The relationship between citrus thrips, Scirtothrips aurantii (Thysanoptera: Thripidae), abundance and fruit size in mango orchards
Population levels of the citrus thrips, Scirtothrips aurantii Faure (Thysanoptera: Thripidae), were monitored for two consecutive seasons in mango (Mangifera indica L. (Anacardiaceae)) orchards in the Mpumalanga province of South Africa. Yellow sticky card traps were used to monitor adult numbers, while counts on the fruit were conducted to monitor numbers of adults and larvae. Fruit size was measured throughout the season. Hoerl's function (Y = aXb ecX) was used to describe the relationship between the number of S. aurantii on the fruit and fruit size, as well as the number on the traps and fruit size. A notable feature in the population dynamics of S. aurantii was the rapid decline in numbers after the population peak had been reached. The highest numbers of S. aurantii were present between fruit set and when fruit reached 40 mm in length. Fruit size can therefore be used as an indicator of potentially damaging number. Producers should do regular monitoring from fruit set until fruit reach 40 mm.