Monday, April 1, 2013

Strange Insect on Coleus

                                                                                           Brian Bushe


 The pest on coleus is a scale insect called the greenhouse orthezia, also known as ensign scale, lantana bug, Maui blight and others. The bulk of the insect's body, the large white area, is actually a thick waxy ovisac attached to the abdomen.  Eggs hatch inside this ovisac, and tiny new scale insects emerge.   

                                                                           Brian Bushe

Orthezia infest a wide range of plants from mosses and fungi to grasses, woody shrubs and even small herbaceous plants; it is most commonly found in tropical reagions on lantana and coleus.

Damage occurs as the insect feeds from the phloem tissue of the plant. Copious amounts of honeydew are also produced as the insect feeds; this promotes the growth of the black sooty mold fungus covering the plant.

Biological control - a coccinellid predator beetle (Hyperaspis pantherina)  has proven successful in controlling this scale insect in certain areas. But at times, especially on coleus, the orthezia scale can become out of control. Effective chemical treatment has not been documented, but a thorough spraying of an insecticidal  soap or a horticultural oil may be successful.
On the positive side, orthezia scale itself has been used as a biological control agent of the invasive lantana shrub.