Lars Lund

17 Aug 2021 11:36

Get rid of lice and mites

The greenflies and mites are here. Do you have roses in the greenhouse then it is likely that the roses are the first to get intruders, otherwise greenflies and mites appear on all plants. That includes everything from your hedge to your cucumbers.

Greenflies multiply by virgin birth and give birth to living greenflies. Even in the embryonic stage some greenflies are able to breed for the next generation, and for this reason they can quickly multiply. In the autumn many dies, but they are built in such a way that many lay eggs that can survive winter especially if the winter is mild. It is the same with the Spanish slug. Get rid of them now, then there may be fewer of them next year. Most of them die during winter, but there are some types of lice among Denmark’s 500 species who can make it through a winter. One of them is the green spruce aphid which kills many spruces every year. It was worst for the spruce by the west coast of Denmark.

Lice loves mixed weather
Some years there are many lice and other years there are few. They do not like it too hot nor to cold and not at all too wet. If it is too hot they disappear, and rain makes it difficult for them to stick on plants.

Where there are ants in a tree, a rose, a wine grape and/or other plants so there will be lice. Ants can be annoying when they are where you stay, but otherwise you should be happy to have them and not just kill them when they are not bothering you. Actually, they help you to find out if something is wrong with your plant.

Many lice are disguised so they blend in with what they are eating, and therefore it may be difficult to spot them straightaway. The ants milk the aphids so to speak. In reality they eat the remains of the lice.


Do not overfertilize
Lice like plants that are fertilized a lot, and the more nitrogen you give the plant, the bigger the chances are that the lice will suck out the saps. The lice need nitrogen. But in general there is too much nitrogen in their food, and therefore it is excreted as sugar. This is what the ants want, and this is the substance that may leave stains on the leaves if the ants do not ‘clean up’.

Aphids harms your plants, so you need to get rid of them. They suck the saps so parts of your plant are weaken and die. They suck by sending saliva into the plant. The saliva makes it easier to suck, but it may cause other diseases like virus and bacteria.

Food of the bird
The big dilemma is that aphids are also the main course of many small birds. If we exterminate all lice, then it will affect the bird population. Therefore, you should ally yourself with the birds, the ladybirds and the green lacewings. Let them get a share of the gains.

If the birds cannot do the job then you must help them. Take care of the lice early before they multiply to millions. Squeeze them, brush them off or use the hose to get them away. You must be persistent and repeat this many times. Make sure your plant is doing okay, so it does not get weaken.

Make the soap yourself
If you want to buy your way out of it, there are many insecticides against lice. Some destroy eggs others kill the lice itself. This is done by penetrating the plant and getting to where the sap runs. The sap is then made poisonous for the lice.

Neem oil is not that well-known, but it is very effective. It is also effective against spider mites. It is oil from a South Asian tree Azadirachta Indica. In South Asia it is used as fungicide and against animals that eat your plant or suck sap from the leaves.

You can also make a mixture of 25g (0,88 oz) soft soap dissolved in 1 litre of water and place the mixture in a sprayer. A bit of alcohol will also be beneficial for the mixture.

Coffee grounds between the roses is an old home remedy that keeps the lice away, and apart from that fertilize.

Often mealy bugs sit on vines and should be brushed away with a toothbrush and some alcohol or squeezed and removed with the fingernail.

Here the beans help
Spider mites should be prevented. Beans under the plants or rain catcher are supposedly helping. When it comes to spider mites and soap and oil, you should spray every three days for at least two to three weeks to eliminate all mites including those who hatch when the substance no longer is active.

Om Lars Lund

Lars Lund
Danish horticulturist and journalist
Lars Lund has for many years engaged in the garden and greenhouse. Lars has published many books about greenhouses, and he has participated in many Danish horticultural TV shows. He is a walking garden encyclopaedia, and he has answers for most basic cultivation questions – also the more ambitious ones.  

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