PRESENT USE OF, AND PROBLEMS WITH, BACILLUS-THURINGIENSIS IN NEW-ZEALAND

The use of Bacillus thuringiensis (Bt) as a foliar spray to Control insect pests has received scant attention from New Zealand growers apart from application to kiwifruit during the period of bee pollination. Major problems underlying this lack of use are the very high standards of quarantine and quality demanded of export produce, the relatively high cost of Bt and its shortcomings in efficacy and persistence. A substantial increase in use appears unlikely unless there is a significant reduction in synthetic pesticide use on export crops. In contrast, rapid progress on research into plant transformation in New Zealand has led to proposals to insert Bt genes into an increasing range of crops. Although transgenic plants show great potential for pest control, there is concern that continual expression of Bt proteins in plant tissue will increase the intensity of selection for pest resistance. A particular concern is the possibility that Bt-resistant cosmopolitan pests may spread between different transgenic crops. A plan to combat this problem through the integrated use of different Bt genes in different crops is suggested.