Root Maggots On The Rampage: Wiping Out Delia Species Pests

Ed Wike
Written by
Last update:

Root Maggot Overview

Seeds for Delia species were imported from Australia in the mid 1800s. The idea is that the flies would control weed species. They are used against weeds such as smartweed, quack grass, purslane, and many more.

The root maggots feed on the roots of the plants in the brassica and cabbage family. It can destroy a crop of cabbage in one night, which is why the Delia fly is such a devastating pest of the brassica family. The second most popular are cauliflower, broccoli, turnip and radish. Today, Delia species are classified in three groups by their host preferences: brassica (cabbage and related species), crucifer (mustard, etc.), and turnip.

Other potato and tomato relatives are also hosts of Delia species, but second rank to brassica. Delia root maggots can also feed on base of the grasses when they feed on crops such as grass seedlings.

It is interesting to note that the maggot will not live on bare ground. It is the silty/clay loam soil that provides the best environment for the maggot to develop to maturity.

Types of Root Maggots

You might not have noticed the marauding creatures marching through plant roots. That's because their damage is silent and sneaky. They might eat the roots undisturbed for weeks or months before you see any outward signs.

Different species of these pests will attack different types of plants. For example, when you see symptoms that could be chalked up to root maggots, look for the root-woven patterns that Delia species pests create when they enter a plant. You will soon discover that Ladybirds, Aphids and Fritillaria Mealybug are part of the root maggot family. But then, Delia platura can also attack beetroot, pea and potato seedlings or young plants.

When you discover a problem, don't panic. By the time you see root maggots, the problem has usually progressed substantially. The damage may already be done, but the good news is that your attacks on the root maggots will have a noticeable impact on the plant's recovery.

Life Cycle of Root Maggots

There are a number of insect species that feed on plant roots, but by far the most notorious are root maggots.

Root maggots are flies that lay their eggs around the base of a young plant, in the soil.

The eggs then hatch underground, and a grub-like maggot emerges and begins to feed on the roots.

The maggots then pupate and emerge in the spring as adult flies.

The lifecycle only takes about 2 weeks, but combined with other issues such as drought and fungal diseases, the pest can destroy young plants in the greenhouse.

Common Habitats For Root Maggots

As you probably know, root maggots are one of the most common pests of lawns and gardens. The larvae of these insects feed off the roots of various plants, which of course can greatly inhibit the plant's growth and is very damaging and disheartening for the gardener.

Root maggots thrive in warm, moist environments. The eggs are laid in the spring and the young maggots hatch. The very names of the main root maggots that plague gardens are all derived from the ancient moth that the maggots resemble. These moths eventually became extinct, but their offspring live on as the larvae that do the damage.

Vegetable Root Maggots – the Larvae of the Cabbage Moth

When you think of the species that are likely to be the most troublesome for your home landscape or garden, you probably have in mind a few of the aforementioned maggots. There are many more species that can be damaging to your plants, though. Also, the same species will often have a variety of names. So let's explore some of the most common species of root maggots that you might encounter, starting with the ones that are most common.

What Do Root Maggots Eat?

Ground-feeding adult beetles, known to feeding on seedlings, have a yellowish-brown to dark brown surface, shiny, and thin. Their body is primarily flat, of between 2 and 4 millimeters in length, with an elongated, projecting snout. Their wings are small, with a little more than half of the insect’s body width. Their root-eating habits make Colaspis a destructive pest in cereal crops, especially in corn, barley, and wheat. Adults can lay hundreds or even thousands of eggs, which hatch into tiny black legged larvae in a few days. The grubs (larvae) will feed beneath the soil before tunneling to the surface and pupating. They are specialists in causing damage to cereal crops.

How To Get Rid Of Root Maggots

Marigolds (Tagetes lucida) have some natural antibacterial properties, and this is why they are mixed with compost to enhance the valuable resource of this product. A small amount is mixed with the soil before it is added to the compost pile. The reason is to prevent the rotting smell that usually occurs due to the high moisture content in compost.

The marigold comes in a deep colored orange flower, and it is used mainly because these flowers are used extensively in flower arrangements. They are also used in making perfumes and face packs.

When it comes to its antifungal property, the marigold is extracted in the form of an essential oil and then used as an antifungal treatment for mildew problems in the house.

The well known antibacterial amino acids that are found in the marigold are said to be very strong when it comes to fighting against the diseases that are caused by the bacteria. This is what makes this flower very effective in fighting against the root maggots where it infests the crops.

As the root maggots attack the crops, it mostly affects the carrots and the onions. The root maggots that attack the carrots are a very big problem in the market. The market for carrots is very high, and the root maggots can cause a huge loss.

Organic Root Maggot Control

Store bought chemicals are effective, but a bit too effective. With chemical based root maggot control, the maggots quickly build a resistance to the chemical and the product is rendered ineffective. It is said that it only takes a matter of a few years for this to happen.

For these reasons, why not use an organic root maggot control? Organic methods allows you to control the level of toxicity found in the product, so, farmers are able to control the intensity of the product to kill any maggots in that area, while allowing any that survive to spread untreated.

