EVALUATION OF PHEROMONE TRAPPING FOR PREDICTION OF DIAMONDBACK MOTH INFESTATIONS IN VEGETABLE BRASSICAS

摘要

The use of pheromone traps was investigated as a monitoring tool to forewarn crop scouts of risk periods when diamondback moth (DBM; Plutella xylostella) larval numbers in crops are likely to increase to damaging levels. We monitored traps at five brassica planting sites for 8 months and also counted numbers of DBM larvae on 50-100 plants at each site. Crops were scouted weekly and insecticide application decisions were made using the Crop & Food Research IPM programme. Results showed that increasesin moth trap catches predicted increases in larval infestations in three of four commercial crops in spring by 2-3 weeks and gave 2 weeks warning in four of five summer crops. An epizootic of Zoophthora radicans caused a rapid decline in larval populations in mid to late January at all sites. In these trials, use of the IPM action thresholds led to a 75% reduction in insecticide use on vegetable brassica crops. Overall, pheromone traps were of limited value, except in early spring, because crops neededto be scouted regularly for other pests.