Evaluation of pheromone trapping of diamondback moth (Plutella xylostella) as a tool for monitoring larval infestations in cabbage crops in Samoa

Abstract

Studies were conducted at Aleisa and Alafua in Samoa, during 2004/2005, to assess the propriety of using pheromone trapping of Plutella xylostella as a tool for monitoring larval infestations in cabbage crops. Numbers of adults and larvae of P. xylostella present in cabbage crops were monitored, concurrently, on a weekly basis at the two sites over a period of 13 and 15 months, respectively. Numbers of P. xylostella adults were monitored by using pheromone traps which were set up in cabbage fields, whereas numbers of larvae were monitored through visual observation of cabbage plants in the same fields where the pheromone traps were placed. Results showed that numbers of P. xylostella adults caught in pheromone traps were positively correlated with larval infestations in the crops (r = 0.894 for Aleisa, r = 0.589 for Alafua). Number of moths caught in traps explained 79.9% and 34.4% of variation in larval infestations at Aleisa and Alafua, respectively.