Maggots in garden soil

Identifying Root Maggots And Control Of Root Maggots

Root maggots can be a pain for any gardener who is trying to grow almost any kind of root vegetables or cole crops in their garden. While the root maggot fly is more of a problem in some parts of the country than others, they can affect almost any gardener. Knowing the symptoms of root maggots and control methods will help you keep this troublesome pests out of your garden.

Identifying Root Maggots

Root maggots get their name from the fact that they attack the roots of root vegetables such as:

  • turnips
  • rutabagas
  • onions
  • carrots
  • radish

They also like cole crops such as:

  • cabbage
  • cauliflower
  • collards
  • kale
  • kohlrabi
  • mustard
  • broccoli

The root maggots are the larva of several species of root maggot flies. But, despite the fact that they are of different species, the root maggots look the same and are treated and controlled the same. Root maggots are white and about ¼ of an inch long. Often, an infestation will not be spotted until after damage is done. Damage shows up in the form of holes or tunnels in the roots or tubers of the plant. In a heavy infestation, the plant itself may wilt or turn yellow.

While the damage to root crops by root maggots is unsightly, the parts of the root crop than have not been bored into by the root maggot can still be eaten. Simply cut away the damaged areas.

Root Maggots and Control

The most common method for root maggot treatment is biological/organic control. Common organic cures for root maggot include spreading diatomaceous earth around the plants while they are seedlings, floating row covers over seedlings and using natural predators of root maggots, like Heterorhabditidae or Steinernematidae nematodes or rove beetles, to kill the root maggots. Root maggots organic control is most commonly used due to the fact that these pests feed on plants that will be eaten by people.

Chemicals can also be used as a root maggot treatment. Pesticides will only be effective during specific points in the growing season, as once the maggots have penetrated the root of the plant, it is difficult for chemicals to reach the pests. If you will be using pesticides for root maggot control, apply weekly during the first 8-10 weeks off spring.

As with many other pests, prevention of root maggots is much better than controlling root maggots. Make sure to regularly rotate crops that can be affected by root maggots, especially in beds where you have had problems with them in the past. Removed dead vegetation from the garden each fall and also make sure to destroy (not compost) any plants that were infested with root maggots.

Also, if you find that you are having an ongoing problem with root maggots, consider cutting back on the amount of organic material you have in your garden soil, particularly manure. Root maggot flies prefer to lay eggs in soil that is high in organic material, especially manure based organic material.

If you’re noticing a proliferation of flies, and your brassicas or root vegetables are starting to yellow, it’s a warning sign. You may have an infestation of root maggots. These fly larvae are no joke! Hungrily, they will chew through your plants, causing them to lose vigor, wilt, yellow, and possibly die off.

Rescuing your plants from root maggots is possible! Read on to learn everything you need to know about these garden pests and how to wipe them out.

Good Control Options For Root Maggots:

  • PyGanic
  • Beneficial Nematodes
  • Harvest-Guard Floating Row Covers
  • Diatomaceous Earth
  • Yellow Sticky Traps

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Root Maggot Overview

Common Name(s) Root maggot, cabbage maggot, cabbage root maggot, cabbage fly, turnip fly, root fly, cabbage root fly, onion fly, onion maggot, onion root maggot, seedcorn maggot, bean seed fly
Scientific Name(s) Delia radicum, Della antiqua, Della platura and other species
Family Anthomyiidae
Origin Worldwide
Plants Affected Brassica plants, alliums, peas, beans, corn, some melon species
Common Remedies Soil drenches (with agricultural lime solution or a pyrethrin drench), beneficial nematodes, crop rotation, post-harvest tilling, floating row covers, diatomaceous earth, tarpaper collars, yellow sticky traps

Types of Root Maggots

While there are quite a number of flies in the Delia genus, only a few have reached major pest status. I’ll list the worst offenders below.

Delia radicum, ‘Cabbage Maggot’, ‘Root Maggot’, ‘Cabbage Fly’, ‘Turnip Fly’, ‘Root Fly’, ‘Cabbage Root Fly’

Delia radicum adult fly. Source: janetgraham84new

Found primarily around cruciferous plants, this species of root maggot can be found worldwide. Cabbage root maggot infestation tends to cause a slowing of growth, followed by yellowing of leaves and wilting of plants. For smaller plants like radishes, a root maggot infestation can quickly ruin an entire crop.

There is another relative, Delia floralis (or the “summer cabbage fly”) that looks incredibly similar and eats many of the same plants. It’s similar enough, in fact, that it is often confused with Delia radicum. Thankfully, it can be wiped out with the same techniques.

Delia antiqua, ‘Onion Fly’, ‘Onion Maggot’

Delia antiqua maggots on leek. Source: Wikimedia Commons

Scallions, onions, leeks and other related plants are susceptible to the onion root maggot. Preferring plants in the allium family, they will bore into and devour the tender interior of a leek plant, or eat giant holes through onions. This causes very dramatic yellowing of leaves and visible wilt quite quickly.

