Diseases and insect pests of national orchid-scale insects

The surface of the shell insect's skin is hardened by a hard shell, or there are powdery waxy secretions. The insect body is attached to the plant surface, and the mouthparts are pierced into the plant to absorb juice.

Oviparity or viviparity depends on the species of shellfish, and some species can only be viviparous, so the population is full of females. There are also some species that lay eggs, which need to go through the process of mating, both sexes. Regardless of egg or viviparity, the female does not surpass when she grows up, and her appearance is similar to that of the nymph, but the individual is relatively large. The female lays eggs directly under the body and relies on her own body to protect the eggs. It can lay tens to hundreds of eggs at a time. After the pupal stage, the male becomes a winged adult and flies in to mate with the female.

Scale insects can occur in leaves, leaf sheaths, stems, or even roots of plants. Some scale insects prefer stable places, which thrive under the leaf sheath or at the folds of the leaves, and only when they multiply too much will they spread to the leaf surface or stem, such as the orange powder scale (Planococcus cit-ri). Some are not stable, such as Chrysomphdus ficus and Saissetia coffeae, which are scattered on the back or surface of the leaves.

The damage of shell insects is caused by sucking plant juice at night, and plants will show yellowish-white or yellowish-brown spots or halos where they are sucked. The feeding of the singly existing scale insects on the leaves may cause little marks, and most of the scale insects gathered together will make the whole leaf or stem appear dark brown and shrink because of the large intake. The wound caused by the sucking of plant tissue by shell insects can also cause bacterial infection, making the injured plant vulnerable to disease.

Chen Mingzhao