Scale insects (Coccoidea: Sternorrhyncha) are all sap-sucking bugs that are parasitic on plants. Perhaps no plant family is immune from attack. Many scale species are extremely important pests of fruit, forest tees, shrubs and other ornamental plants, and agricultural and horticultural crops. The world-wide losses and increased production costs attributed to scale insect damage were estimated at 5 billion dollars annually (1996 — probably twice this now). Because of their small size and the fact that they are often hidden in cracks, inside buds or beneath the soil, they are hard to detect and can usually only be identified when stained and mounted on glass slides. Current projects:
- A revision of the soft scale insects of Australia (with P.J. Gullan, Davis, California);
- Redescription of the type species of all eriococcid genera in South America (with Dug. Miller, USDA);
- Revision of the wax scale insects (Ceroplastinae) of Africa (with a redescription of a "lost" Linnaeus species) (with Doug Williams (BMNH) and Jan Giliomee (Stellenbosch));
- The higher classification of the Coccoidea based on the morphology of the adult male.
- A revision of the mealybug family Rhizoecidae based on adult male morphology;
- The identity of a mealybug currently causing billions of dollars worth of damage to cotton and other crops in Asia,
- Several small papers on new species and new genera from Europe and Africa.