Mosquito larvae in the rain barrel: what to do? | larvae and worms

With the summer come the mosquitoes. They sting us in the evening when we are having a barbecue and they keep us awake at night with their annoying whirring. The pests are not only active in the vicinity of ponds and lakes. The rain barrels in the garden are enough to attract thousands of mosquito larvae. How to prevent mosquito invasion? Can it be effectively prevented?

Mosquitoes need water

Mosquitoes (Culicidae) are found almost all over the world. Only in the deserts and in the polar regions do they not occur. In central European regions, the common mosquito and the ring gnat are the most common species. Mosquitoes need water to lay their eggs. Only standing water such as lakes and ponds or rain barrels in the garden are suitable.
A single female mosquito can lay more than 100 eggs per day on hot days. The development of the mosquito proceeds in four stages

  • No
  • Larvae
  • puppet
  • adult insect

Depending on the species, it takes about three weeks from the time the eggs are laid to the finished insect.
Once the eggs are laid, it takes a few days for the mosquito larvae to hatch. Mosquito larvae need oxygen and have to return to the surface of the water again and again. The prerequisite for the larvae to breathe is the surface tension of the water. When the temperatures are warm, it doesn’t take long for the larvae to develop into the finished insects.

Prevention Tips

In order to protect yourself from mosquitoes settling in the garden, it is important to take preventive measures in good time. The females must be prevented from laying the eggs in the water butt. It is helpful to block their access.

Tip 1: Cover up

Cover the rain barrels with lids or special fly screens. Covers have the disadvantage that complete closure is not possible in the access area of ​​the downpipe from the gutter. The mosquitoes find access to the water through small gaps.
Fly screens or nets are a better choice. They prevent egg laying without interfering with catching the water. Cut the net to fit your water butt. A small opening is cut into the net for the downpipe.

Fasten the mosquito net by laying it over the edge of the bin and tying it tightly with a string. Try to close the opening as tightly as possible, also in the area of ​​the downpipe.

Note: Commercial packaging tape is not suitable for attaching the net to the water butt. It would peel off under intense heat and exposure to sunlight. As an alternative to the fly net, you can use garden fleece.

Tip 2: closed rainwater containers

Use closed rainwater containers. There are now various models on the market that are connected directly to the downpipe of the gutter and consequently collect the rainwater safely. These closed systems do not allow mosquitoes to enter.

Tip 3: Protective plants

There are plants that keep mosquitoes away. These spread intense fragrances that are unbearable for the pests. You should take advantage of that.

Suitable plants are

  • scented geraniums
  • sage
  • rosemary
  • catnip
  • basil
  • lavender
  • lemon balm

Mosquito elimination tips

Once the mosquitoes have found an entrance to your water butt, you have a number of options to kill the larvae. For environmentally conscious gardeners, the use of chemical insect repellents is forbidden, because these can also endanger the beneficial insects.

Tip 1: Destroying surface tension

Destroy the surface tension of water. Surface tension is essential for mosquito larvae because they have to breathe on the surface. Without the surface tension and a chance to get oxygen, the larvae eventually drown.
However, the surface tension can be destroyed by adding vegetable oil without harming the environment. Alternatively, you can use biodegradable dishwashing liquid.

Three tablespoons of vegetable oil or washing-up liquid are sufficient for a standard water butt.

You can get special protein preparations from specialist retailers that also destroy the surface tension. These are not as cheaply available as vegetable oil and washing-up liquid, but develop less odor and do not cause foaming. The protein preparations are advantageous for water butts and especially for garden ponds.

Tip 2: Learn rain barrels

If mosquito larvae are cavorting in your rain barrels, it can be helpful to empty them completely. This is a quick and effective solution, especially when there is only a little water in the bins. When the bins are completely full, other options should be used, because the water is urgently needed for the plants in summer.

What are those worms in the rain barrel?

Hobby gardeners often discover small worms in their rain barrel. In most cases, these are also mosquito larvae. These have different appearances and white, red and black mosquito larvae are active in our gardens.
Mosquito larvae can be small and round or elongated like worms.

Sometimes other small animals also discover the advantages of the rain barrel for reproduction:

  • dragonfly larvae
  • caddis fly larvae
  • hopperlings
  • water isopods
  • rat tail larvae
Tip: If you discover dragonfly larvae in your bin, don’t miss the exciting spectacle of the development from the larva to the dragonfly hatching. Always have a camera ready.

Dragonflies are protected and are one of the beneficial insects in your garden.
It is not uncommon for earthworms to get lost in the bin. They often get into the rainwater via the watering cans. However, earthworms will drown if they don’t find their way out quickly.

Kira Bellingham

I'm a homes writer and editor with more than 20 years' experience in publishing. I have worked across many titles, including Ideal Home and, of course, Homes & Gardens. My day job is as Chief Group Sub Editor across the homes and interiors titles in the group. This has given me broad experience in interiors advice on just about every subject. I'm obsessed with interiors and delighted to be part of the Homes & Gardens team.

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