Lice are destructive to your plants. The worst one is the scale, but the absolute worst is the spider mite.

What to do if your plants get infested with lice:

Scales are difficult to eliminate. Actually, there is not much else to do than to pull out the toothbrush, dip it in alcohol and rub them off. Underneath their carapace hide 300 eggs, so rubbing them off is worth it. The females take care of the eggs until they hatch, then the female dies. The small hatched larvae can be difficult to spot, so use a magnifying glass. There are many different kinds of scales, in the greenhouse they typically infest vine and citrus. 

 

Spin doctor

Spider mites are more difficult to eliminate than scales. We spot them too late. There are predatory mites that eat spider mites, but generally it’s not worth it to save that one or those two cucumbers in the greenhouse. Spider mites climb from the soil up the plant. Maybe they were already there when you bought the plant. You can put up a fly catching adhesive paper roll to catch some of the mites on their way up the plant. Put it up when you transplant the cucumber. 

 

Beans may help

Some have good experience with planting beans or tansy in the greenhouse. Try it, maybe it works for you.

Insect soap

No matter which kind of louse you have or get, it is worth trying insect soap. You can make your own soap from 1,7 cup of water, 0,2 cup of liquid lubricating soap and 0,2 cup of rubbing alcohol. For spider mites especially you need to spray several times.