It is the larvae rather than the adult beetles which are so damaging to houseplants. Eggs laid in the compost hatch to give plump, whitish curved grubs with brown heads. These feed on the plant roots and also tunnel into the bases of bulbs, corms and tubers. The first sign of attack is that the plants tend to wilt even when well watered. Later, if no action is taken, the plants may well die. Since there are several possible causes of wilting it is necessary to knock the plant out of its pot to examine the root ball for the presence of these white grubs.
Most pot plants are liable to be attacked by these pests. Those which suffer most are azalea, begonia, cineraria, coleus, cyclamen, ferns, hydrangea,Sarifraga and Sedztm.
Repeat applications of heavy soil drenches of spray-strength insecticide.