Investigating some ecological characteristics of Tuta absoluta (Meyrick) in Sirvan County (Ilam Province, western Iran)

The tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is an important pest of tomato in Iran. Therefore, this study was done to investigate fluctuations in adult male population of this pest using sex pheromone traps in Sirvan County (Ilam Province, western Iran) during a growing season, which lasted before transplanting to the end of growing season.

For conducting this research, 4 tomato farms in Sirvan County were selected and the pest populations were sampled using pheromone traps. The Pearson's correlation coefficient was used to assess the relationship between adult moth density and temperature. For determining optimal sample size, the Green's method was used.

According to results of the present study, there were seven population peaks at intervals of approximately one month. Flight peak of this pest occurred on May 10, June 14, July 19, August 23, October 4, November 8 ,and  December 6, respectively. The highest population density was recorded on July 19 (397.75 moths) and population density of this pest was declined since late November. Studying the relationship between average number of male moths of T. absoluta captured by pheromone traps and average monthly temperature in a growing season showed that with the increase in temperature, population density of moths was also increased. Results of regression analysis indicated that peaks about abundance of male moth coincided with the previous monthly mean temperatures. Taylor's regression model showed a significant and high correlation between mean and variance regarding density of pest population. Statistically, the aggregation index of tomato leaf miner was equal to one. In this study, Green's method was used to estimate optimal sample size. The results showed that the required number of sampling units was decreased with the increase in average population density of the pest so that, when average population density of tomato leaf miner moth in each pheromone trap was one per week, the required number of samples with an accuracy level of 25 and 10% was equal to 1.86 and 11.65, respectively, and when average population density of this pest in each pheromone trap was 10 per week, the required number of samples with an accuracy level of 25 and 10% was equal to 0.37 and 2.32, respectively.

Our results demonstrated that pheromone traps can be used as a suitable sampling method for monitoring population of the tomato leaf miner. This study provided the data about sampling, population distribution, fluctuations in population of tomato leaf miner, and the relationship between population density of the pest and temperature. Our findings can greatly contribute to rational management of this pest in the region.