Delia platura, ‘Seedcorn Maggot’, ‘Bean Seed Fly’

The pupa of the Delia platura root maggot. Source: Wikimedia Commons

Peas and beans are susceptible to the seedcorn maggot as well as corn. However, any larger-seeded edible plants may fall prey to this seed-eater. Burrowing through the soil, it can easily chew through any of the seeds before or during germination.

Life Cycle of Root Maggots

Delia radicum maggots and pupa. Source: Wikimedia Commons

In the spring, the root maggot fly emerges from the soil where it overwintered in pupal form. It feeds on plant nectars to build its strength, then seeks out its preferred larval food source as an ideal location to lay eggs.

Thirty to forty eggs can be laid along the base of the plant or on the ground around it. Often, multiple root maggot flies will lay eggs on the same plant. Eggs hatch within five to fourteen days, which can be disastrous for the plant around which the eggs were placed.

Root maggot larvae then commence feeding on their preferred plant for up to forty days. The damage is not always below the soil. As an example, cabbage maggots can start at the base of the plant and chew their way up into the interior heart, or down through the root mass.

Once satiated, the maggots retreat to form a pupa beneath the soil’s surface. It can take a while for these flies to mature during pupation. There’s usually only one or two generations in a given year.

Common Habitats For Root Maggots

Generally speaking, cabbage flies and their maggots are common around rutabaga, cabbages, turnips, radishes, or other cruciferous, large-rooted vegetables. However, some root maggots prefer allium species like onion or leek. Others prefer the seeds of corn, peas, or beans.

These are primarily agricultural pests, and as they’re soil-dwellers, they can be hard to wipe out in their destructive maggot form.

What Do Root Maggots Eat?

Delia radicum root maggots on a cauliflower stem. Source: Wikimedia Commons

Generally, large-rooted plants of the brassicae or allium families are susceptible. Virtually all cruciferous vegetables can be consumed, even broccoli. While garlic is usually ignored, onions – especially sweet ones – are at risk. And, as mentioned above, some specialize in edible large seeds.

If the plant is a compact mass such as cauliflower or cabbage, it is quite possible to find a root maggot that’s eaten a pathway into the center of the leaf ball.

How To Get Rid Of Root Maggots

Root maggots are tricky because the adult form can easily escape, and the larval form is hidden beneath the soil. Prevention is the best policy, but there are a few other options that can be used to get rid of root maggots.

Organic Root Maggot Control

A traditional method of treating root maggots is with a lime soil drench. Using agricultural lime, soak one cup of lime in a quart of water at least overnight. Strain off the lime itself and then use the water to drench the soil around your plants. Be forewarned, lime can raise the pH of your soil, so it is good to do a soil test before you use this method.

While it should be a last resort measure after all environmental options are considered, you may also use a pyrethrin soil drench. Using a concentrated product like PyGanic, mix the strong pyrethrin solution in water thoroughly, then use that to soak the soil around your plants. This will also combat other pests like flea beetles.

Environmental Root Maggot Control

When the pest is beneath the ground, beneficial nematodes are an excellent defense. These microscopic organisms will quite happily consume larvae of root maggots along with a host of other soil-dwelling pests.

Be sure to rotate your crops after each growing season. Crop rotation is a great way to avoid pest problems year after year, as they never build up in strong numbers in one spot.

When you have harvested the end of your crops, till your soil. Tilling will not help during the growing season, but if you’ve had signs of root maggots, a late-season tilling will disturb their environment and bring some to the surface. Once above ground, they are able to be picked off by passing birds or other predators.

Preventing Root Maggots

Delia platura flies. Source: Martin Cooper Ipswich

Your first line of defense against root maggots is prevention. Floating row covers keep adult flies away from your plants, stopping them from egg-laying. If you’ve had problems with root maggot in prior years, please use this method with caution, as the row covers will also keep newly-emerged adults underneath!

Diatomaceous earth is a deterrent for many types of garden pests. Dusted on your plants and over the surface of the soil, this superfine powder feels like knives to the soft bodies of root maggot flies. It’s harmless to humans and pets. However, diatomaceous earth needs regular applications after rain or heavy watering.

A good soil-surface option is to make tarpaper collars to surround your plants. Roofing tarpaper works well. Cut circles that are 4″ to 6″ in diameter. Make a single straight cut into the center, and then cut out a small circle for your plant’s stem. Place this on the soil around the plant’s stem to discourage egg-laying.

Toilet paper tubes can also be used to deter root maggots. Cut along one side and place it around your plant, and then bury part of the tube in the soil. Be sure to leave at least an inch and a half above the soil’s surface. This creates a protective ring around your plant.

Yellow sticky traps placed around your plants can capture all sorts of flying pests, preventing them from laying eggs. Check your traps regularly and change them when necessary.

While there are people concerned about using sticky traps around wildlife, they’re fine for most urban garden use. If your pets roam freely in your yard, watch them at first to be sure they have no interest in the sticky traps. Any interest indicates that you should try something else to avoid removing the trap from your pet!

Frequently Asked Questions

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

A: It’s quite possible that when you pull out other plants, you will find signs of root maggots as well. With products like cabbage, you can still eat the produce. Just be sure to cut up the head carefully to discard any maggots that have bored into the center.

