First record and bionomics of the mycophagous ladybird Psyllobora bisoctonotata (Mulsant) (Coleoptera: Coccinellidae) in Sudan

摘要

Powdery mildews caused by several fungi, particularly of the genera Erysiphe, Sphaerotheca and Leveillula, are destructive diseases of various cultivated and wild plants during winter season (December-March) in Sudan. Application of synthetic fungicides is the only control measure practiced. Fortuitously, during a field survey, congregations of coccinellid adults and grubs were found associated with powdery mildews on a wild plant, Xanthium brasilicum Vell., locally known as ''Ramtouk'', at Shambat area/Khartoum North. Therefore, the insect was subjected to some bionomical studies conducted during winter season 2011/12. Emphasis was devoted to morphometric investigations, supported with life cycle durations and seasonal trend on the foregoing host. Accordingly, the species was recognized as Psyllobora bisoctonotata (Muls.), a well known powdery mildew feeder in several countries. This is the first record of a mycophagous insect in Sudan. Hence, the important morphological features of the different stages were presented. The rearing of the insect on powdery mildew infected Ramtouk leaves in the laboratory (27.50+/-3.75^oC and 15.83+/-3.82% R.H.) revealed that the mean total lifecycle from egg to adult was 25.28+/-1.57days. The insect appeared on X. brasilicum in a very small number in December, peaked in February, and then gradually declined thereafter coinciding with an increase in temperature and a decrease in powdery mildew infection. So far, the real distribution of this mycophagous species and its host range are waiting for more investigations. Meticulous bio-ecological studies are important to ascertain the proper habitat for such insect throughout the year, and to evaluate its potential role as a biocontrol agent for the powdery mildews.