Meadow gnats don't sting, but can still cause a lot of damage. To be more precise, it is their larvae that can cause entire lawns to die off in an emergency.
Even if meadow gnats (Tipula paludosa) are basically useful insects, mass occurrences in the lawn can quickly become a problem. In this article you will find out how to recognize the damage, the adult animals and the larvae of the crane cranes, as well as various ways of combating them in an environmentally friendly manner.
Recognizing crane flies: way of life and damage
In spite of their middle name - Sumpfschnake - you can find meadow gnats mainly on fresh, medium-heavy, loamy soils with closed turf. Crane flies are fairly easy to spot and distinguish from other insects and their larvae.
Adult crane cranes are relatively large with a body length of up to 2.5 cm and a wingspan of 3 to 4 cm. The body of Tipula paludosa is uniform grey-brown and elongated. Their legs are noticeably long and thin, and their wings are clear and not spotted. If one observes a specimen more closely, one notices a V-shaped seam on the back and the lack of pinpoint eyes between the compound eyes. As with all types of gnats, the mouthparts of meadow gnats are not suitable for stinging. Instead, the adult animals feed on water and nectar. They are neither dangerous to us humans, nor do adult crane gnats damage the lawn.
Tip: At first glance, adult meadow crane flys can be confused with the so-called cabbage crane fly (Tipula oleracea). For a definitive identification, you have to catch a mosquito and look at its eyes. If they are close together and almost touching, it is a cabbage fly. In the case of meadow gnats, the distance is a lot larger.
Immediately after hatching in autumn, the larvae of the meadow crane fly are still very small. However, they grow to a size of up to 4 cm by next spring.The so-called "devil's face" is typical of tipula larvae. Looking at the brownish-grey larva from behind reveals a dark, hard plate surrounded by six white lobe-like appendages. It is a tool used for locomotion. But it was interpreted by creative viewers as a face with two dark eyes and white horns. The actual head capsule is of solid structure and very small. Furthermore, the larvae have neither legs nor any other appendages.
Tip: Despite everything, it is very difficult to distinguish the larvae from other species of gnats. However, it is easy to differentiate from grubs, which can also cause major damage to lawns. The larvae of meadow craneflies are significantly slimmer than grubs and do not show any noticeable thickening or curvature of the body.
The pupae of the larvae during the resting stages are reddish-brown and divided into several segments, the posterior ones of which bear ring-shaped small spines.
Lifestyle
The adult animals hatch from the pupae around mid-August. Because of their short lifespan, the crane flies start mating and laying their eggs right away. Since the females are only able to fly to a limited extent and can only manage a maximum of five meters at a time, they are only found near the habitats of larvae. A female lays 300 to 500 eggs and then dies relatively quickly. The first larvae hatch after 11 to 15 days. A total of four stages are passed through before pupation, two of them in autumn. The third instar larvae occur deeper in the soil and allow hibernation below the frost line. In cold winters, up to 50 percent of the larvae of Tipula paludosa can die. However, if the winter was mild, the majority survived. In the spring, development continues with the last two larval stages. This is where the greatest damage is done, because in the final stage the larvae can grow up to 4 cm long and are therefore real wolverines.
Roughly mid-May, the meadow crane larvae have reached their maximum size. They then migrate deeper into the ground and rest about 3 to 5 cm below the ground surface for about six weeks before pupating and hatching as adult craneflies from mid-August. This is how the meadow gnat creates one generation per year.
Damage
The young, small ones are already eating in autumnMeadow gnat larvae on grass roots and at night or on rainy days also on superficial parts of plants. However, the main damage occurs in spring, especially after mild winters. Then the masses of large meadow crane fly larvae can uproot entire lawns.
Typical signs of an infestation with crane fly larvae are:
- Decreased growth
- Yellow-brown discoloration of leaves
- Withering
- Flocks of bald spots
- More birds on the lawn. They eat the larvae that live near the surface of the soil and can further damage the grass with their scratching.
Difference to fungal diseases: In the case of a meadow gnat infestation, leaves turn uniformly brown and not blotchy. It looks as if the lawn is drying up in places.
If you are unsure, a simple cut of the spade in an affected area will help. In the event of an infestation, you should be able to see the larvae directly, of which up to 600 can occur per square meter in severe cases.
At a glance: What do crane cranes look like in the lawn?
- Adult crane flies: length: up to 1.8 cm (males), 2.5 cm (females); wingspan: up to 3 cm; long, thin legs; solid brownish-grey with clear, immaculate wings.
- larvae: brownish gray; up to 4 cm (in spring); sclerotized, small head capsule; "Devil's Face" on abdomen for locomotion.
- pupae: reddish brown; various segments, the posterior ones with small spines.