Edible roots that have maggot holes through them should also be inspected thoroughly. You may need to discard any portion that’s been bored out. Of course, any signs of spoilage of the root or plant means it should be disposed of.

I recommend tilling your soil thoroughly once you’ve removed the rest of your crop, and perhaps doing a lime soil drench while the rest of your plants are in place. Rotate your root crops out of that location for next year and choose plants which are less appealing to these pests.

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

A: While there’s never been conclusive evidence that these repel root maggots specifically, coffee grounds can deter a number of other pests. Tea leaves are not much different than other leaf products, and don’t have any significant effects on pests. It certainly doesn’t hurt to spread these lightly around your plants. However, I wouldn’t rely on it as your only defense!

The use of coffee grounds as a deterrent for soil-bound pests actually is based on unused coffee and its acidity. When planting your seeds, you can spread a small amount of coffee grounds in the area where you’re planting. Similarly, sprinkle coffee grounds around your transplants when you put them in the ground.

Again, no studies have been done that show that coffee grounds, unused or used, have a significant effect. That doesn’t mean it won’t work, it just means it’s not guaranteed to have an impact.

Have I helped you to solve the rampaging root maggots around your radishes? I certainly hope so! With these pests, prevention is really your best bet. Do you have any techniques that you use that I haven’t mentioned? Let me know in the comments below!

The Green Thumbs Behind This Article:
Lorin Nielsen
Lifetime Gardener
Kevin Espiritu
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Root Maggots?

The timing does suggest that the pest was brought in with the soil mix or the plants. The warmer spring temperature encouraged the hatching of the insects in the soil. That’s why you probably didn’t see them in your winter crops. You may be seeing a big flush of hatching that will settle down as the insects lay eggs and the adults then die off. You may have success planting different types of crop into the beds because the weather conditions will change as we move into summer. However, the problem may reoccur next spring and it sounds like there is a pretty high number of flies and larva so you might try soil solarization to ‘cook’ the soil and hopefully kill off the eggs and remaining larva. Moisten the soil and then cover with clear plastic. You can find big rolls at a hardware store. Seal up the edges with rocks or by burying. Then cross your fingers for a few weeks of warm sunny days. Here’s more information: http://extension.oregonstate.edu/gardening/harness-sun-kill-weeds-plant-diseases-and-pests
Reducing the soil moisture on the surface will also help lower pest pressure. So letting the soil dry out between waterings or using a drip irrigation system may help as well.
Chemical treatments are probably not going to be effective at this point in the growing season. Usually they work best on the soft body larvae not the mobile adults.
Good Luck!

What are Root Maggots?

Online Pest ControlFollow Aug 12, 2016 · 4 min read

Root maggots are pests that feed on succulent roots of vegetable crops such as carrots and turnips. These pests can cause a lot of trouble as they infest your vegetable garden creating black rot and destructing newly planted seedbeds. Fortunately, there are a number of natural solutions you can easily do to get rid of these garden pests.

Frequented Areas

You can usually find root maggots in newly planted seedbeds. During their adult form, they are black flies that measure about the same size as a common housefly. Root maggots lay their eggs at the roots of the crop of their choice, root vegetables or tubers such as radish, rutabaga, carrots, onions, and flowering crucifers such as cauliflower and cabbage.

Normally, they thrive in areas with moist soil, vegetables of choice and tender roots at the early season of planting. Root maggots are typically found across the globe including North America. They are considered as one of the most destructive pests, which affect home gardeners.

Identification — Physical Characteristics of Root Maggots

Root maggots are flies during their larvae stage, which belongs to the insect family Anthomyiidae in the order of Diptera. During their adult stage, root maggots measure about 1/5 inch in length. They are bigger in their larvae stage, which measures about ¼ inch long. Yellowish-white in color, root maggots also have a tapered head. This is what they use to tunnel through the crop’s base and to feed on roots.

An infestation of root maggot is highly destructive. An adult fly can produce about 100 eggs on a single plant approximately in two days or at times, even less. Within 3 to 10 days, the eggs will hatch and become larvae. They will then begin to tunnel into the roots of the vegetables causing grave damage to your crops.

Special Characteristics

The root maggots are famous for their enormous appetites as well as the tunnels they make in any crop of their choice. If your garden has been infested, deep tunnels in the roots, stems and leaves will be visible. Because of the tunnels and surface scars that root maggots leave on plants, the crops will be more vulnerable in having an infection from soft-rot bacteria or be plagued by thrips or springtail pests.

Removal and Preventative Procedures

Eliminating and preventing root maggots from infesting your garden may be hard at times but there are some steps home gardens can do to regulate infestation. If there are any signs of infestation such as surface scars, feeding tunnels or maggots found in your plants, it is highly suggested to implement the checklist below.

· Apply diatomaceous earth at the base of seedlings

At the early stage of the planting season, just right after each rainfall occurs, apply diatomaceous earth (a sand-like material). Once applied, it will result in having a soil that is less attractive to flies and keep them from laying eggs anywhere near your crops. Fortunately, this method is environmentally friendly too.

