boron should also be considered.

3. Rainwater flowing into leaf sheaths

This is also one of the main causes of onion bulb rot. In the late stage of bulb expansion, the 1st to 2nd leaves have already withered and yellowed, and the tips of the 3rd to 4th leaves turn yellow. At this time, because there are no new leaves filling the leaf sheaths inside the bulb, hollows form, causing the leaf sheaths to wrap poorly. During continuous rainy days or sprinkler irrigation, water will flow along the leaves into the bulb, and the bulb is highly susceptible to infection by putrefactive bacteria and then rots. Therefore, after the bulb expands, when field plants begin to lodge, all upright plants should be pressed down to prevent rainwater from flowing into the bulb. At the same time, harvest should be carried out promptly to prevent rotting from rain exposure.

4. Wound infection

During field management, harvest, drying, transportation, and storage of onions, the bulbs are highly susceptible to mechanical damage and wounds. At the same time, larvae in the onion field feeding on the bulbs underground can also cause wounds, thereby triggering rot. Therefore, mechanical damage should be reduced as much as possible. Before planting, 50% phoxim emulsifiable concentrate diluted 800 times can be used as a root drench, or 50% phoxim emulsifiable concentrate diluted 1000 times can be used to control underground pests.

The above is an introduction to the causes of onion bulb rot and control methods. We hope it can help you. If you want to learn more related knowledge, please keep following us.