COMPARATIVE EFFECTS OF BARK AND PEAT BASED COMPOSTS ON THE OCCURRENCEOF VINE WEEVIL LARVAE AND THE GROWTH OF CONTAINERIZED POLYANTHUS

A series of experiments was conducted to investigate the effect of inc lusion of bark in potting composts on the numbers of vine weevil larva e on polyanthus plants. In 1989 more larvae were recovered from plants grown in peat compost than those grown in bark but these results were reversed when the study was repeated in 1990. Numbers of larvae also increased with higher ratios of bark:peat in composts but declined as the size fraction of bark used increased. The degree to which bark was composted did not appear to materially affect the numbers of vine wee vil recovered. A strong, positive, relationship between larval numbers and foliage dry weight was found. Similarly, larval numbers were bigg er with greater root development in bark composts. The results are dis cussed and it is suggested that the use of bark may promote more vigor ous growth in polyanthus and thus enable plants to support more larvae .