· Rotate crops each season

Prior to planting crops, make sure that the soil has not been infested with root maggots during the previous season. If the soil has been previously infested with root maggots, it will more likely result in further contamination or infestation in your planted crops. As it can be difficult to perform crop rotation for most home gardeners, it surely is an effective way to reduce and control root maggots.

· Put protective coverings over transplants or seedlings

Making use of protective coverings can limit the root maggots’ capacity to thrive. This procedure is done by placing floating row covers over transplants and seedlings.

· Use cotton or waterproof discs to protect plants

When your garden has been infested already, make sure to add cotton or waterproof discs near the stem of plants. This could make a strong barrier between the flies and the plants or even the soil in which their eggs are laid.

· Use biological control methods via parasitic wasps or rove beetles

Parasitic wasps feed on maggots that are near the surface of your garden soil. Some species of beetles such as the rove beetle can be very effective too in regulating root maggot populations.

In Store or Chemicals

For pest control, pesticides can be bought both in garden stores and online as they are widely available. But you have to be careful when buying chemicals for the control of root maggots. To date, the U.S. Environmental Protection Agency (EPA) has not registered any pesticides yet for the control these insects. If you decided to regulate root maggots in your garden through the use of chemicals, it is best to consult a pest control professional.

Radish-Cabbage maggot

Delia brassicae

Pest description, crop damage and life history

See:

Common Pests of Vegetable Crops

Pest monitoring Once the crop emerges, watch for wilting, lighter green plants, or reduced growth that may indicate a maggot infestation. Pull up affected plants, and check roots and soil to confirm the presence of maggots. If several rows of seedling plants are infested, plants may be removed and rows replanted. Drenching with insecticide is also an option, but such treatments are difficult, costly, and may not be adequate.

If roots are tunneled but no maggots are present, maggots have left the roots to pupate, and insecticide treatments would be of little value.

Sticky traps and sweep nets also can be used to monitor the adult fly.

Management-biological control

Rove beetles prey on maggot eggs and young larvae. Rove larvae parasitize the pupa stage of the maggot. The parasitic wasp Trybliographa rapae lays its eggs in the maggot larvae if the larvae are close enough to the soil surface. Biological controls cannot be counted on to provide adequate control.

Management-cultural control

Where maggots are a perennial problem, grow seedlings for transplants in fumigated soil in the greenhouse or under frames of clear plastic. Avoid hardening transplants near infested fields. Direct-seeded crops may avoid some injury when a set of drag chains is attached behind the planter to eliminate the moisture gradient in the seedrow. It is believed that adult flies can locate the seed row for egglaying by honing in on the higher moisture levels created when the soil is overturned for planting.

Older plants may outgrow moderate cabbage maggot populations if maintained with a careful irrigation schedule. Always disc under crop residues immediately after harvest. Maggots can survive for some time in crop residue. Do not follow susceptible crops with susceptible crops, unless sufficient time has passed for the residue to dry or decompose completely.

Management-chemical control: HOME USE

  • pyrethrins (often as a mix with other ingredients)-Some formulations are OMRI-listed for organic use.

Management-chemical control: COMMERCIAL USE

  • Chenopodium ambrosioides extract (Requiem 25EC) at 4 to 6 pints formulated product per acre, soil application. REI 4 hr. OMRI-listed for organic use.
  • chlorpyrifos (Lorsban 15G) at 0.03 lb ai/1,000 row ft. REI 24 hr. Apply as an in-furrow drench at planting with at least 40 gal/a total spray. Do not exceed 2.75 lb ai/a or one application per season.

Sugarbeet Root Maggot Sugarbeets

Taxonomy Kingdom: Animalia Phylum: Arthropoda Class: Hexapoda (including Insecta) Order: Hemiptera Family: Aphididae Genus: Pemphigus Species: P. populivenae Subspecies: P. populivenae Scientific Name Pemphigus populivenae
Fitch, 1859 Common Names sugarbeet root aphid

Author: Gary L. Hein

The sugarbeet root maggot, Tetanops myopaeformis, is the most severe insect pest of sugarbeet in many parts of the High Plains region. Infestations begin in late spring and can reduce plant vigor and stand, resulting in lower yields. Effective management of this insect requires knowledge of the insect’s life cycle and information about the current population level.

Identification (and life cycle and seasonal history)

Sugarbeet root maggot adult flies are similar in size and appearance to the house fly (about 1/4 inch). Unlike the house fly, the body is shiny black with few hairs. The wings of this fly are transparent with a smoky-brown patch located on the front of the wing about one-third the distance from the wing base. Also, the legs have yellowish-white bands on the next to last segment (“ankles”), with the rest of the leg being black. The females have pointed abdomens and the males have rounded abdomens.

The eggs are elongate, slightly curved and white. The larvae are white, legless maggots that grow to about 1/3 to 1/2 inch in length. The head end is tapered to a point and the rear end is blunt. The pupae are tan to brown, elongate capsules about 5/16 inch long.

