For the first time in Tajikistan, South American tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) was detected in greenhouses and open field environments in Khatlon region and the region of Republican Subordination. Leaf damage, although lower at the beginning of the season, gradually rose to 15–30% in surveyed sites. Fruit damage also gradually increased during the season. Fruit damage was as high as 20% in the locations surveyed, with the exception of Guliston and Ghayrat Jamoats, which had very low fruit damage. Tuta absoluta is becoming established in Tajikistan. Suitable integrated pest management strategies are needed to reduce the incidence of this invasive pest species.
Tomato is an important vegetable crop in Central Asia, with a production area covering 126,600 hectares (FAO 2017). This area includes Tajikistan, which has about 12,000 hectares planted with tomato in both open field and protected cultivation conditions. Tomato production is constrained by numerous insect pests and diseases. Among these biotic constraints, an invasive pest species, South American tomato leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) has recently become a serious threat to tomato production in several countries in Europe, Asia, and sub-Saharan Africa. It was reported first outside South America, in Spain in 2006 (Urbaneja et al. 2007). Since then, the pest has spread to Mediterranean countries in Europe and North Africa (Desneux et al. 2011). In recent years, it has been reported in sub-Saharan African countries including Nigeria, Niger, and Senegal in West Africa (Guimapi et al. 2016), Tanzania (Chidege et al. 2016), Kenya and Uganda (Tumuhaise et al. 2016) in East Africa, and in the Republic of South Africa (Visser et al. 2017), and South Asian countries including India (Chandrashekar & Shashank 2015; ICAR 2015), Bangladesh (Alam et al. 2016), and Nepal (Bajracharya et al. 2016). In early 2016, T. absoluta damage was noticed in Uzbekistan (Fayad & Adiga 2017), which led to speculation regarding its presence in Central Asia. A recent publication from Kyrgyzstan confirmed the presence of T. absoluta in greenhouses producing tomatoes near Bishkek (Uulu et al. 2017). Hence, we conducted a rapid survey in selected tomatoproducing regions of Tajikistan to check for the presence of T. absoluta.
Four locations—(i) Turmazor-1 village, Dukoni Jamoat of Norak city of Khatlon region (38.6600°N, 69.4504°E), (ii) Navobod village, Hissor Jamoat of Hissor district in the region of Republican Subordination (38.8411°N, 68.9661°E), (iii) Eshonobod village, Guliston Jamoat of Sarband district of Khatlon region (37.8490°N, 68.9022°E), and (iv) Guliston village, Ghayrat Jamoat of Qurghonteppa city of Khatlon region (38.3985°N, 69.2652°E)—were surveyed for the presence of T. absoluta between Mar and Jun 2016. Although tomato, potato, and sweet pepper were surveyed, T. absoluta damage was found only on tomato. Within each selected village, 1 greenhouse or field growing tomato was surveyed. In each greenhouse or field, 10 randomly selected plants in a 100 m2 area were sampled. On each plant, the total number of leaves and the number of leaves damaged by T. absoluta larvae were counted to determine the percentage of leaf damage. Additionally, on each plant, the total number of fruits (if available) and the number of fruits with T. absoluta damage also were recorded. The survey was conducted at an interval of about 10 d until the harvest in each greenhouse or field.
Tuta absoluta damage was found on tomato in all the surveyed regions of Tajikistan. Blotch mines—the typical damage symptom caused by T. absoluta—were observed on the leaf surfaces in all the survey locations. When the plants started setting fruits, T. absoluta pinholes also were observed on fruits. Damage to fruit increased as the season progressed, which was reflected by multiple holes on fruits. In Dukoni Jamoat, the leaf damage increased from 2% (in early Mar) to 30% (in May). Similarly, the fruit damage also increased from 2% (toward the end of May) to 20% in early May (Fig. 1A). A similar trend was recorded in Hissor Jamoat, where the leaf damage increased from 5% in mid-May to 30% by the end of Jun. Although there was no fruit damage in mid-May, it rose to 15% at the end of Jun at this site (Fig. 1B). The fruit damage was very low (0–5%) in both Guliston and Ghayrat Jamoats (Fig. 1C, 1D). However, the leaf damage increased to 15% toward the end of Jul, from an initial damage of only 2% by the end of May in Guliston Jamoat. Leaf damage reached 20% from an initial 1% from Jun to Aug in Ghayrat Jamoat.
This survey confirmed the presence of T. absoluta damaging tomatoes both in greenhouses and in open field conditions in Tajikistan. Since its introduction into Spain in 2006, T. absoluta is continuing to spread in Mediterranean countries, Asia, and Africa. In Africa, it has already reached the Republic of South Africa (Visser et al. 2017). It has invaded northeastern parts of India (Sankarganesh et al. 2017) and the eastern side of Bangladesh. Tuta absoluta is spreading to all those regions predicted to be climatically suitable for its establishment and long-term survival (Tonnang et al. 2015). Central Asia was reported to be a region at high risk for T. absoluta establishment; hence, it is not surprising to have found it in Tajikistan. It already had been reported in Uzbekistan, Afghanistan, and Kyrgyzstan (Fayad & Adiga 2017; Uulu et al. 2017), the countries that surround Tajikistan. Although we did not conduct any systematic survey in Uzbekistan, one of the coauthors of this paper observed that the T. absoluta infestation reached 100% toward the end of Jul 2016 from an initial damage estimate of 10–20% in early Jun in Zangiota district of Tashkent region. Thus, T. absoluta already has become established in some Central Asian countries, including Tajikistan, and it is likely to cause severe economic damage in tomato production based on the high eco-climatic index. Appropriate pest management strategies including quarantine measures should be deployed in this region to prevent further spread of T. absoluta and reduce the economic losses caused by this pest.
Funding for this research was provided by the United States Agency for International Development (USAID).