AbstractA commercial trial of different strategies for suppressing damage by Cryptophlebia leucotreta (Meyrick) to citrus was made in the Transvaal lowveld, South Africa. Different regimes tested were applications of the chitin synthesis inhibitor teflubenzuron at 60 mg a.i./litre and ca 30 litres/tree, inundative releases of the egg parasitoid Trichogrammatoidea cryptophlebiae Nagaraja, and a combination of the two. One objective was to examine whether application of the insecticide earlier in the season than usually recommended would enhance the subsequent impact of parasitoids, native or released. It was found that parasitoid releases throughout the season (1.3 million/ha in total) produced the best overall reduction in damage by C. leucotreta. This was due largely to their better performance than that of any other strategy early in the season. Their impact in the later part of the season was not significantly different from that of release programmes which had begun at a later stage (0·6 million/ha). Very early applications of the teflubenzuron had no apparent impact on crop losses and did not enhance the impact of subsequent parasitoid releases to a significant degree. Teflubenzuron application at a recommended time later in the season was the most successful short-term approach, but its overall impact on crop loss was diminished by damage during the unprotected period before its application. A more appropriate management programme against C. leucotreta might therefore be to combine inundative releases of parasitoids early in the season with later applications of teflubenzuron if economic thresholds show they are required. The two approaches should not be concurrent since parasitoid activity was suppressed by the chitin synthesis inhibitor.
The Impact of Selection with Diflubenzuron, a Chitin Synthesis Inhibitor, on the Fitness of Two Brazilian Aedes aegypti Field Populations