Sugarbeet root maggots overwinter as full-grown larvae about 10 to 14 inches deep in the soil. As temperatures begin to warm in the spring, the larvae move up close to the soil surface and pupate. In western Nebraska, sugarbeet root maggots pupate in April, and flies begin to emerge in early May. The flies move from last year’s sugarbeet fields to the current fields soon after emergence. The flies are not strong fliers, and movement is generally limited to localized flights to adjacent fields. Fly activity in sugarbeet fields increases under warm and calm conditions. During cool or windy periods the flies remain in sheltered areas along field margins (e.g. weedy, grassy areas or tree rows). Peak emergence and fly activity occur in late May or early June. The females lay eggs in the upper 1/4 to 1/2 inch of soil at the base of the sugarbeet plants or in the crown area of the beet. Eggs are laid in batches of a few to as many as 40, and a female will lay over 100 during her life. Survival of eggs and early larval stages is greatly reduced in dry soils. The larvae begin to feed on the sugarbeet roots and continue to feed for three to four weeks. By late June to early July, feeding ceases, but the larvae remain in the soil around the sugarbeet roots.

Plant Response and Damage

Root maggots feed on the surface of the sugarbeet root causing surface scarring. Deeper scarring and malformed roots may result from heavier feeding. Heavy infestations of the sugarbeet root maggot can cause severe stand loss, particularly with small plants, because the maggots feed on and sever the tap root. Severe damage is obvious because plants become severely wilted or die. If stands are not reduced, losses may still result from reduced plant vigor. Other stresses, such as hail, can more severely impact sugarbeet damaged by the sugarbeet root maggot because vigorous plants are necessary for recovery.

Management Approaches

Cultural practices will not eliminate sugarbeet root maggot problems but can reduce the severity of damage. Areas where close rotations of sugarbeet are used will likely have more serious problems because the flies move from the previous year’s sugarbeet fields to the current fields. If sugarbeet fields are concentrated in an area, more flies will be emerging, and damage potential will be increased. Conversely, in areas where there were

Establishing a vigorous sugarbeet plant as early as possible will also aid in reducing sugarbeet root maggot damage. The larger, more vigorous plants can withstand more damage, and stand reduction will be less likely.

Typically granular insecticides applied at planting have been used to control root maggots. Options have included Counter 20CR and 15G, Lorsban 15G, and Temik 15G. Organophosphate insecticides (Counter, Lorsban) sometimes have caused phytotoxicity problems when applied at planting. Counter has been shown to be the least phytotoxic of the organophosphates, and placement of the granules behind the planter press-wheel can reduce, but not eliminate the damage. All these products are influenced by environmental conditions. For example, control with planting time applications of Temik 15G can be severely reduced during wet springs because of its water solubility, and the chemical may be leached below the zone where control is needed.

Use of Lorsban 4E as a lay-by control of sugarbeet root maggots provides flexibility in managing several problems associated with the granular materials; however, proper timing is critical, and applications must be based on fly population information obtained from sticky-trap sampling. Phytotoxicity (leaf curling) can result from Lorsban 4E applications. Injury will be minimal unless the plant is stressed by other factors (e.g. hot and sunny conditions, wind damage, herbicide injury). Because of its phytotoxicity potential, Lorsban 4E should not be applied with Betamix or Progress, at either regular rates or micro-rates. To minimize damage potential, Lorsban 4E should not be applied within two days before or within one day after a Betamix or Progress application.

In areas of very serious maggot damage potential, layby treatments have been used in addition to planting time applications. In years when rainfall between planting and peak fly activity has been sufficient, planting time organophosphate treatments should provide good control and supplemental lay-by treatments should not be needed. However, if very little rain has fallen between planting and peak fly activity, a supplemental lay-by treatment may be needed to provide additional control. Lay-by treatments also may be beneficial in years when peak fly activity occurs later than normal in the season (e.g. mid June in western Nebraska) because planting time treatment would no longer be effective.

Once maggot damage begins to appear in the field, effective options to correct the situation are limited. Irrigation can help reduce damage once the maggots are feeding on the sugarbeet. Moist soil conditions will cause the maggots to move higher on the roots and be less likely to sever the tap root. Irrigation also will reduce water stress and the potential for stand loss. A lay-by nitrogen application may stimulate beet growth to help plants recover from damage. The value of this practice may be questionable if adequate fertility has already been applied. After damage has been observed, Temik 15G, because of its high water solubility, can be knifed in on the water side of the row (furrow irrigation) or banded over the top of the row (sprinkler irrigation) and watered into the soil. Very little control will be obtained if watering (or rainfall) does not occur after chemical application or if the insecticide is applied too late. Other insecticides are not water soluble enough to provide control of established maggots even with watering.

Sampling Adult Populations: Sugarbeet growers in areas where the sugarbeet root maggot is a problem can improve their management by using the orange sticky-stake trapping method originally developed in Idaho (Blickenstaff trap). This method can be used to monitor the development of fly populations in and around sugarbeet fields in May and June. In many areas of the region root maggot populations fluctuate. Without population information it is impossible to make an informed decision on the need to treat or how to treat for sugarbeet root maggot. Growers in these areas may be caught off guard when a problem eventually develops or they may waste dollars on treatments that aren’t needed. In areas where the root maggot is continuously a serious problem, growers have had serious control problems even with the use of planting-time insecticides. The sticky-stake method can be used to determine both the need and the proper timing for a supplemental lay-by treatment that will improve control in these serious situations.

