September 2020
Alliums are Nevada’s largest vegetable crop, with the value of onion and garlic production amounting to $10 million in 2017 (NDA, 2019). These important crops are successfully grown at a very large scale in the State, such as at Snyder Onion, Nevada Onion and Peri and Sons farms in Yerington, and at smaller scales, including here at the Desert Farming Initiative in Reno. However, alliums are not grown without risk. For example, as of mid-August this year over 1,000 people in the US and Canada (including Nevadans) have been sickened by onions tainted with Salmonella – these were distributed from Bakersfield, CA just around the corner (CDC, 2020).
Many Nevada growers are harvesting alliums this time of year, so it is an opportune time to discuss their safe handling and storage. Onions and garlic are eaten raw (as well as cooked), so they are covered by the Produce Safety Rule. Below are key on-farm practices for preventing allium contamination and food borne illnesses, compiled from the National Onion Association and university extension services. Note: the focus of this list is on bulb onion and garlic production, though the allium family does include chives, leeks, and ornamental cultivars.
Key On-Farm Practices:
1. Assess allium fields for risks before planting: The FDA created a useful guide for assessing onion fields (see page 4). The guide recommends an evaluation of adjacent land uses/features and recurrent animal activity that pose risks, and then crop planning considering those risks.
2. Carefully choose, apply and schedule soil amendment: Allow 120 days between application of any raw biological amendments (such as raw manure) or untested soil amendments and harvest. For green or bunching onions with a short planting to harvest timeframe, it’s best to avoid these raw amendments and stick to fully composted or treated fertilizer options with supporting documentation. Read more about safe use of soil amendments here.
3. Control animal activity in fields and examine crop for contamination before harvest: Visibly contaminated alliums (such as by bird feces) should be removed from fields and discarded.
4. Time harvest to avoid wet weather and irrigation splash: Allow for drying and pathogen die off after a rain event or irrigation. Because allium bulbs are often cured in the field after irrigation shut off and we are in a high desert, this is an easy practice to implement!
5. Exclude damaged alliums from harvest: Onions and garlic that are cracked, bruised, dropped or are otherwise visibly damaged should be removed from fields and discarded. Besides leading to internal decay and quality issues, pathogens that make people sick can more easily multiply in damaged bulbs.
6. Check irrigation and wash water quality: Ensure that agricultural water that meets the requirements of the Produce Safety Rule.
7. Manage all food contact surfaces carefully: Between uses make sure to clean (scrub with appropriate soap and brush then rinse with clean water) and sanitize all surfaces that come into contact with alliums. This includes tools and equipment, harvest containers, transport surfaces, washing/packing surfaces, and storage areas. And don’t forget farm worker hands, gloves and clothing – prioritize hygiene practices! Allium packaging should be single use or cleaned and sanitized between uses. Check and follow the EPA label on all cleaners and sanitizers.
8. Ensure air circulation: Do not wrap onions in plastic or store in plastic bags. A lack of air circulation will reduce shelf life and encourage pathogen growth.
9. Consider the storage environment of packaging and harvested alliums: Packaging and harvested bulbs should be stored at least 18 inches away from walls and other pallets to allow proper air movement (as above) and discourage pests. Store onions in a cool, dry, well-ventilated area. Maintain a storage temperature of 45-55°F (out of direct sunlight) and do not store onions with potatoes or other produce that releases moisture.
10. Monitor storage areas for pests: Prepare storage areas to prevent pest intrusion (check door seals, walls and ceilings); develop a pest monitoring schedule and assign responsible staff; and have supplies at the ready for managing pests (such as traps). Discard alliums contaminated by rodents or other pests – animals can carry bacteria, viruses and parasites that make people ill.
It’s best to develop a comprehensive food safety plan for the farm and designate someone to oversee its implementation. Need assistance with produce safety planning or allium practices? Contact DFI for a free call or visit.
