Those of our customers that are in the southern parts of the country are nearing harvest, while customers in the north are only several months into your growing season. No matter what stage your onions are at, preventing onion diseases is crucial for a successful harvest. 

One way to maximize your crop’s potential is to stay proactive about disease prevention throughout the entire growing season. Too often, a wonderful onion crop spoils in storage before it can be completely consumed. In nearly every case, it’s because fungal onion diseases were acquired while the onions were still in the ground.  

onion crop

Leaf wetness: the starting point of all onion diseases

All onion storage diseases share one starting point: leaf wetness. If you get more than 20 inches of rain in your area annually, conditions favor the development of such diseases. Spring of 2019 brought more moisture for the majority of customers. Sadly, once an onion becomes obviously diseased, it’s too late to do anything to save it. Prevention is the key here. You have to take steps to block the diseases from ever taking hold in the first place.  

That means treating your plants regularly with fungicides. You need to keep fungal spores from attaching to the leaves during the growing season, which is why a preventive fungicide program is so important — whether chemical, or all-natural. We offer both below in our Featured Product section.

growing onions

Prevention Strategies

Here are some quick tips for keeping your onions healthy from planting through storage:

  • Use pre-emergent herbicides during bed preparation. Onions don’t like to compete with weeds.
  • Rotate the crops every three to four years.
  • Avoid fields with any disease history.
  • Plant in areas where there’s good drainage and air movement to promote rapid drying of foliage, and be sure to orient the rows to take advantage of the predominant airflow.
  • Avoid overhead irrigation.
  • Stop fertilizing your onions about a month prior to harvest, or when they start to bulb.
  • Stop watering once you see the first top fall over, or about a week before harvest.
  • Harvest only after the onion tops are well matured. See the From our Friends section below.
  • Cut the tops when you don’t feel any moisture when you rub right above the neck with your thumb and forefinger.
  • Harvest and handle bulbs gently to avoid wounds, and don’t let them get rained on.
  • Promptly cure the bulbs in a well-ventilated area, so the necks are completely dry before the crop is stored. 
  • If you see any damaged or rotting onions among a stored batch, remove them immediately, hopefully before they have a chance to taint the others.

If you’ll follow these steps, your stored onions are much more likely to last until you’ve eaten them all!  

We hope your crop is off a great start! For many of our customers, spring arrived late. If you have growing questions, please don’t hesitate to give us a call. Contact Customer Service at (830) 876-2430 or visit