Wood Ashes to Deter Onion Maggots

Each year I grow onions in my float garden. It's one product I can "preserve" without much effort: grow, pull, dry, hang, and use.

I plant yellow onions from sets. They grow larger and save longer.  But every year I have a problem with onion maggots, especially if I leave onions in the ground past mid-July.

This year I tried an "old wives tale" to grow some late season onions. I read that using wood ashes on the soil could help deter the pests.

Onion maggots are the larvae form of gray flies. Pupae overwinter in the soil and emerge as flies from May to June. Flies lay their eggs at the base of onions, then the maggots that hatch bore into the onion roots. This cycle repeats itself several times a year.

Crop rotation helps, but once the cycle begins it's hard to break. One organic recommendation is to apply wood stove ashes to the soil to deter egg laying. I figured it was worth a try. I sprinkled ashes over the plot for my onions. I moistened the ash to keep it in place. I then planted the onion sets. Each week I applied additional ashes until the plants were well established, and then after each rain.

When I harvested my onions there were fewer plants destroyed by maggot infestation, and over three quarters were maggot free. Of the remaining plants, many could be salvaged for immediate use by cutting away one or two invaders. I'll try it again next year with my early crop and see if the results are as promising.

Have you used any organic methods of dealing with this pest? -- Margy