The South American tomato pinworm, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae), a devastating pest of tomato plants, originates from South America but it has been considered an invasive pest for Iran since 2010. To assess crop loss caused by this pest, a study was conducted in a 600 m2 field under a randomised complete block design. The impact of different initial densities of T. absoluta, including control (without infestation), one, two, four, and eight T. absoluta eggs on each host plant in the first and second year was investigated with an additional treatment (16 pinworm eggs per host plant) used in the second year. Yield attributes including length and width of fruits, numbers of infested and intact fruits along with their weights were sampled and assessed on a weekly basis. In addition, the correlation between the number of galleries and these characteristics was also investigated. Crop loss data demonstrated that the effect of different infestation levels on fruit size and the weight of intact fruits was not significant over both years. However, the effect of treatment on the percentage and weight of infested fruits was shown to be significantly different in 2014 and 2015. Furthermore, there was a negative significant correlation between the number of galleries and weight of infested fruits in both years. Collectively, these results will be useful for enhancing pest management programs of T. absoluta in Iran.
