Saissetia coffeae (Walker)

Bustillo, Alex, 2015, Part II. Pests, Compendium of Coffee Diseases and Pests, United States of America: The American Phytopathological Society, pp. 45-60 : 48

Male hemispherical scales, Saissetia coffeae (Walker) ( Hemiptera : Coccidae ),

are rarely found, and it is presumed that most reproduction occurs primarily through parthenogenesis. The eggs are laid underneath the carapace of the adult female. The eggs are translucent or whitish just after oviposition and later turn pale yellow and ultimately orange. The first instars are called crawlers. They are flat, oval, and greenish brown to pale amber; have six legs; and are about the same size as the eggs. This is the only mobile stage of female hemispherical scales. Crawlers move about the leaf area in search of a suitable feeding site until one is found. The remaining two nymphal stages are essentially stationary at the site selected by the crawler, and only under adverse conditions do female nymphs move small distances. The body color of the last two instars ranges from pale yellow to greenish brown to dark pink. The second and early third instar body shape has an irregular outline and lies flat. Toward the end of the third instar, the hemispherical scale undergoes a rapid growth phase, until it is about the size of the adult. The mature female hemispherical scale has a convex, light to dark yellow-brown, smooth and polished, helmet-shaped carapace ( Fig. 86 ). The adult stage is incapable of locomotion and is about 2 mm long.

Females have a 2- to 3 -day waiting period before laying eggs, which they do for 4-6 days before dying. The average number of eggs laid per female varies from 250 to 400. Since females are not capable of wandering once they have settled and start feeding, long-range dispersal occurs by passive transport of infested plant material. Short-range dispersal occurs as crawlers search for places to settle and feed. The adult males have wings but are incapable of long flights and are wind transported. Males live only a few hours, emerging in the late afternoon to mate. Because of their tiny size, short life, and evening activity, it is rare to find adult males in the field.

Damage

Hemispherical scales are found clustered on the shoots, leaves, and young fruits of plants. They are often arranged in an irregular line near the edge of the leaf blade. Hemispherical scales feed on plant juices and cause debilitation of older plants, deformation of infested plant parts, loss of leaves, re ­ tarded plant growth, and even death of nursery plants. Honeydew secreted by the hemispherical scale forms a film on the leaves and a black fungus (sooty mold) grows on it. Ant activity is frequently noticed, protecting the hemispherical scales and feeding on the honeydew.

Population Management

Parasitoids known to attack hemispherical scale include Encyrtus infelix (Embleton) , Encyrtus barbatus Timberlake , Tomocera californica Howard , Microterys flavus (Howard) , Scutellista cyanea Motschulsky , and Aneristus ceroplastae Howard. It is also very common for hemispherical scales to be infected by the fungus Lecanicillium lecanii (Zimmerman) Zare & W. Gams. The hemispherical scale is usually controlled by its natural enemies, and chemical treatments are usually not necessary.

Figures

Fig. 86. Saissetia coffeae adult. (Courtesy A. Bustillo, Cenicafé)