Identification and Control Methods for Pests and Diseases of Chinese Cymbidiums

The body surface of scale insects hardens and is covered with a hard shell, or they secrete a powdery waxy substance. The insect body attaches to the plant surface, and its mouthparts pierce into the plant to suck sap. Whether they are oviparous or viviparous depends on the scale insect species; some species can only reproduce viviparously, so the population consists entirely of females. Some species are oviparous and require a mating process, with both males and females present. Regardless of whether they are oviparous or viviparous, female insects have no wings after growing up, and their appearance is similar to that of nymphs, only larger in size. Females lay eggs directly beneath their bodies, relying on their own bodies to protect the eggs. They can lay dozens to hundreds of eggs at a time. Males go through a pupal stage and become winged adults, which fly to mate with females. Scale insects can occur on the leaves, leaf sheaths, stems, or even roots of plants. Some scale insects prefer concealed locations, multiplying in large numbers under leaf sheaths or in the folds of leaves, and only when their numbers become too great do they spread to the leaf surface or stems, such as the citrus mealybug (Planococcus citri). Some do not have a concealed habit, such as the Florida red scale (Chrysomphalus ficus) and the hemispherical scale (Saissetia coffeae), which are scattered on the underside or upper side of leaves. The damage caused by scale insects results from their sucking plant sap. At the feeding sites, plants show yellow-white or yellow-brown spots or halos. Scale insects that occur singly on leaves may cause small spot marks from feeding, while large numbers clustered together, due to their large feeding volume, cause entire sections of leaves or stems to appear dark brown and shriveled. The wounds created by scale insects piercing plant tissues with their mouthparts can also lead to infection by pathogens, making the affected plants more susceptible to disease. Chen Mingzhao