A three-year survey of Tuta absoluta (Lepidoptera: Gelechiidae) population trendsin Sardinian tomato greenhouses

Abstract: Since 2008 Tuta absoluta has established in Sardinia (Italy) as the key pest ofgreenhouse tomatoes. With the aim of monitoring tomato borer population trends after itsintroduction in one of the most important fresh market tomato production areas of the island,from February 2009 to January 2012 we surveyed ten to fifteen commercial greenhouse crops peryear. In each crop we assessed monthly the mean number of live T. absoluta larvae per tomatoplant, the percentage of plants infested by larvae, the mortality and parasitism of 2nd-4th-instarlarvae, and noted the treatment schedules. The highest levels of tomato borer infestation wereobserved in spring of 2009 (averaging 86 larvae/plant) and, to a lesser extent, in spring of 2010and 2011 (55 and 41 larvae/plant, respectively). While pest density generally declined in summer,it increased moderately during autumn, not exceeding on average 8 larvae/plant, and wasmaintained in winter. In most cases the highest levels of larval mortality were recorded betweenMay and July. Except in a few cases, the contribution of larval parasitism to tomato borermortality was poor. The insecticides most commonly used by growers for pest management wereinitially abamectin, azadirachtin and spinosad, but during the survey period the latter twoproducts were gradually replaced by Bacillus thuringiensis-based insecticides and emamectinbenzoate.