Prevent worms in apples and maggots in root vegetables

Question: I had a lot of problems with worms in my apples last year. I also had maggots in my radishes and beets. Is there any way to prevent these?

Answer: Yes, you can control wormy apples and maggots in your root vegetables.

Worms in apples are actually the larvae of the codling moth. They become active in east Idaho about mid to late June. Codling moths lay their eggs on developing fruit. Eggs hatch into worms which bore into the fruit. Insecticides such as malathion and carbaryl (Sevin) kill the worms as they hatch. Spinosad is an organic insecticide which is equally effective and safer to use. Spinosad is usually only available at full service nurseries and garden stores or online. Insecticides need to be applied every two weeks until about August first.

Codling moth traps can be placed in trees to trap the male moths. They are attracted to the pheromone in the traps. If enough traps are placed in trees, virtually all the male moths are trapped. Without fertilization, the female moths lay infertile eggs. Large trees may need up to five traps. Three traps is normal for most semi-dwarf trees. If you have some large neighboring trees which do not have traps, your traps may not be completely effective.

The maggots in root vegetables are the larvae of a fly. Maggots also attack other plants in the cabbage family including cauliflower, broccoli, turnips, collards, and kohlrabi. As soon as plants emerge from the ground after seed planting, the flies lay eggs next to the stems. The larvae hatch after a few days and bore into the roots.

You can apply pesticide next to plants when transplanting or seed before covering. Pesticides can be applied in either granular or liquid form. Sevin is available as a dust which can be sprinkled on. If plants are already up and growing, drench the soil around plants with a liquid application of Sevin, Spinosad or other insecticides.

Diatomaeous earth is a natural pesticide which is very effective on maggots. It must be applied at planting time before the maggot eggs hatch.

Another good organic approach is to cover susceptible plants with floating row cover at planting time or before seedlings emerge. This is a fine mesh plastic fabric which allows 90 percent of light and moisture through. Beneficial nematodes will also control root maggots. They are often available from full service nurseries and garden stores or can be purchased online.

Allen Wilson can be contacted at