Lemongrass is a fairly robust plant that is easy to cultivate if you can meet the demands for light and warmth. However, fungus gnats can be hard on lemongrass.
The fungus gnat is not hidden from us. If you look closely when watering, you can see the small insects flying up. Adult animals are harmless. The larvae of the fungus gnat, on the other hand, pose a problem. Even a small injury to the stalks is enough for the pests to penetrate. The root can also be affected. That is why you have to be extra careful when watering. The fungus gnat prefers to lay its eggs in moist substrate. Therefore you should always water moderately. It is also a good idea to water potted plants from below.
The larvae of the fungus gnat can generally damage lemongrass in a number of ways. The fungus gnats can cause feeding damage to the leaves and growth damage by infesting the roots, as well as a stunted growth habit.
What do fungus gnats look like and how do you recognize an infestation?
The fungus gnat is found worldwide. Even extreme habitats are not avoided. The insects have been detected in the Antarctic as well as in high mountain regions over 4,000 meters above sea level. Some species live in burrows, while other fungus gnats live in the hot desert sun by burrowing into the sand. However, the fungus gnat mainly lives in more hospitable regions, namely in forests, on pastures or in the home garden, where it seeks hiding places in the plants and leaves. Fungus gnats can even survive in flower pots on the window sill. That's why you have to check the lemongrass more frequently, especially during the winter period.
The fungus gnat belongs to the diptera family and, like about 1,800 other species, belongs to the mosquito suborder. There are around 600 species of mosquitoes in Europe alone. The name fungus gnat can be traced back to the dark body and dark wings. The mosquitoes are about five millimeters long and have a slender body. The larvae, which are the real threat to lemongrass, are light to greyish in color and havea fully formed head pod.
By the way, the fungus gnats are easy to recognize by their slightly dancing flight. The mosquitoes themselves die after a few days and only have the task of mating and reproduction. The larvae can consume mushrooms, bark or foliage. Their excrement in turn serves as food for microorganisms.
How to fight fungus gnats
The trade offers some pesticides against fungus gnats. However, deltamethrin, magnesium phosphide or pirimiphos-methyl are environmental toxins that are not permitted for use in gardens. Inhaling the substances alone can lead to allergies and irritation of the eyes and mucous membranes. It can even explode if it comes into contact with water. So, these substances are a real danger to children, pets and all living organisms. Therefore, do without the chemical club. Fungus gnats can also be effectively combated with natural remedies.
❍ Use yellow stickers against fungus gnats:
In the case of yellow stickers or yellow plates, we are talking about color plates that are provided with glue. These boards can be made of paper or plastic. The trade offers different models. Most of the adhesives used are made of polymers. Some products are coated with polyisobutylene. That's why the yellow stickers also appear wet. Yellow panels that are provided with hot-melt adhesive are less sticky. These adhesives are harmless to he alth and are also used, for example, to attach labels to apples or oranges. Some boards can also be cleaned with petrol after use and used again. More about yellow boards here.
Application:
You can use the yellow boards both indoors and outdoors. Yellow stickers for outdoors should be as heat-resistant as possible and not contain any water-soluble substances. Insects are known to like colors. They seem to be particularly fond of yellow. But there are also green and blue stickers available, which exert a similar attraction. When approaching the stickers, the fungus gnat sticks to the panels. Depending on the plant size, several stickers can be used. You should check the panels weekly and replace them if necessary.
❍ Use home remedies against fungus gnats:
| Home remedies | Effect |
|---|---|
| quartz sand | Put quartz sand on the top layer of soil, the soil appears dry and the fungus gnats appearare prevented from laying eggs on the dry surface. You can use small pebbles as well as bird sand. |
| Matches | Put a few matches in the ground around the plant with the tip down and the sulphur-containing components will be dissolved by the watering. The larvae die off and the fungus gnats are prevented from laying eggs again. |
| Nutmeg | Nutmeg contains the active ingredient myristic acid, which is comparable to an insecticide in its effect. |
| Carnivorous Plants | Placing carnivorous plants (e.g. venus flytrap) near lemongrass will help control fungus gnats. However, carnivorous plants are powerless against the larvae. |
❍ Use nematodes against fungus gnats in the bucket:
Nematodes are a particularly effective and natural method of combating fungus gnats. These are worms that are invisible to the naked eye and are simply added to the irrigation water. They hit the ground and then infest and kill the larvae of the fungus gnat. For this you need to water several times. It can then take a few weeks for all the larvae to die off.
Prevent infestation with fungus gnats - Here's how
Since the fungus gnat prefers to lay its eggs on a moist surface, you should ensure that the soil can dry well after watering. A layer of sand or pebbles also has this effect. Always remove standing water from plant pots, because lemongrass does not tolerate waterlogging.
When buying potting soil, you should also pay attention to quality. Cheap products are often already infested with fungus gnats. Infested soil should be replaced immediately. You can dispose of the soil on the compost provided that you do not use the compost as a natural fertilizer for house plants.
By the way:
The method favored by some plant lovers of heating soil infested with fungus gnats in the microwave for a certain amount of time with the aim of to kill larvae. The soil also loses important nutrients in the process, ultimately making it unsuitable as potting soil.