The orange sticky-stake trapping method should be deployed early — the first week of May in western Nebraska — to catch the first fly activity of the season. As the season progresses, the size and duration of the fly population can be determined. Information gained from the use of the sticky-stake fly traps can be used to:

1. Determine the current population level in the field and assess the need for insecticide treatments in subsequent years in adjacent fields. Anyone just learning to use the trapping system should use this option. This allows one to get used to the trapping method and gain insight into the fly population level in your area. The presence or lack of dying beets in the field is not an accurate way to determine if flies are a problem. Monitoring the flies can give a reasonable idea as to the damage potential of the maggots in the area.

2. Determine the damage potential for the current root maggot fly populations. Decisions can then be made on the need for lay-by insecticide treatments and the proper timing of these treatments.

Using Trap Data in Decision-making

1. Record the number of sugarbeet root maggot flies caught on each trap at each observation.

2. Keep an accumulated total for the traps and determine the field average. The accumulated total is determined by adding the number of flies in a trap since the beginning of the season (number of flies per trap).

3. Decisions can be made concerning the use of an insecticide the next year based on the average accumulated fly trap catch for the field.

a. If fly populations are very low with a total accumulated catch per trap of less than 20 flies for the season, a planting time treatment would likely not be needed; however, the fly population will need to be monitored the next year to determine if it’s building and may pose a threat.

b. If fly populations are moderate with a total accumulated catch per trap of 20-80 flies for the season, the damage potential is moderate and one of several treatment options can be used.

  • Apply a planting time soil insecticide to control the root maggot problem. This can be effective, however many factors influence the insecticide in the weeks between planting and when it is needed. Also, because of the phytotoxicity risk from some products, this option should be used only when there is demonstrated risk from root maggots (i.e. previous damage or high fly populations).
  • Use an early lay-by application of a granular soil insecticide for root maggot control. This option reduces the risk from phytotoxicity, but lack of water (precipitation) to move the chemical into the soil may reduce control. This would be the best option if overhead sprinkler irrigation is possible.
  • Forego an at-plant insecticide and rely on a liquid lay-by application based on the trapping threshold to provide control of the maggot population. This option works well, but fly monitoring and proper timing are critical. (See No. 4 below.)

c. If fly populations are very high (more than 80 per trap), a planting time soil insecticide may be the best option to begin control of root maggots. If the fly populations in a field treated at planting are very high during the season, a lay-by application of Lorsban 4E can provide supplemental control to the planting time application. This has been shown to be quite effective in situations of severe root maggot damage.

4. Decisions can be made concerning lay-by treatments and timing for the current year.

a. If the total accumulated catch per trap never exceeds 40 flies, the damage potential is low.

b. If the total accumulated catch per trap exceeds 40 flies by peak fly activity (before trap catches begins to drop off), a significant potential for damage exists and if no planting time insecticide was used, some type of rescue treatment would be in order. Peak fly activity usually occurs between May 20 and June 10 (in Nebraska). Lay-by treatments should be timed according to the timing of significant fly activity. Rescue treatments applied after major larval activity has begun are too late and will be of little use. When using liquid lay-by treatments, timing is critical. They should be applied when the threshold of 40 flies per trap is reached. This may occur before the actual peak fly activity period is noted on the sticky traps. If the period of high fly activity is extended 7-10 days after the first treatment, a second liquid insecticide treatment may be needed to control the later population. These treatments must target control of not only the flies but also a significant residual activity of the insecticide on the soil surrounding the sugarbeet. Chlorpyrifos (Lorsban and other generics) is the only insecticide that has shown consistent effectiveness when applied in this way. Other products will provide only adult control which is not adequate if conditions are favorable for maggot survival.

Sugarbeet Root Maggot Trap Construction: 1. Traps are made from a 2″by2″ wooden board that has been painted white and a garden stake, approximately 1″by10″, that has been painted a bright (not fluorescent) orange color. (Similar plastic orange stakes are available commercially.) Attach the garden stake to the 2X2 about 1″ to 2″ from the top of the stake so that a white border surrounds the stake. When the 2X2 is driven into the ground, the bottom of the orange stake should be about 1 foot above the soil surface.

2. Tangletrap, an insect trap adhesive, is placed only on the orange stake in a thin layer. Adding too much adhesive will only lead to a very messy trap, but care must be taken to add enough to be able to catch the flies.

Trap Placement in the Field 1. Traps should be placed out about May 1 and monitored into the second week of June.

2. Four traps should be placed around the perimeter of the current year’s sugarbeet field.

a. Traps should be placed at the edge of the field in a fence-row or next to a ditch just out of the range of the cultivator so they will not be knocked over during field operations.

b. Two traps should face north or west and two should face south or east. This arrangement will usually allow two traps to escape being coated with dirt after a strong wind.

c. The orange stake on the trap should face the sugarbeet field or be at a 90° angle to the field.

d. Weeds or grass growing around the trap should be cut or pulled for about a 2 foot radius to maintain trap visibility.

