Daylily maggots

Credit: unforth

Q: I have had to throw out three daylilies because all the buds were distorted from small worms. The remaining two have some buds affected this way. I have Sevin, that is supposed to work against these but I am reluctant to use it – even if I just put on the ground only around the affected plants – because of its effects on bees, etc. How safe is this product? And what would you suggest I use?

Carbaryl (trade name “Sevin”) is being phased out of the marketplace, e.g. Sevin Garden Dust is discontinued as of July 16, 2009. Carbaryl is very effective on a wide range of insects but unfortunately is highly toxic to bees and beneficial insects, e.g. earthworms, due to its long residual activity. Also, I do not believe this product will work for this particular insect problem.

“Hemerocallis Gall Midge” (Contarinia quinquenotata) is originally from Europe and was identified back in 2001. This insect is established in the Lower Mainland and Bowen Island. The main symptom is swelling and distortion of daylily flowers (Hemerocallis cv.). Upon opening a distorted flowerbud you will encounter numerous white maggots about 3 mm long. The adult is a small fly barely visible to the naked eye. It overwinters in the ground as a pupa, and emerges as an adult fly in early May to early June to lay eggs on daylily buds. There is only one generation per year.

Only early-flowering daylilies are susceptible to this insect. If one is vigilant by removing infested flowerbuds early in the season, you can usually control this problem. Or plant later-flowering daylilies to hopefully escape damage. No pesticide is currently registered for homeowners.