Sugarcane scale (Aulacaspis tegalensis)
Adult scales are pear-shaped (females) to elongated (males). The scale mainly attacks stalks and leaf sheaths but can also be found on leaves as a result of crowding on the stalks. In the case of severe infestation, the cane stalks are almost entirely covered by scales. When gravid, the female's body is 1.8 mm long and 0.9 mm wide. After egg-laying, the female shrinks and loses her pink colouration. Eggs are laid under the females scale. Upon hatching the crawlers (young immature mobile stage) wander looking for a feeding site. They insert their needle-like mouthparts and suck plant sap and do not move again. They then develop a thick, waxy scale cover.
Crawlers can be dispersed considerable distances by wind or movement of vegetation by field workers and transport. This scale is a serious pest of sugarcane causing yield loss (both of canes and sugar content) and making extensive replanting necessary. Yields losses of over 30% percent have been reported in Tanzania (Bohlen, 1973).
- Use of clean planting material will delay scale population build-up. Washing or hot-water treatment kills the scales.
- Practise plant sanitation in pruning infested plants. In many cases, the crawler stage (dissemination life stage) can be spread from plant to plant by pruning equipment or by infested clippings that are not discarded properly. A good practice is to clean pruning equipment before moving to new plants and to destroy infested clippings. Uproot and burn heavily infested sugarcane plants.
- Scales are usually attacked by parasitic wasps; leave alternate infested plants to allow this wasps to survive and to built-up.
- Spray of white oils (foliage and stalks) is effective against young scales. However, care should be taken, since mineral oils may be phytotoxic.