Meyer lemon trees, though fairly resistant to many diseases and pests, can suffer infestations from certain species. Ants, for example, will often cause bring scales and aphids to a tree as the ants seek to feed on the secretions the scales and aphids produce. Unfortunately, the scales and aphids, along with mites, will do damage to the tree as they feed off it. A homemade spray of dish soap and water can help control them. There are also horticultural oils that work well, too.
Scales can be vigorous parasites of Meyer lemon trees. They feed on the tree sap present in its leaves or stems, depriving it of vital nutrients. Ants will move the scales from tree to tree in order to "farm" them for their milky honeydewlike secretions. They'll also protect the scales from beneficial pest insects. Many species have waxy-looking coverings and can resemble oyster shells. They may also even look like very small and shiny pearls.
Ants actually farm aphids and protect them from beneficial pest insects. In turn, as with scales, ants eat the secretions aphids produce. In some cases, aphids feeding off a tree can transfer harmful plant viruses to it. Infested trees typically display curled-up leaves as well as black, sooty mould on their surfaces. Common aphids are mostly yellow, black or green in colour and display two small tubes at the ends of their bodies.
Meyer lemon trees can suffer infestations from mites, especially spider mite types. Like the other pests, they also feed on sap in the leaves, turning them greyish or bronze in colour. This gives an unpleasant look to the tree. If you suspect they're present, look for webbing on the leaves. Extremely small and difficult to see, spider mites range in colour from red and brown to yellow and green.
If you suspect an infestation from one of these pests on your tree, there's a homemade spray you can try. Mix a mild solution of water and dish soap and spray it on affected areas. It'll cover their bodies and suffocate them. Additionally, horticultural oil in a 1 per cent strength, sprayed in the same manner, works well. Neither spray will harm most beneficial pest insects such as ladybirds, which like to feed off aphids.