Frit Fly: All You Need to Know for Effective Control and Prevention

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Frit flies are small insects that can cause issues in agricultural settings. These flies are slightly over 0.062 inches in length, with a shiny black appearance and tiny yellow markings on their legs. The eggs of these flies are a pure white color, and they measure around 0.03 inches long with a finely detailed, ridged surface. Adult frit flies are primarily known for their impact on turfgrass, affecting its overall health and quality.

Mature larvae of frit flies are yellow and approximately 0.125 inches in length. One distinctive feature is their black, curved mouth hooks, which allow them to feed and survive on their host plants. The pupae start as a yellowish hue, later turning to a dark brown color. Knowing about the life cycle and characteristics of frit flies can help with pest management steps, ensuring healthier growth and minimal damage to crops or grass.

Frit Fly: An Overview

Life Cycle and Identification

Frit flies are small pests, slightly more than 0.062 inch long. They are shiny black with yellow markings on their legs. The life cycle of the Frit fly consists of four stages: eggs, larvae, pupae, and adults.

  • Eggs: Pure white and .03 inch long with a finely ridged surface.
  • Larvae: .125-inch long, yellow, and have black, curved mouth hooks.
  • Pupae: Begin as yellow, then turn dark brown.

Commonly Affected Crops

Frit flies primarily affect cereal crops such as:

  • Wheat
  • Barley
  • Oats
  • Corn

Importance in Agriculture

Frit flies pose a significant threat to agriculture due to their feeding habits. Frit fly larvae cause damage to plants by feeding on the stems and roots, which may lead to stunted growth or even plant death in severe infestations. Some examples of agricultural problems caused by frit flies include:

  • Reducing crop yield
  • Affecting plant health
  • Increased costs for pest control

Agriculturalists are concerned with managing Frit fly populations to minimize their impact on crop production. Strategies to control Frit flies include crop rotation, resistant varieties, and targeted pesticide application.

Life Cycle Stages and Development


  • Laid on grasses/cereals
  • Hatch into larvae

The life cycle of the Frit Fly begins with females laying their eggs on grasses and cereals. These eggs typically hatch into larvae within 3-4 days.


  • Feed on grasses/cereals
  • 3 larval stages

The larvae are the second stage, during which they feed on grasses and cereals. There are three larval stages (or instars) before they transform into pupae.


  • Transition stage
  • Develop in soil

Pupae are the transition between larvae and adults. They develop in soil near the base of plants. This development usually takes place during winter and spring.


  • Reproduction
  • Short-lived

The final stage, adults, are responsible for reproduction. They are short-lived but can lay several batches of eggs throughout their life.

Stage Features
Eggs Laid on grasses/cereals
Larvae Feed on grasses/cereals
Pupae Develop in soil
Adults Reproduce

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Infestations and Crop Damage

Affected Crops and Symptoms

Frit Fly infestations impact several crops, such as:

  • Maize: Yellow central leaf and dead shoots
  • Wheat bulb fly: Ears, central leaf, and tillers

Infestation symptoms include:

  • Yellowing of central leaf
  • Dead heart in shoots
  • Weakened tillers

Leaf Sheaths and Dead Hearts

Frit Fly larvae attack leaf sheaths of plants, causing dead hearts in maize shoots. Examples of damage include:

  • Central leaf decaying inside whorl
  • Shoot death in severe infestations

Monitoring and Assessing the Severity

Monitoring methods:

  • Regular crop inspection
  • Focus on vulnerable growth stages

Assessing severity:

  • Count affected plants
  • Assess percentage of infested tillers

Management and Control Methods

Cultural Approaches

Implementing cultural approaches can help manage Frit Fly populations. One effective method is the use of break crops. Break crops are non-host plants grown between two susceptible crops, reducing the chance of Frit Fly infestation.

Another option is ploughing, which buries Frit Fly larvae, interrupting their life cycle. Ploughing should be done after harvest and before planting susceptible crops.

Chemical Controls

Chemical controls may also be employed in Frit Fly management. Pesticides, such as insecticides, can be used to decrease Frit Fly populations. Chlorpyrifos, an active ingredient in Dursban WG, is often used for Frit Fly control. Moreover, Agri-Linc offers a range of chemical control options.

