The following insects are common leaf insects.
Greenfly or Aphids are small greenish insects which passively feed on sap of phloem vessels of the plant. Aphids can be very troublesome for plants. The lice primarily reside on the younger parts of a plant. Lice are harmful because they can transmit viruses and cause chlorosis, growth disorders, dehydration and necrosis. The damage may get worse because the lice secretes a substance (honeydew), on which sooty molds may develop. Aphids can also transmit the Closterovirus.
The whitefly is a kind of Heteroptera-like insect that can transmit viruses. The larvae of the whitefly feed on the underside of the leaves. They secrete a sticky, toxic saliva; honeydew. Sooty mold develops in the honeydew. Affected leaves turn black. Whiteflies often occur in greenhouses. Therefore, contamination can occur throughout the year. The same applies to the Fungus Gnats. Because a high resistance has been developed against existing pesticides, treatment with alternative means is an excellent method.
Spider mite is the infection of spider mites on plants. They feed on plant juices, which they suck from the phloem sap from plant leaves. Heavily affected and necrotic leaves can no longer perform their original function, which weakens and eventually kills the plant.