How to Fight Onion Soft Rot
- 1). Apply granular insecticides at planting to control insects such as the onion maggot that can both wound the onion and transmit the bacteria that results in onion soft rot.
- 2). Prevent bruising and wounding of onion plants during harvest and handling. Injured plants are most vulnerable to onion soft rot.
- 3). Cut off roots when lifting onions from the ground to encourage drying of foliage and necks.
- 4). Rotate crops on a three-year cycle with resistant crops such as grains to remove the pathogens from the soil.
- 5). Spray bulbs with copper bactericides two weeks before bulb initiation to control the growth of the bacteria that causes root rot. Storms can cause wounds to leaves and bulbs. If copper-based bactericides are sprayed on injured leaves and bulbs within hours of these wounds occurring, bacteria growth may be reduced as well. Once soft rot symptoms occur, however, there is no controlling it.
- 6). Continue spraying on a five- to 10-day schedule. Follow the label directions for application, and in dry conditions, add enough water to make sure you have adequate coverage with the bactericide.
- 7). Avoid using overhead irrigation once onions start to bulb, which occurs when the bulb grows to twice the diameter of the neck. The water can spread the bacteria to uninfected bulbs and soil.
- 8). Cut onion bulbs about 1/2 inch above the neck when harvesting to prevent potential bruising or injury to the bulb.
- 9). Harvest onions only after they have fully matured to ensure the necks are dried, which provides a barrier to prevent bacteria from entering after the bulbs have been harvested.
- 10
Cure bulbs with abundant air so that the necks of the onions are dry before they are stored. - 11
Remove any bulbs that show signs of bruising or other injury before storing to prevent the soft rot bacteria that may be present in these bulbs from spreading to healthy bulbs. - 12
Store harvested bulbs at between 32 and 36 degrees Fahrenheit in an area with less than 70 percent humidity.