But, for this approach to work the growers must have a system in place that allows him to keep track of which rows have had a product applied too, so that the rows that have not had the product applied are the rows that would be sprayed with a chemical treatment.

For this system to work, you will need a pesticide that is non-degradable and cannot be wiped off. This is where IPC 1064 comes in. IPC 1064 is a non-degradable, highly specialized insecticide. It has a residual life in soil of up to 8-9 months, does not breakdown in the environment and is a grease-like substance that the maggots cannot wipe off.

Environmental Root Maggot Control

As you can see from the growing range of areas that are being affected, these root maggots are beginning to cause a lot of economic trouble.

The solution is therefore, to take measures to eliminate as many of them from your land as possible.

The first thing that you must ensure is that the area that you are taking measures against is completely cleaned. Any rubble or damaged organic remains must be removed.

Once this is done, you must then move to treat the remaining root areas. As soon as the process of transferring the grubs begins, the adult root-maggot will begin to eat it, so ensure that the proper timing is exact or the next crop will be in just as much trouble.

If you miss the right window of opportunity, this can lead to the root maggots just moving to find new hosts.

The last and most effective step is to ensure that the entire crop is protected from any further invasion of adult root maggots. A barrier around the perimeter as well as nodes that are found at specific points along the root are vital to protecting your crops.

It is also good practice to ensure all known entry points are sealed, either through repairing them, or buying quality root maggot fencing is also very important.

Preventing Root Maggots

You can’t be there to guard against all possible dangers, but you can take some simple precautions. So do a prespray of your plants before you place them in the ground.

When choosing your plants, look around for any signs of damage. If any is seen, shake it out and discard it.

Warm, damp, stagnant soil creates the protective environment that root maggots need. Avoid watering your garden from overhead by installing sprinklers or drain the water away, even if this means you have to create bigger ditches to channel the water away. This will help speed up the soil drying period and discourage the maggots from coming out.

Preventing root maggots are quick and Easy. Use a garden fork to turn over the top 2–3 inches of soil, release any larvae, scrape away the top layer of soil, and then place a barrier between your plants and the soil. The best barrier is newspaper, but make sure that you have at least 4–6 layers over the soil surface, and make certain to put a barrier over the seeds as well. (The larvae, in its first stage, is quite tiny). Over time, the newspaper will decompose, and you’ll be left with an organic mulch.

Frequently Asked Questions

Q1: Why do I need a maggot trap?

A1: You need a maggot trap to control maggots because the natural life cycle of the maggot is to burrow into the ground and pupate for several weeks. If you do not kill the maggot, it will soon be a fly and will be laying maggots of its own.

Q2: How do I keep the maggots away?

A: You prevent maggots by limited the space, light and food the maggot can find. By drilling small holes in the wooden fence where it meets the ground, you reduce the amount of space to let you know if maggots are living there. By using the wooden plank to shade the fence and stopping your lawnmower from cutting the grass over a particular area, the maggot will not have as much food to survive. By placing maggot traps (with insecticide) at regular intervals along the fence, you reduce the number of maggots living in that area and making new ones. The three areas of focus are space, light, and food; you do this by using a maggot trap.

Q3: How do I know if the maggots are in the root zone?

Q: I pulled out a plant and found root maggots, but my other plants look okay.

Will they get root maggots too?

A: No. The maggots you have found are likely from the root maggot fly or a false root maggot. I can tell you that your plant will not get root maggots (if you plant is healthy) because the maggots require a certain micro habitat.

Root Maggots are actually fly larvae. They burrow into the roots and then eat the root. It is similar to an infection. If the roots are already dead, nutrient deficient or otherwise stressed, then the burrowing larvae can create the best conditions for the fly to lay its eggs.

Any plant can get root maggots although some plants are more susceptible to attack. These include but are not limited to: Begonias, chrysanthemum, and marigolds (tender varieties). The root maggot is affected by the combination of hot and dry conditions and appears to have thrived with the recent dry spell we have been having. If you notice maggots in the soil, they likely came from a fly that was laying eggs on the plants or plant pots. More than likely they came from your garden and now will not attack your indoor plants.

Q: Do used coffee grounds and tea leaves keep out root maggots?

At this time of year, gardeners are rushing to finish up summer gardens and prevent fall hyacinths and daffodils from making home in adjacent ground. Unfortunately, many of these are plagued by root maggots, the larvae of the dark green, black or brown hoverfly (Family Syrphidae). Spraying with a mosquito dunghill or applying a poison such as pyrethrum, is part of the usual control strategy. But both have disadvantages. The former merely attracts the adult hoverfly, which may already be heavily burdened with pollen or sipping nectar, so that they fail to lay eggs in your soil. As a result, your problem may soon return next season. On the other hand, there is a high risk that these chemicals kill any beneficial insects and earthworms. If you want to protect your plants, without the downside of ecological damage, there is a very simple and aesthetic solution, which is touted by the organic gardening fraternity. It’s used coffee grounds. The reason why this gentle household product is a good idea is that the larvae die as soon as they ingest the grounds. And because they may be a by-product of a morning cuppa, the idea is doubly appealing.