- Damage: Withering and brown discoloration of grass up to patches of bare patches in the lawn.
Fighting crane flies
Once you have discovered the first flies in your garden, the question quickly arises: "How do I fight Tipula larvae in the lawn?" The synthetic-chemical control of meadow crane fly larvae in the lawn has been prohibited for some time. However, there are still a variety of control options, some of which are very compatible with the environment and leave other useful insects in the soil unharmed.
Nematodes against crane fly larvae
Nematodes of the species Steinernema carpocapsae parasitize the larvae of crane cranes andsome other pests. The tiny roundworms, which cannot be seen with the naked eye, look for the larvae in the soil and penetrate them. There they continue to multiply and thereby kill the meadow crane fly larvae. It does this by releasing a bacterium, which in turn releases a toxin. The first treatment successes are already visible after seven days. When the old larva runs out of food, the nematodes abandon it and go in search of new hosts. This goes on until they run out of larvae and eventually die off themselves. Combating crane runners in the lawn with nematodes is a sustainable, chemical-free method that is harmless to humans and the environment. An efficiency of 80 to 90 percent can be achieved.
Control of crane cranes with nematodes only makes sense between mid-September and mid-October, i.e. two to three weeks after the flight of the imagines, the fully formed and sexually mature insects. With increasing age, the larvae develop better defense mechanisms and become more and more resistant. During this period, our Plantura SC nematodes are used against mole crickets, crane cranes and cutworms. A packet with ten million nematodes is enough for about 20 square meters. The nematodes can be conveniently ordered and delivered to your home. They can be stored in the refrigerator for up to six weeks before use.
Tip: Choose a cloudy, rather rainy day for the application, because the nematodes are sensitive to UV radiation. The soil should also be kept moist afterwards, otherwise there is a risk that the nematodes will dry out.
Insecticides against crane flies
In grassland and on lawns, no insecticides are generally permitted against crane flies. Apart from that, these synthetic substances often affect other beneficial insects in addition to their intended effect. They can also have negative effects on us humans or pets. Luckily there is no need for insecticides to control the cranefly, as there are plenty of other ways to control them.
Fighting crane flies with calcium cyanamide
The best effect with calcium cyanamide against Tipula is achieved when the fertilizer is applied in early spring, i.e. from around March. The younger the larvae are, the more sensitive they are. theSoil temperature should already have reached 3 - 8 °C. If 30 to 40 g of fertilizer per square meter are then applied on rainy days, efficiencies of 40 to 60 percent can be achieved. But beware, in the long run, fertilization with calcium cyanamide also has many disadvantages, as you can read about in our special article on calcium cyanamide fertilizers.
Home remedies for meadow gnats
Mechanical action can also be taken against the larvae, for example by rolling the lawn while the larvae are still in an early stage of development. Aerating rollers with spikes are particularly suitable here.
Scarifying also causes lasting damage to the larvae, but also to the lawn. Therefore, scarifying should be combined with overseeding.
On small areas, you can also distribute coasters with a bait mixture of ten parts moist wheat bran and one part sugar. The tipula larvae in the lawn are strongly attracted to this, leave the ground and go into the saucers. There they can then be collected in the early morning hours. Pieces of black foil or plastic have a similar effect.
Finally, you can also cover small areas of lawn with fleece as soon as you spot the first flying gnats in August. This prevents the gnats from laying their eggs in this patch of grass. It is important that the fleece is as light as possible and permeable to air and water so that the lawn is damaged as little as possible. Only remove the fleece for lawn mowing. The last adult animals die around mid-September, so that the fleece can then be completely removed from the lawn.
At a glance: How can you fight crane gnats?
- Responding to mosquitoes with synthetic insecticides is not allowed.
- Nematodes are a sustainable, safe way to combat them. The tiny roundworms kill the larvae of the meadow crane fly in the lawn by parasitizing them.
- Fertilization with calcium cyanamide can affect the crane fly larvae, whereby calcium cyanamide is detrimental to the lawn in the long term.
- Rolling and scarifying can also kill cranefly larvae.
- Bait traps will lure larvae out of the ground for you to collect.
- Small lawn areas can be covered with fleece.
An infestationprevent
Some of the above measures also serve to prevent an infestation of meadow gnats. For example, you can prevent egg laying by covering the lawn with fleece, foil or cardboard. Occasional rolling or scarifying also keeps them in check. In addition, the promotion of predators of meadow gnats counteracts an infestation of your lawn. This includes many birds such as blackbirds and starlings. We have summarized how you can make your garden more bird-friendly in a separate article.
A he althy, lush green lawn needs a lot of care. Because not only pests, but also fertilization at the wrong time or incorrect mowing can affect the lawn. That's why it's important to know what maintenance work is required for the lawn all year round and what you have to pay attention to.