Knowledgebase

onion fly larvae #755235

Asked June 10, 2021, 7:41 AM EDT

Hello! My white onions and some of my garlic were infected with onion fly larvae when I harvested them a few weeks ago. Is there anything that can be done to prevent this from happening, and will the soil in those two areas ever be viable to grow onions or garlic again? Thanks!

Howard County Maryland

Expert Response

You might have been observing signs and symptoms of Allium Leafminer, a fly that is increasingly becoming a pest in agriculture and home crops of all Alliums (garlic, onion, leeks, chives). If you want to send us photos of the damage you have seen on bulbs/foliage, we can take a look.

Allium Leafminer overwinters in the pupal stage. Remove all Allium plant residues from your garden. Light cultivation or fluffing of the soil in the garden bed can help expose remaining pupae to predators.

This insect has two generations per season. Rotate your onions and garlic, if possible, to a different part of the garden and use floating row cover material in March and September to exclude mated females from laying eggs. Spinosad and neem oil are effective organic insecticides.

More detailed information:

https://extension.umd.edu/resource/allium-onion-leafminer

https://www.pvga.org/wp-content/uploads/2017/04/Pest-Alert-ALM.pdf

https://extension.umd.edu/resource/floating-row-cover

Christa

Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 10, 2021, 1:30 PM EDT

Thank you for the information about the Allium Leafminer. I do believe that I have had a major infestation in both my onion and garlic crops. Should I pull the remaining onions that were planted in the fall or leave with the hopes that the yellows were not impacted like the whites. These were just unnamed onion sets that I purchased at a garden center. I don’t know if some varieties are more/less susceptible.

I am attaching photos of both garlic and onions. Both had the brown larvae and many also had a heavy infestation of tiny black bugs.

Thanks for the suggestions,

Kathy Kaberle

On Jun 10, 2021, at 1:30 PM, Ask Extension <<personal data hidden>> wrote:

The Question Asker Replied June 19, 2021, 6:16 PM EDT

The "brown larvae" are pupae. The "tiny black bugs" may be feces. They would be found in the mined leaves but once larvae are feeding around bulbs/cloves it may appear this way. We do not know for sure. If the "bugs" are not moving they are likely feces. Pull out the fall-planted onions if they have feeding symptoms. You should check foliage and lower stems closely. You can expect this pest to be a perennial problem so use row covers during flights in April and September.

Marian

onion fly larvae #755235

Expert Response

Loading ...