Controlling the insect pests infecting your root vegetables

Root maggots are a common garden pest, but there are several remedies available

Sometimes gardeners are very disappointed to find that when they harvest some of their of vegetables such as root vegetables and/or those from the cruciferous family (turnips, rutabagas, radishes and parsnips) as well as other vegetables such cauliflower, broccoli, onions, carrots, they are full of holes. Most likely they holes have been made by root maggots and/or wireworms.

Prior to harvest the most common indicator that you may have pests, are stunted, yellowed and deformed leaves. If the infestation isn’t addressed right away, the entire crop may be lost because of the tunnels the worms create in the roots of the vegetable(s). Prevention and prompt action can help to salvage the crop and possibly prevent future infestations.

You would be hard-pressed to distinguish a root maggot fly from a regular, small housefly, unless you observed the insect laying eggs in early spring. Female root maggot flies can lay more than one-hundred eggs at the base of a single plant over several days. The eggs hatch in ten days or fewer, and the young larvae burrow into the plant roots, eating as they go, damaging and often killing the vegetables. The larvae then mature and emerge as adults allowing the adult females to lay more eggs.

Good garden hygiene can help to control most insect pests but if you think that you have root maggots, find, remove and destroy any infected plants as soon as you notice any indicators of infestation. Make sure to throw the infected plants in the garbage so that they are removed from your property as composting may not kill all the worms and you can re-infect when you add the compost to the garden. Rake up any plant debris throughout the season and all dead stems and leaves at the end of the growing season.

The most efficient manner of controlling root maggots is to prevent the flies from laying eggs on crops. One method, is to protect the crops with floating row covers, lightweight fabric that allows light and water to pass but keeps bugs out. This method works only when the row covers are in place before any eggs are laid otherwise, the larvae will thrive, protected beneath the row covers. An alternative is to position circular cardboard or tar paper disk around each crop transplant. Each disk should be at least ten centimetres in diameter, with a center hole cut out that is sufficiently large enough for the plant’s stem. Then cut from one edge to the circle, left for the stem, to allow for installation around the plant. Lay flat on the soil surface around the base of the seedling. Plastic tub lids can also be used instead of cardboard and will not break down during the growing season.

As root maggot flies lay their eggs in cracks in the soil at the base of edible plants the installation of the disks as described above can prevent many eggs from being laid but below is a list of a few other techniques and homemade treatments that have proven quite effective for many gardeners:

Layer wood ash, rock phosphate or diatomaceous earth around your plants about two to three centimetres thick.

Mix one part of powdered lime to four parts of water. Allow the solution to sit overnight then remove the clear water to pour on the soil around the base of vulnerable plants.

Add beneficial nematodes or rove beetles to the garden soil. Beneficial nematodes, are microscopic organisms that inflict damage to the maggots, ultimately killing them. Predatory rove beetles eat maggots and will not harm your existing vegetation. (Nematodes and rove beetles are often available at garden centers or via mail-order)

Apply a hot pepper treatment to the soil by combining three hot peppers, three cloves of garlic, and a chopped onion to a blender. Pour in thirty milliliters of liquid dish soap and three cups of water. Blend until smooth. Let the blended mixture sit for 24 hours, and then pour it through a strainer and into a jar. Pour the strained liquid directly onto the affected areas of the soil. The strained pulp should be disposed of in the garbage, not the composter. Take extra caution to not get it on your skin or clothing.

It can be very disheartening at the end of a growing season to harvest your crop only to find that insects have been enjoying the fruits of your labour. Hopefully this article can help you identify a possible maggot infestation early and prevent loss of your crops.