3. Traps should be monitored at least twice a week.

a. Count or record the number of sugarbeet root maggot flies for each trap.

b. The sticky traps do collect flies other than sugarbeet root maggot flies, so correct identification is essential for an accurate control. See the earlier description of the flies.

c. Flies should be cleaned off the trap and fresh adhesive applied. If adhesive remains clean and sticky, dead flies can be picked off and sticky material left for the next trap check. Take care to keep the adhesive material on the trap sticky. Dirt and other insects, if numerous, can limit the fly catch because of limited or no sticky surface to catch the flies. The most common problems in reduced stickiness results from dust storms or high insect numbers, particularly flies near feedlots.

The best decisions for managing the sugarbeet root maggot can only be made when you know what the potential for damage is in your fields. The best information to determine that potential can only be obtained from trapping the maggot flies with the orange sticky stake method. Knowing the potential for SBRM damage is essential to saving money on unneeded insecticide applications while avoiding damage from this insect when populations build to damaging levels.

Product List for Sugar Beet Root Maggots:

Insecticide Product per Acre Preharvest Interval, remarks
Counter 15GR, CRR 15G: 4.0-8.0 oz/1000 row ft

CR: 3.0-6.0 oz/1000 row ft

Applied banded at planting

or post emergence; REI 72; PHI 110 days.

chlorpyrifos 15G

(Lorsban plus generics)

4.5-9.0 oz/1000 row ft

6.5-9.0 oz/1000 row ft Note: chlorpyrifos 15G is labeled for T-band application at planting, but this application can be significantly phytotoxic to beets when applied in this fashion, especially when used on lighter soils.

T-band at planting time.

Post plant 2-4 true leaf stage; REI 24 hrs.

Lorsban 4E band 1.33-2.0 pt./A Use as primary treatment to control root

maggot larvae. See label for timing instructions. PHI 30 days; REI 24 hrs. High rates may be phytotoxic.

Lorsban 4E broadcast 0.5-1.0 pt./A Apply based on field trap monitoring

for adult fly control. PHI 30 days; REI 24 hrs.

Lorsban 4E broadcast: 2.0 pt./A

band: 0.66-1.33 pt./A

Use as supplemental treatment following

an at-plant insecticide treatment for larval control. PHI 30 days; REI 24 hrs.

Temik 15GR 7.0-14.0 lbs./A Apply at planting or post-emergence.

Potential for groundwater contamination. See label for environmental precautions and restrictions. PHI 90 days; REI 48 hrs.

Thimet 20GR 3.4-4.5 oz/1000 row ft Apply at planting, not in contact with seed.

REI 72 hrs.

Thimet 20GR 4.9-7.5 lbs/A Apply post emergence to dry foliage

in band;PHI 30 days; REI 72 hrs.

RRestricted use pesticide 1Labeled for chemigation.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.

How to Get Rid of Cabbage Root Maggots

  • If you see flies in the air, scout for eggs in the soil. Run your fingers through the top layers near the bases of your plants. Destroy any eggs found.
  • You can try installing ‘cabbage collars’ at the base of the stem. These can be made from cardboard and will simply be a skirt around the base of the plant. It protects the plants from egg laying.
  • Sticky traps in the garden are effective at trapping cabbage flies. They are available at most nurseries.
  • Check with your nursery about using nematodes as a biological control for root maggots. Another biological control are wasps, so leave them alone.
  • Carefully dig up your plants and swish their roots in cold water to remove the maggots, then replant them. Either allow the maggots to drown in the water or feed them to your chickens for a tasty snack.
  • Check with your local Cooperative Extension for your area’s regulations on chemical control.
  • Old folk advice from The 1963 Old Farmer’s Almanac says that the smell of tar in tar paper was effective against cabbage root maggots.

Prevent Cabbage Root Maggots

  • Most red cabbage varieties have some resistance to cabbage root maggots.
  • Floating row covers can be effective when set out at time of transplant. It is possible for overwintering pupae to emerge from beneath the cover. Make sure edges are sealed.
  • Late planting can be a successful tactic in tricking pests.
  • Practice crop rotation.
  • Till garden in the fall and spring to expose overwintering fly pupae.
  • If you’d like to keep cabbage root maggots away from more valuable plants, try planting radish as a trap. Many maggots will be attracted to the radish, and then you can destroy it.

Cabbage worms are another common pest of the cabbage family. Click here to deter imported cabbageworms.

Root maggots can be extremely destructive garden pests. As they feed they can destroy the root systems of plants causing slow and irregular growth and even death. They are particularly troublesome for early season plantings.

Unseen, underground, they feed on the root systems of many different vegetable crops including cabbage, radishes, turnips, carrots, and onions. Plants suffering from root maggot attacks may appear yellowish, stunted, and will sometimes wilt during the day when sunlight is at its peak. Tunneling that occurs as the maggots feed also leaves plants open to rot diseases such as black rot.

