Field Monitoring of Cruciferous Insect Pest Populations by Synthetic Sex Pheromone Traps in Chiang Mai Cauliflower Production Areas

บทคัดย่อ

Field monitoring of the diamondback moth (DBM), Plutella xylostella (Linnaeus) and the common cutworm (CW), Spodoptera litula (Fabricius) adult insect populations by the synthetic sex pheromone traps were conducted during 1995-1997 cauliflower growing seasons at Sarapee, Chiang Mai, to determine the densities and  population dynamics of the insect pests in correspondence with the meteorological data.  The total area of study was 800 m² (0.8 ha) and was divided into thirty plots of  5 m long and 2 m wide, the crop spacing was 30x30 cm,  and there was a total of 75 cauliflower plants on each plot. The DMB population attained its first peak of 819  insects on January 2, 1966, during the harvest time of the third cropping of  the 1995 growing season, then remained low through the first cropping of  the 1996 growing season. The population then  reestablished and  reached the second peak of 859 insects on March 5, 1966, and continued diminished through the second crop plantation with a small peak of 279 insects during the mid harvest time.   The adult insects of less than 100 insects per sampling date were detected through the third crop plantation, then sharply increased and attained a triple peak of more than 500 insects, during the first crop plantation of the 1997 growing season.  The DBM population had never exceeded 330 insects through the rest of the field trial.       The CW population continued increased during the first six sampling dates then attained the maximum peak of 1,465 insects on December 12, 1995.   The adult population reached a triple peak of more than 600 insects per sampling date during the second crop plantation, then remained low through the rest of the study, never exceeded 370 insects per sampling date.

                  Although the meteorological factors including the temperature, relative humidity, and the rain precipitation displayed inconsistently correlated with both the DBM and the CW populations, the rainfall seemed to exert the negative correspondence with the DBM adult population. This insect population exhibited persistently declined through the rainy seasons of both the 1996 and 1997 growing seasons.