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Onion Growers Alert
All Crops Treasure Valley, Treasure Valley - Idaho, Eastern Idaho, Magic Valley, Northern Idaho, Treasure Valley Oregon
Cull Onion Disposal
Posted on: March 4, 2026 by Jemila Chellappa
Growers are reminded that the deadline to dispose of existing cull onion piles is March 15 to help prevent the buildup of onion pests such as onion maggot.
Key Requirements
All existing cull onion piles must be disposed of by March 15.
From March 15 to July 1, any new cull piles must be disposed of within one week of creation.
Proper disposal is essential to reduce pest development and protect nearby onion fields.
Management Options
If cull onions cannot be buried in a timely manner, piles may be treated with an approved insecticide labeled for cull piles or non-crop areas.
Approved options previously identified include:
Malathion products
Gowan Malathion 8 Flowable – EPA Reg. No. 10163-21
Malathion 5 EC – EPA Reg. No. 66330-220
(Malathion is generally the most economical option.)
Azadirachtin products
AzaGuard – EPA Reg. No. 70299-17
Ecozin Plus 1.2% ME – EPA Reg. No. 5481-559
Gowan Aza-Direct – EPA Reg. No. 71908-1-10163
Always read and follow pesticide label instructions before application.
Additional Regulations
In Malheur County, Oregon, no more than 80 tons of onion debris may be buried per acre.
State regulations related to onion maggot management and cull disposal can be found in the links below.
Additional Resources
Oregon rule: https://secure.sos.state.or.us/oard/viewSingleRule.action
Idaho rule (onion maggot section begins on page 8): https://adminrules.idaho.gov/rules/current/02/020605.pdf
