Cassava Shoot Parasitism by Larvae of Neosilba perezi Romero & Ruppell (Diptera, Lonchaeidae) in Southeastern São Paulo State, Brazil

Among the pests of cassava, the shoot fly Neosilba perezi (J. L Romero & R F Ruppell) is one of the most prevalent. It attacks mainly the terminal shoots and causes infected plants to produce lateral shoots. Reports on this species are rare or inexistent; thus, the purpose of this study was to assess three different areas for N. perezi infestation. The survey commenced in March 2008 and ended in February 2009. Fortnightly analyses were performed starting 45 days after planting, calculating the rate of parasitism by N. perezi larvae in each study area. The areas were correlated separately for each parameter: fortnightly mean temperature, fortnightly mean rainfall, and plant age. The N. perezi larvae occurrence rate was higher in area 1 – which presented the highest population peaks in autumn and winter. There was only a single population peak in area 2, in winter; and area 3 presented the weakest population peak among the three, in November. The shoot fly population dynamics in the studied region is separately correlated to temperature, rainfall and plant age: temperatures above 23ºC, relatively high rainfall and older plants seem to have a negative effect on populations of this insect. Finally, a new species of parasitoid of N. perezi was found in the sampled areas.