Plumbagin, a napthoquinone from the plant Plumbago zeylanica, delayed pupation when topically applied to newly moulted final instars of the leaf eating caterpillar Opisina arenosella Walker (Lepidoptera: Oecophoridae). Pupae from treated larvae emerged into non-viable adults and had abnormalities such as deformed wings and shrunken abdomens; they also died much before the control insects. The results suggest that plumbagin interferes with the process of development and ecdysis of the insect.

The phytochemical ptumbagin, isolated from Plumbago zeylanica L., was applied in 2 and 5 μl doses of 0.1% concentration on the surface of Dysdercus koenigii F. adults and its effect on the haemocytes of the bug, studied by transmission electron microscopy. All the five haemocyte types viz. the prohaemocyte, plasmatocyte, granular haemocyte, oenocytoid, and the adipohaemocyte are affected within a period of 24–48 hr. The effect begins with an acute state of vacuolization of the cells and a gradual destruction of the organelles, followed by dissolution of the plasma membrane and passing out of the internal organelles, like the mitochondria and the endoplasmic reticulum. This phenomenon is responsible for a consistent elimination of the haemocytes from the blood, leading to lowering of the resistance and mortality of the insects.