Assessment of thrips damage in citrus orchards in Tunisia.
Before the 2000s, damage produced by thrips have been considered rare or absent in Tunisian citrus orchards. However, during these ten last years and since the first report of the species Pezothrips kellyanus, fruit scars attributed to thrips are increasingly being reported. This study aimed to assess thrips damage on citrus and susceptibility of different citrus species and orange varieties to these pests. The relationship between thrips damage and frequency of pesticide use was also studied. The assessment of thrips damage was achieved by visual observation of 200 to 1000 mature fruits from each of the 101 visited orchards located in different regions in Cap-Bon, Bizerte and Mornag during December, January and February from 2015 to 2017. The examined citrus species and orange varieties were Lemon, Bergamot, Grapefruit, Clementine, Mandarin, Navel, Maltaise, Valentia Late and Double Fine oranges. Frequency of insecticide treatments and type of active ingredients in visited citrus orchards were noted in relation with damage rate. Fruit scars caused by thrips were 20% on average for all citrus species and orange varieties. Bergamot and Lemon seem to be the most sensitive citrus species to P. kellyanus, while Maltaise and Navel oranges were the most orange varieties affected by marbling caused by other thrips species. Data provided by 94 citrus orchards showed that damage increases with the rise of the number of pesticide applications per year. In fact, thrips are currently common in citrus orchards in Tunisia. However, their harmfulness may become more severe as the management of citrus pests is based mainly on broad-spectrum insecticides that eliminate the beneficial insects and could enhance thrips populations. The introduction of new invasive species could also contribute to increase economic importance of thrips.