How to Identify Root Maggots

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Adults are dark grey flies that look like a common housefly, only smaller. They are about ⅕ of an inch in length. They will lay their eggs in the soil at the base of their chosen host plants. The maggots which hatch from the eggs are yellowish-white, legless larvae. They have a tapered or even pointed head and their tail end is blunt.

Root Maggot Life Cycle

Adults first emerge in the early spring from pupal cocoons in the soil where they’ve spent the winter. They will begin to mate quickly. Females can deposit anywhere from 50 to 200 eggs at a time. They will lay their eggs in plant stems at the soil line, or in cracks in the soil close to the plant stems.

Within a few days, the eggs will hatch and the newly born maggots will burrow down into the soil where they will feed on roots, root hairs, and germinating seeds. They will continue to feed for one to three weeks, depending on their environment, before going into the pupal stage to transform into adults. Several generations will be produced each year.

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Floating row covers – The female flies are especially attracted to the moisture in newly planted seed rows when it comes time to lay their eggs. Cover new seedbeds, making sure that coverage extends at least 6 inches on all sides of the seed rows. This will prevent the mature females from getting in to lay their eggs in the first place.

Paper collars – When transplanting plants, a heavy paper collar (or other similar material) can be used around the base of the plants to prevent egg laying around the stem.

Beneficial nematodes – Nematodes are microscopic parasites that live naturally in soil. They can be purchased online or in gardening centers. They are safe for plants, people, and pets, but will actively seek out and destroy root maggots as well as many other garden pests. These tiny creatures will also continue to hunt and help your garden for up to 18 months. You can pick up the beneficial nematodes at your local store or .

Pyrethrin spray – Pyrethrin is a natural insecticide derived from the chrysanthemum flower. It can be effective against root maggots and the adult flies, but you will need to soak the soil well to achieve a good effect on the maggots underground. Bayer Advanced Grub spray is a recommended option for dealing with root maggots, and any pests affecting the roots or soil of your plants.

Rototiller – After harvest, promptly use a rototiller to destroy and bury leftover crop debris. This will help to remove suitable food for any existing root maggots as well as destroy any overwintering sites and cocoons that may exist in the soil.

Root maggots can multiply very quickly if left unchecked. Unfortunately, they can also be hard to identify since they are underground. If you notice yellowing or stunted growth on your plants but can’t seem to find evidence of other pests, it might be well worth your time to get down to the roots of one or two specimens and check for root maggots. The sooner you react to any problem you find, the better the results you’ll get for your efforts.

How to Rid Your Garden of Maggots Once a Year

Maggots are fly larvae that can be found on rotting vegetation and around the roots of garden plants such as corn, onions, turnips, carrots, cabbage, and even fruit trees. They can cause a lot of damage to the plants by eating their root systems, destroying their method of obtaining water or nutrients from the soil.

Usually, if you’ve spotted maggots, your garden plants are already damaged. While there are many ways to get rid of these garden pests when you see them, the best way to fully protect your garden is to take preventative measures once a year. Follow these steps to get rid of any maggots you currently have and reduce the chance of getting more maggots.

Step 1 – Find the Maggot Infestation

If your otherwise healthy plants are suddenly wilting or if their growth has been stunted, there’s a good chance you have a maggot infestation. The best way to find out if you have this problem is to carefully pull a few of the plants from the soil and examine the roots. If you see just one squirming grayish- or yellowish-white worm, then you know you have a maggot problem. Use your gloved hand to shake the soil to see if there are any more.

If they’re small, then you know they’ve just recently hatched and probably haven’t done much damage. Large maggots are older and have likely had a chance to do more damage to your plants by eating more of their root systems.

Step 2 – Stop the Spread

There’s not a lot you can do to save an infested plant. If your lucky enough to have caught the problem early, there are a few things you can do to stop any other plants from becoming infected.

First you need to remove the dying plants and the soil around the dying plants. The rot from dying plants will attract the root maggot fly which increases the chance of it laying more eggs and starting the cycle all over again. The soil around the destroyed plants also needs to be removed in case it is infested with eggs.

Infested plants and soil should be burned or thrown out in a double sealed plastic garbage bag. Do not compost them.

Step 3 – Kill Any Missed Maggots and Eggs

Even after completing the above step, there’s a chance you could have missed a single maggot or fly egg pod which will start the maggot cycle all over again if not treated.

Dust your plants with diatomaceous earth. It’s a fine powder made out of the fossilized remains of a type of hard-shelled algae. It dries out maggots and other garden pests causing them to die.

Apply beneficial nematodes to your garden when it’s damp. Nematodes are living organisms that will eat maggots. Simply add them to water and spray over the surface of your garden when the temperature is at least 55 degrees Fahrenheit. Water the nematodes for two days after application.

Step 4 – Prevent Future Infestations

Prevent maggot flies from laying their eggs near your plants by covering them with floating row covers. The flies prefer to lay their eggs in cool, moist conditions. Try solarizing your plant beds to make them drier and warmer.

Keep your compost away from your garden since rotting vegetation will attract flies. Also keep garbage away from your garden and regularly clean out garbage cans.

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