However, some cons to consider are the risks of insecticide resistance and possible harm to non-target organisms.

Integration with Natural Enemies

Integrating natural enemies with other management methods can effectively suppress Frit Fly populations. Some benefits include:

  • Decreased reliance on chemical controls
  • Lower chances of pesticide resistance
  • Reduced environmental impact

In conclusion, managing Frit Fly populations requires a combination of cultural, chemical, and biological methods. By incorporating these strategies, successful control of this pest can be achieved.

Preventing Frit Fly Damage

Crop Rotation and Ploughing

Crop rotation helps reduce the risk of Frit Fly infestation. Rotating between winter wheat, barley, and spring oats can prevent the buildup of pests like Oscinella frit. By alternating winter cereals with other crops, you can disrupt their life cycle, making it harder for adult flies to lay their eggs. Additionally, ploughing destroys the Frit Fly pupae in the soil, further reducing infestation levels.

For example, a possible crop rotation would be:

  • Winter wheat
  • Spring oats
  • Barley

Monitoring and Early Detection

Detecting Frit Fly infestations early is crucial. Adult flies and maggots can cause significant crop damage if left unchecked. Using a white sheet to monitor the presence of flies in your fields can help you identify potential infestations. This will allow you to take action, such as applying insecticides or adjusting your crop rotation, before the damage becomes severe.

Insecticide Resistance Management

Timely and responsibly managing insecticide use is important in preventing Frit Fly damage. A robust resistance management plan helps avoid overreliance on one type of insecticide, minimizing the likelihood of pests developing resistance. By rotating the insecticides used and following the recommendations on pesticide lists, you can maintain the effectiveness of your treatments.

When choosing an insecticide, consider the following:

  • Mode of action
  • Application method
  • Potential impact on non-target species
Insecticide Pros Insecticide Cons
Effective pest control Risk of resistance development
Can be applied as a preventive measure Potential harm to non-target species

In conclusion, preventing Frit Fly damage in crops like wheat, barley, and oats involves several strategies: crop rotation and ploughing to break the pest’s life cycle, monitoring for early detection of infestations, and responsible insecticide resistance management. Attention to these practices helps reduce the risk of crop injury and ensures the continued productivity of your fields.

Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Grass Fly


Small fly type bug
Location: Colorado Springs CO
July 7, 2011 12:39 pm
A friend gave me a Meyer lemon tree and it is now blooming. The blooms are very fragrant and are attracting these very small yellow and black fly type insects. They look like a type of fly to me but maybe they are a bee? Thanks for any help identifying it.
Signature: Eva Seifert

I think I may have found out what it is, a grass fly.


Hi Eva,
Congratulations on identifying your Grass Fly in the genus
Thaumatomyia.  Both the genus and family, Chloropidae, the Frit Flies, are new to our site.  We verified your identification on BugGuide which indicates the larvae feed on Aphids.  Perhaps that is why the fly is attracted to your lemon.

Letter 2 – Grass Fly is classified as Frit Fly


Subject: Thaumatomyia glabra
Location: Northeast Florida
June 23, 2012 10:15 pm
I always enjoy reading What’s That Bug and it’s been awhile since I sent in a photo. I saw this tiny fly (about 2-3mm) on a lantana plant in my yard in northeast Florida. When I looked at the photo and saw the coloring and details, at first I thought it looked like some kind of Hover Fly. I went to BugGuide and started searching, and I finally found my fly (I think)– Thaumatomyia glabra. If you would like to include it on What’s That Bug, you’re welcome to do so.
Signature: Karen in FL


Hi Karen,
Thanks for your compliments.  We checked BugGuide and learned that your species,
Thaumatomyia glabra, is classified in the Frit Fly family Chloropidae and the Grass Fly subfamily Chloropinae and that “‘The larvae of Chloropisca glabra are peculiar among Chloropids in being predaceous on root aphids.’ — Sabrosky, 1935”.  It seems they are among the most beneficial members of the family because BugGuide states on the family page:  “Larvae feed on grass stems. Some are serious pests of cereals. Some scavengers, some parasitic or predaceous” and “They are attracted to the eyes, sometimes are called eye gnats. They are vectors of yaws and pink eye.”  Thank you so much for sending us your photo.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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